Whole body oxygen uptake and evoked torque during subtetanic isometric electrical stimulation of the quadriceps muscles in a single 30-minute session.
OBJECTIVE
To evaluate the time course of fatigue in torque output and oxygen uptake during isometric subtetanic neuromuscular electrical stimulation (NMES) to facilitate the design of NMES-based rehabilitation protocols that can accumulate a defined aerobic exercise volume within a given time period.


METHODS
Single-arm intervention study with within-subject comparisons.


METHODS
University research laboratory.


METHODS
Volunteer sample of healthy men (N=11; mean age, 34.2 ± 11.5 y; range, 19-53 y; body mass, 79.1 ± 11.7 kg; range, 58-100 kg).


METHODS
A single 30-minute session of continuous bilateral isometric quadriceps NMES at 4 Hz evoking a mean twitch amplitude of 12% of the maximum voluntary contraction.


METHODS
Whole body oxygen consumption rate (V˙o2), and evoked torque were measured simultaneously throughout.


RESULTS
Mean increment in V˙o2 was 596 ± 238 mL/min, and average exercise intensity during the session was 3 ±.47 metabolic equivalents. The V˙o2 and torque declined slowly at a rate of -.54%±.31% and -.47%±.57% per minute, respectively.


CONCLUSIONS
Despite having a higher incremental V˙o2, the observed fatigue rate was considerably less than that previously reported during intermittent isometric tetanic stimulation, suggesting that subtetanic isometric NMES is more sustainable for exercise interventions aimed at accumulating a therapeutic aerobic exercise volume.
School of Electrical, Electronic and Communications Engineering, University College, Dublin, Ireland. Electronic address: minogue@bmr.ie.
Conor M
CM
Minogue
School of Public Health, Physiotherapy and Population Science, University College, Dublin, Ireland.
Brian M
BM
Caulfield
School of Electrical, Electronic and Communications Engineering, University College, Dublin, Ireland.
Madeleine M
MM
Lowery
D000328:Adult; D004558:Electric Stimulation; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D008297:Male; D055686:Metabolic Equivalent; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology; D010101:Oxygen Consumption / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D012016:Reference Values; D019415:Torque; D055815:Young Adult
Electric stimulation; Fatigue; Oxygen consumption; Rehabilitation