Chrono-Physiological Specificity: Differential Circadian Responses to Training in Runners, Jumpers, and Throwers

Abstract Introduction: While circadian variations in athletic performance are recognized, it is unclear if these rhythms are uniform across different athletic disciplines. Athletes in power (throwers), endurance (runners), and mixed-power (jumpers) events have distinct physiological profiles, which may lead to different intra-day responses to training. Objective: This study aimed to analyze and compare the circadian variations of motor and cardiac variables among three distinct groups of state-level athletes—runners, jumpers, and throwers—throughout a bimodal training day. Methods: Sixty male athletes were stratified into three groups: runners (n=20), jumpers (n=20), and throwers (n=20). Key motor (speed, agility) and cardiac (cardiorespiratory endurance, resting pulse rate) variables were measured at four time points: 06:00, 10:00, 14:00, and 18:00, corresponding to before and after morning and evening workouts. Results: Analysis of the data reveals distinct patterns of circadian response among the groups. While all groups showed performance peaks post-workout, the magnitude of change differed. Runners, for example, demonstrated the most pronounced improvement in cardiorespiratory endurance after the morning session. Throwers, whose sport is less aerobically demanding, showed a less significant change in this variable but maintained high levels of power-related metrics. Jumpers exhibited a mixed profile. Furthermore, resting pulse rate recovery patterns appeared to differ, with runners showing a more rapid return to baseline compared to the other groups, particularly after the evening session. Conclusion: Circadian responses to training are not universal but are discipline-specific. The physiological demands of an athlete's sport appear to moderate their intra-day fluctuations in motor and cardiac function. This suggests the need for chrono-physiological specificity in training design, where workout timing and intensity are tailored not just to general circadian principles, but also to the unique profile of the athlete's event.