October 15, 2007
Exercise ETC's Review of Exercise Related Research
Compiled by Chris Marino, MS, CSCS
Director of Education, Exercise ETC
Creatine Supplementation Increases Muscle Mass in Older Adults
"Sarcopenia" is to muscle as "osteoporosis" is to bone. The age-associated decline in muscle mass becomes pathological when it reaches 2 standard deviations below the average peak muscle mass that is attained at around the age of 30. It’s estimated that functional impairment due to sarcopenia affects a quarter of adults over age 75.
Although resistance exercise is the best method for increasing lean mass across all age groups, gains in lean mass are dependent on hormones, such as testosterone, which facilitate anabolic activity. Levels of anabolic hormones are substantially lower in older adults than in younger adults, thereby delaying increases in muscle hypertrophy that would occur with resistance exercise alone. Due to the urgency presented by conditions such as sarcopenia, researchers are seeking alternative ways to augment the effects of resistance exercise on muscle hypertrophy in older adults. Creatine may be one such alternative.
A recent study assessed whether creatine monohydrate and conjugated linoleic acid would increase lean body mass, decrease fat mass, and increase strength when used in combination with resistance exercise in older adults. Thirty-nine men and women between the ages of 65 and 85 participated in 6 months of resistance training while supplementing with creatine monohydrate and conjugated linoleic acid. Researchers measured muscle strength & endurance, a variety of performance-based tasks, body composition and other markers.
The results were positive. Although resistance exercise alone improved functional capacity and strength, greater improvement in endurance, strength and lean mass as well as lower fat mass, were observed in the creatine monohydrate and conjugated linoleic acid group. In this study, the combination of creatine monohydrate and conjugated linoleic acid did effectively augment the increase in lean mass associated with resistance exercise.
It's important to note that this is the first known study to evaluate use of creatine monohydrate and conjugated linoleic acid along with resistance exercise in the older adult population, and that further studies should be published before any recommendations can be made to the public. As always, fitness professionals should use caution before recommending nutrition supplements to clients, and any client wanting to use any supplement should be advised to speak with a registered dietitian or a physician first.
Tarnopolsky, M. (2007) Creatine monohydrate and conjugated linoleic acid improve strength and body composition following resistance exercise in older adults. PLoS ONE. 2(10): 991.
Can Static Stretching Actually Improve Performance?
Static stretching has become quite controversial in performance training over the past decade. Research has reported that there are no apparent injury reduction benefits for pre-exercise stretching and some speculate that static stretching could actually increase injuries in sports that are explosive in nature because of decreased force potential in a muscle that's been stretched for as little as 15 seconds. Interestingly, a recent study published in Medicine and Science in Sports and Exercise now suggests that de-conditioned populations may experience performance gains with static stretching alone.
Thirty-eight participants were randomly assigned to stretching and control groups. The stretching group participated in lower-extremity static stretching 3 days per week for 40-minutes over 10 weeks. No other exercise activities were permitting during this period. Researchers assessed flexibility, explosive power via 20-meter sprint, standing long jump and vertical jump, strength via 1RM testing for knee flexion and extension, and strength endurance via total repetitions at 60% 1RM in knee flexion and extension.
Although flexibility did improve 18% over the course of the study, what surprised researchers was the significant increase in performance measures. Among tests of power, standing long jump, vertical jump, and 20-meter sprint participants all improved. Strength improved 15.3% for knee flexion and 32.4% for knee extension, whereas knee flexion endurance and knee extension endurance increased 30.4% and 28.5%, respectively. Controls showed no improvement in any of the variables assessed.
The results of this study indicate that static stretching might benefit individuals who are not capable of participating in a traditional exercise program. This may explain some of the perceived strength benefits attained when a deconditioned individual starts a yoga program. Athletes and other well-conditioned populations are not expected to see similar benefits.
Kokkonen, J. et al (2007) Chronic static stretching improves exercise performance. Medicine and Science in Sports and Exercise. 39(10): 1825-31.
Is Soy Protein As Effective as Whey Protein?
The combination of resistance exercise and adequate protein intake is essential for increasing lean body mass. Although optimal protein sources are derived from whole foods, supplemental protein is popular because it is convenient and effective in providing the essential amino acids necessary for building muscle. Supplemental proteins are typically divided into two categories: soy products and milk-based (whey and casein).
Soy foods contain phytoestrogens or isoflavones, which are found to both promote and inhibit estrogenic activity. This may deter individuals from using soy-based proteins because an increase in estrogen results in reduced testosterone production. Milk proteins contain a greater number of BCAA (branch-chain amino acids) when compared to soy. BCAA’s, including leucine, isoleucine and valine have been found to have important properties in muscle hypertrophy. Unfortunately, research directly comparing the two types of protein and their effects on hypertrophy is lacking... until now.
Researchers had twenty participants ingest 50g of either Soy concentrate, Soy isolate, Soy Isolate with Whey Blend, or a Whey Blend only while on a 12-week resistance training program. Twenty-five grams were taken with 10-12 oz of water within 1 hour of resistance training. An additional 25g was ingested later during the day. Pre- and post-measures of body composition, testosterone, estradiol, and SHBG in addition to total cholesterol, LDL, and glucose were evaluated.
Interestingly, all protein sources were equally effective at increasing lean body mass. The testosterone/estradiol ratio was increased in all groups while estradiol decreased. The greatest increase in testosterone/estradiol was found in the soy isolate + whey blend group, while estradiol was lowest in the whey blend group.
In actuality, most manufacturers use a combination of milk and soy-based proteins in their products. The researchers speculate that reductions in testosterone as a result of soy proteins may be dose dependent and that the smaller amounts in mixed protein powders is not sufficient to cause androgens to decline. There was no decline in testosterone in any of the groups in this study.
It's important to note that the sponsors of this study included The Solae Company, which is a major manufacturer of Soy-based products. The impact of their contribution to the published results cannot be ascertained.
Kalman, D. et al (2007) Effect of protein source and resistance training on body composition and sex hormones. Journal of the International Society of Sports Nutrition. 4(1): 4
Low Bone Mass Common in Women Runners
Weight-bearing activities are known to promote increased bone mineral density (BMD), especially in women under 30. Therefore, it would be logical to conclude that the impact-nature of running would improve BMD. A recent study, however, found that intercollegiate female runners have the lowest bone mineral density (BMD) than athletes in other sports.
Researchers at Michigan State University collected data from 99 female NCAA division 1 athletes in 12 sports and compared BMD values controlling for body mass and menstrual dysfunction. Compared to all other sports, runners had lower total BMD and BMD at the pelvis and lumbar spine. Although not significantly different from runners, swimmers presented with lowest BMD in the legs.
If running is an intense weight-bearing activity that should increase BMD, what factors are voiding the projected gains? The researchers speculate that calorie intakes in female runners may be insufficient relative to the costs of higher volumes of training. They also cite the possibility of a high incidence of eating disorders and low calcium intake in long-distance runners.
The results of this study should encourage athletic trainers to be aware of the concerns for stress fractures and bone injuries in this population. Coaches and parents should address psycho-social factors that are contributing to undereating while emphasizing the need to prevent osteoporosis in youth.
Mudd, L.M., et al (2007) Bone Mineral Density in Collegiate Female Athletes: Comparisons among Sports. Journal of Athletic Training. 42(3):403-408