EC2ON Masters Thesis

The Constant Force Resistive Exercise Unit The Constant Force Resistive Exercise Unit (CFREU) as a Device for Maintaining (CFREU) as a Device for Maintaining

Muscular StrengthMuscular Strength

Paul E. Colosky Jr, ATCPaul E. Colosky Jr, ATCDepartment of Health and Exercise Department of Health and Exercise

ScienceScience

Colorado State UniversityColorado State University

Fort Collins, CO 80523Fort Collins, CO 80523

Master’s Thesis Defense: Spring 2001Master’s Thesis Defense: Spring 2001

Committee: Matthew Hickey, Ph.D., Robert Gotshall, Ph.D., Vinson Sutlive, Ph.D., Susan James, Ph.D.

OutlineOutline

• Objective, specific aim, and hypothesis• Review of literature• History of Countermeasure• CFREU description • Methods and Results• Conclusions and Recommendations

ObjectiveObjective

• To determine if the Constant Force Resistive Exercise Unit (CFREU) can maintain muscle strength (one repetition maximum) during a 10-week maintenance program as compared to free weights.

Specific Aim and HypothesisSpecific Aim and Hypothesis

I). Can the CFREU machine maintain muscular strength similar to free weights over 10-weeks.

Hypothesis:Hypothesis:

- Strength training exercise performed to maintain muscular strength is as effective using the Constant Force Resistive Exercise Unit as conventional free weights.

Physiological Effects of SpaceflightPhysiological Effects of Spaceflight

• Cardiovascular deconditioning

• Negative calcium balance

• Decreased plasma volume

* Musculoskeletal Deconditioning:– Bone mineral loss

* Muscle atrophy

Effects of Spaceflight on the Musculoskeletal Effects of Spaceflight on the Musculoskeletal System (Skeletal Muscle Atrophy)System (Skeletal Muscle Atrophy)

Effects on strength:– 5% weekly reduction in maximal voluntary

knee extensor (quadriceps) strength during isometric, concentric and eccentric contractions (Tesch & Berg, 1998).

– Effects have been prevented during bed rest using a combination of endurance and resistance training (Convertino, 1996).


Effects on structure:– Using MRI techniques, muscle volume (CSA) changes

occur as quickly as 8 days during shuttle missions, with losses of 3.3% for the anterior calf, 2.9% for the posterior calf, 2.5% for the quadriceps, 3.2% for the hamstrings, and 2.0% for the intrinsic back (LeBlanc et al., 1995).

– During 37 days of bed rest the knee extensors lost 15%, which averaged approximately 3% loss per week (Berg et al., 1997).

Adapted from Nicogossian et al., 1993

Requirements for exercise Requirements for exercise countermeasures countermeasures

((Johnson Space Center Exercise Physiology Johnson Space Center Exercise Physiology Laboratories)(Ruttley, 2000)Laboratories)(Ruttley, 2000)

• Ability to allow dynamic eccentric and concentric exercise, ideally with an increased eccentric to concentric ratio.

• Ability to maintain a constant force over an entire exercise range.

• Safe to use, easy to operate, uses no power to operate.

• Design can be used in various gravity environments.

History of Exercise Countermeasures in History of Exercise Countermeasures in the U. S. Space Programthe U. S. Space Program

Treadmill

- excellent for cardiovascular conditioning, minimal effect on musculoskeletal system.

Rubber band devices


F = k∆x

Adapted from Designing ResistanceTraining Programs, Fleck & Kraemer,1997.

Penguin suits



Isokinetic Dynamometer




• Hydraulic or pneumatic machines

• Other sci-fi countermeasures

The Constant Force Resistive Exercise The Constant Force Resistive Exercise Unit (CFREU)Unit (CFREU)

- allows for concentric and eccentric contractions

- full range of motion

- easy weight selection

ProceduresProcedures

• 9 subjects (males and females)

• CFREU (n = 5) and FW (n = 4) groups

• Workout at 67% pretest 1RM, 3 days/week for 8 - 10 weeks (left leg only)

Instruments

Leg extension/leg curl device configured for free weights.

Leg extension/leg curl device configured for CFREU.

Procedures (cont.)

• One Repetition Maximum Protocol– Graded 1RM of left leg at W-2, W15, and W30

(Kokkonen et al., 1998).

– Lifts were preceded by 10-15 minutes of warm-up and followed with a cool down. Between sets, 3-5 minute rest periods were allowed to decrease the risk for injury.

Data Analysis

- Data was analyzed using the statistical analysis computer program SAS.

- The alpha level chosen for this study is p < .05.

- For N=9, a repeated measures analysis of variance was used to compare pre, wk 5, and post 1-RM’s.

Results

Percent improvement in 1RM between the CFREU and FW during leg extension.

31.54

13.66

0.00

10.00

20.00

30.00

40.00

Groups

Pe

rce

nt CFREU

FW

Results

Percent improvement in 1 RM between the CFREU and FW during leg flexion.

36.57

7.38

0.00

10.00

20.00

30.00

40.00

Groups

Pe

rce

nt

CFREU

FW

5 Weeks

ResultsLeg extension/Leg curl performance variables (mean SD; N = 9)

Group

CFREU FW

Mean SD Increase (%) Mean SD Increase (%)

1 Repetition Maximum (kg)Leg extensionPre 32.36 5.17 43.60 14.215 Weeks 41.21 9.37 27.33 46.43 9.37 6.50Post 42.57 9.16 3.30 49.55 11.38 6.72Overall Gains 31.54 13.66

Leg flexionPre 25.43 3.93 38.40 6.10

34.73 5.22 36.57 42.08 6.55 9.60Post 34.73 6.96 0.00 41.23 4.38 -2.02Overall Gains 36.57 7.38

* significantly different (p < 0.05)

*

*

*

DiscussionDiscussion

• Results of this study reflect overall strength improvements in 1RM for the CFREU and FW groups during leg extension and leg curl exercises

• Possible explanations:– CFREU may have produced greater resistance than that

selected




selected– Subjects in the CFREU group were inherently able to

increase muscle strength faster than the FW group

Discussion

Pre 5 WK Post

1-R

epe

titio

n M

axi

mu

m (

kg)

0

10

20

30

40

50

60

Mean (SE)D8855F2820M0477N9336R7479

Comparison of the individual 1RM to pre, 5 wk, & post training means for leg extension using the CFREU.

Discussion

Pre 5 WK Post

1-R

epe

titio

n M

axim

um

(K

g)

0

10

20

30

40

50

Comparison of the individual 1RM to pre, 5 wk, & post training means for leg flexion using the CFREU.

Mean (SE)D8855F2820M0477N9336R7479

Discussion

Pre 5 WK Post

1-R

epet

ition

Ma

xim

um (

kg)

0

20

40

60

80

Mean (SE)P2493P2703S6020V4415

Comparison of the individual 1RM to pre, 5 wk, & post training means for leg extension using FW.

Discussion

Pre 5 WK Post

1-R

epe

titio

n M

axim

um (

kg)

0

10

20

30

40

50

60

Comparison of the individual 1RM to pre, 5 wk, & post training means for leg flexion using FW.

Mean (SE)P2493P2703S6020V4415





increase muscle strength faster than the FW group– Test machine specificity





increase muscle strength faster than the FW group– Test machine specificity– CFREU configuration applies a smaller range of

resistive torque on the knee joint compared to FW

θ

θ

CFREU Free WeightsKnee angle 45°

KneeKnee

AnkleAnkle

Redirect pulley

Free Weights

Knee Angle (degrees)

θ Cos θ

Pull Force (Newtons)

Effective Force (Newtons)

0 0 1 133.5 133.5 25 25 0.91 133.5 120.15 45 45 0.71 133.5 94.79 65 65 0.42 133.5 56.52 90 90 0 133.5 0

T = Force * ⊥ Distance

Cos θ * Force = Effective Force

CFREU Knee Angle

(degrees) θ Cos

θ Pull Force (Newtons)

Effective Force (Newtons)

0 30 0.87 133.5 116.15 25 10 0.98 133.5 130.83 45 8 0.99 133.5 132.17 65 25 0.91 133.5 121.49 90 90 0 133.5 0

T = Force * ⊥ Distance

Cos θ * Force = Effective Force

θ

θ

CFREU Free WeightsKnee angle 45°

ConclusionsConclusions

• Use of the CFREU to maintain strength resulted in significant increases in 1RM during the 10-week maintenance program.

• All subjects in the CFREU group showed increases in 1RM at 10-weeks compared to their pre test values illustrating that the device did maintain strength during the course of the study.

RecommendationsRecommendations

• Use a free weight machine that is similar to the CFREU configuration (weight stacks operated through the same pulley system).

• Extend total time of the study allowing subjects time to adapt to the type of resistance provided by the CFREU.

• Larger sample size may be needed to account for diverse athletic backgrounds.

• Test other exercise configurations

• Test CFREU as a countermeasure for use in microgravity using simulated microgravity (bed rest study).

AcknowledgementsAcknowledgements

• Marvin Criswell, Ph.D.• Timothy Tong, Ph.D.• Vinson Sutlive, Ph.D.• M.L. Johnson, Ph.D.• James zumBrunnen, Ph.D.• Jonathan Dory• Maile Ceridon• John Zentner• Derek Abbott• Sarah Driesen

• Tara Ruttley• Dolores Price• McNair Scholars Program• JSC Exercise Physiology Labs• CSU Sports Medicine

* Funded by the CSU Space Grant


Effects on structure: slow twitch vs. fast twitch

Shenkman et al., 1998

60 days 120 DaysHumans FT ST FT ST

Soleus 34% 29% 34% 48%

Vastus Lateralis 12% 14% 32% 14%

Effects of Spaceflight on the Musculoskeletal Effects of Spaceflight on the Musculoskeletal System (Bone Loss)System (Bone Loss)

Bone Loss:Bone Loss:– 0-10.1% bone loss in the spine, 1-11% bone loss in the

femoral neck, and 0- 9.5% loss in the tibia bone of cosmonauts after long-duration fights > 6 months (Baldwin et al., 1996).

– Bed rest studies have shown 1% bone loss in load bearing muscle (Nicogossian & Pool, 1993).

Muscle Response to ExerciseMuscle Response to Exercise

• Resistance training:Resistance training:– Muscle hypertrophy/hyperplasia– Decrease in mitochondrial density– Decrease in capillary density

• Endurance training:Endurance training:– Increase in mitochondrial density– Increase in capillary density

– Minimal impact on CSA of muscle

EC2ON Masters Thesis

Health & Medicine

Transcript of EC2ON Masters Thesis