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Theses and Dissertations--Kinesiology and Health Promotion Kinesiology and Health Promotion

2018

ROLE OF SKELETAL MUSCLE MASS IN SEX-DEPENDENT POWER ROLE OF SKELETAL MUSCLE MASS IN SEX-DEPENDENT POWER

OUTPUT DURING FLYWHEEL RESISTANCE TRAINING OUTPUT DURING FLYWHEEL RESISTANCE TRAINING

Paul A. Baker University of Kentucky, paulbaker0050@outlook.com Digital Object Identifier: https://doi.org/10.13023/etd.2018.313

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Recommended Citation Recommended Citation Baker, Paul A., "ROLE OF SKELETAL MUSCLE MASS IN SEX-DEPENDENT POWER OUTPUT DURING FLYWHEEL RESISTANCE TRAINING" (2018). Theses and Dissertations--Kinesiology and Health Promotion. 54. https://uknowledge.uky.edu/khp_etds/54

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The document mentioned above has been reviewed and accepted by the student’s advisor, on

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Paul A. Baker, Student

Dr. Lance Bollinger, Major Professor

Dr. Heather Erwin, Director of Graduate Studies

ROLE OF SKELETAL MUSCLE MASS IN SEX-DEPENDENT POWER OUTPUT DURING FLYWHEEL RESISTANCE TRAINING

_______________________________________________________

THESIS _______________________________________________________

A thesis submitted in fulfillment of the requirements for the degree of Master of

Science in the College of Education at the University of Kentucky

By

Paul Anthony Baker

Lexington, Kentucky

Director: Dr. Lance Bollinger, Assistant Professor of Kinesiology and Health Promotion

Lexington, Kentucky

2018

Copyright © Paul Anthony Baker 2018

ABSTRACT OF THESIS

Background: To determine the role of muscle mass in sex-dependent differences in power output during flywheel resistance training (FRT). Methods: Twenty recreationally active (≥ 2 resistance exercise bouts per week), subjects (10 M, 10 F) completed 2 bouts of resistance exercise using a flywheel resistance training (FRT) device (Exxentric kbox 4 Pro) separated by at least one week. Each session consisted of 3 sets of 4 exercises (squat, bent-over row, Romanian deadlift, and biceps curl) with varying moments of inertia (0.050, 0.075, and 0.100 kg/m2, respectively) in random order. Each set consisted of 5 maximal effort repetitions with 3-minute recovery between sets. Average power, peak concentric and peak eccentric power were recorded and normalized to whole-body skeletal muscle mass (as calculated from bioelectrical impedence analysis). Additionally, linear regression analysis was used to determine the association between muscle mass and highest power output observed among all three inertial loads. Results: Absolute average, peak concentric and peak eccentric power for all lifts was significantly higher for males compared to females except for peak eccentric power for biceps curl which showed no significant difference. After normalizing to skeletal muscle mass, power output remained significantly higher for men in Row average power and peak concentric power as well as average power for biceps curl. A significant main effect of inertial load was noted for both absolute and relative power output for all exercises except for squat average power and peak concentric power. Regression analysis revealed that power output increases linearly with skeletal muscle mass (R2 = 0.37-0.77). Conclusions: Differences in power output between sexes during resistance exercise can largely be explained by differences in muscle mass. Indeed, muscle mass accounts for approximately 37-77% of the variance in power output during FRT depending on the exercise. Increasing inertial load tends to decrease power output during FRT. KEYWORDS: sex differences, iso-inertial training, eccentric, performance testing

____________Paul Baker_______

____________July 28, 2018________

ROLE OF SKELETAL MUSCLE MASS IN SEX-DEPENDENT POWER OUTPUT DURING FLYWHEEL RESISTANCE TRAINING

By

Paul Anthony Baker

__________________Dr. Lance Bollinger____ Director of Thesis

__________________Dr. Heather Erwin_____ Director of Graduate Studies

_________________July 28, 2018____________ Date

iii

ACKNOWLEDGMENTS

The following thesis, could not have been finished without the aid and helpful

advice of Dr. Lance Bollinger. Your willingness to always meet and discuss any

issues I had was very much appreciated. Your support and helpful demeanor were

exactly what I needed in an advisor. I feel as though you are not only my advisor but

a friend and that means a lot. In addition, Dr. Mark Abel and Dr. Chris Morris your

helpful suggestions and comments went a long way in writing and refining my

thesis. This process while often stressful at times has allowed me to learn so much

about the research process. I am excited to pursue a Ph. D. degree further down the

road because of my experiences with my thesis and helpful faculty at the University

of Kentucky.

I would also like to thank my family and friends that helped me during this

process. My mom and dad offered continual support both emotionally and

financially, while I pursued my Master’s Degree. My girlfriend, Katie Worcester was

also greatly helpful in helping me reach this point. Her constant support and love

went a long way in continuing through this entire thesis project. Her willingness to

always proof read my rough drafts, challenge my thoughts and discuss ideas was

greatly appreciated. I would also like to thank my best friend Jensen Goh who

encouraged me to never give up and pulled late nights with me working on my

thesis. Most importantly, I would like to thank all the subjects that volunteered to

participate in the study, without you none of this would have been possible.

iv

TABLE OF CONTENTS

Acknowledgments ................................................................................................................................. iii List of Tables ............................................................................................................................................ vi List of Figures ......................................................................................................................................... vii Chapter 1: Introduction ........................................................................................................................ 1 Chapter 2: Literature Review ............................................................................................................. 5 2.1. Flywheel Based Resistance Training ............................................................................... 5 2.2. Comparisons Between FRT, Weight Stack and Resistance Training ................... 6 2.3. Eccentric Muscle Contractions ........................................................................................... 8 2.4. Male & Female Performance Differences.....................................................................10 Chapter 3: Methodology .....................................................................................................................12 3.1. Experimental Approach to the Problem ......................................................................12 3.2. Subjects .....................................................................................................................................12 3.3. Wingate Anaerobic Test .....................................................................................................13 3.4. Strength Testing ....................................................................................................................13 3.5. Flywheel-based resistance exercise testing................................................................14 3.6. Statistical Analyses ...............................................................................................................15 Chapter 4: Results .................................................................................................................................17 4.1. Squat...........................................................................................................................................17 4.2. Row .............................................................................................................................................18 4.3. RDL .............................................................................................................................................19 4.4. Biceps Curl ...............................................................................................................................20 4.5. Skeletal Muscle Mass Predicts Power Output During FRT....................................21 4.6. Wingate Anaerobic Test .....................................................................................................21 Chapter 5: Discussion and Conclusions .......................................................................................23 5.1. Practical Applications ..........................................................................................................28 References ...............................................................................................................................................39 Vita……………………………………………………………………………………………………………………45

vi

LIST OF TABLES

Table 1, Subject Characteristics ......................................................................................................30 Table 2, Physical Characteristics and Exercise Responses (Wingate)…………………….31

vii

LIST OF FIGURES

Figure 1 a-f………………………………………………………………………………………………………..32 Figure 2 a-f…………………………………………...…………………………………………………………...33 Figure 3 a-f………………………..……………………………………………………………………………....34 Figure 4 a-f………………………………………………………………………………………………………..35 Figure 5 a-d ……………………………………………………………………………………………….……...36 Figure 6 a-d…………………………………………..……………………………………………………..........37 Figure 7 a-d…………………………………….………………………………………………………….……...38

1

INTRODUCTION

Muscular power is a crucial element for performance; not only for the elite

but also the recreational athlete (5, 32, 42, 49). Power can be defined as the product

of force and velocity or analogously as the dividend of work over time. Performing

greater work in a short amount of time will yield a greater power (42). Training to

increase muscular power has become widely known to help aid athletic

performance (33). Throughout the years resistance training has been the common

means to train muscular power. However, flywheel resistance training (FRT), also

called iso-inertial training has recently has emerged as a modality to increase and

directly measure power output during exercise (10).

FRT was originally used as a means of quantifying work of elbow flexors by

Hill (27) in the early 1920’s. More recently Berg and Tesch (7) studied the use of

FRT as a device to prevent muscle atrophy for astronauts. Since this time, FRT has

started to increase in both performance enhancement and clinical settings (18, 21,

22, 36, 48, 52). FRT operates independently of gravity and thus is drastically

different than gravity-dependent forms of resistance training (RT) such as free

weights or weight stacks. During traditional dynamic constant external resistance

(DCER) training, the eccentric phase is under stimulated by ~50% (20, 25). FRT

uses the moment of inertia (equal to half the mass times the square of the radius) of

a disk to provide external resistance which allows for maximal voluntary force to be

produced throughout the concentric and eccentric phase. Since eccentric muscle

contractions are known to be more forceful than concentric or isometric muscle

actions, this gravity independent form of training allows for maximal stimulation in

2

the eccentric phase. Eccentric loading has been suggested to be more advantageous

than traditional RT and may induce greater training adaptations.

Several studies have examined the effect of FRT on increasing power and

strength. Naczk et al. (39,41) found muscle power increases in both the lower and

upper extremities following FRT. Onambélé et al. (29) found that FRT produced a

greater increase in power than traditional RT. Another study by Tesch et al. (53)

found that FRT produced similar strength and muscle hypertrophy adaptations

compared to traditional RT. Studies have also compared electromyography (EMG)

activity of FRT to that of traditional RT. A study by Norrbrand et al. (44) had

subjects complete five weeks of training with a traditional weight stack or FRT. The

FRT group displayed greater EMG activity of the quadriceps during concentric and

especially eccentric knee extensions compared to the weight stack group. The

higher EMG activity seen in the FRT group is most likely due to its unique loading

features. A meta-analysis by Marota-Izquierdo (37) including nine studies compared

FRT to traditional RT. The study found that FRT compared to traditional weight

stack machines elicited greater improvements in concentric and eccentric strength,

muscle power and strength, muscle hypertrophy, vertical jump height and running

speed. However, another meta-analysis (55) of seven studies (four independent

from those used by Marota-Izquierdo) concluded that no significant difference

exists in concentric or eccentric strength following FRT or gravity-dependent RT.

Based on the literature, FRT offers a unique stimulus to the working muscles in the

form of eccentric overload. Eccentric overload can be defined as a greater amount

of work being done in the eccentric phase compared to the concentric phase of an

3

exercise. However, the efficacy of FRT compared to traditional RT remains

controversial. It should be noted, however, most of the studies were performed on

males, or did not distinguish between males and females in their analyses.

Males typically have more muscle mass when compared to females (24, 33).

Strength differences between males and females have been well documented in the

literature (47) with males showing significantly higher absolute strength than

females (31). However, when values are normalized to fat-free mass or muscle

mass, these differences are usually lessened or disappear entirely (9, 24, 29). Baker

and Nance (5) studied the relationship between 10 and 40 meter running speed and

strength & power tests, 3RM for squat and 3RM for power clean, and jump squats.

Absolute strength and power scores were shown to not be significantly related to

the 10 or 40-meter performance scores. However, power output relative to body

mass was significantly related to sprint performance. Another study sought out to

determine if gender variances in muscle mass could explain the differences in

sprinting (30 and 300m) and cycling (Wingate Anaerobic Test, WAnT) performance

(49). Power output that was relative to lower extremity muscle mass was

significantly related to sprint performance. Sex differences in peak and mean power

output during the WAnT appear to be due to lower extremity muscle mass.

However, it should be noted that power output during this study was measured on a

cycle ergometer, which consists almost entirely of concentric muscle actions.

Few studies have examined the role of muscle mass in power output during

dynamic RT consisting of both concentric and eccentric muscle actions. Martinez-

Aranda (34) studied the effects of inertial loading on power, force, work and

4

eccentric overload between males and females (n=11 per group) during FRT

unilateral knee extension. As expected, men displayed significantly higher absolute

power at all six inertial settings. The study discussed that sex appears to be a

critical variable to consider when using FRT. It is stated that going forward studies

employing FRT in males and females should consider muscle and/or lean body mass

when examining power.

The current study sought to examine the effects of muscle mass between

sexes on power output during FRT with four different exercises. Most of the studies

on FRT have only used exercises that were limited to machines such as leg press, leg

extension, and bicep curl. Squat, row, RDL, and biceps curl were selected because

they mimic movements typically performed during free weight resistance exercise.

This selection of exercises also allows for investigation of multi-joint and single-joint

exercises of the lower and upper body. Based on the current literature, we

hypothesized that absolute power output would be higher in males, but this effect

would be curtailed when normalized to muscle mass. We further hypothesized that

power output both concentrically and eccentrically; would decrease with increasing

inertial load.

5

Literature Review

Flywheel Based Resistance Training

Flywheel based resistance training (FRT), sometimes referred to as “iso-

inertial resistance training,” has recently gained popularity for its apparent effects

on muscle power output as well at its ability to quantify resistance exercise

performance in near real-time. During FRT, the rotational displacement of a

flywheel with known dimensions and mass is measured and used to calculate

performance variable such as concentric power (W), eccentric power (W), average

power (W), average force (N) and total work (kJ). A flywheel, with a known mass

and dimensions, will provide a given moment of inertia: I=1/2MR2. Mass (M) and

radius (R) can be manipulated to increase the moment of inertia (I). By rotationally

accelerating the flywheel through a concentric muscle action, a centrifugal force is

generated that increases with increasing flywheel speed. Eccentric muscle force

must be exerted to overcome the moment inertia of the flywheel at the end of each

repetition. Thus, faster movement will yield greater force, work, power. The

rotating flywheel requires force in order for it to stop. The force required to stop

the wheel is the eccentric muscle contraction. A faster breaking speed will require

more eccentric force to stop (43). Due to the inertial nature of this exercise, FRT can

provide a variable, unlimited amount of external resistance.

The FRT has been shown to be effective in maintaining muscle mass and

increasing maximal force output during long-term bedrest (2,3). FRT operates

independently of gravity and thus is drastically different than gravity-dependent

forms of resistance training such as free weights or weight stacks.

6

FRT was originally used as a means of quantifying work of the elbow flexors by Hill

(27) in the early 1920’s. More recently Berg and Tesch (8) studied the use of FRT as

a device to prevent muscle atrophy for astronauts while in space. FRT has increased

in both performance enhancement and clinical settings over the past couple of

decades (21, 22, 35, 36, 47, 51). The emphasis lately has been on performance with

FRT being used to improve strength and power. Both strength and power have been

shown to be important in terms of sport performance (56,57). Stone et al. (52)

found that maximum strength can contribute to muscular power. FRT appears to be

beneficial at increasing power and strength. Naczk (39,41) showed significant

increases in muscle power for both the upper and lower extremities following FRT.

Therefore, it is possible that increased power output following FRT is a function of

increased muscle strength, which is largely determined by skeletal muscle mass.

However, the relationship between muscle mass and FRT power has not previously

been explored.

Comparisons Between FRT, Weight Stack and Resistance Training

Several studies have examined the differences and similarities between

traditional RT, weight stack, and FRT. Berg & Tesch (8) showed that lower

extremity FRT could produce similar velocities and muscular damage comparable to

RT using free weights. A study by Norrbrand et al. (43) had subjects perform

unilateral knee extensions with a weight stack or FRT. The FRT group saw increases

of all four quadricep muscle with the weight stack group only seeing an increase in

the rectus femoris. Another study by Tesch et al. (53) found that FRT produced

similar strength and muscle hypertrophy adaptations compared to that of

7

traditional RT. Studies have also compared EMG activity of FRT to traditional RT. A

study by Norrbrand et al. (45) even found greater EMG activity of the quadriceps in

FRT knee extension compared to a weight stack group. The higher EMG activity

seen in the FRT group is most likely due to its unique loading features. Norrbrand

(46) saw quadriceps muscle use in the leg press is equivalent if not greater with

FRT. More important it was found that total work was much higher in the FRT

group (especially in the eccentric phase). However, due to the use of two

independent machines with differing cams (and thus different mechanical

advantage/efficiency) these could not be compared statistically. Thus, it appears

that FRT may provide a preferential overload during the eccentric phase of muscle

contraction.

Increases in athletic performance have also been examined with de Hoyo et

al. (19) finding that FRT produced greater improvements in 20-m sprint time, 10-m

flying-sprint time and counter-movement jump height. A study by Onambélé et al.

(47) found that FRT produced a greater power increase than RT. A meta-analysis by

Marota-Izquierdo et al. (37) including nine studies compared FRT to traditional RT.

This study found that, compared to traditional weight stack machines, FRT elicited

greater improvements in concentric and eccentric strength, muscle power and

strength, muscle hypertrophy, vertical jump height and running speed. However,

another meta-analysis of seven studies (four independent from those used by

Marota-Izquierdo) concluded that no significant difference exists in concentric, or

eccentric strength following FRT or gravity-dependent RT (55). Based on the

8

literature it appears that FRT offers the same if not greater improves in power and

strength; with eccentric EMG activity being higher in FRT.

Eccentric Muscle Contractions

It is already widely known that eccentric muscle contraction is crucial for

producing performance adaptations such as hypertrophy, strength and power (20).

Healthy skeletal muscle has the capacity to produce greater force in the eccentric

phase than the concentric phase (50). The exact mechanisms behind why eccentric

contractions are more forceful than concentric or isometric muscle actions are not

entirely known but increased reliance on non-contractile proteins, such as titin

appears to contribute to this effect (26). A study by Hather et al. (25) used a

concentric, concentric/eccentric and control group to study the importance of

eccentric contraction to muscular adaptations. The findings showed that optimal

muscle hypertrophy is not attained unless eccentric muscle actions are performed

during resistance training. With eccentric contractions being so crucial to training

adaptions it is important to apply ample stimuli to produce desired adaptations.

Traditional RT involves concentric and eccentric using the same external resistance

throughout repetitions of a set. If the same external load is being applied

throughout the entire repetition then the eccentric phase is under stimulated.

During normal RT with concentric-eccentric contractions performed at maximal

intensity, approximately 50% underloading of the eccentric phase is occurring (20,

25). FRT uses the moment of inertia of a rotating disk to generate resistance which

allows for maximal voluntary force to be produced throughout both concentric and

eccentric phases with a greater eccentric overload. This type of loading has been

9

suggested to be more advantageous than traditional resistance training and may

induce greater training adaptations.

Flywheel based inertia training applies an eccentric overload during each

repetition. That eccentric overload can aid in decreasing that underload percentage

mentioned in (20, 25). Using eccentric overload in a training protocol has been

shown to increase power (23). Fernandez-Gonzalo et al. (21) assessed strength and

muscle mass training adaptations to eccentric overload in FRT. The study found

that the eccentric-overload resistance elicited increases in strength, power, and

muscle mass. This result showed that despite more eccentric overload subjects

were still able to adapt to the increased stimulus.

A study by Norrbrand, (43) had fifteen males perform a 5-week training

program that consisted of either regular RT or FRT with coupled concentric–

eccentric knee extensions 2–3 times per week. The FRT group saw an increase of

6.2% whereas, the RT group saw an 3.0% increase in quadricep muscle volume.

Since the FRT device has a greater eccentric component it can offer greater stimulus

than regular RT and it may be more beneficial for muscular adaptations. Tous-

Fajardo et al. (54) even showed that an eccentric overload program for hamstring

development can reduce the incidence of hamstring strains in elite soccer players.

The eccentric overload component of FRT to elicit muscle hypertrophy has also

been researched (23, 36).

It is well accepted that muscle size is related to strength (13, 38). The

efficacy of the flywheel eccentric overload to induce muscle hypertrophy has been

studied in the literature (21, 22, 43, 54). Maroto-Izquierdo (37) implemented a 6-

10

week FRT and RT eccentric overload training protocol. The study found greater

vastus lateralis muscle volume in the FRT group compared to RT. Based on the

literature, FRT appears to provide a unique stimulus to the working muscles in the

form of eccentric overload. However, most of the studies were performed on males,

or did not distinguish between males and females in their analyses which is

important to consider.

Male & Female Performance Differences

Strength and power differences between males and females have been well

documented in the literature (48,49). However, when muscular strength is

normalized fat free mass (FFM) or muscle mass (MM), these differences are usually

lessened or disappear entirely (9, 24). Bishop (9) examined differences in upper

and lower body strength in males and females with similar physical activity. The

study found that absolute strength and upper body strength was greater in males

than females. When the absolute values were normalized to fat-free weight and

muscle cross-sectional area, sex differences were negated in all lifts except the curl

and bench press. Hosler (30) also examined strength differences between sexes and

once body composition and size were taken into account, sex only accounted for a

variance of 2% in leg strength and 1% arm strength respectively. Males and females

even have similar responses to adaptations produced from RT protocols (16, 28).

Abe (1) implemented a 12-week upper and lower body RT protocol. The study saw

similar increases in muscle thickness between sexes. Thus, it appears that sex-

specific differences in strength are largely due to differences in muscle mass. To

11

date, the role of muscle mass in sex-specific differences in power output have not be

systematically examined.

A study by Kraemer (32) examined sexes differences in strength and power

using traditional RT. The study found that absolute power output values were 44%

lower in females than in males. Importantly, this study did not normalize power

output to FFM or MM to see if differences were negated. Martinez-Aranda (35)

studied the effects of inertia loading on power, force, work and eccentric overload

between sexes during FRT. Six different inertia settings (0.0125, 0.025, 0.0375,

0.05, 0.075, 0.100 kg*m2) were used to perform uni-lateral knee extension with 11

males and 11 females. The study found that power decreased as inertia loading

increased with males showing slower decreases than females. The highest power

production was recorded at 0.0375 kg*m2. Differences seen in absolute power

between sexes was clear in the study, with males being 43.7% higher than females.

These authors concluded that sex appears to be an important variable to consider

when using FRT. It was stated in the article that going forward studies employing

FRT in males and females should consider lean body mass and/or muscle mass.

FRT can be a useful tool for power and strength development both for

performance and in a clinical setting. The majority of studies on FRT have only used

exercises such as leg press, leg extension, and bicep curl; with more complex multi-

joint exercises not being explored as much. The differences between males and

females regarding FFM or MM in these studies is not always considered. These

differences can dramatically affect strength and power between sexes. When it

comes to FRT the effect of muscle mass on power may play a crucial part.

12

METHODS

Experimental Approach to the Problem:

All research procedures were approved by the university Institutional

Review Board. Prior to participation, all subjects provided written informed

consent. All participants were screened for participation by use of a health history

questionnaire, a Physical Activity Readiness Questionnaire (PARQ), and resting

electrocardiogram (EKG). Participants visited the exercise physiology laboratory on

three separate occasions, separated by at least seven days each as previously

described (10). Anthropometric measures (Height, Weight, Hip/Waist), body

composition (bioelectrical impedance analysis, BIA), peak anaerobic power

(Wingate Anaerobic Test, WAnT), and one repetition maximum (1RM) testing for

following four lifts: Squat, Bent-Over Row (Row), Romanian Deadlift (RDL) and

Biceps Curl were completed on the first visit. These exercises were selected because

they mimic movements typically performed during free weight resistance exercise.

For the following two sessions subjects completed a warm-up on a cycle ergometer

followed by 3 sets of 5 maximal-effort repetitions for the four lifts listed above using

a flywheel resistance training device (Exxcentric Kbox 4 Pro). Each set consisted of

a different inertia load (0.050, 0.075, and 0.100 kgm2).

Subjects:

This study recruited a convenience sample of twenty recreationally active (≥

2 resistance exercise bouts per week), subjects (10 M, 10 F) presenting with no

more than minimal risk according to ACSM guidelines (1) and no recent injuries.

Subject characteristics can be found in Table 1.

13

Body mass was taken by use of electronic scale and height (to the nearest 0.1

kg) by stadiometer. Waist and hip circumferences were measured by using a

spring-loaded flexible tape measure at the smallest portion of the torso between the

ribs and the iliac crest (waist) and the largest circumference around the gluteal

region. Percent body fat and predicted muscle mass were measured by using a

(Body Stat 1500) (at 50 kHz) Skeletal muscle mass was calculated using the formula:

((Height2 / Impendence 50 x 0.401) + ((Sex (M=1, F=2) x 3.825) + (Age – 0.071)) +

5.102 as previously described (31). Muscle mass measures via this technique

compare favorably to MRI-based measures for whole-body muscle mass (R2 = 0.86,

SEE = 9%)(31).

Wingate Anaerobic Test:

Wingate Anaerobic Test (WAnT) was performed using a Monark Cycle

Ergomedic Test Cycle with 7.5% of the subject’s body mass being added to the

carriage. Following a 5-minute warm-up, subjects pedaled on the unloaded cycle

ergometer until a pedal cadence of 110 RPM was achieved, upon which the loaded

basket was dropped. Subjects continued to pedal as fast as possible for 30 sec.

Peak, average, minimum power, power drop and work were recorded.

Strength Testing:

One Repetition Maximum Testing (1RM) was performed to assess muscular

strength of the squat, Romanian deadlift, row, and biceps curl. Subjects were

requested to perform submaximal warm up sets of 10, 6, and 3 repetitions using a

standard 45-lb barbell or smith machine. Subjects were then asked to perform a

near maximal 1 repetition effort for each lift. Weight lifted was increased by 5-10%

14

for subsequent sets until the weight could no longer be successfully lifted. The

highest load successfully lifted was recorded as the 1RM. For safety purposes,

spotters were provided during all 1RM testing.

Flywheel-based resistance exercise testing:

During the second visit and third visits, subjects performed a 5-minute

warm-up on a cycle ergometer. Subjects then performed a sub-maximal warm-up

set of each exercise on the FRT device to provide familiarization before the three

sets. Subjects then completed three sets of five maximal effort repetitions for the

following exercises: (row, RDL, biceps curl, and squat) using inertia loading of 0.050,

0.075, and 0.100 kgm2 (in random order). Each set consisted of 6 repetitions (1

submaximal warm up and 5 maximal concentric and eccentric contractions). For

the squat exercise, subject wore a belt around the waist that was attached to the

flywheel device with a tether. For the other three exercises a 0.60kg bar attachment

was connected to the tether on the flywheel device. To minimize error due to

flywheel tether length, all sets of a single exercise. The order of inertial loads was

chosen randomly by a member of the research team.

For the squat exercise subjects were asked to descend, flexing at the knees

until thighs were approximately parallel to the floor, then stand until fully erect. For

RDL, subjects were instructed to lower the bar to shin height, bending at the waist

with their back straight and knees slightly bent, then stand up until fully erect. For

the bicep curl, subjects were instructed to curl the bar to their chest while not

extending the back. For row, subjects were instructed to stand flexed at the hip with

back straight and parallel to the floor with knees slightly flexed. Subjects then

15

pulled the bar to their chest by retracting their scapula and flexing their elbows.

Subjects were given three minutes rest between each set of flywheel exercise.

Throughout testing, average, concentric and eccentric peak power were measured

through the Exxentric app connected to a mobile device (iPad). Average Power was

quantified as the mean power over the course of one entire repetition (consisting of

both concentric phase and eccentric phases). Peak concentric and eccentric power

was recorded as the highest power output obtained between both testing sessions.

Data are then averaged over a 40 msec window and transmitted via Bluetooth to an

iOS device (iPad 3 mini) as previously described (10). Due to the poor

reproducibility of FRT-based power measures, the highest observed measures for

average power peak concentric power, peak eccentric power between two sessions

was reported. This method of data collection allows for a greater data sampling at

high rotational speeds. The highest observed measures for average power, peak

concentric power, peak eccentric power was recorded. Average power was

determined over the course of a single repetition (both concentric and eccentric

phases).

Statistical Analyses

Descriptive statistics were compared by a T-test which to assess differences

between males and females. Average, peak concentric, and peak eccentric power

were compared through a two-way repeated measures ANOVA with α = 0.05 and

Holm-Sidak post-test when appropriate. Linear regression analysis was performed

to determine the relationship between muscle mass (independent variable) and

16

power output (dependent variable) for the four different lifts. All statistical

analyses were made via Graph Pad Prism 7.

17

RESULTS

Males displayed significantly higher body weight and muscle mass, but not

fat mass, than females. Males were also leaner, as indicated by significantly lower

body fat percentage (M: 18.3 ± 3.2 v. F: 28.3 ± 4.7%, p < 0.001) and greater skeletal

muscle percentage (M: 39.9 ± 2.6 v. F: 32.4 ± 3.3%, p < 0.001). There was no

significant difference between sexes for age (Table 1).

Squat

Males displayed higher absolute peak average power at all 3 inertial loads

compared to females during the flywheel squat (Figure 1a). Power values below are

listed in order of smallest to largest rotational inertia (0.050, 0.075, 0.100 kgm2).

Absolute average power values for males on the squat were approximately 150%

higher (545.61 ± 339.65, 505.37 ± 248.95, 499.40 ± 274.73W) than females (215.99

± 94.72, 211.43 ± 101.07, 188.76 ± 82.99W). However, there was no statistical

difference between males (15.45 ± 8.43, 14.52 ± 7.11, 14.33 ± 7.53W) and females

(10.28 ± 4.22, 10.09 ± 4.65, 9.00 ± 3.76W) for average power after normalizing to

whole-body skeletal muscle mass (Figure 1b). Absolute concentric peak power

showed similar trends with males showing approximately 70% greater power

(886.47 ± 234.33, 840.89 ± 154.94, 831.10 ± 182.22W) than females (515.39 ±

238.46, 512.17 ± 248.83, 471.52 ± 220.18 W) (Figure 1c). When normalized to

muscle mass, males concentric peak power (25.29 ± 5.43, 24.18 ± 4.46, 23.97 ±

5.38W) showed no difference with female’s concentric peak power (24.68 ± 11.32,

24.56 ± 11.81W, 22.62 ± 10.43W) (Figure1d). Lastly for squat, absolute eccentric

peak power for males (937.84 ± 296.01, 853.88 ± 200.01, 828.63 ± 228.50W) was

18

significantly greater, approximately 75% more than females (546.45 ± 243.13,

497.61 ± 215.19, 459.43 ± 199.47W) (Figure1e). When peak eccentric power was

normalized to muscle mass males (26.95 ± 8.14, 24.51 ± 5.36, 23.92 ± 6.78W) power

outputs were no different compared to females (26.33 ± 11.76, 23.68 ± 9.55, 21.99 ±

9.18W) (Figure 1f). Inertial load was not significantly related to average power or

peak concentric power squat power output (p>0.05).

Row

Males displayed higher average power at all 3 inertial loads compared to

female in both absolute and relative (Figure 2a-b) terms for the flywheel row.

Absolute average peak power values for male were 150% greater (503.57 ± 211.67,

451.14 ± 177.17, 442.05 ± 222.64W) than females (197.14 ± 75.71, 172.26 ± 67.91,

162.13 ±72.2W). The relative average peak power values for males was

approximately 34% greater (14.23 ± 4.99, 12.85 ± 4.42, 12.47 ± 5.18W) than

females (9.36 ± 2.95, 8.13 ± 2.56, 7.71 ± 3.01W). Males displayed higher absolute

concentric peak power at all 3 inertial loads, approximately 110%% greater (649.62

± 185.29, 566.60 ± 138.72, 537.32 ±156.75W) compared to females (318.35 ±

123.04, 250.77 ± 80.61, 256.33 ± 94.87W) (Figure 2c). When values were

normalized to muscle mass, a main effect for sex persisted (approximately 25%

higher power output for males), but post testing revealed no significant difference at

any one inertia loading (Figure 2d). Males displayed higher eccentric peak power at

all 3 inertial loads in absolute terms, approximately 100% greater (793.72 ± 268.88,

690.84 ± 213.09, 634.66 ± 189.14W) compared to females (420.42 ± 164.11, 323.00

± 116.60, 336.69 ± 145.25W) (Figure 2e). There were no statistical differences

19

between males (22.38 ± 6.35, 19.66 ± 5.38, 18.09 ± 4.97W) and females (20.10 ±

6.86, 15.46 ± 4.94, 16.17 ± 6.59W) in relative eccentric peak power after

normalizing data to whole-body skeletal muscle mass (Figure 2f). The inertial load

was significantly related to row power output for average, peak concentric and

eccentric power regardless of normalized or raw data (p < 0.05).

RDL

Males displayed higher average peak power at all 3 inertial loads compared

to females in both absolute and relative terms (Figure 3a-b). Males and females

average peak absolute power was approximately 170% higher than females (709.35

± 542.82, 670.78 ± 446.16, 566.03 ± 328.85W) (250.70 ± 81.71, 236.57 ± 84.352,

207.01 ± 71.368W) respectively. Males and females average peak relative power

was 65% higher in men compared to females (20.47 ± 12.00, 19.64 ± 9.74, 16.69 ±

6.90W) (12.05 ± 3.81, 11.29 ± 3.69, 9.92 ± 3.23W) respectively. Males at absolute

concentric peak power (835.79 ± 371.99, 779.25 ± 298.08, 678.81 ± 221.16W) was

approximately 95% greater than females (429.08 ± 143.85, 398.60 ± 142.68, 346.95

± 126.59W) (Figure 3c) were statistically different. Relative values for concentric

peak power for males (24.51 ± 6.29, 23.43 ± 5.00, 20.39 ± 3.18W) were not

statistically different from female’s relative values (20.67 ± 6.79, 19.11 ± 6.55, 16.67

± 5.90W) (Figure 3d). Absolute eccentric peak power for males (903.13 ± 457.75,

888.32 ± 355.36, 778.15 ± 346.69W) was statistically different than females (414.18

± 148.47, 412.21 ± 163.41, 368.42 ± 147.46W) (Figure 3e) and approximately 115%

greater. Relative eccentric peak power values for males (25.62 ± 8.89, 25.66 ± 6.99,

22.99 ± 6.51W) were not statistically different from females (19.91 ± 6.74, 19.74 ±

20

7.34, 17.66 ± 6.74W) (Figure 3f). Inertial load was significantly related to RDL

power output for average, peak concentric and eccentric power regardless of

normalized or raw data (p < 0.05).

Biceps Curls

Men displayed approximately 170% higher absolute average peak power

(282.20 ± 203.68, 264.25 ± 171.97, 224.07 ± 131.59W) at all 3 inertial loads

compared to females (96.48 ± 39.14, 85.75 ± 30.07, 81.62 ± 26.06W) (Figure 4a).

When values were normalized to muscle mass there was a main effect for sex but no

effect at any one inertia loading (Figure 4b). Relative values for average peak power

for males (7.77 ± 4.58, 7.33 ± 3.98, 6.28 ± 3.16W) and females (4.64 ± 1.81, 4.12 ±

1.38, 3.91 ± 1.12W). There was a significant main effect for males to display higher

peak concentric power (by approximately 55%), but no effect at any one inertia

loading (Figure 4c). Males and females’ absolute peak concentric values (297.77 ±

143.75, 300.89 ± 155.07, 253.56W) (201.17 ± 107.20, 177.49 ± 85.06, 167.29 ±

71.59W). Normalized to muscle mass there was no difference between males (8.24

± 2.96, 8.32 ± 3.37, 7.15 ± 2.17W) and females (9.67 ± 4.97, 8.59 ± 4.12, 8.07 ±

3.43W) (Figure 4d). For eccentric peak power at absolute and normalized values

there was no statistical significance between sexes (Figure 4e-f). Absolute peak

eccentric power for males (509.86 ± 319.24, 515.92 ± 296.75, 429.47 ± 243.25W)

and females (331.12 ± 179.40, 318.59 ± 151.14, 299.60 ± 124.34W). Relative peak

eccentric power for males (13.96 ± 7.23, 14.22 ± 6.79, 11.87 ± 5.66W) and females

(15.86 ± 8.25, 15.44 ± 7.35, 14.40 ± 5.69W). The inertial load was significantly

21

related to biceps curl power output for average, peak concentric and eccentric

power regardless of normalized or raw data (p < 0.05).

Skeletal muscle mass predicts peak power output during FRT

To further analyze if muscle mass is a predictor of power, linear regression

analysis was performed. Muscle mass explained 43% (squat), 66% (Row), 50%

(RDL) and 51% (Biceps Curl) of the variance in average power (Figure 5a-d).

Muscle mass explained 54% (squat), 77% (row), 68% (RDL), and 38% (Biceps Curl)

of the variance in concentric power. Muscle mass explained 50% (squat), 67%

(row), 70% (RDL), Biceps Curl (37%). All linear regressions were shown to have

significance (p < 0.05).

Wingate Anaerobic Test

For the WAnT, measures of peak power, average power, minimum power,

power drop and work were recorded and examined. Absolute values were recorded

as well as normalizing values to each subject’s muscle mass. (Table 2)

Results were compared by un-paired t-Test between males and females. Absolute

peak power was significantly higher (p < 0.001) in males, but thus was eliminated

when power output was normalized to muscle mass (p = 0.7). Absolute average

power was significantly higher in males and this effect persisted after normalizing

to skeletal muscle mass. Minimum power absolute values were significantly greater

for males (p < 0.001), but this effect was eliminated when power output was

normalized to muscle mass (p = 0.02). Power drop (% change from peak to

minimum power) in males was significantly higher (p < 0.05) but when normalized

to muscle mass showed no difference (p = 0.7). Absolute work values showed

22

significant difference between males and females (p < 0.001) but when normalized

no difference was shown (p = 3).

23

DISCUSSION

The major findings of the present study are: 1) differences between power

output between sexes can largely be explained by muscle mass 2) muscle mass is a

significant predictor of peak power output during FRT. Together these findings

suggest that muscle mass plays a vital role in power production during FRT. To the

best of our knowledge this was the first study to directly examine the role of muscle

mass in FRT power output among sexes.

Strength and power production are often highly correlated with increased

performance (42, 56, 57). Previous studies have examined absolute strength and

power between males and females usually finding males with significantly higher

strength and power (30, 48, 49). In these studies males usually have higher weight

and muscle mass than females (9, 24, 28, 30, 32). The current study showed similar

findings with males displaying much higher muscle mass and weight than females.

All absolute peak power output values in males were clearly higher than females.

This finding is in line with other studies that examined absolute peak power output

(47,48). Studies such as (28,32) did not consider FFM or MM to account for the

differences seen in power output between sexes. While not focused on power found

FFM and MM can usually account for differences in strength between sexes (9, 24,

30, 49). Maroto-Izquierdo (37) found significant differences between males and

females and mentioned that muscle mass should be taken into consideration. Based

on these findings the original hypothesis was made that muscle mass would

determine power output during FRT. The original hypothesis that absolute peak

values between males and females would be statistically different but when

24

normalized would show no difference largely held true for the different exercises

performed in the current study. While most of the lifts showed this, the squat

showed this trend across all three variables when normalized to whole body muscle

mass. For average, concentric and eccentric power this trend held true as seen in

(Figure 1 a-f).

The squat being the only exercise that followed the trend across all three

variables could be explained by it being the only exclusively lower body exercise

and by females being weaker in the upper extremities. Laubach (34) found that sex

differences in strength are much higher in the upper body, with women’s upper

body strength being 40% lower than males. All the other exercises in the current

study performed on the flywheel involved the upper extremities. The RDL being a

lower body lift still required subjects to hold on to the bar thus involving the upper

body. The squat was the only exclusively lower body compound movement exercise

included in the study. Laubach (34) also found that males and females lower body

strength is more closely related. The simple case could be made that males and

females usually have more similar amounts of lower body muscle mass than upper

body muscle mass. The inclusion of more exclusively lower body exercises could

have shown if this held true across other exercises.

The other three lifts were not as clear regarding absolute and relative power

outputs as the squat. On the row, only eccentric power showed similar trends

where absolute peak power values were different but when normalized there was

no difference. Row concentric power showed differences in absolute values, and in

relative there was a main effect for sex but no effect at any one inertia load. This

25

result shows that power output still shows a difference between sexes but not at any

given inertia load. For the RDL on both concentric power and eccentric power

absolute values were statistically different but when normalized there were no

differences. For the biceps curl none of the variables held up to the hypothesis and

results were unclear, with every variable showing a different result. The squat, row

and RDL largely hold up to the hypothesis where the biceps curl did not. The biceps

curl is the only true single joint isolation exercise included in the study. This

exercise is not usually trained for power or strength and used mostly for muscle

hypertrophy. This deduction is also supported by the bicep curl having the lowest

power output of all four exercises. All the other exercises performed in the study

are often loaded heavier and done in lower reps than the biceps curl during typical

RT. The subjects recruited for the study were not accustomed to performing one

repetition maximum or maximum effort bicep curls. This lack of familiarization

could have affected the results shown. The other three lifts seemed more familiar to

the subjects because they were more accustomed to performing these lifts with

heavier loads.

To further examine the effect of muscle mass on power output linear

regressions were performed. All regressions ran showed significance at (p < 0.05).

Average power showed moderate correlations (R2 =0.42-0.66). The strongest

correlation was seen on the row (R2 = 0.66). Concentric power showed moderate

correlations (R2 = 0.38-0.77). The strongest correlation being seen in the row (R2 =

0.77) and RDL (R2 = 0.68) while weakest was found in the bicep curl (R2 = 0.38).

Eccentric power showed moderate correlation (R2 = 0.37-0.70). The strongest

26

correlations being seen in row (R2 = 0.67) and RDL (R2 = 0.70) while weakest was

found in the bicep curl (R2 = .37). On both concentric and eccentric power, the row

and RDL showed the strongest correlation between power output and muscle mass.

A possible explanation is that subjects seemed more accustomed to performing

these two exercises.

On both concentric and eccentric power, the biceps curl showed the weakest

correlation between power output and muscle mass. Again, this goes with the

findings above and further shows that the biceps curl is not meant as a power

exercise. The biceps have the smallest muscle mass engaged compared to all the

other lifts in the study. Very rarely are individuals ever performing maximum effort

on a single joint lift that isolates such a small muscle area. This finding could also be

due to the fact that whole-body muscle mass was quantified rather than region-

specific muscle mass. Given the relatively small musculature of the elbow flexors

compared to whole-body muscle mass, our regression analysis likely

underestimates the relationship between muscle mass and power output during this

exercise.

Since power can be defined as the product of force and velocity, one might

predict that increased skeletal muscle mass, and associated increased capacity for

cross-bridge formation, would be associated with increased power production.

Interestingly, the association between muscle mass and power output in the present

study was widely dependent on both exercise and phase (concentric or eccentric).

This finding suggests that factors other than muscle mass, such as exercise

technique or physiological/neurological factors such as rate coding, motor unit

27

recruitment, synchronization of firing rate may contribute significantly to power

output. However, for Squat, Row, and RDL, muscle mass explained the majority of

the variance in power output, indicating this is likely the most significant

contributor to power production during FRT.

Highest power recordings across lifts most commonly occurred at 0.050

kg.m2. It is unknown whether this is the optimal inertia to use for optimizing power

for males or females. Martinez-Aranda et al. (35) showed that power output on the

knee extension was maximized at 0.0375 kg/m2 with power decreasing as higher

inertias were used. The current study showed similar trends with power decreasing

as inertia was increased (0.100 kg/m2). This trend is believed to have continued if

larger inertias were used, example: (0.200 kg.m2). It can be seen based on the two

current studies that power production is not going to be optimized at higher inertias

but instead lower inertias. This makes sense if compared to traditional RT, where

power production is maximized at resistances closer to 50% of 1RM (58). If lower

inertias were used in the current study it is believed that power values would have

gone up similarly to Maroto-Izquierdo’s paper. It is unknown whether a similar

maximum power output would be achieved at 0.0375 kg/m2 considering different

lifts were used rather than just knee extension. Going forward from this study

common exercises performed on the flywheel should be examined to see what

inertia loading maximizes power using a wide array of inertial loadings. Based on

the findings from this study it can be suggested that the optimal inertial load

necessary for peak power during FRT testing is likely task-specific but appears to be

< 0.100 kgm2.

28

The Wingate data (although not the primary focus of this study) showed

similar tendencies of absolute to relative values. The WAnT is currently the gold

standard when it comes to testing power output. Absolute peak power, minimum

power, power drop and absolute work values were statistically different but when

made relative no difference was seen. This finding is similar to those of Perez-

Gomez et al. (49) who showed similar power output per unit leg muscle mass

between sexes. The study concluded that gender differences seen in peak and mean

power output during the Wingate Anaerobic power test were mostly due to lower

body muscle mass. This finding seems to directly coincidence with the current

study findings regarding the Wingate.

In summary, this study examined differences in peak average, concentric, and

eccentric power for four different exercises during FRT with three different inertial

loads between male and females. Absolute values at average, concentric, and

eccentric power were all statistically different between sexes but when normalized

to muscle mass most of those differences disappeared. Linear regressions ran found

moderate correlations between muscle mass and peak power output. Muscle mass

differences between sexes appears to account for most of the variance seen in

power outputs during FRT.

Practical Applications:

Sex-dependent differences seen in power output during FRT and WAnT seem

to be largely due to muscle mass. Indeed, muscle mass may be used as a major

predictor of power output. Traditional RT has been shown to underload the

eccentric phase; with FRT offering a greater eccentric overload. This eccentric

29

overload could offer increased performance adaptations compared to RT alone.

Training specifically to increase hypertrophy may result in increased power output,

although this should be systematically explored. The optimal inertial load necessary

for peak power during FRT testing is likely task-specific, but appears to be < 0.100

kgm2.

30

Table 1. Subject Characteristics. Age, height, weight, and body composition (bioelectrical impedance analysis, BIA) were measured and muscle mass calculated as previously described (31). *p < 0.05 between sexes

Variable Men Women

(n=10) (n=10)

Age (yr) 23.8 ± 4.3 22.6 ± 2.3

Height (cm) 181.9 ± 7.9 165.6 ± 7.4*

Weight (kg) 88.6 ± 8.5 64.7 ± 9.1*

BMI (kg/m2) 26.8 ± 1.8 23.7 ± 3.2*

Waist (cm) 84.6 ± 5.2 71.6 ± 3.5*

Hip (cm) 101.8 ± 5.3 90.5 ± 7.7*

WHR 0.8 ± 0 0.8 ± 0.1

Muscle Mass (kg) 35.0 ± 5 20.8 ± 2.0*

31

Table 2 Wingate Anaerobic Test Performance. Subjects pedaled at maximum velocity for 30 s against a standardized load of 7.5% body mass on a Monarch bicycle. Power output was continuously recorded and normalized to skeletal muscle mass. * p < 0.05 between sexes.

Variable Men Women

(n=10) (n=10)

Peak Power (W) 954.7 ± 124.7 559.3 ± 185.0*

Relative Peak Power (W/kg) 27.5 ± 3.9 26.6 ± 6.8

Average Power (W) 686.1 ± 82.5 389.8 ± 98.6*

Relative Average Power (W/kg) 7.7 ± 0.5 6.0 ± 1.0*

Minimum Power (W) 397.9 ± 70.6 233.4 ± 51.1*

Relative Minimum Power (W/kg) 4.5 ± 0.7 3.6 ± 0.8

Power Drop (W) 556.7 ± 126.3 325.9 ± 163.7*

Relative Power Drop (W/kg) 16.0 ± 3.7 15.3 ± 6.4

Work (kj) 19.9 ± 2.4 11.2 ± 2.7*

Relative Work (kj/kg) 0.6 ± 0.1 0.5 ± 0.1

32

a. b.

d.

e.

c.

f.

Figure 1 a-f. Absolute, but not relative, power output during squat is higher in males than females. a. Absolute average power. b. Average peak power normalized to skeletal muscle mass. c. Absolute concentric peak power. d. Concentric peak power normalized to skeletal muscle mass. e. Absolute eccentric peak power. f. Eccentric peak power normalized to skeletal muscle mass. *p < 0.05 between sexes. Overall p-values indicate main effect of inertial load.

b.

* * *

33

Figure 2 a-f. Absolute and relative are higher in males except for eccentric peak power normalized to skeletal muscle mass. a. Absolute average power. b. Average peak power normalized to skeletal muscle mass. c. Absolute concentric peak power. d. Concentric peak power normalized to skeletal muscle mass. e. Absolute eccentric peak power. f. Eccentric peak power normalized to skeletal muscle mass. *p < 0.05 between sexes. Overall p-values indicate main effect of inertial load.

a.

d.

e. f.

c.

b.

34

Figure 3 a-f. Absolute, but not relative, power output during RDL is higher in males than females except for average power. a. Absolute average power. b. Average peak power normalized to skeletal muscle mass. c. Absolute concentric peak power. d. Concentric peak power normalized to skeletal muscle mass. e. Absolute eccentric peak power. f. Eccentric peak power normalized to skeletal muscle mass. *p < 0.05 between sexes. Overall p-values indicate main effect of inertial load.

a.

d.

e. f.

c.

b.

35

Figure 4 a-f. Main effect of inertia difference between males and females with average peak power normalized to skeletal muscle mass and peak concentric power a. Absolute average power. b. Average peak power normalized to skeletal muscle mass. c. Absolute concentric peak power. d. Concentric peak power normalized to skeletal muscle mass. e. Absolute eccentric peak power. f. Eccentric peak power normalized to skeletal muscle mass. *p < 0.05 between sexes. Overall p-values indicate main effect of inertial load.

a.

d.

e. f.

c.

b.

36

Figure 5 a-d. Muscle mass shows moderate correlation to average power output. a. Squat Average Power (y=24.201x-273.67; R2=0.4289, p<0.05), b. Row Average Power (y=21.811x-248.21; R2=0.6622, p<0.05) c. RDL Average Power (y=38.466x-575.93; R2=0.5022, p<0.05), d. Biceps Curl (y=15.017x-224.28; R2=0.4289, p<0.05).

b.

d.

a.

c.

37

Figure 6 a-d. Muscle mass shows moderate correlation to concentric peak power output. a. Squat Peak Concentric Power (y=27.153x-20.115; R2 = 0.5368, p<0.05), b. Row Peak Concentric Power (y=24.452x-194.49; R2=0.7661, p<0.05), c. RDL Peak Concentric Power (y=35.197x-326.72; R2=0.6778, p<0.05), d. Biceps Curl Peak Concentric Power (y=10.441x-26.196; R2=0.3831, p<0.05).

b.

d.

a.

c.

38

Figure 7 a-d. Muscle mass shows moderate correlation to eccentric peak power output. a. Squat Peak Eccentric Power (y=28.701x-21.258; R2=0.4962, p<0.05), b. Row Peak Eccentric Power (y=29.521x - 205.78; R2= 0.6706, p<0.05), c. RDL Peak Eccentric Power (y=43.648x -519.76; R2= 0.7035, p<0.05), d. Biceps Curl Peak Eccentric Power (y=20.413x-113.51; R2=0.3747, p<0.05).

b.

d.

a.

c.

39

REFERENCES

1. Abe, T., DeHoyos, D. V., Pollock, M. L., & Garzarella, L. (2000). Time course for

strength and muscle thickness changes following upper and lower body

resistance training in men and women. European journal of applied physiology, 81(3), 174-180.

2. Alkner, B. A., Berg, H. E., Kozlovskaya, I., Sayenko, D., & Tesch, P. A. (2003).

Effects of strength training, using a gravity-independent exercise system,

performed during 110 days of simulated space station confinement.

European journal of applied physiology, 90(1-2), 44-49.

3. Alkner, B. A., & Tesch, P. A. (2004). Efficacy of a gravity‐independent

resistance exercise device as a countermeasure to muscle atrophy during 29‐day bed rest. Acta Physiologica, 181(3), 345-357.

4. American College of Sports Medicine. (2013). ACSM's guidelines for exercise

testing and prescription. Lippincott Williams & Wilkins.

5. Baker, D., & Nance, S. (1999). The Relation Between Running Speed and

Measures of Strength and Power in Professional Rugby League Players. The Journal of Strength & Conditioning Research, 13(3), 230-235.

6. Bar-Or, O. (1987). The Wingate anaerobic test an update on methodology,

reliability and validity. Sports Medicine, 4(6), 381-394.

7. Berg, H. E., & Tesch, A. (1994). A gravity-independent ergometer to be used

for resistance training in space. Aviation, space, and environmental medicine,

65(8), 752-756.

8. Berg HE, Tesch PA (1998) Force and power characteristics of a resistive

exercise device for use in space. Acta Astronaut 42:219–230

9. Bishop, P., Cureton, K., & COLLINS, M. (1987). Sex difference in muscular strength in equally-trained men and women. Ergonomics, 30(4), 675-687.

10. Bollinger, L. Brantley, T. Kohl, T. Baker, P. Seay, R & Abel, M. (2017) Construct

Validity, Test-retest Reliability, and Repeatability of Performance Variables

using a Flywheel Resistance Training Device.

11. 11.Canavan, P. K., & Vescovi, J. D. (2004). Evaluation of power prediction

equations: peak vertical jumping power in women. Medicine & Science in

Sports & Exercise, 36(9), 1589-1593.

12. Carroll, K. M., Wagle, J. P., Sato, K., Taber, C. B., Yoshida, N., Bingham, G. E., &

Stone, M. H. (2018). Characterising overload in inertial flywheel devices for use in exercise training. Sports biomechanics, 1-12.

40

13. Caruso, J. F., Hernandez, D. A., Porter, A., & Schweikert, T. (2006). Integrated

electromyography and performance outcomes to inertial resistance exercise. Journal of strength and conditioning research, 20(1), 151.

14. Chiu, L. Z., & Salem, G. J. (2006). Comparison of joint kinetics during free

weight and flywheel resistance exercise. Journal of strength and conditioning research, 20(3), 555.

15. Close, R. I. (1972). Dynamic properties of mammalian skeletal muscles. Physiological reviews, 52(1), 129-197.

16. Colliander, E. B., & Tesch, P. A. (1991). Responses to eccentric and concentric

resistance training in females and males. Acta Physiologica, 141(2), 149-156.

17. Cronin, J. B., McNAIR, P. J., & Marshall, R. N. (2000). The role of maximal

strength and load on initial power production. Medicine and science in sports and exercise, 32(10), 1763-1769.

18. Cronin, J., & Sleivert, G. (2005). Challenges in understanding the influence of

maximal power training on improving athletic performance. Sports Medicine, 35(3), 213-234.

19. de Hoyo, M., Sañudo, B., Carrasco, L., Domínguez-Cobo, S., Mateo-Cortes, J.,

Cadenas-Sánchez, M. M., & Nimphius, S. (2015). Effects of traditional versus

horizontal inertial flywheel power training on common sport-related tasks.

Journal of human kinetics, 47(1), 155-167.

20. Dudley, G. A., Tesch, P. A., Miller, B. J., & Buchanan, P. (1991). Importance of

eccentric actions in performance adaptations to resistance training. Aviation, space, and environmental medicine, 62(6), 543-550.

21. Fernandez-Gonzalo, R., Lundberg, T. R., Alvarez-Alvarez, L., & de Paz, J. A.

(2014). Muscle damage responses and adaptations to eccentric-overload

resistance exercise in men and women. European journal of applied

physiology, 114(5), 1075-1084.

22. Fernandez-Gonzalo, R., Nissemark, C., Åslund, B., Tesch, P. A., & Sojka, P.

(2014). Chronic stroke patients show early and robust improvements in

muscle and functional performance in response to eccentric-overload

flywheel resistance training: a pilot study. Journal of neuroengineering and rehabilitation, 11(1), 150.

23. Friedmann-Bette, B., Bauer, T., Kinscherf, R., Vorwald, S., Klute, K., Bischoff,

D., ... & Bärtsch, P. (2010). Effects of strength training with eccentric overload

on muscle adaptation in male athletes. European journal of applied

physiology, 108(4), 821-836.

41

24. Frontera, W. R., Hughes, V. A., Lutz, K. J., & Evans, W. J. (1991). A cross-

sectional study of muscle strength and mass in 45-to 78-yr-old men and women. Journal of applied physiology, 71(2), 644-650.

25. Hather, B. M., Tesch, P. A., Buchanan, P., & Dudley, G. A. (1991). Influence of

eccentric actions on skeletal muscle adaptations to resistance training. Acta Physiologica, 143(2), 177-185.

26. Herzog, W., Duvall, M., & Leonard, T. R. (2012). Molecular mechanisms of

muscle force regulation: a role for titin?. Exercise and sport sciences reviews,

40(1), 50-57.

27. Hill, A. V., & Hartree, W. (1920). The four phases of heat‐production of muscle. The Journal of physiology, 54(1-2), 84-128.

28. Hoffman, T., Stauffer, R. W., & Jackson, A. S. (1979). Sex difference in strength. The American journal of sports medicine, 7(4), 265-267.

29. Onambélé, G. L., Maganaris, C. N., Mian, O. S., Tam, E., Rejc, E., McEwan, I. M., &

Narici, M. V. (2008). Neuromuscular and balance responses to flywheel

inertial versus weight training in older persons. Journal of biomechanics,

41(15), 3133-3138.

30. Hosler, W. W., & MORROW JR, J. R. (1982). Arm and leg strength compared

between young women and men after allowing for differences in body size

and composition. Ergonomics, 25(4), 309-313.

31. Janssen, I., Heymsfield, S. B., Baumgartner, R. N., & Ross, R. (2000). Estimation

of skeletal muscle mass by bioelectrical impedance analysis. Journal of applied physiology, 89(2), 465-471.

32. Kraemer, W. J., Mazzetti, S. A., Nindl, B. C., Gotshalk, L. A., Volek, J. S., Bush, J.

A., ... & Fleck, S. J. (2001). Effect of resistance training on women’s

strength/power and occupational performances. Medicine & Science in

Sports & Exercise, 33(6), 1011-1025.

33. Kraemer, W. J., & Newton, R. U. (2000). Training for muscular power. Physical

medicine and rehabilitation clinics of North America, 11(2), 341-368.

34. Laubach, L. L. (1976). Comparative muscular strength of men and women: a

review of the literature. Aviation, Space, and Environmental Medicine, 47(5),

534-542.

35. Martinez-Aranda, L. M., & Fernandez-Gonzalo, R. (2017). Effects of inertial

setting on power, force, work, and eccentric overload during flywheel

resistance exercise in women and men. The Journal of Strength &

Conditioning Research, 31(6), 1653-1661.

42

36. Maroto-Izquierdo, S., García-López, D., & de Paz, J. A. (2016). Functional and

muscle-size effects of flywheel resistance training with eccentric-overload in professional handball players. Journal of human kinetics, 60(1), 133-143.

37. Maroto-Izquierdo, S., García-López, D., Fernandez-Gonzalo, R., Moreira, O. C.,

González-Gallego, J., & de Paz, J. A. (2017). Skeletal muscle functional and

structural adaptations after eccentric overload flywheel resistance training: a

systematic review and meta-analysis. Journal of science and medicine in sport, 20(10), 943-951.

38. Maughan, R. J. (1984). Relationship between muscle strength and muscle cross-sectional area implications for training. Sports medicine, 1(4), 263-269.

39. Naczk, M., Brzenczek-Owczarzak, W., Arlet, J., Naczk, A., & Adach, Z. (2014).

Training effectiveness of the inertial training and measurement system.

Journal of human kinetics, 44(1), 19-28.

40. Naczk, M., Naczk, A., Brzenczek-Owczarzak, W., Arlet, J., & Adach, Z. (2016).

Efficacy of inertial training in elbow joint muscles: influence of different

movement velocities. The Journal of sports medicine and physical fitness, 56(3), 223-231.

41. Naczk, M., Naczk, A., Brzenczek-Owczarzak, W., Arlet, J., & Adach, Z. (2016).

Impact of inertial training on strength and power performance in young

active men. The Journal of Strength & Conditioning Research, 30(8), 2107-

2113.

42. Newton, R. U., & Kraemer, W. J. (1994). Developing Explosive Muscular

Power: Implications for a Mixed Methods Training Strategy. Strength & Conditioning Journal, 16(5), 20-31.

43. Norrbrand, L. (2008). Acute and early chronic responses to resistance exercise

using flywheel or weights. Institutionen för fysiologi och farmakologi/Department of Physiology and Pharmacology.

44. Norrbrand, L., Fluckey, J. D., Pozzo, M., & Tesch, P. A. (2008). Resistance

training using eccentric overload induces early adaptations in skeletal

muscle size. European Journal Of Applied Physiology, 102(3), 271-281. doi:10.1007/s00421-007-0583-8

45. Norrbrand, L., Pozzo, M., & Tesch, P. A. (2010). Flywheel resistance training

calls for greater eccentric muscle activation than weight training. European journal of applied physiology, 110(5), 997-1005.

46. Norrbrand, L., Tous-Fajardo, J., Vargas, R., & Tesch, P. A. (2011). Quadriceps

muscle use in the flywheel and barbell squat. Aviation, space, and environmental medicine, 82(1), 13-19.

43

47. Onambélé, G. L., Maganaris, C. N., Mian, O. S., Tam, E., Rejc, E., McEwan, I. M., &

Narici, M. V. (2008). Neuromuscular and balance responses to flywheel

inertial versus weight training in older persons. Journal of biomechanics,

41(15), 3133-3138.

48. Paulus, D. C., Reiser, R. F., & Troxell, W. O. (2008). Peak lifting velocities of

men and women for the reduced inertia squat exercise using force control.

European journal of applied physiology, 102(3), 299-305.

49. Perez-Gomez, J., Rodriguez, G. V., Ara, I., Olmedillas, H., Chavarren, J.,

González-Henriquez, J. J., ... & Calbet, J. A. (2008). Role of muscle mass on

sprint performance: gender differences?. European journal of applied

physiology, 102(6), 685-694.

50. Roig, M., O'Brien, K., Kirk, G., Murray, R., McKinnon, P., Shadgan, B., & Reid, D.

W. (2008). The effects of eccentric versus concentric resistance training on

muscle strength and mass in healthy adults: a systematic review with meta-analyses. British journal of sports medicine.

51. Romero-Rodriguez, D., Gual, G., & Tesch, P. A. (2011). Efficacy of an inertial

resistance training paradigm in the treatment of patellar tendinopathy in

athletes: a case-series study. Physical Therapy in Sport, 12(1), 43-48.

52. Stone, M. H., Sanborn, K. I. M., O'bryant, H. S., Hartman, M., Stone, M. E.,

Proulx, C., ... & Hruby, J. (2003). Maximum strength-power-performance

relationships in collegiate throwers. The Journal of Strength & Conditioning

Research, 17(4), 739-745.

53. Tesch, P. A., Ekberg, A., Lindquist, D. M., & Trieschmann, J. T. (2004). Muscle

hypertrophy following 5‐week resistance training using a non‐gravity‐

dependent exercise system. Acta Physiologica, 180(1), 89-98.

54. Tous-Fajardo, J., Maldonado, R. A., Quintana, J. M., Pozzo, M., & Tesch, P. A.

(2006). The flywheel leg-curl machine: offering eccentric overload for

hamstring development. International journal of sports physiology and performance, 1(3), 293-298.

55. Vicens-Bordas, J., Esteve, E., Fort-Vanmeerhaeghe, A., Bandholm, T., &

Thorborg, K. (2018). Is inertial flywheel resistance training superior to

gravity-dependent resistance training in improving muscle strength? A

systematic review with meta-analyses. Journal of science and medicine in

sport, 21(1), 75-83.

56. Wisløff, U., Castagna, C., Helgerud, J., Jones, R., & Hoff, J. (2004). Strong

correlation of maximal squat strength with sprint performance and vertical

jump height in elite soccer players. British journal of sports medicine, 38(3), 285-288.

44

57. Young, W. B. (2006). Transfer of strength and power training to sports

performance. International journal of sports physiology and performance, 1(2), 74-83.

58. Zink, A. J., Perry, A. C., Robertson, B. L., Roach, K. E., & Signorile, J. F. (2006).

Peak power, ground reaction forces, and velocity during the squat exercise

performed at different loads. Journal of strength and conditioning research,

20(3), 658.

45

Vita

1. Huntington, West Virginia

2. University of Kentucky – Bachelors of Exercise Science

Ashland Community & Technical College – Associates of Science

3. Fitness Staff – University of Kentucky MoveWell

Graduate Assistant – University of Kentucky Kinesiology Department

Teachers Assistant – University of Kentucky Kinesiology Department

Peer Mentor – University of Kentucky Kinesiology Department

Research Assistant – University of Kentucky College of Human Health

Sciences

4. Hackensmith Award (Outstanding Graduate Student KHP 2016-2017)

Hackensmith Award (Outstanding Undergraduate Student KHP 2014-2015)

Awarded Bernard “Skeeter” Johnson Scholarship (2015)

5. Bollinger, L. Brantley, T. Kohl, T. Baker, P. Seay, R & Abel, M. (2017) Construct

Validity, Test-retest Reliability, and Repeatability of Performance Variables

using a Flywheel Resistance Training Device.

6. Paul Anthony Baker