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Predicting the effect of muscle length on fatigue during electrical stimulation
Author(s) -
Marion M. Susan,
Wexler Anthony S.,
Hull Maury L.,
BinderMacleod Stuart A.
Publication year - 2009
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.21459
Subject(s) - muscle fatigue , functional electrical stimulation , ankle , electromyography , mathematics , mechanics , physical medicine and rehabilitation , stimulation , physics , medicine , anatomy
Mathematical models have been developed to predict fatigue during functional electrical stimulation, but the predictive accuracy at different muscle lengths is unknown. The objectives of our study were to: (1) experimentally determine the relationship between knee extension angle (20°, 40°, 65°, and 90°) and fatigue of the quadriceps muscles, and (2) predict that relationship using a mathematical model. A computer‐controlled stimulator sent trains of pulses to surface electrodes on the thighs of five subjects while forces were measured at the ankle. A two‐component mathematical model was developed. One component accounted for force, and the other accounted for fatigue. The model was fit to the data, and parameters were identified at 90°. The fitted subject‐averaged r 2 value was 0.89. The model was used to predict fatigue at the remaining angles, and the subject‐averaged r 2 values were >0.75. Therefore, at least 75% of the variability in the measurements was explained by the model. The force model is explicitly dependent on angle, and the fatigue model is explicitly dependent on force; therefore, the dependence of fatigue on knee angle was implicit. Muscle Nerve, 2009