DISCUSSION

The present study showed that one month of yoga training increased tweezer dexterity scores significantly in volunteers but not in deputed subjects. A retest effect could be ruled out as the groups who did not practice yoga showed no change.

Manual dexterity and the ability to perform rapid, fractionated movements depends on the presence of an opposable thumb (9) as well as on monosynaptic connections between the primary motor cortex and the ventral horn motor neurons in the cervical spinal cord (10). For example, in certain new-world primates where the corticospinal fibres end on neurons in Rexed's laminate of the intermediate zone, dexterity is markedly less.

Dexterous or skilled actions depend on the speed of gross movements of hand and arms, manual rhythm, and co-ordination of eye and finger control (11). The present study showed that the practice of yoga improved the performance in the tweezer dexterity task under assessment. An indirect correlation between high anxiety and poor performance in a motor task using a peg board was inferred by Stocker (12), who observed, a trend of least efficient motor performance correlated with high anxiety. Yoga practice for four to eight weeks has been shown to reduce symptoms and objective indicators of anxiety in patients with anxiety neurosis (13). Hence the anxiety-reducing effect of yoga may be responsible for the improvement in tweezer dexterity scores observed in the present study.

The difference in the response of the two groups who received yoga training could be related to three factors viz. (i) age, (ii) gender, and (iii) motivation.

The group average age of the volunteers for yoga training was 23.1 ± 4.4 years, whereas the average age of the deputed subjects was 32.5 ± 4.1 years. However there were four subjects who had exactly the same age in the two groups. The average percentage change among these four volunteers was 20.4%, whereas the four age matched, deputed subjects had an average percentage increase of 2.3%. Though there were only four age matched subjects among the two groups, these results suggest that the differences in age may not have contributed to the differences in performance between the two groups as the same trend was observed. Also, as described earlier, in a previous report the performance in a peg moving task was stable between the third and fifth decade of life (6). While the peg moving task was not same as the dexterity task used in the present study, the results of the peg moving study (6) may be extrapolated to support the conclusion that age differences were not responsible for the differences in performance between the volunteer and the deputed groups in the present study.

In the present study there was also no effect of gender on the dexterity scores after yoga, as the day 30 (after yoga) scores of the male and female volunteers were not significantly different. However the scores of both these groups were significantly higher than the day 30 scores of the deputed subjects, who were all males. These results suggest that gender differences did not influence the outcome.

The difference in motivation to learn yoga therefore remains the factor most likely to have influenced the performance of subjects in the dexterity task. It would have been preferable to have studied a non-yoga motivated group, but this was not possible in the present study. Further studies on groups receiving yoga training, in which motivation of each subject is rated and correlated with objective assessments, would help in understanding the contribution of this factor.