External power output changes during prolonged cycling with electrical stimulation
D. Theisen , C. Fornusek , J. Raymond , G. M. Davis
This study analysed external power output and physiologic responses in 5 individuals with paraplegia during 40 minutes of electrical stimulation leg cycle exercise. Cycling was performed on a motor-driven isokinetic ergometer that enabled precise determinations of power output. Electrical stimulation was increased to 120-140 mA within the first 5 minutes and remained constant thereafter. Power output increased to 10.7 ± 3.0 W after 2 minutes, dropped to 5.3 ± 1.8 W after 6 minutes and subsequently recovered to 8.2 ± 2.2 and 6.1 ± 2.3 W after 19.5 and 40 minutes, respectively. Oxygen consumption increased to 0.47 ± 0.09 l/min after 6 minutes and declined during the second half of the exercise bout. Gross mechanical efficiency after 19.5 minutes was elevated compared with the value after 6 minutes. Heart rate was significantly increased at the end of the trial. The time-dependent variability of power output and physiological responses question the concept of steady state for this form of exercise.
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