The 800-m (m) run is part of Physical Education classes in Cameroon, after which arrhythmias may occur during recovery. Hence, this study aimed at determining relationship between 800-m run loads on cardiac autonomic recovery among school adolescents. Forty-two male adolescents (aged [17 ± 1] years) performed 800-m. Post-exercise heart rate variability (HRV) was recorded during 5-min (min) (HRV5-min) and 15-min (HRV15-min) in time: Standard deviation of normal to normal (SDNN); Root mean square of successive differences (RMSSD) and frequency domain (LH: Low frequency, HF: High frequency, TP: Total power). Rating of Perceived Exertion (RPE) and blood lactate concentration (BLa) were measured after exercise. In HRV5-min, RPE was associated with SDNN (r = −0.44, p < 0.01) and RMSSD (r = −0.38, p < 0.05). BLa was correlated with SDNN (r = −0.38, p < 0.05) and RMSSD (r = −0.56, p < 0.001) in the time-domain, LF (r = −0.64, p < 0.001), HF (r = −0.58, p < 0.001) and TP (r = −0.61, p < 0.001) in frequency-domain. Moreover, RPE was correlated with LF (r = −0.44, p < 0.01), TP (r = −0.49, p < 0.01) while exercise duration with HF (r = −0.38, p < 0.05). In HRV15-min, BLa was correlated with RMSSD (r = −0.53, p < 0.001) and SDNN (r = −0.68, p < 0.001). RPE was negatively correlated SDNN (r = −0.53, p < 0.01) and RMSSD (r = −0.44, p < 0.01). BLa was associated with HF (r = −0.55, p < 0.001), TP (r = −0.50, p < 0.01) and RPE with LF (r = −0.51, p < 0.01), HF (r = −0.50, p < 0.01), TP (r = −0.49, p < 0.01). In addition, exercise duration was negatively linked to HF (r = −0.36, p < 0.05). This study outlined that in untrained adolescents an increase of 800-m loads is associated with a slow vagal indexes of HRV during the recovery. © 2023 Chengdu Sport University
