Oxygen uptake and heart rate kinetics during heavy exercise: a comparison between arm cranking and leg cycling
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This study examined the oxygen uptake (V?O2) 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 V?O2. The time constants for phase II V?O2 (t) and HR (t) kinetics were determined by fitting a monoexponential curve from the end of phase I until 3 min of exercise. V?O2 t and HR t values were significantly (P<0.001) slower in arm cranking [V?O2 t = 66.4 (3.0) s; HR t = 74.7 (4.4) s] than in leg cycling [V?O2 t = 42.0 (1.9) s; HR t = 55.6 (3.5) s]. The V?O2 slow component (V?O2SC) 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 V?O2SC and the slower V?O2 t with arm exercise are consistent with a greater recruitment of metabolically inefficient type II muscle fibres during arm cranking than during leg cycling.
European Journal of Applied Physiology