The effect of leg exercise and of arm exercise in sitting and standing body positions on energy output and on some cardiorespiratory parameters was studied in seven male subjects. Oxygen uptake (VO2), heart rate (fH), pulmonary ventilation (VE) and respiratory frequency were measured at rest, in the 7-8th min of submaximal work (300, 600, 900 kpm/min), and at maximal effort. Significantly higher Vo2, fH, and VE in arm cranking than in cycling were found at submaximal work loads above 300 kpm/min. Though the maximal work load in arm exercise was 50-60% of that in cycling, Vo2 in arm work was at maximal effort only 22% lower than in leg exercise while the difference in fH was insignificant. No differences were found in arm work between the results obtained at any work level in sitting and standing body positions. The only postural difference in arm work was a 13% higher work load achieved at maximal effort when standing than when sitting. Differences in fH between arm and leg exercise were much smaller for the same Vo2 than for the same work load and were time dependent. While fH quickly leveled off in leg exercise, fH in arm cranking rose steadily during the first 6 min of work which created the fH differences observed in the 7-8 min of submaximal arm arm and leg exercise. At submaximal work levels a tendency to synchronize the respiratory frequency with the frequency of the rotatory movements was more apparent in arm cranking than in cycling.

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We monitored gas exchange and muscle activity during two commonly used modes of passive leg exercise as a means of assessing the degree of passivity associated with these techniques. Additionally, we measured the rapid changes in ventilation at the start and end of the passive exercise to assess changes that occur in the fast exercise drive to breathe during passive exercise. We monitored seven subjects at rest and during 5 min of passive exercise using (1) cycling movements performed on a tandem bicycle and (2) leg extension movements performed in a chair apparatus. The increase in measured parameters from rest to passive exercise were all higher while using the tandem bicycle compared to the chair apparatus: ventilation [3.09 (0.63) versus 0.35 (0.38) l x min(-1)], leg muscle electromyogram [8.3 (1.6) versus 1.6 (0.6) microV], carbon dioxide production [0.092 (0.018) versus -0.002 (0.001) l x min(-1)] and oxygen consumption [0.158 (0.046) versus -0.008 (0.007) l x min(-1)]. Passive exercise on the tandem bicycle was also associated with a significantly larger fast exercise drive to breathe at both the start and end of motion, compared to the chair apparatus [start: 5.59 (0.74) versus 3.08 (0.79) l x min(-1), end: 3.38 (0.79) versus 1.75 (0.54) l x min(-1)]. The fast exercise drive to breathe at the end of exercise was significantly smaller (60%) than at the start for both modes. We conclude that passive exercise on an upright bicycle contains a significant active component that contributes both neural and metabolic influences toward the physiological adjustments observed. Furthermore, we conclude that adaptation occurs in the fast exercise drive to breathe accompanying passive limb movement.

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