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Similar hormonal responses to concentric and eccentric muscle actions using relative loading
Robert R Kraemer1, Daniel B Hollander, Greg V Reeves
1Department of Kinesiology and Health Studies, Southeastern Louisiana University, SLU 10845, Hammond, LA 70402, USA. rkraemer@selu.edu
European Journal of Applied Physiology
|December 22, 2005
Summary
Resistance exercise using relative loading showed similar growth hormone (GH), total testosterone (T), and free testosterone (FT) responses for both concentric (CON) and eccentric (ECC) muscle contractions. This finding contrasts previous research using absolute loading.
Area of Science:
- Exercise Physiology
- Endocrinology
- Sports Science
Background:
- Conventional resistance training involves sequential concentric (CON) and eccentric (ECC) muscle contractions.
- Previous research indicated greater growth hormone (GH) response with absolute concentric loading compared to eccentric.
- The role of relative loading on endocrine responses (GH, total testosterone [TT], free testosterone [FT]) requires further investigation.
Purpose of the Study:
- To investigate and compare the endocrine responses (GH, TT, FT) to CON and ECC muscle contractions under relative loading conditions.
- To test the hypothesis that relative loading would result in similar GH responses but greater TT and FT responses after ECC contractions.
Main Methods:
- Seven recreationally trained young men participated in a counterbalanced study.
- Participants completed six upper and lower body exercises (lat pulldown, leg press, bench press, leg extension, military press, leg curl) in both CON and ECC trials.
- Exercises were performed at 65% of a 1-repetition maximum (1-RM) for each contraction type, with ECC 1-RM set at 120% of CON 1-RM. Blood samples were collected pre-exercise, immediately post-exercise, and 15 minutes post-exercise.
Main Results:
- Growth hormone (GH) levels significantly increased in both CON and ECC trials, with no significant difference between the two.
- Total testosterone (TT) levels did not show significant alterations in either trial.
- Free testosterone (FT) concentrations increased significantly following both CON and ECC contractions.
Conclusions:
- Under relative loading conditions, both CON and ECC muscle contractions elicit similar GH responses.
- Relative loading results in comparable increases in total and free testosterone for both CON and ECC contractions.
- These findings suggest that the type of muscle contraction (CON vs. ECC) may not differentially impact endocrine responses when normalized for relative intensity.