Hysteresis behaviour of psychobiological variables during exercise

Abstract Objectives The rating of perceived exertion (RPE) and the heart rate (HR) have been widely studied and monitored during exercise, but their hysteresis behaviour is still unexplored. Our aim was to study the hysteresis behaviour of RPE and HR in triathletes and non-athletes. Design Cross-sectional study. Method Eighteen triathletes at different competitive levels (elite n = 9, non-elite n = 9) and ten students were tested while cycling and running, using a pyramidal protocol (incremental/decremental workloads). The hysteresis area, considered positive when values of the dependent variables (RPE and HR) at the same workload were higher in the decremental phase than in the incremental phase, and vice versa for the negative areas, was calculated in all tests. The Wilcoxon matched-pairs test and Kruskal Wallis ANOVA were applied to detect intra- and inter-group differences, respectively, of RPE and HR values during the incremental and decremental phases, as well as between cycling and running. Results The following results were observed: a) an incoherent relationship of RPE with HR and workload, b) positive hysteresis areas of RPE and HR in all groups during cycling and running, c) a partial negative hysteresis area of RPE, but not of HR, in the triathlete groups, d) larger hysteresis areas of RPE and HR in students than in triathletes, and e) larger hysteresis areas in cycling than in running. Conclusions the study of the hysteresis behaviour of RPE and HR reveals the history dependency of both variables, highlights their incoherent or non-unique relationship during a pyramidal exercise, and questions their widely assumed linear association to workload intensity. The hysteresis area is proposed as a new non-invasive marker of exercise stress and tolerance that should be further investigated.