Exercise is Medicine

by Jade Teta, ND, CSCS, and Keoni Teta, ND, CSCS

The New Science of Building Muscle

Muscle development and fat loss are linked. It is quickly becoming apparent that poor clinical outcomes for weight loss are likely a result of diet and exercise prescriptions that don’t discriminate between the types of weight lost. Losing muscle has clinical consequences for long-term maintenance of a healthy weight. This month, we review why muscle is important to metabolism and what exercise science has to say about the most effective ways to build muscle.

Metabolic Consequences of Muscle Loss

It has been known for quite some time that the low-calorie/aerobic exercise model creates a much less efficient metabolism in the long run. A 1999 study published in the Journal of the American College of Nutrition showed just how damaging the standard weight loss model can be to metabolic efficiency.¹ This study looked at a group of obese individuals who were put on a very low-calorie diet and assigned to one of two exercise regimens. One group followed the popular aerobic exercise model (walking, biking, or jogging four times per week), while the second group did resistance training three times per week and no aerobic exercise.

At the end of the 12-week study, both groups lost weight, but the difference in muscle vs. fat loss was striking. The aerobic group lost 37 pounds over the course of the study. The resistance-training group lost 32 pounds. Of the 37 pounds lost by the aerobic group, 10 pounds of muscle was lost on average. In comparison, the resistance-training group lost fat exclusively and had no muscle wasting. This had consequences on resting metabolic rate. At the conclusion of the study, the aerobic group participants were shown to be burning 210 fewer calories at rest per day, while the resistance-training group actually increased their metabolism by 63 calories per day.

The above study shows just how detrimental a loss of muscle mass can be. A review published in the January 2007 issue of Sports Medicine highlights some very important reminders to physicians and exercise enthusiasts.² First, basal metabolic rate (BMR) accounts for over two-thirds of the calories burned at rest, and more than half of BMR can be accounted for by how much muscle a person has. So, the most reliable way to enhance or maintain the metabolic rate is through the development and maintenance of muscle tissue.

By employing a low-calorie diet and aerobic exercise regimen, we may be making things worse, not better. Dietary restriction decreases BMR by 10% to 20%.² Adding aerobic exercise to the mix does nothing to reverse this and may actually enhance the loss of metabolism through a wasting of muscle tissue. It was shown as far back as 1988 that a slowed BMR is a predictor of fat gain over the course of a 2-year period.³ In this study, those with the slowest metabolic rate had a 4-fold increase in gaining 15 or more pounds over the next 2 years.

Muscle Growth May Be Individualized

The common understanding with muscle development has been to use moderately heavy weights for 3 to 5 sets in a repetition range of 8 to 12 repetitions.⁴ This method has been fairly well established through many different studies and reviews over the years, and is reliable for most individuals.^4,7 However, a few newer studies show that there may be more to the picture.

Two studies published in the Journal of Strength and Conditioning Research (March 2008) suggest that there is not simply one protocol to build muscle. These studies, published by Dr. C. Martyn Beaven, usher in a new era in our understanding of what it takes to build muscle.^5,6 In the first study, professional rugby players were given different exercise protocols that included the same exercise to determine testosterone production. Testosterone release with exercise is a direct predictor of the muscle-building potential of the exercise.^4,7 The only difference in the protocols was in their set, rep, weight, and rest schemes.

One, the “muscle-building” protocol, involved 4 sets of 10 reps with moderately heavy weight and 2 minutes’ rest between exercises. Another, the “strength protocol,” involved 3 sets of 5 reps using heavy weights and longer rests (3 minutes). The next was an endurance protocol, which involved lighter weights and a set and rep scheme of 5 sets of 15 reps. The rest period in this protocol lasted only 1 minute. The final protocol, which acted as a control, involved light weight and low reps with a 1-minute rest between each exercise.

Surprisingly, the muscle-building protocol did not come out as the clear winner for testosterone production as would be predicted. In fact, each protocol seemed to favorably alter testosterone production in at least some participants. After seeing these results, the authors did a follow-up study wherein they stratified each individual to the protocol that delivered the maximum testosterone release for that person. When they looked at the results from the second study, the authors found that a significant majority of participants could increase both size and strength with their particular protocol, whether it involved light weights and high reps or heavy weights and low reps.

Final Thoughts

Taken together, the results reviewed above shows several important facts about muscle gain. First, resistance training is the essential component to losing fat while maintaining muscle and metabolic efficiency. Next, there is not one protocol best for all people; instead, muscle gain is unique for the individual and depends on the individual hormonal response to the exercise protocol. Stratifying people to a workout protocol that suits their individual metabolic tendencies may make muscle-building more predictable and efficient.

Notes

1. Bryner et al. Effects of resistance vs. aerobic training combined with an 800 calorie liquid diet on lean body mass and resting metabolic rate

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   J Am Coll Nutr. 1999;18:115–121.

2. Hansen et al. The effects of exercise training on fat-mass loss in obese patients during energy intake restriction. Sports Med. 2007;37(1):31–46.

3. Ravussin et al. Reduced rate of energy expenditure as a risk factor for body-weight gain. N Engl J Med. 1988;318(8):467–472.

4. Kraemer et al. Hormonal responses and adaptations to resistance exercise and training. Sports Med. 2005;35(4):339–361.

5. Beaven et al. Salivary testosterone and cortisol responses in professional rugby players after four resistance exercise protocols. J Strength Cond Res. 2008;22(2):426–432

6. Beaven et al. Significant strength gains observed in rugby players after specific resistance exercise protocols based on individual salivary testosterone responses. J Strength Cond Res. 2008;22(2):419–425

7. Hayes et al. Interactions of cortisol, testosterone, and resistance training: influence of circadian rhythms. Chronobiol Int. 2010;27(4):675–705.