A number of reports have described the physiological changes associated with diverse relaxation techniques (Harding, 1996; Smith, Amutio, Anderson, & Aria, 1996; Broms, 1999). Relaxation guided by instructions has been shown to be more effective in reducing physiological arousal than a control session of supine rest (Sakakibara, Takeuchi, & Hayano, 1994). Also, after exercise the heart rate and blood pressure returned to the baseline level sooner, when subjects practiced guided relaxation compared with recovery after rest while supine or seated (Bera, Gore, & Oak, 1998). Specific relaxation techniques may be more effective for certain persons, based on their psychophysiological characteristics (Weinstein & Smith, 1992), and isometric "squeeze" relaxation has been found to be more likely to induce relaxation compared to meditation, for individuals who have difficulty focusing and less developed stress coping strategies (Weinstein & Smith, 1992).
However, most reports describe post relaxation effects on a group level, regardless of individual differences at base line. Also, most instructions to relax make use of imagery (Rickard, Collier, McCoy, Crist, & Weinberger, 1993) and breathing (Toivanen, Lansimies, Jokela, & Hanninen, 1993). With this background, the present study was conducted to assess whether the present subjects who had a group mean of 30.2 months experience of yoga practice, showed greater reduction in physiological arousal after "Guided relaxation" (with instructions) as compared to "Supine Rest" (without instructions). This was considered interesting as both practices (i.e., relaxation with instructions and rest in the supine position are considered to be relaxing by yoga practitioners). Also yoga practice is believed to help reach a state in which external instructions to relax are no longer necessary. Guided relaxation was based on yoga, with breath awareness and chanting, as is usual in yoga practice (Nagendra & Nagarathna, 1988). (ii) As a second aim, subjects were categorized as two groups, based on their baseline levels of LF/HF ratio of the heart rate variability components, which indicate the cardiac autonomic control, and the changes of the two categories of subjects after guided relaxation are presented separately.