Exercise limitation or regulation?
Much of how we think and interpret the basis of human physical performance is related to the notion of biological limitation. That is, that a biological system has by nature some upper limit that if exceeded will fail and cellular catastrophe will ensue. The basis of a physiological limitation is a necessary construct because it underpins our understanding of the capabilities that can be manipulated through training. As such, there have been a number of factors proposed to limit human exercise performance, usually referred to as the ‘cardinal exercise stopper’. These include muscle acidification, glycogen depletion, respiratory muscle fatigue, perception of effort, muscle pain and a maximally achieved heart rate. Although these factors relate to physiological limitation, the competing model of exercise regulation presents a departure from this classical view to one that posits that a system built to regulate muscular-metabolic rate by psycho-physiological feedback allows humans to optimally adjust their level of performance during heavy exercise. There is now good evidence that during high intensity cycling and running, individuals adjust their skeletal muscle recruitment strategy to enable the successful completion of the exercise bout. In this presentation, evidence for this alternative model of exercise regulation will be presented. In particular, evidence from studies where additional environmental strain has been imposed will illustrate that exercise regulation is perhaps an adaptation across multiple systems which work together to ensure survival rather than leading to cellular catastrophe.