Abstract
The effects of endurance training on cardiac myocyte and capillary were studied morphometrically in rats following a treadmill running program. Twenty-two male Wistar strain rats at 4 weeks of age were divided into three groups: 1) sedentary control (Cont; N=8), 2) 45 m/min, inclined 0% training (T-A; N=8), 3) 35 m/min, inclined 10% training (T-B; N=6). Rats in T-A and T-B were subjected to a running program at 60 min/day, 5 days/wk for 10 weeks. In comparison with Cont, absolute ventricular mass in both T-A and T-B increased by 17% (p < 0.01) and resting heart rate decreased by 7.4% (p < 0.05). Endurance training does not lead to a significant increase of cardiac myocyte cross-sectional area in trained groups. Capillary density in trained groups was not significantly different from Cont. Capillary lumen diameter in T-A and T-B, however, were increased by 12 and 21% (p < 0.05), respectively. Measurements of capillary luminal surface density (mm^2/mm^3) in trained groups were unchanged compared with Cont. These results suggest that endurance training does not stimulate the proliferation of new capillaries, but induce to increase capillary luminal surface area paralleled in cardiac hypertrophy.
