Physiologic Effects of Yoga
March 1, 2001
Physiologic Effects of Yoga
March 2001; Volume 4; 29
The literature assessing the physiologic effects of aerobic training has relied on cardiopulmonary outcome measures. Several studies involving yoga have used these outcomes as well. Less has been quantified about yoga’s effects on strength, flexibility, and standardized measures of functioning used in the assessment of arthritis therapies.
Raju and colleagues compared physiological parameters including heart rate, blood pressure, minute ventilation, the oxygen and carbon dioxide content of expired air and blood lactate, and pyruvate levels in two groups of elite athletes.1 National competitors in judo, volleyball, and other sports were followed for two years by submaximal and maximal treadmill testing. One group performed their usual physical workouts, while the other group also practiced daily pranayama under the supervision of a yoga instructor.
Both groups significantly reduced oxygen consumption at rest after exercise. The experimental group also improved in oxygen consumption per unit work after exercise testing and had lower resting blood lactate levels. The authors suggested that pranayama practice could augment the known benefits of aerobic exercise. The study was limited by its small size and the heterogeneity of the participants and their training programs. Only 12 participants completed the full two-year study.
A second study used treadmill testing to evaluate the effect of four weeks of yoga training on six healthy female volunteers.2 Eight postures and breathing techniques were practiced daily during two 90-minute sessions. Maximal exercise testing was performed before and after the four-week period. At the end of the experimental intervention, all participants showed a significant reduction in percentage body fat with a corresponding increase in lean body mass. Participants also showed significant reductions in minute ventilation, oxygen consumption per unit work, heart rate, and respiratory quotient after exercise.
While this study documented that yoga practice led to rapid improvements in cardiorespiratory efficiency, the generalizability of the results to patients impaired by musculoskeletal disease is unclear. The participants in the study were physical education teachers with a mean age of 26 years.
Another study assessed blood pressure responses in sedentary, elderly participants recruited from the community, a group perhaps more reflective of patient populations with musculoskeletal disease.3 Two groups, comprised of 20 men and women each, underwent a six-week program of either exercycle-based or yoga-based training. The exercise bicycle was used for 20 minutes, preceded and followed by 10-minute warm-up and cool-down periods. Yoga training consisted of a warm-up followed by a series of static yoga postures and breathing exercises and a 20-minute relaxation period. At the completion of the study, both interventions had resulted in a reduction in heart rate and an increase in oxygen consumption following exercise. In addition, unlike those in the aerobic group, the yoga practitioners experienced an increase in baroreflex sensitivity, reflecting a change in parasympathetic activity, and suggesting an increase in vagal tone.
Grip strength is a standard outcome measure in studies of patients with arthritis of the hands. The effect of one pranayama (breathing control) technique on grip strength was assessed in another recent study.4 Grip strength was measured by dynamometer in a group of 130 teenagers attending a residential Indian yoga camp. Participants were randomly divided into five groups and instructed in five different breathing techniques, in addition to the same basic yoga training. Right nostril breathing, left nostril breathing, and alternate nostril breathing techniques all led to bilateral increases in grip strength, but breath awareness and hand gesture groups showed no improvement. The authors suggested that the observed differences might be related to reduced oxygen requirements or the training effect of doing additional breathing exercises compared to the two groups who did not improve.
References
1. Raju PS, et al. Comparison of effects of yoga and physical exercise in athletes. Indian J Med Res 1994;100:81-86.
2. Raju PS, et al. Influence of intensive yoga training on physiological changes in six adult women: A case report. J Altern Complement Med 1997;3:291-295.
3. Bowman A, et al. Effects of aerobic exercise training and yoga on the baroreflex in healthy elderly persons. Eur J Clin Invest 1997;27:443-449.
4. Raghuraj P, et al. Pranayama increases grip strength without lateralized effects. Indian J Physiol Pharmacol 1997:129-133.
March 2001; Volume 4; 29
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