Dynamic and steady-state ventilatory and gas exchange responses to arm exercise

Previous studies have suggested that, for the same power output, arm exercise requires higher oxygen uptake (VO2), carbon dioxide output (VCO2), and ventilation (VE) than leg exercise and that response kinetics are slower. To evaluate these differences, four healthy subjects performed a total of 95 arm cranking tests. Each subject performed several tests at each of three or four power outputs spaced evenly below the maximum the subject could sustain (average = 53 W). Breath-by-breath responses to identical stimuli were averaged. End-exercise blood lactate was determined at each power output. Responses were compared to leg exercise responses in these subjects (J. Appl. Physiol. 67:547-555, 1989). For power outputs unassociated with lactic acidosis, differences between steady-state VO2, VCO2, and VE responses for arm and leg exercise were not significant. At higher power outputs, the higher VO2, VCO2, and VE during arm exercise were well correlated with higher lactate. For power outputs not engendering lactic acidosis, the time constants (tau) for VO2, VCO2 and VE were not greatly different for arm than for leg exercise. For each variable, at higher power outputs tau became longer by an amount correlated with higher lactate level. Like leg exercise, the slower kinetics of VO2 and VE (but not VCO2) at higher power outputs were well described as a superimposed slower component. We conclude that both dynamic and steady-state responses of VE and gas exchange to arm exercise do not differ substantially from those to leg exercise so long as the power output does not elevate blood lactate.