Abstract
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 r2 value was 0.89. The model was used to predict fatigue at the remaining angles, and the subject-averaged r2 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.
Original language | English (US) |
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Pages (from-to) | 573-581 |
Number of pages | 9 |
Journal | Muscle and Nerve |
Volume | 40 |
Issue number | 4 |
DOIs | |
State | Published - Oct 2009 |
Keywords
- Functional electrical stimulation (FES)
- Isometric
- Mathematical model
- Muscle fatigue
- Muscle length
ASJC Scopus subject areas
- Clinical Neurology
- Cellular and Molecular Neuroscience
- Physiology (medical)
- Physiology