The RPE value after the ECC+ (16.3 ± 0.6) was greater than the TRAD protocol value after exercise bouts 1 (14.3 ± 0.3) and 2 (13.3 ± 0.5). No other differences were observed for RPE. No differences in total training volume were observed between the bout 1 TRAD protocol (4652 ± 146 kg) and the bout 2 (4561 ± 234 vs 4299 ± 197 kg) TRAD and ECC+ protocols, respectively.
Furthermore, our results indicate that TT concentrations are not elevated after resistance exercise in previously untrained subjects, which is consistent with findings by Kraemer et al. (24) but inconsistent with others (34). Additionally, we observed a decrease in TT and BT concentrations 45-60 min after exercise under all conditions, which is similar to findings by Tremblay et al. (34). The observed reductions in postexercise TT and BT observed in our study may indicate that testosterone 1) followed normal metabolic pathway biotransformation and/or 2) became bound to androgen receptors and stimulated protein synthesis (3). Future research designed to determine the metabolic fate of testosterone and its subfractions after resistance exercise may elucidate the effect of endogenous testosterone on localized skeletal muscle hypertrophy.
Previous research on resistance-trained subjects suggests that eccentric-only muscle actions result in a blunted GH response (8,21) and a similar (21) or reduced (8) testosterone response compared with concentric-only resistance exercise matched for absolute intensity. Additionally, similar pre- and postexercise GH (20) and testosterone (2,20) responses have been reported after eccentric-only and concentric-only muscle actions matched for relative exercise intensity. Our study provides novel data indicating that coupled concentric and overloaded eccentric muscle actions seem to have little effect on the postexercise GH and testosterone response. These results suggest that the concentric muscle action is primarily responsible for the neuroendocrine responses after resistance exercise, because the addition of overloaded eccentric muscle actions altered neither the GH nor testosterone responses compared with TRAD. Future research evaluating longitudinal anabolic hormone responses and/or local muscle growth factor responses to ECC+ may contribute to an understanding of the mechanism(s) responsible for the heightened muscular adaptations associated with ECC+.
We observed that BT concentrations are greater after resistance exercise, despite constant TT concentrations. Bioavailable testosterone is composed of approximately 4% free and approximately 96% albumin-bound testosterone fractions and reportedly reflects the total concentration of testosterone that is capable of traversing cell membranes, binding with androgen receptors, and stimulating protein translation (27). Our results indicate that an alteration in the free:albumin-bound:sex hormone-binding globulin (SHBG)-bound testosterone ratio occurred, suggesting an acute increase in bioactive androgen availability after both ECC+ and TRAD. Previous reports from others indicate that free testosterone increases acutely after resistance training (1,34). Although we did not directly measure free testosterone concentrations, it is plausible that changes in the free testosterone fraction influenced our TT and BT results. Given the influence of binding proteins on both the biological effects and measurement of testosterone, studies designed to carefully measure the postexercise free, albumin-bound, and SHBG-bound fractions of testosterone are indicated.
We report that the RPE after the ECC+ was greater than that after the TRAD. These results corroborate previous reports indicating that RPE is associated with both exercise intensity and lactate accumulation (25). However, our findings contrast those of Hortobagyi et al. (16), who report that RPE responses were significantly lower after ECC+ compared with TRAD. Studies designed to evaluate the RPE responses would enhance current understandings of fatigue and exertion as they relate to resistance exercise.
The neuroendocrine, metabolic, and performance responses to resistance exercise are of concern when prescribing resistance training protocols. The results from our study indicate that ECC+ results in similar neuroendocrine responses to TRAD, suggesting that ECC+ is a suitable alternative to TRAD when muscular hypertrophy and strength are desired outcomes. However, the heightened lactate concentrations and RPE associated with ECC+ indicate that ECC+ may not be as appropriate for clinical populations that experience muscular fatigue, pain, and/or weakness associated with their condition. Future research designed to evaluate the neuroendocrine, metabolic, and performance responses to ECC+ training, in both healthy and at-risk populations, may provide additional insight into the appropriateness of exercise prescriptions using ECC+.
In summary, neither ECC+ nor TRAD resulted in increased postexercise TT concentrations, whereas postexercise BT increased similarly between groups. Both resistance exercise protocols resulted in similar acute increases in GH after exercise. Additionally, ECC+ resulted in a greater lactate accumulation and RPE than TRAD. In conclusion, our results suggest that acute alterations in postexercise anabolic hormone responses may not be the primary mechanism explaining the heightened muscular adaptations associated with ECC+.
This material is the result of work supported with resources and the use of facilities at the Malcolm Randall VA Medical Center, Gainesville, FL. The results of this study do not constitute endorsement of the product by the authors or ACSM.
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