29

Chapter II

REVIEW OF RELATED LITERATURE

The related literature reviewed for better understanding of

the problem and to interpret the results systematically, they are

presented in this chapter. The reviews were collected from various

sources like books, journal, and periodicals and provide back ground

information to the study and help us to understand various concepts

of combination of endurance and resistance training on selected

dependent variables.

The literature in any field forms the foundation upon which

all future work will be built. If one builds upon the foundation of

knowledge provided by the review of literature, the investigator might

not miss some similar work already done on the same topic. The

reviews of the literature have been classified under the following

headings:

1. Studies on endurance and resistance training on selected

variables.

2. Summary of the literature.

30

1.Studies on endurance and resistance training on selected

variables

Ferrauti, et al., (2010) investigate the effects of a

concurrent strength and endurance training program on running

performance and running economy of middle-aged runners during

their marathon preparation. Twenty-two (eight women and 14 men)

recreational runners were separated into 2 groups (n = 11; combined

endurance running and strength training program [ES]: nine men,

two women and endurance running [E]: seven men, and four women).

Both completed an 8-week intervention period that consisted of either

endurance training (E: 276 6 108 minute running per week) or a

combined endurance and strength training program (ES: 240 6 121-

minute running plus two strength training sessions per week [120

minutes]). Strength training was focused on trunk (strength

endurance program) and leg muscles (high-intensity program). Before

and after the intervention, subjects completed an incremental

treadmill run and maximal isometric strength tests. The initial values

for _VO2peak (ES: 52.06 6.1 vs. E: 51.1 6 7.5 ml_kg21_min21) and

anaerobic threshold (ES: 3.5 6 0.4 vs. E: 3.4 6 0.5 m_s21) were

identical in both groups. A significant time 3 intervention effect was

found for maximal isometric force of knee extension (ES: from 4.6 6

1.4 to 6.2 6 1.0 N_kg21, p < 0.01), whereas no changes in body mass

occurred. No significant differences between the groups and no

31

significant interaction (time three intervention) were found for _VO2

(absolute and relative to _ VO2peak) at defined marathon running

velocities (2.4 and 2.8 m_s21) and submaximal blood lactate

thresholds (2.0, 3.0, and 4.0 mmol_L21). Stride length and stride

frequency also remained unchanged. The results suggest no benefits

of an eight week concurrent strength training for running economy

and coordination of recreational marathon runners despite a clear

improvement in leg strength, maybe because of an insufficient sample

size or a short intervention period.

Wong, et al., (2010) examined the effect of concurrent

muscular strength and high-intensity running interval training on

professional soccer players' explosive performances and aerobic

endurance. Thirty-nine players participated in the study, where both

the experimental group (EG, n = 20) and control group (CG, n = 19)

participated in 8 weeks of regular soccer training, with the EG

receiving additional muscular strength and high-intensity interval

training twice per week throughout. Muscular strength training

consisted of 4 sets of 6RM (repetition maximum) of high-pull, jump

squat, bench press, back half squat, and chin-up exercises. The high-

intensity interval training consisted of 16 intervals each of 15-second

sprints at 120% of individual maximal aerobic speed interspersed with

15 seconds of rest. EG significantly increased (p < or = 0.05) 1RM

back half squat and bench press but showed no changes in body

32

mass. Within-subject improvement was significantly higher

(p < or = 0.01) in the EG compared with the CG for vertical jump

height, 10-m and 30-m sprint times, distances covered in the Yo-Yo

Intermittent Recovery Test and maximal aerobic speed test, and

maximal aerobic speed. High-intensity interval running can be

concurrently performed with high load muscular strength training to

enhance soccer players' explosive performances and aerobic

endurance.

Gergley (2009) examined the effect of two different modes of

lower-body endurance exercise (i.e., cycle ergometry and incline

treadmill walking) on lower-body strength development with

concurrent resistance training designed to improve lower-body

strength (i.e., bilateral leg press one repetition maximum [RM]). Thirty

untrained participants (22 men and eight women, ages 18-23) were

randomly assigned to one of 3 training groups (resistance only [R],

N = 10; resistance + cycle ergometry [RC], N = 10; and resistance +

incline treadmill [RT], N = 10). The three training groups exercised

twice per week for nine weeks. The reduced frequency of exercise

treatments were selected specifically to avoid overtraining for

in-season athletes attempting to maintain off season conditioning.

Body mass and body composition measurements were taken pre- and

post-training. Before training began, three weeks of training, six

weeks of training, and after training, the participants also performed a

33

1RM test for lower-body strength. More importantly, this study

indicates that the mode of endurance exercise in concurrent training

regimens may play a role in the development of strength. Specifically,

it seems that cycling is superior to treadmill endurance training for an

individual with the goal of developing strength in a multijoint

movement (i.e., leg press or squat) in the lower-body because it more

closely mimics the biomechanical movement of these exercises.

Karavirta, et al., (2009) examined that both strength and

endurance training have several positive effects on aging muscle and

physical performance of middle-aged and older adults, but their

combination may compromise optimal adaptation. This study

examined the possible interference of combined strength and

endurance training on neuromuscular performance and skeletal

muscle hypertrophy in previously untrained 40–67-year-old men.

Maximal strength and muscle activation in the upper and lower

extremities, maximal concentric power, aerobic capacity and muscle

fiber size and distribution in the vastus lateralis muscle were

measured before and after a 21-week training period. Ninety-six men

[mean age 56 (SD 7) years] completed high-intensity strength training

(S) twice a week, endurance training (E) twice a week, combined

training (SE) four times per week or served as controls (C). SE and S

led to similar gains in one repetition maximum strength of the lower

extremities [22 (9)% and 21 (8)%, P<0.001], whereas E and C showed

34

minor changes. Cross-sectional area of type II muscle fibers only

increased in S [26 (22)%, P=0.002], while SE showed an inconsistent,

non-significant change [8 (35)%, P=0.73]. Combined training may

interfere with muscle hypertrophy in aging men, despite similar gains

in maximal strength between the strength and the combined training

groups.

King, et al., (2009) conducted a study to increase speed,

power and agility using a selection of exercises on the Versa Pulley.

Healthy, active men (n=5) and women (n=2) with a history of

participation in athletics. Backgrounds ranged from football,

wrestling, track and field, volleyball and cross country. The average

age for subjects was 28.86 years (SD= 6.79). All exhibited a variety of

speed, power and quickness, voluntary as subjects. Each subject was

taken through testing procedure with instruction. Also, throughout

the four-week study an observer watched the subjects perform each

exercise to ensure proper technique was used for each repetition.

Power was assessed through Vertical Jump (VJ) test, Speed and

agility was determined by using a 36.58.m Dash and photoelectric

timing system. Speed, power, and agility improved using the Versa

Pulley following a four-week specific training program of 12 exercises.

The Versa pulley allowed for low resistance and the development of

speed and quickness. Body balance and control were necessary and

emphasized in performing all exercises; exercises ceased when proper

35

technique was compromised. Timing, concentration, and being

focused are important components of performance and injury

prevention; the Versa Pulley enhanced these components of fitness.

The Versa Pulley in this study was used for the development of

multiplanes of movement in the lower extremities using low resistance

for the development of speed and quickness.

Santtila, Kyrolainen and Hakkinen (2009) examined to

what extent an eight-week endurance-based military training period

interferes with muscle strength development in the conscripts (n = 72)

compared with that caused by sport-related military training with

added strength training (ST) or endurance training (ET). More

specifically, we examined the effects of these three training modes on

maximal isometric force, maximal rate of force development (RFD),

electromyography (EMG), and muscle thickness of the lower and

upper extremities. The measurements included isometric force-time

parameters of leg and arm extensors and EMG activity from the

vastus lateralis, vastus medialis, rectus femoris, and triceps brachii

muscles. The eight week basic training period combined with added

ST and ET significantly improved maximal bilateral isometric force of

the arm extensors in ST by 11.8% (p < 0.001), ET by 13.9%

(p < 0.001), and normal training (NT) by 7.8% (p < 0.05). Strength

training and ET showed significant increases in maximal EMG activity

of the trained arm muscles. A significant increase was observed in

36

maximal RFD of the upper extremities only in ST by 28.1% (p < 0.05).

Both ST and ET increased their maximal leg extension strength by

12.9% (p<0.01) and 9.1% (p<0.05), respectively, whereas no

significant change occurred in NT (5.2%, p=0.45). No significant

changes were observed in the shape of the force-time curves of leg

extensors. No increases occurred in muscle thickness either in the

lower or upper extremities. The present BT training with a large

amount of endurance-based military training interfered with strength

development, and especially, explosive power development of the lower

extremities in the ST group. The optimal improvements in

neuromuscular characteristics may not be possible without some

decreases in the amount of the endurance-based military training

and/or some increases in the amount of the maximal/explosive

strength training during the BT.

Burne (2008) studied the concurrent strength and

endurance training. Concurrent strength and endurance training

inhibits the development of isoinertial strength when compared with

strength training alone. Concurrent training interferes with lower

body isoinertial strength development at fast (>1.68rad.s-1) but not

slow speeds (<1.68rad.s-1) of muscular contraction. The effect

endurance training has on strength development when associated

with concurrent training programs is unclear. However, it has been

demonstrated that endurance running combined with resistance

37

training appears to inhibit isokinetic strength development when

compared with isokinetic strength training alone. It has also been

indicated that subjects with a history of endurance training may be

less susceptible to any negative effects of concurrent training on

strength development. Concurrent strength and endurance training

appears to inhibit strength development when compared with strength

training alone. At present there are a few hypotheses including

overtraining, conflicting physiological adaptations, muscle fibre type

hypertrophy, endocrine changes or acute fatigue as the proposed

mechanisms for lack of strength development associated with

concurrent training. However, there is lack of conclusive evidence in

this region as many of the concurrent training studies are single

study investigations which examine adaptations to specific forms of

strength and endurance training. It is also difficult to compare results

in the literature when studies differ markedly in their design factors

including mode, frequency, intensity, frequency of training and

training history of subjects. Therefore, further research is required to

investigate these causes and identify other possible mechanisms

responsible for the observed inhibition in strength development after

concurrent training.

Chtara, et al., (2008) examined the influence of the

sequence order of high-intensity endurance training and circuit

training on changes in muscular strength and anaerobic power. Forty-

38

eight physical education students (ages, 21.4 +/- 1.3 years) were

assigned to 1 of 5 groups: no training controls (C, n = 9), endurance

training (E, n = 10), circuit training (S, n = 9), endurance before

circuit training in the same session, (E+S, n = 10), and circuit before

endurance training in the same session (S+E, n = 10). Subjects

performed 2 sessions per week for 12 weeks. Resistance-type circuit

training targeted strength endurance (weeks 1-6) and explosive

strength and power (weeks 7-12). Endurance training sessions

included 5 repetitions run at the velocity associated with VO2max

(VO2max) for a duration equal to 50% of the time to exhaustion at

VO2max; recovery was for an equal period at 60% VO2max. Maximal

strength in the half squat, strength endurance in the one-leg half

squat and hip extension, and explosive strength and power in a

five-jump test and countermovement jump were measured pre and

post-testing. No significant differences were shown following training

between the S+E and E+S groups for all exercise tests. However, both

S+E and E+S groups improved less than the S group in one repetition

maximum (p < 0.01), right and left 1-leg half squat (p < 0.02),

five-jump test (p < 0.01), peak jumping force (p < 0.05), peak jumping

power (p < 0.02), and peak jumping height (p < 0.05). The

intra-session sequence did not influence the adaptive response of

muscular strength and explosive strength and power. Circuit training

alone induced strength and power improvements that were

39

significantly greater than when resistance and endurance training

were combined, irrespective of the intra-session sequencing.

Davis (2008) evaluated the effects of concurrent strength

and aerobic endurance training on cardiovascular and cardio

respiratory adaptations in college athletes and compared two

concurrent exercise (CE) protocols. Separate experiments were

performed on 30 women (mean age 19.6 years) and 20 men (20.4

years). In both experiments, subjects were divided into two groups

(serial CE and integrated CE) matched for initial physical condition

and trained in a vigorous 3-day per week CE program of nine (men) to

11 (women) weeks. The two CE training protocols were equilibrated for

exercise mode, intensity, and volume, differing only in the timing and

sequence of exercises. During training, serial CE discernibly (p<0.05)

increased cardiovascular adaptation in women, indicated by reduction

(-5.7%) in active heart rate (HR) (HR/aerobic exercise intensity),

whereas integrated CE discernibly reduced active HR in women

(-10.7%) and men (-9.1%). Before and after comparisons in the larger

sample of women showed that serial CE discernibly reduced systolic

and diastolic blood pressure (BP) (-8.7% and -14.0%, respectively),

increased estimated [latin capital V with dot above]o2max (18.9%),

and produced a trend (0.10 > p > 0.05) toward reduced resting HR

(-4.9%). Integrated CE in women discernibly reduced systolic and

diastolic BP (-13.2% and -12.6%, respectively), increased estimated

40

[latin capital V with dot above]o2max (22.9%), and produced a trend

toward reduced resting HR (-2.4%). Integrated CE produced

discernibly larger gains than serial CE or a trend for four of six

training adaptations. Effect sizes were generally large (60.0% of

discernible differences). We conclude that, for cardiovascular and

cardio respiratory adaptations in athletes, strength and endurance

training are compatible and that exercise timing and sequence

significantly influence training adaptations, complimenting our

previous similar conclusions for strength, muscle endurance, body

composition, and flexibility.

Esteve, et al., (2008), determine the effects of a running-

specific, periodized strength training program (performed over the

specific period [8 weeks] of a 16-week macrocycle) on endurance-

trained runners’ capacity to maintain stride length during running

bouts at competitive speeds. Eighteen well-trained middle-distance

runners completed the study (personal bests for 1500 and 5000 m of

3 minutes 57 seconds 6 12 seconds and 15 minutes 24 seconds 6 36

seconds). They were randomly assigned to each of the following

groups (6 per group): periodized strength group, performing a

periodized strength training program over the eight week specific

(intervention) period (2 sessions per week); nonperiodized strength

group, performing the same strength training exercises as the

periodized group over the specific period but with no week-to-week

41

variations; and a control group, performing no strength training at all

during the specific period. The percentage of loss in the stride length

(cm)/ speed (m_s21) (SLS) ratio was measured by comparing the mean

SLS during the first and third (last) group of the total repetitions,

respectively, included in each of the interval training sessions

performed at race speeds during the competition period that followed

the specific period. Significant differences (p < 0.05) were found in

mean percentage of SLS loss between the 3 study groups, with the

periodized strength group showing no significant SLS change (0.36 6

0.95%) and the 2 other groups showing a moderate or high SLS loss

(21.22 6 1.5% and 23.05 6 1.2% for the non-periodized strength and

control groups, respectively). In conclusion, periodized, running-

specific strength training minimizes the loss of stride length that

typically occurs in endurance runners during fatiguing running

bouts.

Yamamoto, et al., (2008) studied the effects of CT on

distance running performance in highly competitive endurance

runners. Specific key words (including running, strength training,

performance, and endurance) were used to search relevant databases

through April 2007 for literature related to CT. Original research was

reviewed using the Physiotherapy Evidence Database (PEDro) scale.

Five studies met inclusion criteria: highly trained runners (>or= 30

mile x wk(-1) or >or= 5 d x wk(-1)), CT intervention for a period >or= 6

42

weeks, performance distance between 3K and 42.2K, and a PEDro

scale score >or= 5 (out of 10). Exclusion criteria were prepubertal

children and elderly populations. Four of the five studies employed

sport-specific, explosive resistance training, whereas one study used

traditional heavy weight resistance training. Two of the five studies

measured 2.9% improved performance (3K and 5K), and all five

studies measured 4.6% improved running economy (RE; range =

3-8.1%). After critically reviewing the literature for the impact of CT on

high-level runners, we conclude that resistance training likely has a

positive effect on endurance running performance or RE. The short

duration and wide range of exercises implemented are of concern, but

coaches should not hesitate to implement a well-planned, periodized

CT program for their endurance runners.

Mikkola (2007) studied the effects of concurrent explosive

strength and endurance training on aerobic and anaerobic

performance and neuromuscular characteristics, 13 experimental (E)

and 12 control (C) young (16–18 years) distance runners trained for

eight weeks with the same total training volume but 19% of the

endurance training in E was replaced by explosive training. Maximal

speed of maximal anaerobic running test and 30-m speed improved in

E by 3.0 ± 2.0% (p < 0.01) and by 1.1 ± 1.3% (p < 0.05), respectively.

Maximal speed of aerobic running test, maximal oxygen uptake and

running economy remained unchanged in both groups. Concentric

43

and isometric leg extension forces increased in E but not in C. E also

improved (p<0.05) force-time characteristics accompanied by

increased (p<0.05) rapid neural activation of the muscles. The

thickness of quadriceps femoris increased in E by 3.9 ± 4.7% (p<0.01)

and in C by 1.9 ± 2.0% (p<0.05). The concurrent explosive strength

and endurance training improved anaerobic and selective

neuromuscular performance characteristics in young distance

runners without decreases in aerobic capacity, although almost 20%

of the total training volume was replaced by explosive strength

training for eight weeks. The neuromuscular improvements could be

explained primarily by neural adaptations.

Mokkloa, et al., (2007), examined the effects of concurrent

endurance and explosive strength training on electromyography

(EMG) and force production of leg extensors, sport-specific rapid force

production, aerobic capacity, and work economy in cross-country

skiers. Nineteen male cross-country skiers were assigned to an

experimental group (E, n = 8) or a control group (C, n = 11). The E

group trained for 8 weeks with the same total training volume as C,

but 27% of endurance training in E was replaced by explosive

strength training. The skiers were measured at pre- and post training

for concentric and isometric force-time parameters of leg extensors

and EMG activity from the vastus lateralis (VL) and medialis (VM)

muscles. Sport-specific rapid force production was measured by

44

performing a 30-m double poling test with the maximal velocity

(V(30DP)) and sport-specific endurance economy by constant velocity

2-km double poling test (CVDP) and performance (V(2K)) by 2-km

maximal double poling test with roller skis on an indoor track.

Maximal oxygen uptake (VO2max) was determined during the maximal

treadmill walking test with the poles. The early absolute forces (0-100

ms) in the force-time curve in isometric action increased in E by 18

+/- 22% (p<0.05), with concomitant increases in the average

integrated EMG (IEMG) (0-100 ms) of VL by 21 +/- 21% (p<0.05).

These individual changes in the average IEMG of VL correlated with

the changes in early force (r = 0.86, p<0.01) in E. V(30DP) increased

in E (1.4 +/- 1.6%) (p < 0.05) but not in C. The V(2K) increased in C

by 2.9 +/- 2.8% (p < 0.01) but not significantly in E (5.5 +/- 5.8%,

p < 0.1). However, the steady-state oxygen consumption in CVDP

decreased in E by 7 +/- 6% (p<0.05). No significant changes occurred

in VO2max either in E or in C. The present concurrent explosive

strength and endurance training in endurance athletes produced

improvements in explosive force associated with increased rapid

activation of trained leg muscles. The training also led to more

economical sport-specific performance. The improvements in

neuromuscular characteristics and economy were obtained without a

decrease in maximal aerobic capacity, although endurance training

was reduced by about 20%.

45

Verney, et al., (2006) investigated the effects of combined

lower body (LB) endurance and upper body (UB) resistance training on

endurance, strength, blood lipid profile and body composition in

active older men. Ten healthy still active men (73 ± 4 years, VO2peak:

36 (31–41) ml min−1 kg−1) were tested before and after 14 weeks of

combined training (3 times week−1). Training consisted of 3 × 12 min

of high intensity interval training on a bicycle for endurance

interspersed by 3 × 12 min of UB resistance exercises. VO2peak

during leg cycling and arm cranking, isokinetic torque of knee

extensor and shoulder abductor and the cross-sectional area (CSA) of

several muscles from UB and LB were measured. Sagittal abdominal

diameter (SAD) and abdominal fat area were measured on MRI scans.

Total body composition was assessed by hydrostatic weighing (HW)

and dual-energy X-ray absorptiometry (DEXA). Blood lipid profile was

assessed before and after training. By the end of the training period,

VO2peak (l min−1) increased significantly by nine and 16% in leg

cycling and arm cranking tests, respectively. Maximal isokinetic

torque increased both for the knee extensor and shoulder abductor

muscle groups. CSA increased significantly in deltoid muscle.

Percentage of body fat decreased by 1.3% (P < 0.05) and abdominal fat

and SAD decreased by 12 and 6%, respectively (P < 0.01). There was

also a significant decrease in total cholesterol and low-density

lipoprotein. Thus, combined LB endurance and UB resistance training

46

can improve endurance, strength, body composition and blood lipid

profile even in healthy active elderly.

Chtara (2005) examined the effects of the sequencing order

of individualised intermittent endurance training combined with

muscular strengthening on aerobic performance and capacity. Forty

eight male sport students (mean (SD) age 21.4 (1.3) years) were

divided into five homogeneous groups according to their maximal

aerobic speeds (VO2max). Four groups participated in various training

programmes for 12 weeks (two sessions a week) as follows: E (n=10),

running endurance training; S (n=9), strength circuit training; E+S

(n=10) and S+E (n=10) combined the two programmes in a different

order during the same training session. Group C (n= 9) served as a

control. All the subjects were evaluated before (T0) and after (T1) the

training period using four tests: (1) a 4 km time trial running test; (2)

an incremental track test to estimate VO2MAX; (3) a time to

exhaustion test (tlim) at 100% VO2MAX; (4) a maximal cycling

laboratory test to assess VO2MAX. Circuit training immediately after

individualized endurance training in the same session (E+S) produced

greater improvement in the four km time trial and aerobic capacity

than the opposite order or each of the training programmes performed

separately.

Izquierdo, et al., (2005), studied the effects of a 16-week

training period (2 days per week) of resistance training alone (upper-

47

and lower-body extremity exercises) (S), endurance training alone

(cycling exercise) (E), or combined resistance (once weekly) and

endurance (once weekly) training (SE) on muscle mass, maximal

strength (1RM) and power of the leg and arm extensor muscles,

maximal workload (W(max)) and submaximal blood lactate

accumulation by using an incremental cycling test were examined in

middle-aged men [S, n = 11, 43 (2) years; E, n = 10, 42 (2) years; SE,

n = 10, 41 (3) years]. During the early phase of training (from week 0

to week 8), the increase 1RM leg strength was similar in both S (22%)

and SE (24%) groups, while the increase at week 16 in S (45%) was

larger (P<0.05) than that recorded in SE (37%). During the 16-week

training period, the increases in power of the leg extensors at 30% and

45% of 1RM were similar in all groups tested. However, the increases

in leg power at the loads of 60% and 70% of 1RM at week 16 in S and

SE were larger (P < 0.05) than those recorded in E, and the increase in

power of the arm extensors was larger (P<0.05) in S than in SE

(P<0.05) and E (n.s.). No significant differences were observed in the

magnitude of the increases in W(max) between E (14%), SE (12%) and

E (10%) during the 16-week training period. During the last 8 weeks

of training, the increases in W(max) in E and SE were greater (P<0.05-

0.01) than that observed in S (n.s.). No significant differences between

the groups were observed in the training-induced changes in

submaximal blood lactate accumulation. Significant decreases

48

(P<0.05-0.01) in average heart rate were observed after 16 weeks of

training in 150 W and 180 W in SE and E, whereas no changes were

recorded in S. The data indicate that low-frequency combined training

of the leg extensors in previously untrained middle-aged men results

in a lower maximal leg strength development only after prolonged

training, but does not necessarily affect the development of leg muscle

power and cardiovascular fitness recorded in the cycling test when

compared with either mode of training alone.

Glowacki, et al., (2004) determined whether endurance and

resistance training performed concurrently produces different

performance and physiologic responses compared with each type of

training alone. Untrained male volunteers were randomly assigned to

one of three groups: endurance training (ET, N=12); resistance

training (RT, N=13); and concurrent training (CT, N=16). The following

measurements were made on all subjects before and after 12 wk of

training: weight, percent body fat, peak oxygen consumption

(VO(2peak)), isokinetic peak torque and average power produced

during single-leg flexion and extension at 60 and 180 degrees, one-

repetition maximum (1RM) leg press, 1RM bench press, vertical jump

height, and calculated jump power. Weight and lean body mass (LBM)

increased significantly in the RT and CT groups (P<0.05). Percent

body fat was significantly decreased in the ET and CT groups.

VO2peak was significantly improved only in the ET group. Peak torque

49

during flexion and extension at 180 degrees.s(-1) increased in the RT

group. Improvements in 1RM leg press and bench press were

significant in all groups, but were significantly greater in the RT and

CT compared to the ET group. Jump power improved significantly

only in the RT group, and no group showed a significant change in

vertical jump height. Concurrent training performed by young,

healthy men does not interfere with strength development, but may

hinder development of maximal aerobic capacity.

Balabinis, et al., (2003) compared the effects of concurrent

strength and endurance training to strength training and endurance

training alone. The results of this study showed concurrent strength

and endurance training to improve anaerobic power better than

strength training alone, and improve VO2max better than endurance

training alone. Twenty-six male basketball players were divided into

four groups: endurance group, strength group, strength and

endurance group, and control group. All groups, except the control

group, trained four times a week for seven weeks. The strength and

endurance group performed both the endurance group’s, and the

strength group’s programs on the same day, with a seven-hour

recovery period between sessions. Improvements in vertical jump,

anaerobic power (via Wingate test), and aerobic capacity (via one mile

walk) were higher for the strength and endurance training group than

for the endurance group or strength group on all measures. The

50

strength training alone group increased anaerobic power; however this

group also decreased aerobic capacity. The endurance training only

group increased capacity, but decreased anaerobic power. The results

of this study contradict others that have shown concurrent strength

and endurance training to produce smaller gains in strength than

strength training alone. However other studies have used different

training modes, intensities, and frequencies to produce different

results.

Häkkinen, et al., (2003), investigated effects of concurrent

strength and endurance training (SE) (2 plus 2 days a week) versus

strength training only (S) (2 days a week) in men [SE: n=11; 38

(5) years, S: n=16; 37 (5) years] over a training period of 21 weeks. The

resistance training program addressed both maximal and explosive

strength components. EMG, maximal isometric force, 1 RM strength,

and rate of force development (RFD) of the leg extensors, muscle

cross-sectional area (CSA) of the quadriceps femoris (QF) throughout

the lengths of 4/15–12/15 (L f) of the femur, muscle fibre proportion

and areas of types I, IIa, and IIb of the vastus lateralis (VL), and

maximal oxygen uptake (V˙O2max) were evaluated. No changes

occurred in strength during the 1-week control period, while after the

21-week training period increases of 21% (p<0.001) and 22%

(p<0.001), and of 22% (p<0.001) and 21% (p<0.001) took place in the

1RM load and maximal isometric force in S and SE, respectively.

51

Increases of 26% (p<0.05) and 29% (p<0.001) occurred in the

maximum iEMG of the VL in S and SE, respectively. The CSA of the

QF increased throughout the length of the QF (from 4/15 to 12/15 L f)

both in S (p<0.05–0.001) and SE (p<0.01–0.001). The mean fibre areas

of types I, IIa and IIb increased after the training both in S (p<0.05

and 0.01) and SE (p<0.05 and p<0.01). S showed an increase in RFD

(p<0.01), while no change occurred in SE. The average iEMG of the VL

during the first 500 ms of the rapid isometric action increased

(p<0.05–0.001) only in S. V˙O2max increased by 18.5% (p<0.001) in

SE. The present data do not support the concept of the universal

nature of the interference effect in strength development and muscle

hypertrophy when strength training is performed concurrently with

endurance training, and the training volume is diluted by a longer

period of time with a low frequency of training. However, the present

results suggest that even the low-frequency concurrent strength and

endurance training leads to interference in explosive strength

development mediated in part by the limitations of rapid voluntary

neural activation of the trained muscles.

Jung (2003) determined by several characteristics,

including maximum oxygen consumption (VO2max), lactate threshold

(LT), and running economy. Improvements in these areas are

primarily achieved through endurance training. Recently, however, it

has been shown that anaerobic factors may also play an important

52

role in distance running performance. As a result, some researchers

have theorised that resistance training may benefit distance runners.

Because resistance training is unlikely to elicit an aerobic stimulus of

greater than 50% of VO2max, it is unlikely that resistance training

would improve VO2max in trained distance runners. However, it

appears that VO2max is not compromised when resistance training is

added to an endurance programme. Similarly, LT is likely not

improved as a result of resistance training in trained endurance

runners; however, improvements in LT have been observed in

untrained individuals as a result of resistance training. Trained

distance runners have shown improvements of up to 8% in running

economy following a period of resistance training. Even a small

improvement in running economy could have a large impact on

distance running performance, particularly in longer events, such as

marathons or ultra-marathons. The improvement in running economy

has been theorised to be a result of improvements in neuromuscular

characteristics, including motor unit recruitment and reduced ground

contact time. Although largely theoretical at this point, if resistance

training is to improve distance running performance, it will likely have

the largest impact on anaerobic capacity and/or neuromuscular

characteristics. The primary purpose of this review is to consider the

impact of resistance training on the factors that are known to impact

distance running performance. A second purpose is to consider

53

different modes of resistance exercise to determine if an optimal

protocol exists.

Murphy (2003) investigated the kinematic differences

between individuals with fast and slow acceleration. Twenty field sport

athletes were tested for sprint ability over the first three steps of a

15m sprint. Subjects were filmed at high speed to determine a range

of lower body kinematic measures. For data analysis, subjects were

then divided into relatively fast (n=10) and slow (n=10) groups based

on their horizontal velocity. Groups were then compared across

kinematic measures, including stride length and frequency, to

determine whether they accounted for observed differences in sprint

velocity. The results showed the fast group had significantly lower

(~11-13%) left and right foot contact times (p<0.05), and an increased

stride frequency (~9%), as compared to the slow group. Knee

extension was also significantly different between groups (p<0.05).

There was no difference found in stride length. It was concluded that

those subjects who are relatively fast in early acceleration achieve this

through reduced ground contact times resulting in an improved stride

frequency. Training for improved acceleration should be directed

towards using coaching instructions and drills that specifically train

such movement adaptations.

Millet, et al., (2002), examined the influence of a

concurrent HWT+ endurance training on CR and the VO2 kinetics in

54

endurance athletes. Fifteen triathletes were assigned to

endurance+strength (ES) or endurance-only (E) training for 14 wk.

The training program was similar, except ES performed two HWT

sessions a week. Before and after the training period, the subjects

performed 1) an incremental field running test for determination of

VO2,_ and the velocity associated (V402m.), the second ventilatory

threshold (VT2): 2) a 3000-m run at constant velocity, calculated to

require 25% of the difference between VO2m, and VT2 to determine

CR and the characteristics of the VO2 kinetics; 3) maximal hopping

tests to determine maximal mechanical power and lower-limb

stiffness; 4) maximal concentric lower-limb strength measurements.

After the training period, maximal strength were increased (P < 0.01)

in ES but remained unchanged in E. Hopping power decreased in E

(P<0.05). After training, economy (P<0.05) and hopping power

(P<0.001) were greater in ES than in E. VO2m leg hopping stiffness

and the VO2 kinetics were not significantly affected by training either

in ES or E. Additional HWT led to improved maximal strength and

running economy with no significant effects on the VO2 kinetics

pattern in heavy exercise.

Baker (2001) studied the fourteen professional (NRL) and 15

college-aged (SRL) rugby league players were observed during a

lengthy in-season period to monitor the possible interfering effects of

concurrent resistance and energy-system conditioning on maximum

55

strength and power levels. All subjects performed concurrent training

aimed at increasing strength, power, speed, and energy-system

fitness, as well as skill and team practice sessions, before and during

the in-season period. The SRL group significantly improved 1

repetition maximum bench press (1RM BP) strength, but not bench

throw (BT Pmax) or jump squat maximum power (JS Pmax) over their

19-week in-season. The results for the NRL group remained

unchanged in all tests across their 29-week in-season. The fact that

no reductions in any tests for either group occurred may be due to the

prioritization, sequencing, and timing of training sessions, as well as

the overall periodization of the total training volume. Having athletes

better conditioned to perform concurrent training may also aid in

reducing the possible interfering effects of concurrent training.

Correlations between changes in 1RM BP and BT Pmax suggest

differences in the mechanisms to increase power between stronger,

more experienced and less strong and experienced athletes.

Docherty and Sporer (2000) made a research work to

review of the current research on the interference phenomenon

between concurrent aerobic and strength training indicates modest

support for the model proposed in this article. However, it is clear that

without a systematic approach to the investigation of the phenomenon

there is lack of control and manipulation of the independent variables,

which makes it difficult to test the validity of the model. To enhance

56

the understanding of the interference phenomenon, it is important

that researchers are precise and deliberate in their choice of training

protocols. Clear definition of the specific training objectives for

strength (muscle hypertrophy or neural adaptation) and aerobic power

(maximal aerobic power or anaerobic threshold) are required. In

addition, researchers should equate training volumes as much as

possible for all groups. Care needs to be exercised to avoid

overtraining individuals. There should be adequate recovery and

regeneration between the concurrent training sessions as well as

during the training cycle. The model should be initially tested by

maintaining the same protocols throughout the duration of the study.

However, it is becoming common practice to use a periodised

approach in a training mesocycle in which there is a shift from high

volume and moderate intensity training to lower volume and higher

intensity. The model should be evaluated in the context of a

periodised mesocycle provided the investigators are sensitive to the

potential impact of the loading parameters on the interference

phenomenon. It may be that the periodised approach is one way of

maintaining the training stimulus and minimising the amount of

interference. The effects of gender, training status, duration and

frequency of training, and the mode of training need to be regarded as

potential factors effecting the training response when investigating the

interference phenomenon. Other experimental design factors such as

57

unilateral limb training or training the upper body for one attribute

and the lower body for another attribute, may help establish the

validity of the model.

Gorostiaga, et al., (1999) studied the effects of 6-weeks of

heavy-resistance training on physical fitness and serum hormone

status in adolescents (range 14–16 years old) 19 male handball

players were divided into two different groups: a handball training

group (NST, n = 10), and a handball and heavy-resistance strength

training group (ST, n = 9). A third group of 4 handball goalkeepers of

similar age served as a control group (C, n = 4). After the 6-week

training period, the ST group showed an improvement in maximal

dynamic strength of the leg extensors (12.2%; P<0.01) and the upper

extremity muscles (23%; P<0.01), while no changes were observed in

the NST and C groups. Similar differences were observed in the

maximal isometric unilateral leg extension forces. The height of the

vertical jump increased in the NST group from 29.5 (SD 4) cm to

31.4 (SD 5) cm (P<0.05) while no changes were observed in the ST

and C groups. A significant increase was observed in the ST group in

the velocity of the throwing test [from 71.7 (SD 7) km · h−1 to

74.0 (SD 7) km · h−1; P < 0.001] during the 6-week period while no

changes were observed in the NST and C groups. During a

submaximal endurance test running at 11 km · h−1, a significant

58

decrease in blood lactate concentration occurred in the NST group

[from 3.3 (SD 0.9) mmol · l−1 to 2.4 (SD 0.8) mmol · l−1; P < 0.01]

during the experiment, while no change was observed in the ST or C

groups. Finally, a significant increase (P < 0.01) was noted in the

testosterone:cortisol ratio in the C group, while the increase in the

NST group approached statistical significance (P < 0.08) and no

changes in this ratio occurred in the ST group. The present findings

suggested that the addition of 6-weeks of heavy resistance training to

the handball training resulted in gains in maximal strength and

throwing velocity but it compromised gains in leg explosive force

production and endurance running. The tendency for a compromised

testosterone: cortisol ratio observed in the ST group could have been

associated with a state of overreaching or overtraining.

Leveritt, et al., (1999) conducted a study to find out

whether concurrent strength and endurance training appears to

inhibit strength development when compared with strength training

alone. The understanding of the nature of this inhibition and the

mechanisms responsible for it is limited at present. This is due to the

difficulties associated with comparing results of studies which differ

markedly in a number of design factors, including the mode,

frequency, duration and intensity of training, training history of

participants, scheduling of training sessions and dependent variable

selection. Despite these difficulties, both chronic and acute

59

hypotheses have been proposed to explain the phenomenon of

strength inhibition during concurrent training. The chronic

hypothesis contends that skeletal muscle cannot adapt metabolically

or morphologically to both strength and endurance training

simultaneously. This is because many adaptations at the muscle level

observed in response to strength training are different from those

observed after endurance training. The observation that changes in

muscle fibre type and size after concurrent training are different from

those observed after strength training provide some support for the

chronic hypothesis. The acute hypothesis contends that residual

fatigue from the endurance component of concurrent training

compromises the ability to develop tension during the strength

element of concurrent training. It is proposed that repeated acute

reductions in the quality of strength training sessions then lead to a

reduction in strength development over time. Peripheral fatigue

factors such as muscle damage and glycogen depletion have been

implicated as possible fatigue mechanisms associated with the acute

hypothesis. Further systematic research is necessary to quantify the

inhibitory effects of concurrent training on strength development and

to identify different training approaches that may overcome any

negative effects of concurrent training.

Hepple, et al., (1997), studied the resistance and aerobic

training in older men: effects on O2 peak and the capillary supply to

60

skeletal muscle. Both aerobic training (AT) and resistance training (RT)

may increase aerobic power ( O2peak) in the older population;

however, the role of changes in the capillary supply in this response

has not been evaluated. Twenty healthy men (age 65-74 yr) engaged in

either nine wk of lower body RT followed by nine wk of AT on a cycle

ergometer (RT AT group) or 18 wk of AT on a cycle ergometer (AT AT

group). RT was performed three times per week and consisted of three

sets of four exercises at 6-12 repetitions maximum. AT was performed

three times per week for 30 min at 60-70% heart rate reserve. O2 peak

was increased after both RT and AT (P < 0.05). Biopsies (vastus

lateralis) revealed that the number of capillaries per fiber perimeter

length was increased after both AT and RT (P < 0.05), paralleling the

changes in O2 peak, whereas capillary density was increased only after

AT (P < 0.01). These results, and the finding of a significant correlation

between the change in capillary supply and O2 peak (r = 0.52), suggest

the possibility that similar mechanisms may be involved in the

increase of O2 peak after high-intensity RT and AT in the older

population.

Kraemer, et al., (1995) studied the thirty-five healthy men

were matched and randomly assigned to one of four training groups

that performed high-intensity strength and endurance training

(C; n=9), upper body only high-intensity strength and endurance

training (UC; n=9), high-intensity endurance training (E; n = 8), or

61

high-intensity strength training (ST; n=9). The C and ST groups

significantly increased one-repetition maximum strength for all

exercises (P<0.05). Only the C, UC, and E groups demonstrated

significant increases in treadmill maximal oxygen consumption. The

ST group showed significant increases in power output. Hormonal

responses to treadmill exercise demonstrated a differential response to

the different training programs, indicating that the underlying

physiological milieu differed with the training program. Significant

changes in muscle fiber areas were as follows: types I, IIa, and IIc

increased in the ST group; types I and IIc decreased in the E group;

type IIa increased in the C group; and there were no changes in the

UC group. Significant shifts in percentage from type IIb to type IIa

were observed in all training groups, with the greatest shift in the

groups in which resistance trained the thigh musculature. This

investigation indicates that the combination of strength and

endurance training results in an attenuation of the performance

improvements and physiological adaptations typical of single-mode

training.

Kraemer, et al., (1995) examined the physiological

adaptations to simultaneous high-intensity strength and endurance

training in physically active men. This study had two groups training

for strength and endurance simultaneously. One used the muscles of

the lower body for endurance and full body for strength (Group C)

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while the other performed strength training on the upper body and

endurance training on the lower body (Group UC). There were also

groups that trained independently for strength (ST group) and

endurance (E group). Thirty five men were assigned to one of the four

groups. The high-intensity strength training work outs consisted of 10

RM and 5 RM load schemes using a combination of universal weight

machines and free weights. The high-intensity endurance running

work outs consisted of long distance runs of maximum distance in 40

minutes and sprint intervals from 200- 800m with exercise to rest

ratios progressing from 1:4 to 1:0.5. The C and ST groups significantly

increased 1 RM strength for all exercises. Only the C, UC, and E

groups demonstrated significant increases in treadmill maximal

oxygen consumption. The ST group showed significant increases in

power output. There were the following significant changes in muscle

fibre areas: types I, IIa, and IIc increased in the ST group; types I and

IIc decreased in the E group; type IIa increased in the C group; and

there were no changes in the UC group. Significant shifts in

percentages from type IIb to type IIa were observed in all training

groups, with the greatest shifts in the groups which resistance trained

the thigh musculature. From the data it was suggested that type IIb

muscle fibres are not recruited to the same extent during high

intensity endurance training as they are during heavy resistance

training. It appears that only the quantity and not the quality of

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contractile proteins are affected by simultaneous training. It was

concluded that simultaneous training appears to be more detrimental

to potential strength and power gains than to VO2max.

McCarthy (1995) examined the effects of combining

conventional 3 d[middle dot]wk-1 strength and endurance training on

the compatibility of improving both [latin capital V with dot above] O2

peak and strength performance simultaneously. Sedentary adult

males, randomly assigned to one of three groups (N = 10 each),

completed 10 wk of training. A strength-only (S) group performed

eight weight-training exercises (4 sets/exercise, 5-7 repetitions/set),

an endurance-only (E) group performed continuous cycle exercise (50

min at 70% heart rate reserve), and a combined (C) group performed

the same S and E exercise in a single session. S and C groups

demonstrated similar increases (P < 0.0167) in 1RM squat (23% and

22%) and bench press (18% for both groups), in maximal isometric

knee extension torque (12% and 7%), in maximal vertical jump (6%

and 9%), and in fat-free mass (3% and 5%). E training did not induce

changes in any of these variables. [latin capital V with dot

above]O2peak (ml[middle dot]kg-1min-1) increased (P < 0.01)

similarity in both E (18%) and C (16%) groups. Results indicate 3

d[middle dot]wk-1 combined training can induce substantial

concurrent and compatible increases in [latin capital V with dot

above]O2peak and strength performance.

64

Hennessy and Watson (1994) conducted a study which

compared the effects of 4 preseason training programs on endurance,

strength, power, and speed. Fifty six subjects were divided into 4

groups : an endurance (E) group completed a running program 4

days/week; a strength (S) group trained 3 days/week; an (S+E) group

combined the S and E training program 5 days/week; a control group

did not train. After 8 weeks, the E and S+E groups had similar gains

in endurance running performance, the S group had no change while

the C group showed a decline. The S+E and S groups made gains in

strength but the C and E groups did not. Power (vertical jump

performance) and speed (20m sprint time) gains were only noted for

the S group. It was concluded that training for strength alone results

in gains in strength, power, and speed while maintaining endurance

but while S+E training produces gains in endurance and upper body

strength, it compromises gains in lower body strength and does not

improve power or speed.

Hickson, et al., (1988) found that the addition of heavy

resistance training to the training routines of well trained cyclists and

runners improved endurance performance. Strength training

consisted of five sets of five repetitions for the squat, three sets of five

repetitions for knee extensions and flexions and three sets of 25

repetitions for toe raises. Subjects strength trained three days per

week using as much weight as possible for each exercise. After ten

65

weeks of strength training 1 RM squat was increased an average of

27%. VO2 max during cycling and treadmill running was unchanged

by the heavy resistance training. Short term endurance was increased

during cycling and running by 11 and 12% respectively. Cycling time

to exhaustion at 80% of VO2max increased by 20%, while performance

times for the 10km run were unchanged. The authors stated that

there were no changes in total body mass, thigh girth or muscle fibre

size and that therefore any potential negative influences on

performance did not represent limiting factors to the results. It was

determined that the strength gains likely reflect learning specific

activation and motor unit recruitment patterns rather than

intramuscular adaptations. It was concluded that certain types of

endurance performances, especially those requiring FT fibre

recruitment could be improved by strength training.

2. Summary of the Literature

The reviews are presented under the one section namely

studies on endurance and resistance training on selected dependent

variables [n=8). All the research studies that are presented in this

section prove that combination of endurance and resistance training

methods contribute significantly for better improvement in all the

criterion variables.

66

The independent and dependent variable for the current

study are combination of endurance and resistance training and the

change of level of selected speed, strength and performance variables.