This activity, also called strength training, increases muscle strength and mass, bone strength and the body's metabolism. The final result of effective resistance training is weight loss, better body image, improved muscle tone and strength, as well as enhanced self-esteem.
This body-improvement effort includes the use of free weights, weight machines and calisthenics. When using free weights, dumbbells and bars stacked with weight plates, users are responsible for both lifting the weight and determining and controlling their body position through the range of motion. Weight machines, on the other hand, dictate the body's movement. Calisthenics, such as chin-ups, push-ups and sit-ups, incorporate the body as the source of resistance. In recent years, resistance tubing, involving the use of an elastic band for resistance to active muscles, has become popular.
Consuming additional nutrients may be necessary during intense resistance exercise to allow for maximal "expression" of muscle and strength gains may seem logical. Television commercials in the off-hours show that the use of general and specific dietary supplementation appears to be widespread among both serious and casual athletes with a multitude of specific formulas offered. Scientific support for specific "hyper" nutrition to aid muscle growth has been periodically claimed; however, any support for the use of these nutrients is usually nonquantitative and often unsystematic, and conclusions are often open to subjectivity. This has led to confusion in the literature on what specific and general nutrition is of value for numerous conditions, including augmentation of the effects of exercise on muscle mass and strength.
A more quantitative approach to identifying beneficial nutrients is suggested through meta-analysis of the data. This technique minimizes subjectivity by standardizing selections, data pooling, and data analysis to draw conclusions. This scientific approach has been adopted by a team of researchers to determine whether supplementation of dietary components, above normal intakes or above the requirement, increases lean mass gains associated with resistance training above that of the appropriate control treatment. A secondary objective was to determine whether dietary supplementation during resistance training could augment strength gains.
A New Study
The authors of "Effect of Dietary Supplements on Lean Mass and Strength Gains with Resistance Exercise: A Meta-Analysis" are Steven L. Nissen and Rick L. Sharp, from the Iowa State University, Ames, IA. Dr. Nissen is a professor at Iowa State University, which owns the patents related to HMB. In addition, Dr. Nissen is the Chief Executive Officer (CEO) of Metabolic Technologies, Inc., which is the licensee of the HMB patents. HMB is the subject of part of the meta-analysis. The findings appear in the February 2003 edition of the Journal of Applied Physiology.
Methodology
The researchers defined the term "supplement" as any oral product designed to increase the effects of resistance-training exercise. A list of substances was compiled from the product lists of eight dietary-supplement marketing companies, a review of six magazines targeted specifically at the body-building community, and five published scientific reviews on dietary supplements. The compiled list contained about 250 supplements and was used to search the literature.
The search was confined to clinical trials only. Titles were rejected if they indicated that the study did not involve a dietary supplement, or clearly did not involve any form of resistance exercise, or the subjects suffered from an abnormal health condition. Only studies using healthy adults (>18 years of age) were included for analysis. There was no discrimination of gender, and no restrictions were placed as to the exercise history of the subjects, although training was recorded as a variable.
Only randomized, placebo-controlled studies published in peer review journals were selected. Studies were excluded if there was any dietary restriction imposed that could compromise the hypertrophic consequences of the resistance exercise. The study had to be at least three weeks in duration and had to involve subjects carrying out a full-body (all major muscle groups) resistance-training regimen two or more times per week.
The primary outcome criteria was lean body mass. Estimates of lean mass could be in the form of lean body mass, fat-free mass/weight, or fat and bone-free mass or if data was provided to calculate one of these variables. Strength was the secondary outcome criterion, but papers were not rejected if they failed to report strength data. Strength data were standardized within a study by averaging the percent change for all reported strength measures.
Results
- Of the approximately 250 candidate supplements, only 48 studies (in 40 citations) met all the inclusion criteria. Of these, six supplements were supported by greater than one citation each: creatine (n = 18), HMB (n =9), chromium (n = 12), DHEA (n =2), rostenedione (n = 3), and protein (n =4, with relaxed inclusion criteria).
- Of the original list of 250 substances marketed as dietary supplements, creatine (methyl guanidine-acetic acid) and HMB (ß-hydroxy-ß-methylbutyrate, produced in the body and in certain foods such as catfish and alfalfa) were the only supplements found to be effective in increasing lean tissue gain with resistance training.
- With regard to lean gain, creatine and HMB have similar effects, with lean gain approximately doubling over the placebo group. Although this could suggest a similar mechanism of action, the literature would suggest independent mechanisms.
Conclusions
In summary, of the more than 250 dietary products available, only HMB and creatine supplements have sufficient scientific evidence showing that lean body mass and strength gains accompanying resistance training are augmented with their use. These findings could have a significant impact on the purchasing decisions of those resistance-training enthusiasts who seek body enhancement through the use of supplements.
The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.
Journal
Journal of Applied Physiology