Kinetics of oxygen uptake during arm cranking with the legs inactive or exercising at moderate intensities

The purpose of this study was to compare the kinetics of oxygen uptake (VO(2)) during arm cranking with the legs inactive or exercising. Each subject (n = 8) performed three exercise protocols: 6-min arm cranking at an intensity of 60% of peak oxygen uptake (VO(2peak), AC(60)) and 6-min combined arm cranking and leg cycling in which AC(60) was added to on-going leg cycling at an intensity of 20% or 40% of VO(2peak) (LC(20) and LC(40): AC(60)LC(20) and AC(60)LC(40), respectively). After the onset of arm cranking, VO(2) tended to increase until the end of arm cranking in all of the three exercise modes. The amplitudes of this increase in VO(2) were 0.98 (0.18), 0.93 (0.16) and 0.84 (0.12) l.min(-1) during AC(60), AC(60)LC(20) and AC(60)LC(40), respectively, and there were significant differences between values for each exercise. The data are presented as means and standard deviations. There were no significant differences in the effective VO(2) time constant, partial O(2) deficit, and the difference between the values of VO(2) measured at 3 and 6 min in the three exercise modes. The present results indicate that the amplitude of the increase in VO(2) is reduced during arm cranking with the legs exercising, that this reduction becomes greater with increases in the intensity of leg cycling, and that the rate of increase in VO(2) is not affected by the additional muscle mass of the legs exercising below moderate intensities. The decrease in the amplitude of increase in VO(2) might be caused by reduction in oxygen supply to the exercising arms due to large muscle mass and/or overlaps of activity of stabilizing muscles during combined arm and leg exercise.