Flexibility is not Related to Stretch-Induced Deficits in Force or Power

Abstract

Previous studies have demonstrated that an acute bout of static stretching may cause significant performance impairments. However, there are no studies investigating the effect of prolonged stretch training on stretch-induced decrements. It was hypothesized that individuals exhibiting a greater range of motion (ROM) in the correlation study or those who attained a greater ROM with flexibility training would experience less stretch-induced deficits. A correlation study had 18 participants (25 ± 8.3 years, 1.68 ± 0.93 m, 73.5 ± 14.4 kg) stretch their quadriceps, hamstrings and plantar flexors three times each for 30 s with 30 s recovery. Subjects were tested pre- and post-stretch for ROM, knee extension maximum voluntary isometric contraction (MVIC) force and drop jump measures. A separate training study with 12 subjects (21.9 ± 2.1 years, 1.77 ± 0.11 m 79.8 ± 12.4 kg) involved a four-week, five-days per week, flexibility training programme that involved stretching of the quadriceps, hamstrings and plantar flexors. Pre- and post-training testing included ROM as well as knee extension and flexion MVIC, drop and countermovement jump measures conducted before and after an acute bout of stretching. An acute bout of stretching incurred significant impairments for knee extension (-6.1% to -8.2%; p < 0.05) and flexion (-6.6% to -10.7%; p < 0.05) MVIC, drop jump contact time (5.4% to 7.4%; p < 0.01) and countermovement jump height (-5.5% to -5.7%; p < 0.01). The correlation study showed no significant relationship between ROM and stretch-induced deficits. There was also no significant effect of flexibility training on the stretch-induced decrements. It is probable that because the stretches were held to the point of discomfort with all testing, the relative stress on the muscle was similar resulting in similar impairments irrespective of the ROM or tolerance to stretching of the muscle. Key PointsA correlation and training study were used to examine the effects of increased range of motion on stretch-induced changes in force and jump measuresAn acute bout of stretching incurred significant impairments for knee extension and flexion MVIC, drop jump contact time and countermovement jump height.Neither study showed any significant relationship between ROM and stretch-induced deficits.

Keywords: Flexibility; force; jumps; static stretching.

Figure 1.

Experimental design.

Figure 2.

Changes in knee extension maximal voluntary isometric force (MVIC) before and following an acute bout of static stretching to the point of discomfort. Asterisks indicate significant differences in stretch-induced MVIC force prior to and after a four-week stretch training programme. Bars represent means of the group while vertical lines indicate standard deviation.

Figure 3.

Changes in knee flexion maximal voluntary isometric force (MVIC) before and following an acute bout of static stretching to the point of discomfort. Asterisks indicate significant differences in stretch-induced MVIC force prior to and after a four-week stretch training programme. Bars represent means of the group while vertical lines indicate standard deviation.