1. Introduction
Improvement in athletic performance is highly correlated to the training load of the athlete 1,2 and to the alternation between periods of intense and light training. 3–5 Indeed, sport participation characteristics in high-level sports require careful modulation of both training volume and intensity, in the short term and the long term, to help athletes reach their highest performance level.6 Monitoring of training load is fundamental for trainers to fine-tune the athlete’s daily program.7 Although period of training should be quantifiable, there is no single indicator or methodology applicable to different training types. Endurance athletes generally use volume as the main outcome, but this does not account for training intensity. Similarly, the latter aspect also deserves attention in sports characterized by high demands in strength and power.