Effect of β1‐selective and non‐selective β‐blockade on work capacity and muscle metabolism

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Abstract
Summary. Six well‐trained men were studied while performing a maximal bicycle exercise. The seven experiments included in this study were randomized in a double‐blind cross‐over fashion. On each occasion the subjects were given either placebo or 40, 80, or 160 mg propranolol (non‐selective blockade) or 25,50, or 100 mg atenolol (β1‐selective blockade). After completion of the study each subject had performed once under each of the seven treatments. Heart rate, maximal oxygen uptake (V̇o2max), blood lactate and performance time to exhaustion were measured. A muscle biopsy from vastus lateralis was taken at exhaustion after placebo, 80 mg propranolol and 50 mg atenolol trials, for analysis of ATP, creatine phosphate (CP), glucose‐6‐phosphate (G‐6‐P), glucose and lactate. The performance time was reduced (Po2max was equally reduced by both blockers. Performance time, on the other hand, was reduced to a greater extent (PPPo2max propranolol reduced performance time to a greater extent than atenolol suggests that β2‐blockade may reduce performance by mechanisms additional to those that affect oxygen transport. One possible mechanism is a retardation of glycolysis.

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