Oxygen uptake and heart rate kinetics during heavy exercise: a comparison between arm cranking and leg cycling

This study examined the oxygen uptake (VO(2)) and heart rate (HR) kinetics during arm cranking and leg cycling at work rates above the anaerobic threshold (AT). Ten untrained male subjects [21.6 (1.3) years] completed two 7 min 15 s constant-load arm cranking and two leg cycling tests at a power output halfway between the mode-specific AT and peak VO(2). The time constants for phase II VO(2) (tau) and HR (tau) kinetics were determined by fitting a monoexponential curve from the end of phase I until 3 min of exercise. VO(2) tau and HR tau values were significantly (P < 0.001) slower in arm cranking [VO(2) tau = 66.4 (3.0) s; HR tau = 74.7 (4.4) s] than in leg cycling [VO(2) tau = 42.0 (1.9) s; HR tau = 55.6 (3.5) s]. The VO(2) slow component (VO(2SC)) accounted for a significantly (P < 0.001) greater percentage of the total exercise response during arm cranking [23.8 (1.6)%] than during leg cycling [14.2 (1.5)%]. The greater relative VO(2SC) and the slower VO(2) tau with arm exercise are consistent with a greater recruitment of metabolically inefficient type II muscle fibres during arm cranking than during leg cycling.