Effect of testosterone administration and weight training on muscle architecture

The purpose of this study was to assess muscle architecture changes in subjects who were administered supraphysiologic doses of testosterone enanthate (TE) and concurrently performed heavy resistance training.

Ten subjects were randomly selected from the 21 subjects who participated in a previously published study (12). Subjects were allocated to one of two groups as per Giorgi et al. (12) and received either a saline-based placebo (nonTE) or a 3.5-mg.kg-1 body weight dose of TE by deep intramuscular injection once a week for 12 wk. Subjects also performed heavy resistance training using exercises that targeted the triceps brachii muscle. Before and after the training period, free-weight one-repetition-maximum (1-RM) bench press strength was tested, muscle thickness and pennation of the triceps brachii lateralis were measured using ultrasound imaging, and fascicle length was estimated from ultrasound photographs.

There were no significant between-group differences in muscle thickness changes despite a trend toward increased thickness in TE subjects (TE, 23.5%, vs nonTE, 13.8%). However, 1-RM bench press performance and muscle pennation increased significantly in TE subjects compared with nonTE subjects (P < 0.05). There was also a trend toward longer fascicle lengths in the muscles of nonTE subjects.

The results of the present study suggest that the use of TE in conjunction with heavy resistance training is associated with muscle architecture changes that are commonly associated with high-force production. Since there was little difference between the groups in muscle thickness, changes in pennation and possibly fascicle length may have contributed to strength gains seen in TE subjects.