Artikkel 11- Performance Effects of 6 Weeks of Anaerobic Production

8/12/2019 Artikkel 11- Performance Effects of 6 Weeks of Anaerobic Production

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PERFORMANCE EFFECTS OF 6 WEEKS OF AN AEROBIC

PRODUCTION

TRAINING IN

JUNIOR

ELITE

SOCCER

PLAYERSJRGENINGEBRIGTSEN,1 SHAHERA. I. SHALFAWI,2 ESPEN TNNESSEN,3 PETERKRUSTRUP,4 AND

ANDREASHOLTERMANN5AU11Department of Sport, Center for Practical Knowledge, University of Nordland, Bod, Norway; 2Department of PhysicalEducation, Prince Sultan University, Riyadh, Saudi Arabia; 3Department of Physical Training, Norwegian Olympic SportCenter, Oslo, Norway; 4Department of Sport and Health Sciences, College of Life and Environmental Sciences, University ofExeter, Exeter, United KingdoAU2 m; and 5National Research Center for the Working Environment, Copenhagen, DenmarAU3 k

ABSTRACT

Ingebrigtsen, J, Shalfawi, SAI, Tnnessen, E, Krustrup, P, and

Holtermann, A. Performance effects of 6 weeks of an aerobicproduction training in junior elite soccer players. J Strength

Cond Res XX(X): 000000, 2012This study investigates

the performance effects of a 6-week biweekly anaerobic speed

endurance production training among junior elite soccer play-

ers. Sixteen junior (age 16.9 6 0.6 years) elite soccer players

were tested in the Yo-Yo Intermittent Recovery test level

2 (IR2), 10-m and 35-m sprints, 7 3 35-m repeated-sprint

ability (RSA) tests, countermovement jump and squat jump

tests, and randomly assigned to either a control group (CG)

performing their normal training schedule, which included 4

weekly soccer training sessions of approximately 90 minutes,

or a training group performing anaerobic speed endurance

production training twice weekly for 6 weeks in addition to their

normal weekly schedule. We found that the intervention group

significantly improved (p , 0.05) their performance in the

Yo-Yo IR2 (63 6 74 m) and 10-m sprint time (20.06 6

0.06 seconds). No significant performance changes were

found in the CG. Between-group pretest to posttest differen-

ces were found for 10-m sprint times (p , 0.05). No significant

changes were observed in the 35-m sprint times, RSA, or jump

performances. These results indicate that short-term anaerobic

production training is effective in improving acceleration and

intermittent exercise performance among well-trained junior

elite players.

KEYWORDSanaerobic speed endurance training, Yo-Yo IR2

performance, repeated-sprint performance, association football

INTRODUCTION

S

occer is an intermittent sports activity character-

ized by frequent activity changes, multiple specific,intense actions (e.g., tackles, turns, headers, drib-

bles), and high-speed running bouts of a relativelyshort duration (19,23). The ability to perform with maximal

intensity for short periods of match play (e.g., 5-minute peri-

ods) and the ability to maintain high-intensity performance

throughout a full game have been shown to be important

factors in performance and are measures that may be used to

assess differences in performance parameters at both whole-

team and individual-player levels (9,20,22,26,27). Progressive

decreases in the performance of high-intensity activities, par-

ticularly toward the end of match play, are well documented

(1,2628), and there is evidence of reduced high-speed sprint

performance after periods of intense match activities (25). A

reduction in the ability to perform high-intensity activities

during or toward the end of the game has been identified as

soccer-specific fatigue and has been linked to the intermit-

tent intense exercise profile of the game (14). These findings

suggest that anaerobic capacity is a key performance indica-

tor in soccer players and that training interventions aimed at

improving anaerobic capacity may result in improved per-

formance during soccer matches (19,21).

Anaerobic training is defined as training above maximal

aerobic work capacity, with the aim of stimulating anaerobic

energy production (17), and can be further divided into 2

types of training: speed training, defined as training of short

maximal duration (215 seconds at .95% of the maximal

speed) with relatively long breaks between (.10 times the

exercise time), and speed endurance training (17), which has

been further divided into production training and main-tenance training. Speed endurance maintenance training

aims to increase the ability to sustain high-intensity activities

(3), and it involves 225 exercise bouts, lasting 590 seconds,

with a rest of 100300% of the exercise duration at 50100%

of the maximum speed attained. Speed endurance produc-

tion training aims to improve the ability to perform

Address correspondence to Jrgen Ingebrigtsen,[email protected].

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maximally for a relatively short period (3) and is performedat 70100% of the maximum speed, for 1040 seconds, in

312 repetitions, with a minimum of rest .500% of theactivity time. Undertaken concurrently, these 2 types of

training activities have been shown to improve the abilityof soccer players to perform high-intensity activities more

frequently and for longer periods of time and to recover

faster from the high-intensity activities that characterizethe sport (3,5,17,19,30).

Speed endurance training has also been shown to increase

muscle glycogen content (32), which is the most importantsubstrate for energy production in football (5) and so may

further contribute to improved performance via this effect.Anaerobic production training has also been associated with

a reduced rate of glycogen degradation during supramaximal

activities (18) and increased fat oxidation during intense sub-maximal activity (6). Therefore, anaerobic speed enduranceproduction training in trained athletes may be a relevant

stimulus for decreasing the net rate of muscle glycogenolysis

during submaximal activity (17). Fatigue toward the end ofthe game (2,9,21) has mainly been linked to depleted glyco-gen stores in a large proportion of the individual muscle

fibers (24). Therefore, it is hypothesized that speed endur-

ance training in general, and anaerobic production trainingspecifically, would be beneficial for soccer players (17).

However, only a few studies have investigated the effects of

various speed endurance training regimes among soccerplayers (10,12,16,37). These studies have found improvements

in Yo-Yo Intermittent Recovery test level 1 performances

(628%) (10,16,37), repeated-sprint ability (RSA; ;2%)(10,37), 40-m sprint speed (12), and maximal aerobic speed

(12). To the authors knowledge, no previous study has inves-tigated the effects of anaerobic speed endurance production

training on the Yo-Yo Intermittent Recovery test level 2 (IR2)performance in soccer players, although this test is consideredto be highly indicative of a players anaerobic energy produc-

tion capacity (4,20,23). Therefore, we aimed to investigate the

effect of 6 weeks of biweekly production training on Yo-YoIR2, and repeated-sprint performance (RSA), on 10- and

35-m sprint times, and jumping ability in countermovementjumps (CMJs) and squat jumps (SJs), in a group of junior elitesoccer players. We hypothesized that the anaerobic speed

endurance production training group would improve Yo-YoIR2 performance, mean sprint times during the RSA test, and

increase sprinting speeds and jumping performance.

METHODS

Experimental Approach to the Problem

Performance testing was undertaken at the sports facilities ofthe Department of Sports at the University of Nordland in

Norway, to test the effect of 6 weeks of anaerobic speedendurance production training on Yo-Yo IR2 performance,

repeated-sprint performance, sprint times over 10 and 35 m,

and jumping ability in CMJ and SJ. Pretests and posttestswere conducted on 2 consecutive days, before and after the

6-week intervention period. The first test day includeda Yo-Yo IR2 test, whereas CMJ, SJ, 35-m sprint, and 7 335-m RSA were tested on the second test day. The Yo-YoIR2 performances from the pretest were used to match and

then randomly assign the players to the training group andthe control group (CG). The study was conducted during

the last 6 weeks of the precompetition phase.

In line with what was described by Krustrup et al. (23), theYo-Yo IR2 test was performed on an indoor artificial soccerpitch, using a portable CD player to control the speed incre-

ments (Denon DC 1015, Denon Brand Company, Japa AU4n). The7 3 35-m repeated-sprint tests and the 35-m sprints were

measured on an indoor basketball court. Mean sprint times,as described by Svensson and Drust (36), were calculated later

using Microsoft Excel (Microsoft Corp., US AU5A). Maximal

sprint speed times and repeated-sprint test times were mea-sured and recorded by the wireless Brower Speed Trap IISystem (Brower Timing Systems, UT, USA). The test-retest

reliability of this system has been evaluated elsewhere, and it

is considered to be a useful tool for measuring running speed(34). Jump heights in the CMJ and SJ were calculated basedon impulse at takeoff from the force platform (AMTI, model

OR6-5-1) and saved to a Dell Latitude computer (Pentium 4)

using the AccuPower software 1-6-3. Body mass (kilograms)and stature (meters) were measured before and after the inter-vention period using an electronic scale (A&D Company

Limited, Tokyo, Japan) and a stadiometer (KaWe Medizin-tecknik, Asperg, Germany). The body mass index (kilograms

per square meter) and the reciprocal ponderal index

(cm$kg20.333) were calculated from these measurements(29). Pretest and posttest measurements were performed at

the same time of the day.

Subjects

A high-level elite junior soccer team of 19 outfield playerswas included in the study. The players had a mean age,

stature, and body mass of 16.9 60.6 (6SD) years, 180.9 64.6 cm, and 75.1 67.7 kg, respectively. The subjects regularlyperformed 46 weekly soccer sessions with their team and

on average exercised 12.0 6 1.8 h$wk21 in their normaltraining cycle. The team also regularly competed withinthe regional senior series.

Two players from the initial training group and 1 from theCG dropped out during the intervention period, and

therefore, a total of 16 players met the inclusion criteria for

the study, being present at both the pretest and the posttest,and completing 90% of the intervention training (training

group). The 8 training group and 8 CG subjects were aged

16.9 6 0.4 vs. 16.9 6 0.8 years and had body masses andstatures of 74.6 64.9 vs. 73.5 6 9.6 kg and 179.4 6 4.9 vs.

182.5 63.9 cm, respectively. The study was conducted ac-cording to the Helsinki Declaration and approved by the

local ethics committee and the Privacy Ombudsman for

Research (project number 25772) of the Norwegian SocialScience Data Service committee. All the players gave their

Production Training Effects in Soccer Players

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written informed consent to participate in the study, andparental approval was also obtained.

Procedures

All the players were pretested on 2 consecutive days 8 weeksinto the 15-week preseason training period. The players

were instructed not to participate in any kind of hardexercise for 2 days before the laboratory testing. The players

were also given nutritional advice, emphasizing the impor-tance of maintaining a normal fluid intake and diet before the

testing days. The same advice was given before posttesting.Pretests and posttests were conducted at the same time of

the day on the same days of the week.Test day 1 began with recording of anthropometric data

before the players went through a 15-minute warm-upsession, consisting of approximately 8 minutes of running

at 7080% of the peak heart rate, followed by 4 minutes ofaccelerations and decelerations over 4060 m and followed

by a 3-minute period of dynamic stretching (at moderatespeed) of the hip extensors, hip flexors, hamstrings, and

quadriceps femoris. The Yo-Yo IR2 (23) started when everyplayer had been positioned on the designated track. The test

was led by 2 experienced investigators, who ensured thatplayers completed the test according to the previously

described criteria (23).

On the second test day, the players followed a warm-upsimilar to that of the day before. Three CMJ and 3 SJ tests

were then conducted with a minimum of 3 minutes ofrecovery time between jumps. The CMJ was performed withhands on hips from a standing position on the force

platform, and a countermovement that decreased the kneeangle to approximately 908 was performed before jumping.

The SJ was performed directly from a squatting position

with a 908 knee angle and hands on hips. After that, theplayers ran three 35-m maximal sprints and were given

a break of at least 3 minutes between sprints. Finally, therepeated-sprint test was conducted with a 7 3 35-m maxi-mal sprint every 30 seconds. The players were given at least

one 10-minute break between each of the 4 tests. During the

35-m sprints and the repeated-sprint tests, the players startedfrom a standing position with the foot on a marked line

10 cm behind the first set of photocells, and the timer wasinitialized when the players broke the beam of the photocell.

Times were recorded after 10 and 35 m in both sprint tests.The mean sprint time was used for analysis because it hasbeen described as a good indicator of a players ability to

perform several consecutive sprints (13,36).

The Training Intervention

The CG followed the teams regular training plan (Mondays at

6.00 PM, Wednesdays

at 4.15 PM, Thursdays at

6.00 PM, and Fridays at

6.00 PM) during the inter-

vention period. Generally,team soccer training

consisted of warm-up exer-

cises (low-intensity run-

ning and short passing

exercises), technical and

tactical sessions in small

TABLE1. Production training program performed by the intervention group.*

Week-session Running activities Intended intensity (in % of max running speed)

Breaks

(reps/sets)

Total exercise

time (min)1-1 2 Sets 5 Reps 30 s 90, 90, 100, 100, 100 3/5 min 341-2 1 Set 8 Reps 40 s 80, 90, 90,90,90,90,90,90 4 min 33.52-1 2 Sets 5 Reps 30 s 90, 100, 100, 100, 100 3/5 min 342-2 1 Set 8 Reps 40 s 80, 90, 90, 90, 90, 90, 90, 90 4 min 33.53-1 2 Sets 5 Reps 30 s 100, 100, 100, 100, 100 3/5 min 343-2 1 Set 8 Reps 40 s 80, 90, 90, 90, 90, 90, 90, 90 4 min 33.54-1 2 Sets 6 Reps 30 s 90, 100, 100, 100, 100, 100 3/5 min 414-2 1 Set 8 Reps 40 s 80,90,90,90,90,90,90,90 4 min 33.55-1 2 Sets 6 Reps 30 s 90, 90, 100, 100, 100, 100 3/5 min 415-2 1 Set 10 Reps 4 0 s 80, 80, 90, 100, 100, 100, 100, 90, 90, 90 4 min 42.56-1 2 Sets 6 Reps 30 s 90, 90, 100, 100, 100, 100 3/5 min 416-2 1 Set 10 Reps 4 0 s 80, 80, 90, 100, 100, 100, 100, 90, 90, 90 4 min 42.5

TABLE2. Average HR distribution during training.*

HR-zone (% Max HR) 8085% 8590% 9095% 95100%Absolute time in zone (min) 44.9 6 16.9 43.6 6 14.7 28.7 6 18.6 5.0 6 5.5Relative time in zone (%) 26.6 6 5.4 25.8 6 7.1 15.9 6 8.4 2.9 6 2.7

*HR = heart rate.Data are reported as mean 6 SD.

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TABLE

3.

Mean

results(6SD)oftheYo-YoIR2,73

35-mrep

eatedsprint,73

35-musedegree(%),35-m

sprint,10-msprint,10-to35-m,

CMJ,SJ,and

body

massbetween

andwithingroupsfrom

pretesttoposttest.*

Variable

Traininggroup

Controlgroup

Between-groupdiffe

rences

Pretest

Posttest

Change

95%

CI

Pretest

Posttest

Cha

nge

95%

CI

Difference

95%

CIES

Yo-YoIR2(m)

5596

133

6226

166

636

74

2125

to1

4446

121

4286

107

2166

87

257to89

796

41

28

to166z

1.0

73

35-m

Meantime(s)

5.496

0.15

5.446

0.17

20.056

0.27

20.17

to0.27

5.856

0.30

5.496

0.29

20.086

0.25

20.13to0.29

0.046

0.13

20.24

to0.31

0.1

35mMax(s)

5.046

0.11

4.996

0.12

20.056

0.08

20.02

to0.12

5.106

0.14

5.146

0.24

0.056

0.13

20.15to0.06

20.106

0.05

20.21

to0.02

0.1

0-to10-m

Sprint(s)

1.886

0.05

1.826

0.05

20.066

0.06

0.01

to0.11

1.886

0.05

1.906

0.09

0.026

0.06

20.07to0.03

20.076

0.03

20.14

to0.01

1.3

10-to35-m

Fly(s)

3.176

0.09

3.176

0.08

0.016

0.07

20.07

to0.06

3.226

0.11

3.256

0.16

0.036

0.07

20.09to0.03

20.026

0.04

20.10

to0.06

0.3

CMJ(cm)

37.06

4.3

37.16

4.6

0.16

4.3

23.7

to3.5

37.56

4.0

35.26

3.2

22.36

4.1

21.1to5.7

2.46

2.1

22

.1

to6

.9

0.6

SJ(cm)

32.56

2.5

31.16

3.4

21.46

4.4

22.3

to5.1

29.76

3.2

29.16

2.6

20.66

3.1

22.0to3.2

20.76

1.9

24

.9

to3

.3

0.2

Body

mass(kg)

74.66

4.9

75.86

5.8

1.26

1.6

22.5

to0.1

73.56

9.6

74.46

9.6

0.96

1.5

22.1to0.4

0.46

0.8

21

.3

to2

.0

0.2

*CI=confidenceinterval;CMJ=countermovementjump;ES=

Cohensd(effectsize);SJ=squatjump.

p,

0.05.

zp,

0.1.




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and larger groups, and ended with small-sided games(4 vs. 4) and games including more players (commonly 8

vs. 8 or 9 vs. 9). Core training (e.g., sit-ups and planks),balance training (e.g., ankle strength exercises), and various

chest, back and coordination exercises (e.g., ladder drills)were also used sporadically The intervention group (IG)

went through 2 additional weekly sessions (Wednesday eve-

nings at 9.45 P Mand Friday afternoons at 4.15 P M) of anaer-obic speed endurance production training during the 6-weekintervention period. The training program and correspond-

ing heart rates for the IG are presented inT1 Tables 1 and 2.Each 30- or 40-secondT2 interval was performed across an

outdoor artificial soccer pitch, and the participants thereforehad to perform a 1808 turn every time they reached the

sideline of the pitch.

Statistical Analyses

All raw data were exported to Microsoft Excel and SPSS15.0 for Windows for further analysis. A 2-way mixed

intraclass correlation (ICC) of reliability was calculated forall measured variables in this study. All the measured

variables were assessed by a Shapiro-Wilks test and foundto be normally distributed. Levenes test for equality of means

showed no significant differences in the group variances.Therefore, a paired sample t-test was used to detect differ-ences between pretest and posttest means within eachgroup. An independent sample t-test was used to detectpossible differences between the groups. The effect size(Cohensd) calculation (31) was used to detect the effective-ness of the production training for the training group. Thescale developed by Batterham and Hopkins (8) was used to

determine the size of the possible effects. The significancelevel was set top#0.05 for all analyses, and the 95% con-fidence interval (95% C I) was also calculated for all the mea-

sured variables.

RESULTS

Thepvalue for all reliability measures were p, 0.01. Fur-thermore, the reliability for the SJ was ICC = 0.85, for the

CMJ, it was ICC = 0.90, for the 10-m sprint time, it wasICC = 0.77, and for the 35-m sprint time, it was ICC = 0.96.

The IG significantly improved (p, 0.05) in the Yo-Yo IR2running distance by 63 6 74 m, and 10-m sprint time from

the pretest to posttest by 0.06 6 0.06 seconds, with no sig-nificant changes in the other variables measured (Table 3).

No significant changes from the pretest to posttest werefound in any of the variables within the CG.

When comparing results between the groups, we found

that the IG had a statistically significant improvement overthe CG for the 10-m sprint time (p, 0.05) and tended to bedifferent for Yo-Yo IR2 performance (p= 0.07). The effect(Cohensd) of the training intervention on the IG was veryhigh on the Yo-Yo IR2 and 10-m sprint time, moderate onboth the RSA and the CMJ, and trivial on the other variablesmeasured (

T3

Table 3).

DISCUSSION

The main findings of this study were that 6 weeks of

biweekly speed endurance production training sessions

significantly improved 10-m sprint performance and the

Yo-Yo IR2 test scores. In comparison, the CG did not showimprovements in test performances.

The biweekly production training for 6 weeks generated

a 0.06-second improvement in the 0- to 10-m sprint time.

Previous research has shown that explosive sprints account

for as much as 2224% of sprints across all player positions

in elite football (Champions League from 2002 to 2006) (13),

and that most sprints are of a very short duration (23 sec-

onds) within soccer match play (7,27). Sprinting has also

been associated with the most important phases of match

play, such as creating goal scoring opportunities and scoring

goals (33). The improvement we found corresponds to the

equivalent of about 33 cm in a 10-m sprint and could there-

fore have significant effects within match play. As anaerobic

speed endurance production training is generally consideredto improve performance during short-term, high-intensity

intermittent exercise, for example, from a 30-second to

3-minute duration (17,19), the significant and positive train-

ing effect on the 10-m sprint time was somewhat unex-

pected. A likely explanation is that a high number of

accelerations were performed during each training session,

as the participants had to stop, turn, and accelerate a number

of times. Although no previous studies have examined the

effects of the present form of production training on accel-

eration speed, Bravo et al. (10) investigated the effect of

repeated-sprint training with long breaks (4 minutes)

between sets on acceleration speed, and they did not find

any improvement on 0- to 10-m sprint times after imple-

menting a 7-week 6 3 40-m repeated-sprint training, with

a 1808 directional change every 10 or 20 m. The shorter

acceleration distance may have contributed to the lack of

adaptation found in this study (10) and may explain why

our results demonstrate an adaptive effect.The players of the IG significantly improved their Yo-Yo

IR2 performance. Previously, only one comparable study has

examined changes in Yo-Yo IR2 after a 2-week production

training stimulus (37), and observed a nonsignificant

improvement in the performance of 57 AU6m. Several mecha-

nisms may account for the present findings of an improve-

ment in the Yo-Yo IR2 performance, including elevated

creatine kinase, glycolytic and oxidative enzyme activities

(5), improved muscle buffering capacity (15), and an

increased muscle Na+-K+ pump a2-isoform protein expres-

sion (37). AU7We recognize, however, that a limitation of thisstudy is that the pretest and posttest differences observed

between the 2 groups may be partly explained by the extra

6080 minutes of activity per week performed by the IG. It is

also possible that the improved Yo-Yo IR2 performance

reflects an improvement in subjects ability to change direc-

tion and reaccelerate (10), because the players in the IG


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performed this action frequently during the trainingintervention.

No changes in the RSA within the IG or between thegroups were observed. This indicates that the present type of

production training is not a sufficient stimulus to improveRSA after 6 weeks of production training in trained soccer

players. Furthermore, no significant changes were observed

in the 0- to 35-m or 10- to 35-m sprinting times, indicatingthat the present form of biweekly production training isinsufficient to stimulate increases in sprinting speed among

trained soccer players over a period of 6 weeks (10,12,16).Jump test performance scores did not change significantly

during the training period. However, a moderate effect onCMJ was revealed. This finding is consistent with the

improved acceleration speed. We speculate that the effect

on CMJ performance may be caused by the numerous decel-erations, turns, and accelerations performed during the pro-duction training intervention, which consequently leads to an

increased reactive strength and power output (33,35).

The relatively short recovery period between the Yo-Yo IR2 test and the other tests (24 hours) is also a potentialconcern, because glycogen stores may have been affected,

although previous research has shown only moderate

reductions (9%) in muscle glycogen after the Yo-Yo IR2 test(23). Recovery time between the jump tests, the speed test,and the repeated-sprint test may also affect the present

results, although it has been shown that allowing 3 minutesbetween within-test repetitions, 10 minutes between the var-

ious tests, and limiting test activity to 10 seconds are sufficient

for recovery of energy stores (11).

PRACTICAL APPLICATIONS

This study offers evidence that biweekly anaerobic speed

endurance production training is an effective means ofimproving acceleration and intermittent running perfor-mance among trained soccer players, as long as this training

is performed with turns and accelerations, and is of a 30- to

40-second duration. Enhanced anaerobic capacities resultingfrom this training are likely to be of immediate, practical

significance for soccer players, because it has been shown(19) that top teams have superior capacity in speed andhigh-intensity intermittent endurance when compared with

bottom teams (25) and that this may be a significantperformance outcome indicator at both whole-team and

individual-player levels. However, generalization of these

results to senior elite and less-trained soccer players shouldbe undertaken with caution, because only 16 junior elite

soccer players took part in this study. Further studies

should investigate whether the effects of anaerobic speedendurance training can be optimized by specific combina-

tions with other types of soccer training. Nonetheless, asthe time available for training in junior teams is limited, an

important finding of this study is that bouts of short-duration

high-intensity exercise totaling 6080 min$wk21 can beeffectively implemented alongside regular soccer sessions.

ACKNOWLEDGMENTS

The authors wish to thank the players for their efforts and

Fredrik Be and rjan Nygard for their contribution duringdata collection. They would also like to thank Suzanne Scott

for correction of the manuscript. Present data were collectedat the laboratory of the Department of Sport, University of

Nordland.

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Artikkel 11- Performance Effects of 6 Weeks of Anaerobic Production