Exercise efficiency during arm ergometry: effects of speed and work rate

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Abstract
The purpose of this investigation was to determine the effects of increasing work rate and speed of movement on efficiency during steady-state arm crank ergometry (ACE). Ten men exercised at speeds of 50, 70, and 90 rpm and four power outputs (15, 30, 45, and 60 W). O2 uptake determinations were made using open-circuit spirometry and energy expenditure was calculated from the respiratory exchange ratio. Gross (work accomplished/energy expended), work (unloaded cranking as base-line correction), and delta (measurable work as base-line correction) efficiencies were computed. A curvilinear relationship was found to exist between work rate and energy expenditure, which dictates that both delta and work efficiency will decrease with increments in work. Work (range 20–29%) and delta (range 14–30%) efficiencies decreased with increases in power output. The result that gross efficiency (range 6–15%) increased with increments in work was due to the decreasing effect of the resting metabolic rate on the total energy expended. Gross, work, and delta efficiencies were lower (P less than 0.05) at 90 rpm when compared with the same work rate at 50 and 70 rpm. Although all of the exercise efficiencies tended to be lower at 70 rpm compared with work at 50 rpm, the difference was significant (P less than 0.05) only at 45 and 60 W. These data suggest that delta and work efficiencies during ACE are decreased with increments in either speed or power output. However, gross efficiency increases as a function of power output but decreases as a function of speed of movement.