Influence of contraction frequency on cardiovascular responses during the upper and lower body exercise

This study examined the relation between pedal frequency and cardiovascular responses during arm (AE) and leg (LE) ergometry. Twenty-six subjects completed three experimental sessions. Each session consisted of 10 min of steady-state exercise on AE or LE at 40, 60, or 80 rev·min^-1. Oxygen uptake (VO₂) and cardiac output (Q) were measured during each exercise. Arteriovenous oxygen difference (a-vO₂diff) was calculated by dividing VO₂ by Q. VO₂ was greater at 80 than at either 40 or 60 rev·min^-1 during both AE and LE. Q was greater at 60 than 40 rev·min^-1 during AE and at 80 than 40 rev·min^-1 during LE. a-vO₂diff was greater at 80 than 40 or 60 rev·min^-1 during AE, but remained unchanged during LE. It appears that the greater VO₂ at 80 rev·min ^-1 during AE is due to an increase in peripheral O₂ extraction. However, an enhanced systemic circulation may be the principal cause for the greater VO₂ seen at 80 rev·min^-1 during LE.