DISCUSSION

In the present study, HGS and HGE increased significantly after six months of yoga training. This is consistent with our earlier finding that yoga training produces a significant increase in HGS (7). Raghuraj et al (9) have reported that pranayam training results in significant increase in the HGS of both hands. On the other hand, Dash and Telles (11) have concluded that yoga training produces an increase in motor speed for repetitive finger movements, but not in strength or endurance. The increase in HGS and HGE in our yoga group is consistent with the findings of Tran et al (10) who have reported that eight week hatha yoga training results in a significant increase in is kinetic muscular strength and isometric muscular endurance. Raju et al (15) have also reported that yoga training results in a significant increase in maximal work output with a significant reduced level of oxygen consumption per unit work. Some of the yogic postures in our study like bakasan, bhujangasan and shalabhasan involve sustained isometric contraction of the shoulder, chest and arm muscles. Consequent improvement in the strength and endurance of these muscles can explain the significant increase in HGS and HGE. Although HGS and HGE are simple methods to assess skeletal muscle strength and nutritional status, normative data on these parameters is limited. These tests can be used to determine the effectiveness of health-promoting programs like yoga training. They can also be used as objective clinical measures for determining the severity of the disease process and effectiveness of rehabilitation programs. Hence, there is a need to carry out further studies on these parameters in normal subjects and patients with neuromuscular and nutritional disorders. 

In the present study MEP and MIP increased significantly following six months of yoga training in our group I subjects. Our results do not agree with those of Gopal et al (16) who have reported a lower MEP in yoga trained subjects as compared to untrained ones. However, the present findings are consistent with those of our earlier work (7). Chen and Kuo (17) have reported that inspiratory muscle endurance is greater in physically active men than sedentary men. The increase in MEP and MIP in our yoga group indicates that yoga training improves the strength of the expiratory as well as inspiratory muscles. Mukh-bhastrika included in our present training program involves powerful strokes of exhalation, which trains the subject to make full use of diaphragm and abdominal muscles. Slow, deep and full exhalation and inhalation during mahat yoga and savitri pranayams also train the respiratory muscles. Respiratory muscles are vital and evaluation of their performance is important. Respiratory pressures are specific and sensitive indices of respiratory muscle strength and they are easy to measure and reproducible. Black and Hyatt (6) have demonstrated that their values are altered before there is alteration in other commonly used pulmonary function tests. Hence, evaluation of respiratory muscle strength is important from physiological as well as clinical point of view. Since the highest MEP is obtained at lung volumes of more than 70% of total lung capacity and the highest MIP is obtained at lung volumes of less than 50% of total lung capacity (16), we measured MEP after full inspiration and MIP after full expiration.

Our present findings that pulmonary function tests such as FEV, FEV1 and PEFR increased significantly after yoga training is consistent with earlier studies. Bhole et al (1) have reported a significant increase in vital capacity after three weeks of yoga training. In a study on 287 college students (both men and women), Birkel and Edgren (2) found that yoga training produced a significant improvement in vital capacity across all categories of subjects that included smokers, asthmatics as well as those with no known lung disease. Joshi et al (5) have reported that pranayam training improves ventilatory functions in the form of increase in FEV, FEV1 and PEFR. Makwana et al (3) and Yadav and Das (4) also found a significant increase in these parameters after yoga training. Thus our results are consistent with the findings of other workers who have reported beneficial effects of yoga training on pulmonary function as measured by spirometry. Vital capacity is a critical component of good health and its determination is important for normal subjects, smokers and patients with respiratory and cardiovascular conditions. PEFR is an inexpensive, accurate and simple test for measuring airway resistance and strength of expiratory muscles. 

The baseline values of our subjects are lower than those reported in the literature. The values for European subjects are known to be higher than the age and sex matched Indian subjects and this has been attributed to racial background and nutritional status. Our subjects were sedentary, from low socioeconomic background and had low weight and BMI. Hence their baseline values were lower than the values reported in the literature. Yoga training resulted in appreciable and statistically significant improvement in all the parameters measured in this study. In conclusion, the present study shows that six month yoga training produces a significant improvement in handgrip strength and endurance, respiratory pressures and spirometric values and this improvement is appreciable in underweight children.

ACKNOWLEDGEMENTS 

The authors wish to thank Department of Science and Technology, Government of Pondicherry and Central Council for Research in Yoga and Naturopathy (CCRYN), New Delhi for funding this research project. We also thank Mr. G. Kumaran for assisting in the yoga training and Miss R. Lalithambiga for her technical assistance.