Relationships Between Electromyographic Characteristics, Mechanical Work Efficiency and Body Temperatures During Running Exercise Test in Men

The purpose of this study was to compare the changes in mechanical work efficiency, body temperatures (mean skin, local skin and mean body temperatures) and bioelectrical muscle activity of the vastus lateralis muscle in untrained male subjects (n=8) performing a dynamic exercise test on a treadmill. The relationships between EMG characteristics and blood lactate concentration were also investigated. The subjects ran at 1% grade with progressive speed of running until volitional exhaustion. During exercise, external work (determined by Snellen’s formula), energy expenditure (determined by measuring oxygen uptake and respiratory exchange ratio), mechanical work efficiency (E%), surface electromyography (EMG), aural, mean body, mean skin and local skin temperatures were determined. EMG was sampled at 1000 Hz and stored in 5/60 s intervals. Mean power frequency (MPF) and average amplitude of EMG (AEMG) were analyzed from row EMG. The amplitude of EMG signals during running correlated negatively with E% (r=-0,548) and positively with blood LA concentration (r=0,442), while MPF correlated positively with mean skin (r=0,358) and local skin (r=0,446) temperatures. The relationships between MPF from one side and mean body temperature and E% from the other were not significant. These findings suggest that: 1) the amplitude of EMG signals is a good indicator of muscle activity 2) the frequency of EMG power spectrum is dependent on changes in skin temperature but it does not well reflect changes in motor unit recruitment during dynamic exercise.