Effect of acute passive stretching on maximum aerobic power and time to exhaustion

Acute passive stretching has been shown to decrease the maximum skeletal muscle force and power during isometric and dynamic contractions, by altering muscle neural activation and the viscoelastic properties and contractility of the muscle-tendon unit. PURPOSE: To assess the effects of acute passive stretching on the maximum aerobic power (V’O2 max) and on a high intensity sub maximal exercise. METHODS: Six active males (23±4 yrs) performed a maximum incremental test on a cycle ergometer to determine V’O2 max and a test at 85% of V’O2 max (W’85) up to exhaustion. Tests were carried out on different days without (control condition, C) and with a preceding stretching routine, in a randomized order. Among variables, we measured power output, oxygen uptake (V’O2), ventilation (V’E), heart rate (fH), blood lactate concentration ([La]) and time to exhaustion (Tlim) of the W’85 exercise. RESULTS: After stretching, in comparison to C: i) maximum power output was 5% lower (p<0.05); ii) V’O2 max was similar (3.80±0.34 vs 3.82±0.25 l/min with stretching and in C, respectively); iii) at maximum exercise, cardiorespiratory variables and [La] were not significantly different; iv) Tlim of the W’85 was shorter (949±255 vs 1228±443 s with stretching and in C, respectively; p<0.05); v) V’O2 at min 4 of W’85 exercise was higher (3.17±0.18 vs 3.04±0.08 l/min with stretching and in C, respectively; p<0.05), but similar at exhaustion (3.38±0.19 vs 3.38±0.16 l/min with stretching and in C, respectively); vi) [La] at min 4 of W’85 exercise was higher (5.5±1.7 vs 4.9±1.5 mM with stretching and in C, respectively; p<0.05), but similar at exhaustion (10.7±1.9 vs 10.5±2.0 mM with stretching and in C, respectively). CONCLUSION: Acute passive stretching significantly reduced maximum power output but not V’O2 max. Moreover, Tlim of W’85 test was significantly shorter when the exercise was preceded by stretching maneuvers. These results show that acute passive stretching does not affect maximum aerobic power but significantly impairs endurance of the high level prolonged exercise. The present findings suggest the hypothesis that stretching affects prevailingly type II motor units, but not type I. Supported by University of Milan FIRST grant 12.1.5059281.16.