Exercise training-induced enhancement in myocardial mechanics is lost after 2 weeks of detraining in rats.

Exercise training is assumed to improve myocardial function; however, the role of detraining and its effect on myocardial parameters are still unclear. The aim of the present study was to evaluate the effect of detraining on ventricular remodeling and myocardial mechanical parameters after an 8 week (5 days/week, 60 min/day) swimming training period. Forty-three female Wistar rats were distributed into six groups: trained (T, n = 9), detrained 2 weeks (D2, n = 8), detrained 4 weeks (D4, n = 8) and their respective controls: untrained (U, n = 5), untrained 2 weeks (U2, n = 5) and untrained 4 weeks (U4, n = 5). Detrained rats underwent training and then remained sedentary (i.e., "detraining") for 2 or 4 weeks. After training, the T group demonstrated increased physical capacity, left ventricular (LV) posterior wall thickness, and LV end-diastolic diameter, along with decreased heart rate, as evaluated by echocardiogram. In addition, the inotropism and lusitropism parameters studied on papillary muscles showed improvement in the T group (P < 0.05). However, after just 2 weeks of detraining, all parameters regressed back to values which were similar to those of the untrained groups. In conclusion, our results confirmed that exercise training is capable of inducing myocardial remodeling and improving contractile performance; however, these changes are completely lost after a short period of detraining.