Duration-controlled swimming exercise training induces cardiac hypertrophy in mice

Abstract

Exercise training associated with robust conditioning can be useful for the study of molecular mechanisms underlying exercise-induced cardiac hypertrophy. A swimming apparatus is described to control training regimens in terms of duration, load, and frequency of exercise. Mice were submitted to 60-vs 90-min session/day, once vs twice a day, with 2 or 4% of the weight of the mouse or no workload attached to the tail, for 4 vs 6 weeks of exercise training. Blood pressure was unchanged in all groups while resting heart rate decreased in the trained groups (8-18%). Skeletal muscle citrate synthase activity, measured spectrophotometrically, increased (45-58%) only as a result of duration and frequency-controlled exercise training, indicating that endurance conditioning was obtained. In groups which received duration and endurance conditioning, cardiac weight (14-25%) and myocyte dimension (13-20%) increased. The best conditioning protocol to promote physiological hypertrophy, our primary goal in the present study, was 90 min, twice a day, 5 days a week for 4 weeks with no overload attached to the body. Thus, duration-and frequency-controlled exercise training in mice induces a significant conditioning response qualitatively similar to that observed in humans. Correspondence

Effect of exercise training and carvedilol treatment on cardiac function and structure in mice with sympathetic hyperactivity-induced heart failure

“…However, we cannot exclude the possibility that swimming training might preclude pathological hypertrophy, since it induces physiological remodeling that is associated with improved cardiac function. In fact, as we observed in WT mice, swimming exercise training led to a physiological hypertrophy, which we showed previously to be associated with beneficial cardiac effects (21).…”

“…Exercise training consisted of swimming sessions 5 days/week with gradually increased duration up to 60 min, for 8 weeks in a warmed water (30-32 o C) swimming apparatus adapted for mice (21). The training sessions were performed during the dark part of light cycle of the mice.…”

“…The training sessions were performed during the dark part of light cycle of the mice. This swimming protocol has been characterized as low to moderate intensity and associated with improved muscle oxidative capacity and resting bradycardia (21).…”

Caffeine and physical training: effects on cardiac morphology and cardiovascular response

“…This cardiac adaptation may provide increased efficiency of the cardiovascular system, increasing the supply of oxygen to muscles during effort. 31,32 However, it can be speculated that the relative weight of the heart is higher because trained animals present a lower body mass.…”

Myocardial Ischemia-Reperfusion/Injury

“…Swimming is well recognized for its effectiveness in inducing myocardial hypertrophy (Evangelista et al, 2003). Exercise can protect cardiac function of the aging heart by protection against; loss of cardiac myocytes, reduction in number of myonuclei, reactive hypertrophy of remaining myocytes, and increased connective tissue in left ventricle (LV) of the aging rat heart.…”