ENDURANCE AND RESISTANCE EXERCISE INDUCE MUSCLE-FIBER TYPE-SPECIFIC RESPONSES IN ANDROGEN-BINDING CAPACITY

This study examined the effects of different exercise training program s on androgen receptor content and receptor affinity to dihydrotestost erone in fast glycolytic (FG) and slow oxidative (SO) skeletal muscle fibers in rats. Twenty-four male Sprague-Dawley rats were equally divi ded into three groups: control, endurance exercise trained and resista nce exercise trained. After the exercise programs were completed, the extensor digitorum longus (EDL), predominantly a FG muscle, and the so leus, predominantly a SO muscle, were isolated, weighed and both andro gen receptor content and affinity to dihydrotestosterone were determin ed. Resistance training evoked a significant (P < 0.05) hypertrophic r esponse in the soleus but not the EDL. Endurance training was not asso ciated with any significant hypertrophy in either the soleus or the ED L. Neither the endurance nor the resistance training program resulted in changes in androgen receptor affinity to dihydrotestosterone. Howev er, alterations in androgen receptor content were noted. The endurance training program resulted in a significant increase in androgen recep tor content in the soleus, but no significant difference in the EDL. T he resistance training program elicited a significant decrease in andr ogen receptor content in the soleus, and a significant increase in the EDL. These results indicate that different exercise stimuli induce ch anges in androgen receptor content that are specific to skeletal muscl e fiber type.