Neuromuscular and circulatory adaptation during combined arm and leg exercise with different maximal work loads

Abstract

Cardiopulmonary kinetics and electromyographic activity (EMG) during exhausting exercise were measured in 8 males performing three maximal combined arm + leg exercises (cA+L). These exercises were performed at different rates of work (mean ± SD; 373 ± 48, 429 ± 55 and 521 ± 102 W) leading to different average exercise work times in all tests and subjects. ${\dot{\hbox{V}}\hbox{O}_{2}}$ reached a plateau versus work rate in every maximal cA+L exercise (range 6 min 33 s to 3 min 13 s). The three different exercise protocols gave a maximal oxygen consumption $({\dot{\hbox{V}}\hbox{O}_{2{\rm MAX}}})$ of 4.67 ± 0.57, 4.58 ± 0.52 and 4.66 ± 0.53 l min⁻¹ (P = 0.081), and a maximal heart rate (HR_max) of 190 ± 6, 189 ± 4 and 189 ± 6 beats min⁻¹ (P = 0.673), respectively. Root mean square EMG (EMG_RMS) of the vastus lateralis and the triceps brachii muscles increased with increasing rate of work and time in all three cA+L protocols. The study demonstrates that despite different maximal rates of work, leading to different times to exhaustion, the circulatory adaptation to maximal exercise was almost identical in all three protocols that led to a ${\dot{\hbox{V}}\hbox{O}_{2}}$ plateau. The EMG_RMS data showed increased muscle recruitment with increasing work rate, even though the HR_max and ${\dot{\hbox{V}}\hbox{O}_{2{\rm MAX}}}$ was the same in all three cA+L protocols. In conclusion, these findings do not support the theory of the existence of a central governor (CG) that regulates circulation and neuronal output of skeletal muscles during maximal exercise.