Effect of Hot Conditions on Voluntary Control of Motor I.jnti' Activity in Humans

Cold ambient temperature conditions are known to affect muscle performance characteristics, such as force output, power, and contraction velocity [ 11. Spectral and aniplitude characteristics of electromyogram (EMG) during inuscle contraction are modulated by the cold and hot ambient temperature [2]. Voluntary control of single motor unit action potentials (MUM') is a widely used method for investigation of fine movements. Local cold application to skin has been shown to be of contradictory impact on the effectiveness of single MUAP control [3]. General moderate cooling of the organism demonstrated very little effect on the MUAP control, even in the state of vigorous cold shivering [4]. The influence of hot environment conditions on fine voluntary control of single motor unit activity still has not been investigated. The aim of the present study was to investigate how effectively man recruits the ordered number of motor unit action potentials in hot versus temperate conditions.