THE EFFECTS OF BETA(2)-AGONISTS AND CAFFEINE ON RESPIRATORY AND LIMB MUSCLE PERFORMANCE

The possibility that respiratory muscle function may be improved by dr ug therapy is of clinical importance, but remains controversial. A ser ies of studies concerning the effects of maximally tolerated dosages o f terbutaline, tulobuterol (a new beta2-agonist) and caffeine on respi ratory muscle strength and limb muscle strength and endurance were und ertaken in normal subjects. Drugs were administered orally, 2 h before study. Caffeine produced a small but statistically significant increa se in the stimulated contraction force at 20 Hz, and a small beneficia l effect on recovery from a fatiguing protocol; maximum voluntary cont raction force of the quadriceps was increased by 3.8%. Terbutaline and tulobuterol had no beneficial effects on either respiratory or limb m uscle function. We conclude that conventional dosages of these broncho dilator drugs do not greatly affect skeletal muscle performance.