Effects of hatha yoga training on heart rate and blood pressure recovery from exercise
PURPOSE: The primary purpose of this study was to determine the effects of yoga training on heart rate (HR) and blood pressure (BP) recovery from a standardized exercise bout. The researchers also aimed to determine if there is modulation of autonomic function, specifically enhanced vagal nerve reactivation (i.e., enhanced parasympathetic activity) and concomitant withdrawal of sympathetic activity, resulting from the yoga training. A quasi-experimental design was used. METHODS: Two groups of 18-25 year old subjects (n = 8 yoga, with 3 males and 5 females; n = 7 stretch and relax [S&R], with 3 males and 4 females) were recruited from activity courses at Humboldt State University. Subjects were tested before and after 4 weeks (two times per week, at 50 min/session) of yoga or S&R class. A graded exercise test on a cycle ergometer was used to determine maximal oxygen uptake (VO2max) pre-intervention. Recoveries (R) from two submaximal tests (at 40% of VO2max and 85% HRmax), administered before and after the interventions were used to measure HR, systolic blood pressure (SBP) and diastolic blood pressure (DBP) at 0, 2, 4, and 6 minutes, as well as T30 and Delta 60 (measures of HRR and autonomic function). To determine if there were differences in the hemodynamic variables (HR, SBP, DBP, and rate-pressureproduct [RPP]) between pre- and post-intervention depending on group and time-period of recovery, four 2 X 2 X 4 mixed factorial ANOVAs were computed (time X group X time-period of recovery). Two 2 X 2 (time X group) mixed-factorial ANOVAs were computed to determine if there were differences in HRR. RESULTS: No significant interactions (p > .05) between time, group, and time-period of recovery were found for HR, SBP, DBP, or RPP. Similarly, no main effects for group were found with respect to these four dependent variables. As expected, there was a significant main effect for timeperiod of recovery (i.e., 0, 2, 4 and 6 minutes) for HR (p = .000), SBP (p = .000), and RPP (p = .000), but not for DBP (p = .142). A significant effect for time (pre- vs. postintervention) was found for SBP (p = .028), but not for HR (p = .622), DBP (p = .076) and RPP (p = .094). No significant (p > .05) interactions or main effects between time and group were found with respect to either HRR variable. DISCUSSION/ CONCLUSION: Across all time-periods of recovery, the interventions collectively resulted in significantly lower mean SBP, with trends towards lower DBP and RPP postintervention when compared to pre-intervention. Yoga training did not result in any better recovery from an exercise challenge than did S&R. No significant changes in autonomic function (HRR) were observed. Absence of a non-intervention control group, the short duration of the interventions, and measurement issues may have influenced the findings.