ORIGINAL ARTICLE  EXERCISE PHYSIOLOGY AND BIOMECHANICS 

The Journal of Sports Medicine and Physical Fitness 2018 July-August;58(7-8):957-65

DOI: 10.23736/S0022-4707.17.07072-4

Copyright © 2017 EDIZIONI MINERVA MEDICA

lingua: Inglese

Effects of stretching and fatigue on peak torque, muscle imbalance, and stability

Pablo B. COSTA ¹ ✉, Cassio V. RUAS ², Cory M. SMITH ³

¹ Exercise Physiology Laboratory, Department of Kinesiology, California State University, Fullerton, CA, USA; ² Centre for Exercise and Sports Science Research, School of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia; ³ Department of Nutrition and Health Sciences, University of Nebraska-Lincoln, Lincoln, NE, USA

BACKGROUND: The present study examined the acute effects of hamstrings stretching and fatigue on knee extension and flexion peak torque (PT), hamstrings to quadriceps (H:Q) ratio, and postural stability.
METHODS: Seventeen women (mean±SD age=21.8±2.1 years; body mass=63.0±10.5 kg; height=164.7±6.2 cm) and eighteen men (25.8±4.6 years; 83.6±13.2 kg; 175.3±6.0 cm) took part in three laboratory visits. The first visit was a familiarization session, and the subsequent two visits were randomly assigned as a control or stretching condition. For the testing visits, subjects performed a postural stability assessment, stretched (or sat quietly during the control condition), performed a 50-repetition unilateral isokinetic fatigue protocol, and repeated the postural stability assessment.
RESULTS: There were no significant differences between control and stretching conditions for initial quadriceps and hamstrings PT, initial H:Q ratio, quadriceps and hamstrings PT fatigue indexes, H:Q ratio Fatigue Index, rating of perceived exertion (RPE), or postural stability (P>0.05). When analyzing 5 intervals of 10 repetitions, significant declines in quadriceps PT were found in all intervals for both conditions (P<0.05). However, a decline in hamstrings PT was only found until the fourth interval (i.e., repetitions 31 to 40) for the stretching condition (P<0.05).
CONCLUSIONS: Stretching the hamstrings immediately prior to long-duration activities may eventually cause adverse effects in force-generating capacity of this muscle group to occur earlier when fatiguing tasks are involved. Nevertheless, no changes were found for the H:Q ratios after stretching when compared to no-stretching.

KEY WORDS: Muscle stretching exercises - Postural balance - Muscle strength