Resistance training is used each day for various reasons: aesthetic appearance, improved performance, sports competitions, rehabilitation, and a plethora of others. In the following reviews, Schroeder et al., (2013), Crewther et al., (2006), and Kraemer WJ & Ratamess N, (2005), resistance training was analyzed for it’s acute responses and possible chronic adaptations to the endocrine system. The hormones, testosterone (T), growth hormone (GH), insulin-growth factor-1 (IGF-1) and cortisol (COR) seem to elevate from hypertrophic resistance type training (e.g. 4 sets, 10-12 repetitions, moderate to high-intensity, and short rest intervals). (Crewther, Keogh, Cronin, & Cook, 2006; Kraemer & Ratamess, 2005; Schroeder, Villanueva, West, & Phillips, 2013)
The first review, by Schroeder et al., (2013) discuss contrasting viewpoints. The authors’ of prevailing perspectives state, “hormones may not be “necessary” to stimulate …hypertrophy; however, as we will support…hormones are “optimal” for maximizing skeletal muscle anabolism and hypertrophy.” The contrasting authors contend that hormonal responses, T, GH, IGF-1, are not necessary to stimulate skeletal muscle hypertrophy and yield little in the way of long-term adaptations. (Schroeder et al., 2013) These contrasting viewpoints, supported by research, can provide more ammunition to bias that hormonal responses are or are not needed to improve skeletal muscle adaptations.
The reviews describe that testosterone, growth hormone (specifically 22kD), insulin-growth factor-1, and various other hormones can fluctuate in men and women. Factors attributing to serum fluctuations range from the training programme, genetic predisposition, sex, fitness level, and the potential for adaptation.(Kraemer & Ratamess, 2005) In terms of resistance training, manipulation of training variables seems to intensify hormonal response but only acutely. In recreationally trained women GH and IGF-1 increased during an acute bout of resistance training, six sets of 10 repetitions. (Gregory et al., 2013) However, GH decreased, still above baseline, at 30 minutes post exercise as did IGF-1 but did continue to elevate over the 8-week experimental term. (Gregory et al., 2013) The authors refer to additional studies that corroborate their findings with untrained compared to trained men.
While the above information implies hormonal responses can optimize adaptations, a plethora of evidence deems them not necessary. Mangine et al., (2015), demonstrated that muscle hypertrophy gains with high-intensity training (3-5 sets, 3-5 repetitions, 90% intensity, longer rest intervals) may provide greater stimulus for resistance trained men. (Mangine et al., 2015) Morphological changes in the intensity-trained group were present with reduced levels of T and IGF-1 after 8-weeks of training. (Mangine et al., 2015) These findings are in agreement with Mitchell et al., (2013) that showed no relationship between serum levels of T, IGF-1, or GH and the magnitude of muscle hypertrophy in recreationally trained men. (Mitchell et al., 2013)
In summary, programming for hormonal responses by way of resistance training should not be the primary principles for variable selection (i.e. volume, intensity, rest intervals, duration, etc…). Coaches should prescribe a spectrum of variables in a periodized format based on the goals for teams or individuals.
Crewther, B., Keogh, J., Cronin, J., & Cook, C. (2006). Possible stimuli for strength and power adaptation: acute hormonal responses. Sports Medicine (Auckland, N.Z.), 36(3), 215–238.
Gregory, S. M., Spiering, B. A., Alemany, J. A., Tuckow, A. P., Rarick, K. R., Staab, J. S., … Nindl, B. C. (2013). Exercise-Induced Insulin-Like Growth Factor I System Concentrations after Training in Women. [Miscellaneous Article]. Medicine & Science in Sports & Exercise, 45(3), 420–428. http://doi.org/10.1249/MSS.0b013e3182750bd4
Kraemer, W. J., & Ratamess, N. A. (2005). Hormonal responses and adaptations to resistance exercise and training. Sports Medicine (Auckland, N.Z.), 35(4), 339–361.
Mangine, G. T., Hoffman, J. R., Gonzalez, A. M., Townsend, J. R., Wells, A. J., Jajtner, A. R., … Stout, J. R. (2015). The effect of training volume and intensity on improvements in muscular strength and size in resistance‐trained men. Physiological Reports, 3(8), e12472. http://doi.org/10.14814/phy2.12472
Mitchell, C. J., Churchward-Venne, T. A., Bellamy, L., Parise, G., Baker, S. K., & Phillips, S. M. (2013). Muscular and Systemic Correlates of Resistance Training-Induced Muscle Hypertrophy. PLoS ONE, 8(10), e78636.http://doi.org/10.1371/journal.pone.0078636
Schroeder, T., Villanueva, M., West, D., & Phillips, S. (2013). Are Acute Post-Resistance Exercise Increases in Testosterone, Growth Hormone, and IGF-1 Necessary to Stimulate Skeletal Muscle Anabolism and Hypertrophy? Medicine & Science in Sports & Exercise, 45(11), 2044–2051.