Browsing by Autor "Favier, Roland"

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Coca chewing for exercise : hormonal and metabolic responses of nonhabitual chewers
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1996) Favier, Roland
Abstract. To determine the effects of acute coca use on the hormonal and metabolic responses to exercise, 12 healthy nonhabitual coca users were submitted twice to steady-state exercise (∼75% maximal O2 uptake). On one occasion, they were asked to chew 15 g of coca leaves 1 h before exercise, whereas on the other occasion, exercise was performed after 1 h of chewing a sugar-free chewing gum. Plasma epinephrine, norepinephrine, insulin, glucagon, and metabolites (glucose, lactate, glycerol, and free fatty acids) were determined at rest before and after coca chewing and during the 5th, 15th, 30th, and 60th min of exercise. Simultaneously to these determinations, cardiorespiratory variables (heart rate, mean arterial blood pressure, oxygen uptake, and respiratory gas exchange ratio) were also measured. At rest, coca chewing had no effect on plasma hormonal and metabolic levels except for a significantly reduced insulin concentration. During exercise, the oxygen uptake, heart rate, and respiratory gas exchange ratio were significantly increased in the coca-chewing trial compared with the control (gum-chewing) test. The exercise-induced drop in plasma glucose and insulin was prevented by prior coca chewing. These results contrast with previous data obtained in chronic coca users who display during prolonged submaximal exercise an exaggerated plasma sympathetic response, an enhanced availability and utilization of fat (R. Favier, E. Caceres, H. Koubi, B. Sempore, M. Sauvain, and H. Spielvogel.J. Appl. Physiol. 80: 650–655, 1996). We conclude that, whereas coca chewing might affect glucose homeostasis during exercise, none of the physiological data provided by this study would suggest that acute coca chewing in nonhabitual users could enhance tolerance to exercise.
Effects of coca chewing on hormonal and metabolic responses during prolonged sbmaximal exercise
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1996) Favier, Roland
Abstract The effects of coca chewing on prolonged submaximal exercise responses were investigated in chronic coca chewers and compared with a group of nonchewers. At rest, coca chewing during a 1-h period was followed by a significant increase in blood glucose, free fatty acid, and norepinephrine concentrations and a significant reduction in insulin plasma level. During prolonged (1-h) submaximal (65-70% peak O2 uptake) exercise, chewers displayed a significantly greater adrenergic activation (as evidenced by a higher level of plasma epinephrine) and an increased use of fat (as evidenced by a lower respiratory exchange ratio). The gradual increase in oxygen uptake (O2 drift) commonly observed during prolonged exercise was blunted in coca chewers. This blunting in O2 drift is not related to coca-induced changes in ventilatory or lactate responses to exercise but could possible be related to an enhanced glucose utilization by chewers during the late phase of exercise. The present results provide experimental evidence of the physiological effects of coca chewing that could explain the better ability of coca users to sustain strenuous work for an extended period of time.
Maximal exercise performance in chronic hypoxia and acute normoxia in high-altitude natives
(Facultad de Medicina, Enfermería, Nutrición y Tecnología Médica, 1995) Favier, Roland
Maximal O₂ uptake (VO₂max) was determined on a bicycle ergometer in chronic hipoxia (CH) and during acute exposure to normoxia (AN) in 50 healthy Young men who were born and had lived at 3,600 m altitude (La Paz, Bolivia). VO₂max was significantly improved (~8%) by AN. However, the difference in VO₂max measured in CH and AN (∆VO₂max) was lower than that reported in sea- level natives (SN) who exercised in chronic normoxia and acute hypoxia. It is shown that high-altitude natives (HN) and SN have a similar VO₂max in normoxia, but highlanders can attain a greater VO₂max when O₂ availability is reduced by alotitude exposure. In addition, in HN, the higher the subject’s VO₂max in hypoxia, the smaller his ∆VO₂max. These results contrast with the data obtained in 14 lowlanders acclimatized to high altitude who showed that their ∆VO₂max was positively related to their VO₂max in hypoxia, as previously reported in SN who exercised in acute hypoxia (A. J. Young, A. Cymerman, and R. L. Burse. Eur. J. Appl, Physiol. Occup. Physiol. 54:12-15, 1985). Furthermore, arterial O₂ saturation of HN behaved differently from acclimatized lowland natives, inasmuch as it fell less during exercise both in CH and AN. HN with high aerobic capacity display a lower exercise ventilation and a reduced arterial saturation, which could explain their inability to improve VO₂max with normoxia. Plasma lactate levels during maximal exercise were in the same range (8-10 mM) as values reported for SN. ∆Work efficiency reached 26-28% in CH as well as in AN, i.e., a value similar to that obtained in SN who exercised in normoxia or hypoxia.