DISCUSSION

The purpose of this study was to determine if yoga training modulates the cardiovascular response to exercise and its time course after the exercise. Yoga training for two months resulted in a significant decrease in basal HR and BP. Calculated RPP and Do P also decreased significantly. Since RPP is an index of myocardial oxygen consumption and load on the heart (7), our results indicate that after yoga training, a given level of exercise is less taxing for the heart. A decrease in DP after yoga training has also been reported by Ray et al (8) who attributed this to a reduction in sympathetic activity. Exercise produced a marked and significant increase in the parameters measured except DP which showed a significant decrease in response to exercise stress. After yoga training, these exercise induced changes (i.e. decrease in DP and increase in other parameters) were significantly reduced. It is interesting to note that before yoga training only MP had returned to pre-exercise value at the end of 10 minutes study period. After yoga training, SP, DP and PP also returned to the pre-exercise basal values indicating faster recovery of cardiovascular parameters after yoga training. Our results are similar to the recent findings of O’ Sullivan and Bell (9) who have reported that physical training blunts the pressure, tachycardiac and vasodilator responses and attributed this to blunting of sympathetic vasodilator activation. Although Bhattacharya & Krishnaswami (1) concluded that yoga training does not produce any marked effect on the physiological parameters of the subjects, there are several reports of beneficial effects of yoga training on physiological functions. Bera & Rajapurkar (4) have reported that yoga training results in significant improvement in cardiovascular endurance and anaerobic threshold. This is consistent with the findings of Muralidhara & Ranganathan (2) that yoga training improves physical efficiency as indicated by significant increase in cardiac recovery index measured by Harvard step test. Our findings of lesser increase in BP, HR and RPP after yoga training are consistent with the findings of Ray et al (8, 10) that yoga training increases muscular endurance, delays onset of fatigue and enables one to perform work at lesser VO2 max. Palatini (11) has reported that in comparison to normotensives, the increase in DP in response to isometric exercise is substantially more in hypertensives. An exaggerated cardiovascular reactivity to the stressors is known to be a risk factor for cardiovascular diseases whereas reduced reactivity is an indicator of fitness. Therefore a reduction in exercise-induced stress on cardiovascular system by yoga training has physiological significance as well as clinical applications. 

ACKNOWLEDGEMENTS 

We gratefully acknowledge the financial support from the Director, Central Council for Research in Yoga & Naturopathy (CCRYN), New Delhi.