A muscle temperature compensation technique for EMG fatigue measures.

Abstract

The use of electromyogram-based fatigue measurements during high-intensity, dynamic activities is confounded by the accompanying increase in muscle temperature. The purpose of this communication was to demonstrate the use of a muscle temperature compensation technique for electromyogram (EMG) fatigue measurements. Subjects were six healthy men (mean age 30.8 +/- 5.6 yr) with no recent history of lower extremity injury. In part 1 of this study, the relationship between muscle temperature and EMG mean power frequency was determined for the vastus lateralis muscle (VL). The VL was heated with diathermy to a temperature of approximately 39 degrees C. Isometric EMG data were collected during the performance of a nonfatiguing protocol as the muscle cooled (39-34 degrees C). In part 2 of this study, the subjects rode a lower-extremity ergometer at workloads of 25%, 50%, and 75% of their VO2max. Isometric EMG and intramuscular temperature data were collected from the VL during intermittent interruptions of the activity. The relationship between muscle temperature and EMG mean power frequency established in part 1 was used with the measured change in muscle temperature to correct for the effect of temperature on the EMG mean power frequency. The results from part 1 revealed a linear relationship between EMG mean power frequency and muscle temperature (N = 5, mean slope = 2.82 +/- 0.27 Hz. degrees C-1, R2 = 0.88 +/- 0.02). The mean slope was used as a muscle temperature compensation factor that quantified the influence of muscle temperature on EMG mean power frequency. For part 2, representative data from a single subject are presented to demonstrate the use of the muscle temperature compensation technique. A muscle temperature compensation technique for EMG mean power frequency analysis has been demonstrated. This technique corrects for the detrimental influence of muscle temperature changes on EMG fatigue measurements, thereby improving the efficacy of EMG fatigue measurements during high-intensity, dynamic activities that result in muscle temperature increases.