Reducing testosterone and estrogen levels using a leuteinizing hormone releasing hormone agonist such as Zoladex® (i.e., chemical gonadectomy) is a common treatment for many prostate and breast cancer patients, respectively. There are reports of surgical gonadectomy inducing cardiac dysfunction, and exercise has been shown to be cardioprotective under these circumstances. Minimal research has been done investigating the effects of chemical gonadectomy and increased physical activity on cardiac function. The purpose of this investigation was to examine the effects of chemical gonadectomy and physical activity on cardiac function. Male (M) and female (F) Sprague Dawley rats received either Zoladex® (ZOL) that suppressed gonadal function for 8 weeks or control implants (CON) and were allowed either unlimited access to voluntary running wheels (WR) or remained sedentary (SED) throughout the treatment period. In vivo and ex vivo left ventricle (LV) function were then assessed, and myosin heavy chain (MHC) expression was analyzed to help explain LV functional differences. Hearts from M SED+ZOL possessed significantly lower aortic blood flow velocity, developed pressure, maximal rate of pressure development, and higher -MHC expression than M SED+CON. Hearts from F SED+ZOL possessed significantly lower LV wall thicknesses, fractional shortening, developed pressure, and higher -MHC expression than F SED+CON. This cardiac dysfunction was not evident in hearts from M or F WR+ZOL, and this was associated with a preservation of the MHC isoform distribution. Thus, an 8-week chemical gonadectomy using ZOL promoted cardiac dysfunction in male and female rats, and voluntary wheel running protected against this cardiac dysfunction.