Skeletal muscle perfusion in electrically induced dynamic exercise in humans

Abstract

Leg blood flow, blood pressure and metabolic responses were evaluated in six men during incremental one-legged dynamic knee extension exercise tests (no load exercise -40 W); one performed with voluntary contractions (VOL) and one with electrically induced contractions (EMS). Pulmonary oxygen uptake was the same in both exercise modes, but the ventilatory coefficient was 2-5 L per L O-2 higher in EMS than VOL (P < 0.05). Heart rate and mean arterial pressure were slightly higher with EMS than VOL at all exercise intensities reaching 138 (EMS) and 126 bpm (VOL), as well as 148 (EMS) and 137 mmHg (VOL) at 40 W, respectively (P < 0.05). Leg blood flow, oxygen uptake and conductance were similar in the two exercise modes. At 40 W, mean muscle blood flow was close to 200 (range: 165-220) mt 100 g(-1) min(-1), mean peak muscle oxygen uptake reached 230 mt kg(-1) min(-1), and mean conductance became as high as around 45 mt min(-1) mmHg(-1), and normalized for muscle size and arterial pressure it approached 100 mt min(-1) 100 g(-1) 100 mmHg(-1). Lactate and ammonia efflux from the leg were higher with EMS than with VOL and the difference became larger with increasing exercise intensity (P < 0.05). Muscle glucose uptake was the same in each exercise mode. Femoral venous K+ concentration increased with exercise intensity and was higher with EMS than with VOL, reaching 5.1 (EMS) and 4.7 mmol L(-1) (VOL) at 40 W (P < 0.05). The study demonstrates that electrically induced dynamic exercise is associated with a marked cardiovascular response similar to voluntarily performed exercise and a more pronounced activation of the anaerobic metabolism of the muscle. Furthermore, as the electrically activated muscle group is well defined, the present results confirm that peak muscle blood flow can reach 200-250 mt 100 g(-1) min(-1).