Effect of continuous and interval aerobic exercise training on baroreflex sensitivity in heart failure.

INTRODUCTION: The ability of continuous aerobic exercise training (AET) to increase baroreflex control and cardiac function in heart failure (HF) has been well described, but the comparison between continuous and interval AET on these functions is inconclusive.

OBJECTIVES: To compare the effects of continuous and interval AET on cardiac function and baroreflex sensitivity (BrS) in an experimental model of HF.

METHODS: Rats were divided into the following groups: continuous training (HF-CT), intense interval training (HF-IIT), moderate interval training (HF-MIT), sedentary group (HF-SED), and sham sedentary (SHAM-SED). Animals underwent surgery to induce HF by ligation of the interventricular coronary artery. Six weeks after surgery, AET was started (8weeks, 3sessions/week). Echocardiography studies to assess cardiac function were performed before and after AET. At the end of the training protocols, the BrS index was assessed by stepwise intravenous infusions of sodium nitroprusside and phenylephrine.

RESULTS: All methods of exercise prevented the HF-induced increase in left ventricular diameter in diastole observed in the HF-SED rats (0.88±0.09 vs. 1.03±0.09cm; P<0.05), but only the HF-CT (28.5±6.3 vs. 39.2±12.7%; P<0.05) and HF-MIT (31.0±8.5 vs. 42.0±10.3%; P<0.05) groups exhibited an increase in ejection fraction. Nevertheless, the HF-CT group was the only group that showed a tachycardia reflex higher than that of the HF-SED group (0.87±0.34 vs. 0.20±0.05bpm/mmHg; P<0.05) and similar to that of the SHAM-SED group (1.04±0.11bpm/mmHg).

CONCLUSIONS: These results suggest that continuous and moderate interval training induced similar improvements in cardiac function but that only continuous training induced higher BrS in HF rats.