Exercise training reversed age-related prolongation of isometric contraction duration in senescent rats (P<0.001) but prolonged it in young adult rats (P<0.05).
Does exercise training alter myocardial function differently in young adult versus old rats?
Exercise training has opposite effects on cardiac muscle contraction duration in young versus old rats, highlighting the importance of age in physiological responses to exercise.
p-value: p=<0.001
To test the hypothesis that age may alter the effect of exercise training on myocardial function, we trained young adult (4-5 mo at study initiation) and old (21 mo at initiation) male Fischer 344 rats to run on a rodent treadmill 5 days/wk for 4.5 mo and compared their myocardial function with that of age-matched sedentary controls. Right ventricular papillary muscles were isolated from the young adult and aged animals and stimulated at the length at which developed isometric tension was maximal to contract isometrically at 12/min, bathed in oxygenated modified Krebs solution, and studied at 28 degrees, 32 degrees, 35 degrees, and 38 degrees C. In the absence of cardiac hypertrophy, exercise training significantly reversed the age-related prolongation of isometric contraction duration in the senescent rat (P less than 0.001). However, exercise training prolonged contraction duration in the young adult rat (P less than 0.05). The relaxation phase was more sensitive than the contraction phase to changes in temperature, especially in the aged rat (P less than 0.02). The ratio of developed tension to time-to-peak tension of the isometric twitch was not affected by exercise training. Because exercise training affects cardiac function in opposite directions from young adulthood to senescence, caution is advised in extrapolating results from exercise studies in young adult rats to populations of older animals.
Li et al. (Tue,) conducted a other in Aging and cardiac muscle function. Exercise training (treadmill running) vs. Age-matched sedentary controls was evaluated on Isometric contraction duration (p=<0.001). Exercise training reversed age-related prolongation of isometric contraction duration in senescent rats (P<0.001) but prolonged it in young adult rats (P<0.05).