Effects of continuous and intermittent endurance exercise in autonomic balance, rating perceived exertion and blood lactate levels in healthy subjects

Abstract

PurposeThe aim of this study was to determinate the changes in the Autonomic Balance, Rating Perceived Exertion (RPE) and blood lactate after continuous versus intermittent exercise protocols. MethodsSeven active and healthy male (33±5.1 years) participated in the study. Each subject performed two exercise protocols: (i) a continuous exercise at 110% of the lactate threshold (CONT). The CONT protocol consisted in continuous running, and the distance covered was the same in meters as it was in the intermittent session, and (ii) an intermittent exercise at 100% of the Peak Treadmill Velocity (INTT). The protocol consisted of 30min of 15s running, interspersed with 15s of passive rest. Autonomic balance was assessed through the LF/HF ratio, before beginning the exercises, immediately finishing the exercises and 24h post-exercise; RPE was evaluated every 5min in each exercise protocol; and blood lactate was measured immediately after both protocols. Alpha level was set at P≤.05. ResultsAutonomic balance did not show significant differences between protocols (P=.60). RPE during INTT exercise was significantly higher than CONT exercise (P=.01). Blood lactate levels after exercise did not show significant differences (P=.68). Heart rate variability parameters in the time domain (mean RR and pNN50) show no statistical differences between both protocols pre and 24h post exercise (P=.24 and P=.61, respectively). ConclusionsThe data suggest that intermittent exercise is perceived more intense than continuous, although both protocols showed similar internal loads in autonomic balance and blood lactate levels.