Could inter-set stretching increase acute neuromuscular and metabolic responses during resistance exercise?
Level 2 - randomized trial
Individual counterbalanced crossover trial in humans
PubMed 31908750 · doi:10.4081/ejtm.2019.8579
What was done
Twelve resistance-trained men performed three knee extension resistance exercise protocols (7 sets of 10 repetitions) in a counterbalanced crossover design. The protocols evaluated were: 1) inter-set static stretching (ISS: 25 seconds of quadriceps stretching within a 40-second rest interval); 2) control (CON: 40 seconds of passive rest); and 3) traditional rest (TRA: 120 seconds of passive rest). Neuromuscular performance (total work, fatigue index, surface electromyography amplitude and frequency) and metabolic responses (muscle swelling and blood lactate) were measured.
What was found
Total work was lower (p < 0.05) and fatigue index was greater (p < 0.05) in ISS compared with CON and TRA. Electromyography (EMG) amplitude was lower (p < 0.05) during the 6th and 7th sets in ISS compared with TRA. EMG frequency was lower (p < 0.05) from the 3rd to 5th sets during ISS compared to CON, and from the 3rd to 7th sets compared to TRA. Muscle swelling and blood lactate increased similarly across all protocols (p > 0.05). Specific numerical averages, variances, and effect sizes were not provided in the abstract.
Why it matters
Inter-set static stretching acutely impairs work capacity and accelerates neuromuscular fatigue during resistance exercise without providing additional metabolic stress over passive rest.
Limits
The study had a small sample size of 12 resistance-trained men and evaluated only a single-joint machine exercise (knee extensions). Only acute, single-session responses were assessed, leaving chronic adaptations in strength and hypertrophy unmeasured. Exact numerical data were not reported in the abstract.
Cited by
- supports Stretching between resistance training sets reduces power and strength output on subsequent efforts.