The effectiveness of 3 stretching techniques on hamstring flexibility using consistent stretching parameters.
Level 2 - randomized trial
Individual randomized controlled trial with four parallel groups
PubMed 15705041 · doi:10.1519/14273.1
What was done
Nineteen young adults (aged 21–35 years) with tight hamstrings (knee extension angle >20° while supine with hip flexed at 90°) were randomized into 4 groups: self-stretching (n = 5), static stretching (n = 5), proprioceptive neuromuscular facilitation with reciprocal inhibition (PNF-R, n = 5), or control (n = 4). Each intervention group received the same dose of one 30-second stretch 3 days per week for 4 weeks. Hamstring flexibility was assessed via knee extension angle at baseline, 2 weeks, and 4 weeks.
What was found
A significant interaction of stretching technique and duration was observed (p ≤ 0.05). Post hoc analysis showed that all 3 stretching techniques increased hamstring length from baseline over 4 weeks, but only static stretching was significantly greater than control at 4 weeks. Exact numerical values, effect sizes, and confidence intervals are not reported in the abstract.
Why it matters
The findings indicate that a minimal dose of static stretching (30 seconds, 3 days per week) can improve hamstring flexibility over 4 weeks, whereas equivalent low doses of self-stretching and PNF-R were insufficient to outperform a control group.
Limits
The sample size is extremely small (total n = 19, with 4–5 participants per arm), creating substantial risk of imprecision and type II error. The abstract lacks raw numeric values, measures of variance, and effect sizes. The results reflect only a single minimal-dose protocol in healthy young adults and may not generalize to other stretching volumes or populations.
Cited by
- context Contracting the glute activates reciprocal inhibition, causing the opposing hip flexor to relax and allowing greater hip range of motion.