In the present randomised study, we found that a breathing exercise program derived from yoga is beneficial for the cardiorespiratory system in healthy elderly subjects. Yoga respiratory training resulted in significant improvements in PEmax and PImax. In addition, yoga respiratory training produced a significant decrease in the LF component of heart rate variability and thus a shift in the sympathovagal balance towards a reduction in sympathetic predominance.
This study has some limitations. The sample was composed of highly motivated healthy volunteers who were used to yoga practice; the general elderly population may find it difficult to learn the respiratory exercises. In addition, the results should be extrapolated with caution to elderly subjects with significant comorbidities, which are extremely common in this age group. On the other hand, the study design allowed us to evaluate heart rate variability without the confounding effects of drugs, including β-blockers, that may interfere with autonomic modulation. The paced breathing during the measurement of heart rate variability may have influenced autonomic variables. On the other hand, yoga practitioners tend to breathe more slowly than non-practitioners, and this would have the effect of shifting the respiratory sinus arrhythmia into the LF band, thus giving the false impression of increased sympathetic activity despite increased parasympathetic predominance. Therefore, paced breathing allowed us to avoid the confounding effects of respiratory training on the respiratory pattern of breathing that would in turn directly affect heart rate variability. Our study showed no effects of yoga respiratory training on spontaneous baroreflex measured by linear analysis. Spontaneous baroreflex may show different results depending on the method of analysis. However, we have found no differences between groups when spontaneous baroreflex was analysed by the squared root of the ratio of the autoregressive powers of R–R interval and systolic blood pressure series in the LF and HF ranges (data not shown).26
Finally, the observation of non-significant effects of yoga training on spontaneous baroreflex and quality of life may be at least in part due to the small sample size.
The progressive loss of muscle mass seen in ageing may be partly responsible for the reduced respiratory capacity in the elderly.27
Physical exercise training has been shown to be beneficial for the elderly and to increase fitness and aerobic capacity.28
The effects of respiratory exercises may vary according to the time of intervention, exercise protocol and population studied. While several previous studies investigated the acute effects of respiratory exercises on both the respiratory9
and cardiovascular9 10
systems, one of the strengths of our study is that we set up a long-term training program. The results may also be dependent on the population studied. Vempati et al29
found an increase in FEV1
after 8 weeks of yoga training in a group of patients with asthma. Our subjects did not have pulmonary disease, and the increases in FVC and FEV1
after yoga training were marginal and did not reach statistical significance compared with the control group. Previous studies reporting negative results of yoga training on FVC and FEV130 31
only investigated the effects of slow breathing. The respiratory exercises used in this protocol (Bhastrika pranayama) are specifically suited to the respiratory system, and exercise both inspiratory and expiratory muscles. Kapalabhati (fast expirations) involve abdominal wall muscles used for expiration, while surya bedhana (slow breath with retention) affects inspiratory muscles in either the inspiratory (concentric isokinetic contraction), retentive (isometric contraction) or expiratory (eccentric isokinetic contraction) phases. Thus, Bhastrika pranayama may increase expiratory as well as inspiratory muscle performance, improving the capacity of the thoracic compartment to create negative and positive pressures in the respiration process. Although the elderly subjects in the present study had PEmax
values in the normal range at study entry, both parameters improved significantly after the yoga program.
The respiratory and cardiovascular systems are tightly linked. In addition to the beneficial effects on the respiratory system, yoga respiratory training resulted in a significant decrease in sympathovagal balance and a marked and significant decrease in the LF component of heart rate variability. These parameters indicate a positive shift in cardiac autonomic modulation towards parasympathetic predominance. It has been previously shown that slow comfortable breaths lead to an increase in parasympathetic modulation.9
Bernardi et al11
found preserved oxygenation without increased minute ventilation in response to hypoxic exposure in yoga trainees compared with a non-trained control group. The authors suggest that yoga respiratory training produced a different adaptive cardiorespiratory strategy. Consistent with this hypothesis, Pomidori et al8
showed that yoga breathing exercises induced greater resting oxygen saturation in patients with chronic obstructive pulmonary disease. We speculate that the effects of yoga respiratory training on sympathovagal balance may be due to a central modulator regulatory effect. Since frailty increases with ageing8
and is characterised as a decrease in many cardiovascular4–7
parameters, it may be that the improvements in respiratory function and cardiovascular autonomic modulation may slow down the frailty process and increase quality of life in elderly subjects. In fact, at least two studies32 33
have investigated the effects of a yoga-based lifestyle modification on subjective well-being, and verified its effectiveness.
In conclusion, 4 months of respiratory training in Bhastrika pranayama increased respiratory function and improved cardiac parasympathetic modulation in a group of healthy elderly subjects. Yoga respiratory training is easy to perform at low cost and may positively influence the cardiorespiratory system. Since frailty develops with ageing with decreases in many cardiovascular4–6
parameters, further studies will be necessary to test the hypothesis that improvements in both respiratory function and cardiovascular autonomic modulation may counteract the development of frailty. The effects of yoga may be broader than observed in this study. At least two studies32 33
have shown that yoga-based lifestyle modification is beneficial for subjective well-being. These effects together may slow down the natural progression of frailty with ageing.