Comparison of the effects of long-lasting static stretching and hypertrophy training on maximal strength, muscle thickness and flexibility in the plantar flexors.
Level 2 - randomized trial
Individual controlled intervention trial
PubMed 37029826 · doi:10.1007/s00421-023-05184-6
What was done
Sixty-nine active participants (30 females, 39 males; mean age 27.4 ± 4.4 years) were allocated into three groups for a 6-week study: an extreme stretching group (continuous plantar flexor static stretching for 1 hour per day, 7 days/week), a conventional resistance training group (plantar flexor hypertrophy training: 5 sets of 10–12 repetitions, 3 days/week), and an inactive control group. Maximal voluntary contraction (MVC), muscle thickness, pennation angle, and flexibility were measured.
What was found
Both stretching and resistance training produced significant improvements compared to controls in MVC (η² = 0.143–0.32, p < 0.006), muscle thickness (η² = 0.11–0.14, p < 0.021), and flexibility (η² = 0.089–0.21, p < 0.046). Pennation angle showed no significant interaction (η² = 0.002–0.08, p = 0.077–0.625). There were no statistically significant differences between the stretching and resistance training groups on any metric (p = 0.37–0.99, d = 0.03–0.4). Absolute baseline and post-intervention numerical values were not reported in the abstract.
Why it matters
High-volume mechanical tension from passive stretching can stimulate muscle hypertrophy and strength gains comparable to resistance training. However, the extreme time commitment required (7 hours versus ~45 minutes per week) heavily limits practical utility.
Limits
The abstract does not clarify whether group allocation was randomized. The extreme stretching protocol (1 hour daily) is impractical for typical training contexts. The trial was short (6 weeks), conducted only in young active adults, and limited exclusively to the plantar flexors.
Cited by
- supports Stretching the calf muscle for one hour a day using a stretching boot resulted in approximately 15% muscle growth in muscle thickness.