Both continuous and high-intensity interval training improved cardiac function early, with ~15% myocardial hypertrophy developing later after 12 weeks in rats.
Does continuous or high-intensity interval training induce different dynamics of myocardial hypertrophy and functional improvement in young adult male rats?
In a rat model, exercise-induced functional cardiac improvements occur early and independently of myocardial hypertrophy, which develops later, with both continuous and high-intensity interval training producing similar degrees of hypertrophy.
Absolute Event Rate: 0% vs 0%
Abstract Background Although exercise-induced hypertrophy has been intensively investigated in the last decades, only few data are available from complex, longitudinal studies to understand the physiology and importance of underlying mechanisms. Experimental investigations allow us to examine certain phenomena in a unified manner and reveal the underlying mechanisms. Purpose In this complex study, we would characterize the dynamics of development of exercise-induced hypertrophy in small animal models of continuous and high-intensity interval training (HIIT). Methods Young adult male rats have been subjected to swim-training (Sw group, n=10, 200 min/day, continuous type training) or treadmill training (Tr group, n=10, alternation of 90%/60% of maximal speed, high-intensity interval training) and were compared to control animals (Co group, n=10). Echocardiography and left-ventricular pressure-volume analysis were performed at 2, 5 and 12 weeks after the start of training program. Results Both type of exercise training was associated with improved functional parameters (increased stroke volume and contractility) without myocardial hypertrophy (post-mortem heart weight Co: 1.05±0.07 g, Sw: 1.10±0.13 g, Tr: 1.07±0.07 g). At 5 week, a developing hypertrophy was observed along with the already observed improved systolic function. After completion of exercise program, we experienced similar degree of hypertrophy (approximately 15%) in swim- and treadmill-trained animals post-mortem heart weight Co: 1.12±0.07 g, Sw: 1.26±0.10 g, Tr: 1.26±0.09 g) with comparable functional improvement (as shown by load-indepenndent contractility indices and mechanoenergetic parameters). Conclusions Our results suggest that exercise-induced functional improvement is (at least partly) independent from myocardial hypertrophy. The mechanical enhancement develops in the early phase, while growth of myocardium follows it later. HIIT and continuous training might be associated with similar degree of hypertrophy.
Oláh et al. (Sat,) reported a other. Both continuous and high-intensity interval training improved cardiac function early, with ~15% myocardial hypertrophy developing later after 12 weeks in rats.