Are Hormonal Changes Necessary To Increase Muscle Mass?

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Are Hormonal Changes Necessary To Increase Muscle Mass?
A Review of A Study

Wilkinson SB, Tarnopolsky MA, Grant EJ, Correia CE, Phillips SM. Hypertrophy with unilateral resistance exercise occurs without increases in endogenous anabolic hormone concentration. European Journal of Applied Physiology. 2006; (in press).
For many years, it’s been postulated that certain resistance training exercises and protocols can internally (endogenously) increase testosterone and growth hormone. The assumptions have been that such increases are either necessary for muscular hypertrophy (increases in muscle mass) or enhance muscular hypertrophy from resistance training.

These assumptions have been embraced by different camps and paradigms of training.

For example, in the high intensity training camp, performing higher repetitions of the squat to stimulate hormonal responses and total body muscular hypertrophy has been recommended for more than 35 years. The high volume training camp recommends performing many sets of different exercises with short rests between sets to simulate hormonal release and muscular hypertrophy.

However, as Wilkinson and colleagues noted in the introduction to their report of their study, there is limited evidence to support these assumptions. Their aim was to study the role of endogenous hormones in producing muscular hypertrophy and they chose an elegant way to examine this relationship.

Wilkinson et al. used unilateral (one limb) training of the quadriceps. In this way, individual factors are controlled. In unilateral training, however, because of some neuromuscular "cross-over education", the untrained limb is likely to show some modest increase in strength. But, the untrained limb generally will show limited or no evidence of muscular hypertrophy.

The unilateral design provides the opportunity to examine what factors are involved in muscular hypertrophy. Wilkinson et al. hypothesized that in the trained limb, unilateral training would result in increases in strength and muscular hypertrophy but without a change in endogenous hormone concentrations. They also hypothesized that the untrained limb would show smaller strength gains than the trained limb and would not show muscular hypertrophy.

Ten young men with no prior resistance training experience were participants in the study. They were randomly assigned to train their dominant or non-dominant leg. After determining 1 RM (1 repetition maximum) for the leg extension and leg press, the participants trained three times per week for eight weeks. For the first four weeks, participants performed three sets of each exercise with 80% to 90% of 1 RM (6-10 repetitions) and with three minutes between sets. In weeks five through eight, the first three sets of each exercise were performed for eight to 10 repetitions with a fourth set performed to voluntary fatigue (5-10 repetitions). Training was progressive with resistance increased based on 1 RM testing every two weeks.

State-of-the-art biopsy, scanning, hormonal, and blood metabolite measurements were used and 1 RM strength testing was used for the trained and untrained legs. Hormonal measurements were taken before the first training session and before the last training session. For those sessions, in addition to the first measure prior to exercise, hormones were measured (testosterone, free testosterone, luteinizing hormone, sex-hormone binding globulin, cortisol, free testosterone to cortisol ratio, growth hormone, and insulin-like growth factor) immediately after training and then again at 30, 60, 90, and 120 minutes after the session.

Leg strength improved about 18% in the trained leg and only about 3% in the untrained leg for leg press. Leg strength improved about 45% in the trained leg and about 15% in the untrained leg for leg extension, with this gain in leg extension in the untrained leg demonstrating the "cross-over effect".

Data indicated that there was an increase in muscle and muscle fiber cross sectional area (CSA) primarily attributable to a change in the percentage and percentage area of Type IIa fiber in the trained but not the untrained quadriceps.

There were no changes for any of the hormones that were measured.

Wilkinson et al. concluded that while it has long been proposed that acute and chronic endogenous hormonal changes are critical for inducing muscular hypertrophy from resistance training, there is little to no evidence and no definitive study to support this long-held assumption.

Wilkinson et al. noted that: "Our interpretation of the current data is that a minimal testosterone concentration is required for basal functioning of the regulatory processes underlying hypertrophy…hypertrophy can occur in the absence of changes in endogenous testosterone" (pp 6-7, in press pdf). Exercise induced increases in endogenous hormones may enhance hypertrophy but such increases as demonstrated by this study are not required.

Bottom-line: There have been long-held assumptions from different training camps and paradigms about the need to resistance train in certain ways to induce endogenous hormonal changes deemed essential for producing muscular hypertrophy. There is little evidence to support those assumptions and, therefore, little or no reason to train in specific ways that have been "prescribed" to induce increases in endogenous hormone release and basal levels.

In the presence of an overload, an adequate diet sufficient in protein to maintain positive protein balance, and adequate time for adaptation and recovery, muscular hypertrophy will occur with any reasonable training protocol with the degree of obtainable hypertrophy primarily dependent upon genetic factors.

Interestingly, either camp – high intensity or high volume – may dismiss the results of this study. The high intensity camp may argue that strength gains and muscular hypertrophy would have been greater with fewer sets (6 for one muscle group in the first part of the study and then eight in the second part) and the use of the squat. The high volume camp may argue that there was too much time (3 minutes) between sets to increase hormonal levels to maximize muscular hypertrophy.

It appears that neither camp would have much evidence for their arguments. The strength gains and muscular hypertrophy shown in this study are within the range of what can be expected with training two to three times per week with just the leg press and leg extension for one set each, and regardless of the time between sets1.

To reiterate, it appears that you do not have to train in an extreme way advocated by different camps to produce increases in strength and muscular hypertrophy.

Reference

Carpinelli RN, Otto RM, Winett RA. A critical analysis of the ACSM position stand on resistance training: insufficient evidence to support recommended training protocols. JEPonline. 2004; 7: 1-64. (see especially pp 12-13 for a review of other short-term studies with people initiating resistance training)