RESPIRATORY SINUS ARRHYTHMIA DURING EXERCISE IN AEROBICALLY TRAINED AND UNTRAINED MEN

Respiratory sinus arrhythmia (RSA) was examined in aerobically trained (AT) and untrained (NT) college-aged males during 12 periods consisti ng oi a 3-min sitting baseline, six common 3-min absolute exercise sta ges, and five 3-min recovery stages that followed voluntary exhaustion to determine the relationship of work and training status to parasymp athetic influence upon the heart. RSA systematically decreased during absolute exercise, was observed at heart rates (HR) above 100 beats.mi n(-1), and progressively increased during recovery. Additionally. inde pendent of work stages, comparative regression analyses were conducted for both the exercise and recovery phases, separately, in which HR wa s regressed on RSA, as well as RSA on %(V) over dot(2max), to contrast the obtained relationships for the AT and NT. No differences were rev ealed as a function of endurance training status as the slopes and int ercepts obtained for the two groups from each of these analyses were s imilar. The within-subject correlations between RSA and %(V) over dot (2max), calculated for each of the individuals across all 12 periods, were consistently negative. Between-subjects correlations of RSA with RR and tidal volume were predominantly nonsignificant, indicating that RSA, as measured here, is independent of individual differences in ve ntilatory activity and, as such, san be compared between groups during exercise. The findings demonstrate that RSA is detectable during both exercise and recovery. even at HR beyond 100 beats.min(-1), and revea ls a similar relationship to HR and metabolic state in both aerobicall y trained and untrained populations.