Relationship between myoelectric signals and blood lactate during incremental forearm exercise

Five men performed incremental forearm exercise by using a modified hand grip dynamometer while external loads (1 Kg metal plate) were added at each succeeding minute until volitional exhaustion occurred. Myo-electric signals were recorded from the belly of the flexor carpi radialis-palmaris longus. By the use of an LSI-11/23 minicomputer, the digitized data were processed for integrated EMG (IEMG) and mean power frequency (MPF) by means of 512 point fast Fourier transform. Data from individuals revealed that venous lactate correlated highly with IEMG (range: 0.977 to 0.857, P less than 0.001) and MPF (-0.960 to -0.862, P less than 0.001) during the incremental exercise. Group data revealed that none of the parameters tested showed any significant changes between the onset of lactate threshold (LT), i.e., the onset of abrupt increases in lactate, and one minute prior to LT. However, when these parameters were tested between LT and one minute after LT, significant differences were observed for venous lactate (t = 3.16, P less than 0.05), IEMG (t = 3.02, P less than 0.05) and MPF (t = 3.84, P less than 0.05). It was concluded that analysis of myo-electric signals may provide a non-invasive measure of lactate threshold after which dynamic equilibrium of lactate production and utilization becomes unbalanced during the incremental forearm exercise.