Comparison of determinants of myocardial oxygen consumption during arm and leg exercise in normal persons

Abstract

Arm exercise assumes an increasingly important role in clinical cardiology as it is used in both exercise testing and training of patients with coronary artery disease. The effects of arm exercise on myocardial oxygen consumption are not well understood; they may differ from the effects of leg exercise. Previous studies have shown that the ischemic threshold is higher in patients performing arm exercise and leg exercise at the same heart rate-blood pressure product. The contribution of other determinants of myocardial oxygen consumption—left ventricular (LV) peak meridional systolic wall stress and contractility—to these observed differences were studied. Thirty healthy subjects exercised to the same peak rate-pressure product during dynamic upper- and lower-extremity exercise. Peak workload was lower during arm exercise (100 ± 16 W) than during leg exercise (170 ± 21 W, p < 0.001). LV wall stress did not differ during either form of exercise (197 ± 44 vs 204 ± 33 dynes/cm 2 × 10 3, arm vs leg, respectively). This was also true of contractility as assessed by the velocity of circumferential fiber shortening (2.8 ± 0.6 vs 2.5 ± 0.4 circ/s, arm vs leg, respectively) and the preejection period/LV ejection time ratio (0.33 ± 0.11 vs 0.31 ± 0.07, arm vs leg, respectively). Normal subjects exercising to a similar rate-pressure product showed the same levels of LV wall stress and contractility for arm and leg exercise despite the lower workload performed with arm exercise.