Cardiovascular adjustments to exercise distributed between the upper and lower body

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Abstract
The present study examined the hemodynamic differences between upper- and lower-body exercise where the total power output (PO) was proportionally distributed between the upper and lower body. Six males completed five combinations of arm-leg exercise at maximal and three submaximal intensities. The ratio of arm PO to total PO for each exercise combination was 0, 25, 50, 75, and 100%. At each submaximal intensity, .ovrhdot.VO2 and cardiac output (.ovrhdot.Q) were not different (P > 0.05) across exercise combinations. Likewise, heart rate (HR) responses were not different for 0, 25, 50, and 75% at level 1 (.hivin.X = 102, 102, 106, 106 beats .cntdot. min-1, respectively), level 2 (.hivin.X = 114, 110, 119, 118 beats .cntdot. min-1, respectively), and level 3 (.hivin.X = 127, 124, 132, 131 beats .cntdot. min-1, respectively). However, HR for 100% (arm-only exercise) tended to be higher than 0% at level 1 (.DELTA.HR = 10 beats .cntdot. min-1; P < 0.01), level 2 (.DELTA.HR = 12 beats .cntdot. min-1, P < 0.06) and level 3 (.DELTA.HR = 10 beats .cntdot. min-1; P < 0.06). At level 1, stroke volume (SV) remained essentially unchanged from 0-75%, while SV at 100% (108 ml) was slightly though not significantly lower (P < 0.10) than 0% (125 ml). At exercise levels 2 and 3, SV remained unchanged for 0 and 25%, however, SV at 50, 75, and 100% were generally lower (P < 0.05) compared with 0%. These results indicate that involving the leg musculature to varying degrees during arm-leg exercise attenuates the hemodynamic differences observed during strict upper body versus strict lower body exercise.