ABSTRACT
The exercise intensity spectrum is composed of identifiable ‘exercise intensity domains’, within which predictable physiological and perceptual responses can be observed. These domains, in turn, are separated by specific metabolic thresholds, namely the lactate threshold (LT) and the maximal steady state (MSS) or critical power (CP). This chapter aims to outline the physiological basis of the thresholds and to broadly describe how exercise testing should be constructed to identify them. The metabolic thresholds of interest, therefore, are the LT and its ventilatory and gas exchange equivalents and the MSS or CP. The protocol used to determine the LT should ensure that each stage is long enough for the participant to achieve a steady state, if possible, and provide a sufficiently small resolution of the threshold itself. The heavy-severe domain boundary typically occurs halfway between the LT and VO2max. In recent years alternative approaches have been developed to characterise the heavy-severe domain boundary, including the 3-min all-out test.
