Electrostimulation improves muscle perfusion but does not affect either muscle deoxygenation or pulmonary oxygen consumption kinetics during a heavy constant-load exercise

摘要

Electromyostimulation (EMS) is commonly used as part of training programs. However, the exact effects at the muscle level are largely unknown and it has been recently hypothesized that the beneficial effect of EMS could be mediated by an improved muscle perfusion. In the present study, we investigated rates of changes in pulmonary oxygen consumption $(dot{V}hbox{O}_{2{rm p}})$ and muscle deoxygenation during a standardized exercise performed after an EMS warm-up session. We aimed at determining whether EMS could modify pulmonary O2 uptake and muscle deoxygenation as a result of improved oxygen delivery. Nine subjects performed a 6-min heavy constant load cycling exercise bout preceded either by an EMS session (EMS) or under control conditions (CONT). $dot{V}hbox{O}_{2{rm p}}$ and heart rate (HR) were measured while deoxy-(HHb), oxy-(HbO2) and total haemoglobin/myoglobin (Hbtot) relative contents were measured using near infrared spectroscopy. EMS significantly increased (P < 0.05) the Hbtot resting level illustrating a residual hyperaemia. The EMS priming exercise did not affect either the HHb time constant (17.7 ± 14.2 s vs. 13.1 ± 2.3 s under control conditions) or the $dot{V}hbox{O}_{2{rm p}}$ kinetics (time-constant = 18.2 ± 5.2 s vs. 15.4 ± 4.6 s under control conditions). Likewise, the other $dot{V}hbox{O}_{2{rm p}}$ parameters were unchanged. Our results further indicated that EMS warm-up improved muscle perfusion through a residual hyperaemia. However, neither $dot{V}hbox{O}_{2{rm p}}$ nor [HHb] kinetics were modified accordingly. These results suggest that improved O2 delivery by residual hyperaemia induced by EMS does not accelerate the rate of aerobic metabolism during heavy exercise at least in trained subjects.