Effect of the short-term beta-adrenoceptor blockade on exercise metabolism in cold weather.

Carbohydrate and lipid metabolism at rest and after 1 h submaximal physical exercise in cold weather (between -1 and -6 C) were studied in ten healthy male subjects treated in a randomized double-blind fashion for 2 days with either placebo, the non-selective beta-adrenoceptor antagonist with high ISA pindolol (10 mg), or the cardioselective drug atenolol (100 mg). Four subjects, on both atenolol and pindolol, complained of muscular fatigue during exercise on beta blockade; four other subjects perceived some fatigue. There were no significant differences in blood glucose or insulin levels between treatments and placebo period. Post-exercise growth hormone levels increased on placebo (p less than 0.01), on pindolol (p less than 0.01), and on atenolol (p less than 0.05), but the alteration was more prominent on pindolol than on placebo (p less than 0.05). The plasma free fatty acid concentrations increased during exercise on placebo and pindolol (p less than 0.05) and on atenolol (p less than 0.01). Serum triglyceride concentrations decreased significantly during exercise on placebo or pindolol (p less than 0.01). Triglyceride levels before exercise were significantly higher on beta blockade than on placebo (p less than 0.05). The metabolic parameters taken before and after exercise did not explain the muscle fatigue experienced by many subjects during exercise.