Coca chewing among high altitude natives: Work and muscular efficiencies of nonhabitual chewers

The leaves of the coca plant (Erythroxylum sp.) have long been chewed by natives of the highland Andes. Folk belief is that the mild stimulant effect is indispensable as an ergogenic aid for strenuous work activities in a high altitude environment. This study explored the exercise responses of 23 nonhabitual coca chewing males who were asked to pedal a bicycle ergometer through a series of submaximal and maximal workloads both with and without coca chewing. The protocol of the exercise test was specifically designed to allow for the determination of work and muscular efficiencies during to submaximal work. The subjects showed no differences between the coca and control work protocols for VO₂max (1/min), VCO₂max (1/min), or maximal work output (watts). Further, there were no differences between coca and control work protocols in oxygen saturation (%), pulmonary ventilation (1/min), or respiratory exchange ratio (VCO₂/VO₂) at any level of work. Coca chewing caused subjects to have a higher heart rate (bpm) and lower oxygen pulse (ml/beat) for most submaximal workloads and higher ventilatory equivalents (VE/VO₂ and VE/VCO₂) above 50% of VO₂max. Although there was a tendency for higher gross efficiencies (GE) during the coca exercise test at lower relative work levels, between 30–40% of the VO₂max, this difference did not reach significance. Mean net efficiency (NE) was higher (P=0.018) at a relative work level of ～32% of the VO₂max for exercise with coca (23.2% vs. 20.8%). This difference was not apparent at any other work level. The mean delta efficiency (DE) was significantly lower (P = 0.012) for exercise with coca (26.7%) than for exercise without coca (28.2%). These efficiency differences suggest a muscle metabolic effect for coca chewing at low workloads whereby less oxygen is consumed by the muscle to perform a given work task. Howeve, given the difficulty of interpreting efficiency values, it is not entirely clear if the differences are indicative of a work performance benefit for coca chewing. © 1995 Wiley-Liss, Inc.