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Predicting fatigue during electrically stimulated non‐isometric contractions
Author(s) -
Marion M. Susan,
Wexler Anthony S.,
Hull Maury L.
Publication year - 2010
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.21603
Subject(s) - isometric exercise , functional electrical stimulation , torque , muscle fatigue , physical medicine and rehabilitation , biomedical engineering , electromyography , simulation , computer science , medicine , physical therapy , stimulation , physics , thermodynamics
Mathematical prediction of power loss during electrically stimulated contractions is of value to those trying to minimize fatigue and to those trying to decipher the relative contributions of force and velocity. Our objectives were to: (1) develop a model of non‐isometric fatigue for electrical stimulation–induced, open‐chain, repeated extensions of the leg at the knee; and (2) experimentally validate the model. A computer‐controlled stimulator sent electrical pulses to surface electrodes on the thighs of 17 able‐bodied subjects. Isometric and non‐isometric non‐fatiguing and fatiguing leg extension torque and/or angle at the knee were measured. Two existing mathematical models, one of non‐isometric force and the other of isometric fatigue, were combined to develop the non‐isometric force–fatigue model. Angular velocity and 3 new parameters were added to the isometric fatigue model. The new parameters are functions of parameters within the force model, and therefore additional measurements from the subject are not needed. More than 60% of the variability in the measurements was explained by the new force–fatigue model. This model can help scientists investigate the etiology of non‐isometric fatigue and help engineers to improve the task performance of functional electrical stimulation systems. Muscle Nerve, 2010