TY  - THES
T1  - Acute effects of stretching on athletic performance : the ability of some exercises in compensating stretching-related performance deficits
A1  - Mahli,Mohammed Rajaai
Y1  - 2012/06/22
N2  - The purpose of the dissertation was to investigate the acute effects of stretching on various athletic performances, and how to quickly compensate the expected stretching-related performance-deficits following static stretching. A number of recent studies researched the acute effects of static stretching on athletic performance were reviewed and analyzed in the theoretical part of the dissertation. The reviewed studies were di-vided into two groups: studies which reported negative effects (49 studies), and studies which reported equivocal effects (39 studies). The practical part of the dissertation consists of three studies with 67 participants (sport students at the Saarland Univer-sity). A repeated measures within-subject design was applied in the three studies.
First study:
Purpose: This study aimed to investigate the acute effects of hamstring static and dy-namic stretching on peak isokinetic concentric torque at a low velocity, the knee angle, at which this peak torque occur, and the hip flexion range of motion.
Methods: 17 sport students participated in this study. Measurement of concentric isokinetic knee flexion peak torque including the angle at peak torque, as well as the hip flexion range of motion were performed before and immediately following four conditions. Subjects attended a total of four testing ses-sions (A, B, C and D) so that the order of the conditions assignment was randomized per person (within-subject design). The four conditions were: (A) hamstring static stretching (three sets of four stretches with 30 seconds holding the stretch). (B) ham-string dynamic stretching (three sets of four stretches with 12-14 repetitions). Condi-tion (C) and (D) consisted of ten minutes passive sitting and were set as control condi-tions. The difference between (C) and (D) was that in (C) both force and flexibility tests were performed, whereas in (D) merely the isokinetic test was performed.
Results: Repeated measures analyses of variance showed no significant differences between the four protocols regarding the peak torque and the angle at peak torque (p=0.474, F= 0.85) and (p=0.59, F= 0.63), respectively. On the other hand, hamstring static and dynamic stretching resulted a significantly greater hip flexion range of mo-tion (p=0.009, F=8.6, ES= 0.37) and (p=0.000, F=33.7, ES=0.55), respectively, when compared to the control condition (C). There was no significant deference between static and dynamic stretching in enhancing the range of motion.
Conclusion: Hamstring static and dynamic stretching enhanced the hip flexion range of motion with neither impairment nor facilitation in isokinetic concentric knee flexion force at low velocity. 
Second study:
Purpose: The aim of the second investigation was to find out which procedure - with or without a prior stretch- would best suit in warm-up program to prepare the athlete for the following training or competition, and which procedure would best suit in re-storing the expected reduction of performance following a stretch. 
Methods: 20 sport students performed triple-hop test on eight separate days before and after completing eight different warm-up protocols in a randomized order. The eight warm-up protocols were: a. 3x10 consecutive maximum vertical jumps (JU), b. 3x8 dynamic half-squats (SQ) with 50% of body weight, c. 3x10 seconds isometric-squats (ISO) by knee angle 120° with 50% of body weight, d. 3 minutes rest with no activity (REST), e. 2 sets of 4 passive static stretching exercises (SS) with a 30 seconds hold followed by 3x10 maximum vertical jumps (SS+JU), f. (SS + SQ), g. (SS + ISO), h. (SS + REST). In the last four conditions the triple-hop test was performed before and immediately after stretching and once again after the second treatment. 
Results: Jump performance following (JU) was significantly better than following SS+JU (F= 7.2, p=0.015, ES=0.12), and following (SQ) and (ISO) were better than following (SS+SQ) and (SS+ISO), respectively, but not significantly. There was no significant difference between the (JU), (SQ), (ISO) and (REST) protocols. There was no significant difference between the (SS+JU), (SS+SQ), (SS+ISO) and (SS+REST) protocols. The half squat exercise showed significant improvements of 5 % (F=18.5, p=0.0004, ES=0.23) in horizontal jump distance which was decreased following static stretching as compared to the condition SS+REST, whereas the improvements in jump performance following the (JU) or (ISO) exercises by 3.7 % and 3.8 %, respectively tended to be significant (p=0.064 and p=0.052).
Conclusion: The implication of a static stretching program in the warming-up phase seemed to be not suitable, especially if the subsequent performances require a high level of power and reactive force production with a rapid stretch shortening cycle. When static stretching combines with dynamic squats with moderate loads, decrements in jump performance may be compensated.
Third study:
Purpose: The third investigation aimed to examine if the expected decrement in jump performance following static stretching could be compensated using weighted jumps  with a light load, and if changes may occur in muscles activity (IEMG). 
Methods: 30 sport students performed in two separate days countermovement jumps prior to static stretching, immediately after static stretching, and once again after weighted jumps (experimental condition), or before and after rest-ing times which matched the duration of static stretching and weighted jumps (control condition). Jump height, time of force plate contact, peak force and muscle activity of four muscles were measured during the countermovement jump. 
Results: Jump height was significantly decreased by 5.3 % (p=0.000) following static stretching (immediately after stretching and before the weighted jumps). There was a significant increase (p=0.000) in jump height by 6.9 % following weighted jumps (per-formance decrement was significantly overcompensated). There were no significant changes in muscles activities between the two conditions across the three test times in all four muscles.
Conclusion: The decreased performance due to static stretching can be compensated using a suitable procedure such as weighted jumps with a light load (30 % of 1-RM). Even more, the combination of static stretching exercises followed by weighted jumps resulted overall in a significant improvement in the jump height by 1.6 %.

KW  - Sportliche Leistungsfähigkeit
KW  - Muskeldehnung
KW  - Dehnübung
CY  - Saarbrücken
PB  - Universitäts- und Landesbibliothek
AD  - Postfach 151141, 66041 Saarbrücken
UR  - http://scidok.sulb.uni-saarland.de/volltexte/2012/4876
ER  -