The aim of this study was to critically observe the energy expenditure, exercise intensity and respiratory changes during a full yoga practice session. Oxygen consumption (trueV˙O2), carbon dioxide output (trueV˙CO2), pulmonary ventilation (V˙E), respiratory rate (Fr) and tidal volume (VT), were measured in 16 physical posture (asanas), five yoga breathing maneuvers (BM) and two types of meditation. Twenty male (age 27.3 ± 3.5 years, height 166.6 ± 5.4 cm and body weight 58.8 ± 9.6 kg) yoga instructors were studied. Their maximal oxygen consumption (trueV˙O2max) was recorded. The exercise intensity in asanas was expressed in percentage trueV˙O2max . In asanas, exercise intensity varied from 9.9 to 26.5% of trueV˙O2max . Highest energy cost was 3.02 kcal min−1. In BM highest V˙E was 53.7 ± 15.5 l min−1. VT was 0.97 ± 0.59, 1.41 ± 1.27 and 1.28 ± l/breath with corresponding Fr of 14.0 ± 5.3, 10.0 ± 6.35, 10.0 ± 5.8 breaths/min. Average energy expenditure in asanas, BM and meditation were 2.29, 1.91 and 1.37 kcal min−1, respectively. Metabolic rate was generally in the range of 1-2 metabolic equivalents (MET) except in three asanas where it was >2 MET. trueV˙O2 was 0.27 ± 0.05 and 0.24 ± 0.04 l min−1 in meditation and Shavasana, respectively. Although yogic practices are low intensity exercises within lactate threshold, physical performance improvement is possible owing to both better economy of breathing by BM and also by improvement in cardiovascular reserve. Other factors such as psycho-physiological and better relaxation may contribute to it.
The study assessed physiological responses to induction to high altitude first to 3,500 m and then to 4,200 m and compared the time course of altitude acclimatization in two groups of male volunteers. The acutely inducted group was transported by aircraft (AI) to 3,500 m in 1 h, whereas the gradually inducted group was transported by road (RI) in 4 days. Baseline recordings of basal cardiovascular, respiratory, and blood gas variables were monitored at sea level as well as at 3,500 m on days 1, 3, 5, and 7. Blood gases were measured on day 10 also. After 15 days at 3,500 m, the subjects were inducted to 4,200 m by road, and measurements were repeated on days 1, 3, and 5, except blood gas variables, which were done on day 10 only. Acute mountain sickness symptoms were recorded throughout. The responses of RI were stable by day 3 of induction at 3,500 m, whereas it took 5 days for AI. Four days in transit for RI appear equivalent to 2 days at 3,500 m for AI. Acclimatization schedules of 3 and 5 days, respectively, for RI and AI are essential to avoid malacclimatization and/or high-altitude illness. Both groups took 3 days at 4,200 m to attain stability for achieving acclimatization.
Regular practice of yoga can maintain or improve antioxidant level of the body. The clinical relevance is that yoga practice can be used to maintain the antioxidant defense system under stressful conditions of training as observed in the case of soldiers and athletes.
Hypobaric hypoxia causes oxidative stress and the antioxidant system of the body plays a vital role in controlling it. Urate contributes up to two-thirds of the antioxidant capacity of human blood. The urate production is catalyzed by xanthine oxidase with a concomitant release of free radicals. This study was designed to appraise the role of urate as an antioxidant at high altitude. The study was conducted on 92 male lowlanders and 66 highlanders after ascent to high altitude at 4560 m. Blood was collected at sea level and after 4 weeks of high altitude exposure. In lowlanders, a significant increase in levels of hydroperoxide (551.4 +/- 4.2 micromol/mL vs. 582.0 +/- 3.55, p < 0.001], protein carbonyl (2.4 +/- 0.11 micromol/mL/mg protein vs. 3.03 +/- 0.11, p < 0.001), TAS (1.02 +/- 0.01 mmol/L vs. 1.19 +/- 0.02, p < 0.001), and UA (298.0 +/- 6.68 micromol/L vs. 383.0 +/- 6.55, p < 0.001) was observed at high altitude. These measurements were significantly lower in highlanders than in lowlanders at high altitude. Total antioxidant status (TAS) and uric acid (UA) showed a positive correlation in lowlanders at sea level and in highlanders at high altitude. Hydroperoxide and TAS also showed a positive correlation in both groups at high altitude. This indicates increased oxidative stress at high altitude despite an increase in antioxidant capacity in lowlanders. To conclude, a hypoxia-induced increase in UA contributes an appreciable portion of plasma total antioxidant capacity, but may not be effective in preventing oxidative stress at high altitude.
Exercise-induced increase in oxygen consumption leads to oxidative stress. On the contrary, hypoxia triggers oxidative stress despite decreased oxygen flux. Therefore, exercise under hypoxia may aggravate oxidative damage. Highlanders are expected to have better antioxidant capacity than lowlanders as a result of adaptation to hypoxia. The present study was undertaken to investigate the effect of exercise on antioxidant system in lowlanders and highlanders at high altitudes (HA). This study was conducted on active male volunteers, randomly selected and categorized into three groups, i.e., lowlanders tested at sea level (LL-SL, n = 35), lowlanders tested at altitude of 4560 m (LL-HA, n = 35) and native highlanders tested (HAN, n = 20) at the same height. Volunteers performed maximal exercise until exhaustion. Blood samples were collected before and after exercise. Both LL-SL and HAN had shown similar VO2max, which was significantly higher than LL-HA. GSH/GSSG ratio significantly increased in LL-SL and decreased in HAN after exercise. With exercise there were a decrease in superoxide dismutase and increase in glutathione peroxidase and catalase activities in HAN. Therefore, the results have suggested that HAN are more susceptible to oxidative stress when subjected to high-intensity exercise than lowlanders. The cumulative effect of higher VO2max and longer duration of exercise in hypoxia may be the reason of higher level of oxidative insult among HAN. Comparatively better management of antioxidant system observed in lowlanders at HA may be explained by the lower VO2max and shorter duration of exercise in hypoxia.
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