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Estimation of critical end-test torque using neuromuscular electrical stimulation of the quadriceps in humans
Janzen, Natalie R. Hight, Robert E. Patel, Darshit S. Campbell, Jason A. Larson, Rebecca D. Black, Christopher D.
Janzen, Natalie R.
Hight, Robert E.
Patel, Darshit S.
Campbell, Jason A.
Larson, Rebecca D.
Black, Christopher D.
Abstract
Characterization of critical power/torque (CP/CT) during voluntary exercise requires maximal effort, making difficult for those with neuromuscular impairments. To address this issue we sought to determine if electrically stimulated intermittent isometric exercise resulted in a critical end-test torque (ETT) that behaved similar to voluntary CT. In the first experiment participants (n = 9) completed four bouts of stimulated exercise at a 3:2 duty cycle, at frequencies of 100, 50, 25 Hz, and a low frequency below ETT (Sub-ETT; ≤ 15 Hz). The second experiment (n = 20) consisted of four bouts at a 2:2 duty cycle—two bouts at 100 Hz, one at an intermediate frequency (15–30 Hz), and one at Sub-ETT. The third experiment (n = 12) consisted of two bouts at 50 Hz at a 3:2 duty* cycle with proximal blood flow occlusion during one of the bouts. ETT torque was similar (p ≥ 0.43) within and among stimulation frequencies in experiment 1. No fatigue was observed during the Sub-ETT bouts (p > 0.05). For experiment 2, ETT was similar at 100 Hz and at the intermediate frequency (p ≥ 0.29). Again, Sub-ETT stimulation did not result in fatigue (p > 0.05). Altering oxygen delivery by altering the duty cycle (3:2 vs. 2:2; p = 0.02) and by occlusion (p < 0.001) resulted in lower ETT values. Stimulated exercise resulted in an ETT that was consistent from day-to-day and similar regardless of initial torque, as long as that torque exceeded ETT, and was sensitive to oxygen delivery. As such we propose it represents a parameter similar to voluntary CT.
Keywords
fatigue, W′, occlusion, torque
Date
2018
Type
Journal article
Journal
European Journal of Applied Physiology
Book
Volume
118
Issue
7
Page Range
1407-1414
Article Number
ACU Department
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Open Access Status
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File Access
Controlled