Effects of short-term high-intensity interval and continuous exercise training on body composition and cardiac function in obese sarcopenic rats.

AIM: We investigated the effects of high-intensity interval and continuous short-term exercise on body composition and cardiac function after myocardial ischemia-reperfusion injury (IRI) in obese rats. METHODS: Rats fed with a standard chow diet (SC) or high-fat diet (HFD) for 20 weeks underwent systolic blood pressure (SBP), glycemia and dual-energy X-ray absorptiometry analyses. Then, animals fed with HFD were subdivided into three groups: sedentary (HFD-SED); moderate-intensity continuous training (HFD-MICT); and high-intensity interval training (HFD-HIIT). Exercised groups underwent four isocaloric aerobic exercise sessions, in which HFD-MICT maintained the intensity continuously and HFD-HIIT alternated it. After exercise sessions, all groups underwent global IRI and myocardial infarct size (IS) was determined histologically. Fat and muscle mass were weighted, and protein levels involved in muscle metabolism were assessed in skeletal muscle. RESULTS: HFD-fed versus SC-fed rats reduced lean body mass by 31% (P < 0.001), while SBP, glycemia and body fat percentage were increased by 10% (P = 0.04), 30% (P = 0.006) and 54% (P < 0.001); respectively. HFD-induced muscle atrophy was restored in exercised groups, as only HFD-SED presented lower gastrocnemius (32%; P = 0.001) and quadriceps mass (62%; P < 0.001) than SC. PGC1-α expression was 2.7-fold higher in HFD-HIIT versus HFD-SED (P = 0.04), whereas HFD-HIIT and HFD-MICT exhibited 1.7-fold increase in p-mTORSer2481 levels compared to HFD-SED (P = 0.04). Although no difference was detected among groups for IS (P = 0.30), only HFD-HIIT preserved left-ventricle developed pressure after IRI (+0.7 mmHg; P = 0.9). SIGNIFICANCE: Short-term exercise, continuous or HIIT, restored HFD-induced muscle atrophy and increased mTOR expression, but only HIIT maintained myocardial contractility following IRI in obese animals.

Aerobic exercise training induces superior cardioprotection following myocardial ischemia reperfusion injury than a single aerobic exercise session in rats

Abstract AIM To compare the amount of cardioprotection induced by a single exercise session with those achieved after an 8-week aerobic exercise training following ischemia reperfusion injury in rats. METHODS Twenty-five male Wistar rats (250-300g) were assigned into a group submitted to physical training (TR; n=12) or a single maximal exercise session (EXE; n=13). Following sedentarism or physical training (8 weeks, 5 sessions/wk, 1h/session at 70% of maximal speed) both groups performed a maximal exercise test. Then, groups were submitted to ischemia reperfusion injury (30 min/1h) through an isolated heart protocol, in which left ventricle developed pressure was measured. RESULTS The TR group presented greater maximal oxygen consumption compared to the EXE group (77.25±20.41 vs 41.32±25.86 ml/Kg/min; P=0.003). Regarding left ventricle developed pressure, no differences were detected between groups at baseline (TR: 89.78±24.40 vs EXE: 81.37±31.84 mmHg; P=0.48). However, after reperfusion, the TR group presented superior intraventricular pressure than EXE group (37.94±18.34 vs 21.59±13.67 mmHg; P=0.03). CONCLUSION Eight-week aerobic training induced greater cardioprotection against ischemia reperfusion injury in rats compared to a single exercise session, due to an increased cardiac function. This suggests that exercise-induced cardioprotection is a multifactorial process that may involve different mediators according to the exercise duration.(AU)