Are Acute Post–Resistance Exercise Increases in Testosterone, Growth Hormone, and IGF-1 Necessary to Stimulate Skeletal Muscle Anabolism and Hypertrophy?
Contrasting Perspectives
PREVAILING PERSPECTIVE
Acute post–resistance exercise (RE) increases in anabolic hormones may not be ‘‘necessary’’ to stimulate skeletal muscle anabolism and hypertrophy; however, as we will support in the following discussion, post-RE increases in these hormones are ‘‘optimal’’ for maximizing skeletal muscle anabolism and hypertrophy. For purposes of this presentation, increases in testosterone (T) and growth hormone (GH) will also imply increases in insulin like growth factor 1 (IGF-1) (22,24). Furthermore, we will limit the discussion of these adaptations to men, while recognizing that training variables such as training history, mode, intensity, volume, and rest interval (RI) length in between sets will have compelling influence on the hormonal responses to RE.
CONCLUDING STATEMENT
The anabolic hormonal milieu is necessary to maximize functional adaptations to RT. Although post-RE elevations in anabolic hormones may not be necessary to acutely stimulate muscle protein synthesis or promote hypertrophy of small muscle masses, these elevations in anabolic hormones are ideal to optimize functional performance gains in whole body skeletal muscle mass and strength in men and women across the lifespan.
E. Todd Schroeder Matthew Villanueva University of Southern California Division of Biokinesiology & Physical Therapy Los Angeles, CA
-----------------------------------------------------------------------------------------------------
CHALLENGING PERSPECTIVE
A pervasive view in the area of endocrine responses to resistance exercise is that acute postexercise hormonal responses of testosterone, growth hormone (GH), and insulin like growth factor 1 (IGF-1) are critical for subsequent skeletal muscle anabolism. If this is the case, then exercise regimes can be manipulated to enhance hormonal responses and thus enhance skeletal muscle adaptations such as strength and muscle mass gain. Despite this alluring prospect, we contend that post exercise increases in testosterone,GH,and IGF-1 are not necessary to stimulate skeletal muscle anabolism and hypertrophy and that measurement of the responses of these hormones yields little in the way of insight into longer-term resistance training-related adaptation.
CONCLUDING STATEMENT
It is time to write the requiem for studies that measure only postexercise hormonal responses and infer a potential effect on hypertrophy. We find that the evidence for such an assertion lacking and causal interpretation unwarranted given the lack of evidence that exercise induced hormones are important in regulating hypertrophy after resistance exercise. Moreover, pharmacologic ablation and exogenous androgen administration are not appropriate models from which to draw conclusions about the effect of exercised-induced changes in hormonal concentrations on hypertrophy.
Daniel W. D. West Stuart M. Phillips McMaster University Department of Kinesiology Exercise Metabolism Research Group Hamilton, Ontario, CANADA