Effect of antihypertensive medications on physical work capacity

Cardiopulmonary fitness as measured by maximal oxygen uptake (VO_2max) is routinely estimated from submaximal heart rate (HR_submax). Propranolol reduces HR_submax and invalidates regression estimates of VO_2max. The present study examines the influence of four additional antihypertensive medications on VO₂ max prediction by measuring VO₂ and HR during exercise testing of 20 normotensive men aged 20 to 30 years. Five medications were assigned by double-blind randomization: (1) hydrochlorothiazide (H) 50 mg/day; (2) II + methyldopa 10 mg/kg/day (H + M); (3) chlorthalidone 50 mg/day + reserpine 0.1 mg/day (C + R); (4) 11 (50 mg) + reserpine (0.125 mg) one/day + hydralazine 0.50 mg/kg/day (C + R + HY), and (5) placebo (P). Each participant exercised before being given medication, ivhile receiving medication, and after medication washout. No antihypertensive drug was associated with significant decrease in P-adjusted resting blood pressure, but H + M and C + R were associated with significantly decreased exercise systolic blood pressure adjusted for P. Multiple t tests did not show a significant effect on the HR-VO₂ relationship for any drug adjusted for P. We conclude that short-term administration of these antihypertensive drugs does not confound HR_submax-estimated VO_2max.