Effects of different stretch durations on the strength of the proximal and distal group of muscles - a randomized trial.

Background: Different researchers have studied the effects of different types of stretching on different muscle groups. Since distal muscles are fully activated and proximal muscles are sub-optimally activated; thus, we might see different responses to stretching in the proximal and distal groups of muscles depending on their muscle activation. Therefore, this study aimed to compare the acute effects of 2, 4, and 8 minutes of intermittent static stretching (SS) on the isometric maximum voluntary contraction force (MVCF) of proximal (Hamstring) and distal (Calf) groups of muscles.

Methods: Two groups pretest-posttest experimental design was used. A total of thirty participants were randomly assigned into two groups, and twenty-eight completed the intervention. In both groups, participants participated in three experimental trials (SS2, SS4, and SS8) on 3 days. 2-minute intermittent stretching (SS2) was performed on day-I, 4-minute (SS4) on day II, and 8-minute (SS8) on day III. Isometric MVCF was measured at pre-intervention, 0-, 10-, and 20-minute post-intervention periods in both groups.

Results: In the proximal group: SS2, SS4, and SS8 did not affect isometric MVCF at the 0-, 10-, and 20-minute post-intervention periods (P > .05). In distal group: SS2 did not affect isometric MVCF at 0- and 10-minute post-intervention periods (P > .05), however at 20-minute, MVCF increased by 11.06% (P < .05). SS4 and SS8 also did not alter isometric MVCF in the Calf at 0-, 10-, and 20-minute post-intervention periods (P > .05). No significant differences were observed between the proximal and distal groups (P > .05).

Conclusion: 2-, 4-, and 8-minute intermittent SS did not affect the isometric strength in both muscle groups. In addition, proximal and distal groups of muscles responded similarly to three different duration intermittent SS.