to address the autonomic mechanisms underlying the bradycardia of physical training in human subjects , we performed a cross-sectional study comparing the heart-rate responses to graded doses of isoproterenol in 7 elite marathon runners and 7 age-matched controls , and a longitudinal study in 12 normal volunteers of the effects of 6 wk of intense physical training on lymphocyte beta-adrenergic receptors identified by l- [ 3h ] dihydroalprenolol .
C0428977
bradycardia
C0022245
isoproterenol