To assess the effect of supramaximal intermittent exercise on long-term cardiac autonomic activity, inferred from heart rate variability (HRV).
Eleven healthy males performed a series of two consecutive intermittent 15-s runs at 95% VIFT (i.e., speed reached at the end of the 30-15 Intermittent Fitness Test) interspersed with 15 s of active recovery at 45% VIFT until exhaustion. Beat-to-beat intervals were recorded during two consecutive nights (habituation night and 1st night) before, 10 min before and immediately after exercise, as well as 12 h (2nd night) and 36 h (3rd night) after supramaximal intermittent exercise. The HRV indices were calculated from the last 5 min of resting and recovery periods, and the first 10 min of the first estimated slow wave sleep period.
Immediate post-supramaximal exercise vagal-related HRV indices were significantly lower than immediate pre-supramaximal exercise values (P < .001). Most vagal-related indices were lower during the 2nd night compared with the 1st night (eg, mean RR intervals, P = .03). Compared with the 2nd night, vagal-related HRV indices were significantly higher during the 3rd night. Variables were not different between the 1st and 3rd nights; however, we noted a tendency (adjusted effect size, aES) for an increased normalized high-frequency component (P = .06 and aES = 0.70) and a tendency toward a decreased low-frequency component (P = .06 and aES = 0.74).
Results confirm the strong influence of exercise intensity on short- and long-term post exercise heart rate variability recovery and might help explain the high efficiency of supramaximal training for enhancing indices of cardiorespiratory fitness.
Al Haddad is with the Laboratoire de Recherche, EA 3300 «APS et Conduites Motrices : Adaptations Réadaptation», Faculté des Sciences du Sport, Université de Picardie Jules Verne, Amiens, France. Laursen is with the School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia. Ahmaidi and Buchheit are also with the Laboratoire de Recherche, EA 3300 «APS et Conduites Motrices : Adaptations Réadaptation», Faculté des Sciences du Sport, Université de Picardie Jules Verne, Amiens, France.