Influence of stretching hamstring and quadriceps femoral muscles on knee peak torque and maximum power

Abstract

Muscle stretching is often used in sports practice in order to increase muscle flexibility and joint range of motion. However, many studies have shown that muscle torque production may be reduced after stretching. The purpose of this work was to assess immediate and late effects of stretching, by proprioceptive neuromuscular facilitation (PNF) techniques, on knee peak torque and maximum power. Fifteen young sedentary female subjects were evenly distributed into three groups: AG, submitted to 12 PNF stretching sessions along four weeks; BG, submitted to only one stretching session just before the final evaluation; and GC, submitted to passive knee mobilization so as not to produce muscle stretching. All of them were assessed, before and after the four-week study, as to knee range of motion (ROM) flexion and extension, as well as to isokinetic dynamometry; variables analysed were knee ROM, peak torque and maximum power. Significant mean ROM differences were found between the three groups (p<0.001), but no differences in isokinetic measures (p>;0.05). A and B groups showed increased ROM at the post-test, and only the C group showed significant increase in all isokinetic variables (p<0.05). Results then suggest that PNF stretching, performed with adequate duration and intensity, may be done before sports practice with no decrease in muscle strength.