From The September 2000 Issue of Nutrition Science News

The Latest from the American College of Sports Medicine

by Edmund R. Burke, Ph.D.

Sports nutritionists recognize the need to keep abreast of the latest research, and every year members of the American College of Sports Medicine (ACSM) hold an annual meeting to share their latest discoveries. ACSM was founded in 1954 to exchange and develop scientific information. Now with close to 12,000 members from the United States and 50 other countries, ACSM includes many of the biggest names in sports nutrition research including Richard Kreider, Ph.D., Matt Vukovich, Ph.D., Bill Kraemer, Ph.D., and Jeff Strout, Ph.D.

More than 25 years ago at a national meeting of the ACSM, the concept of carbohydrate loading was first presented to the athletic community, and just 15 years ago amino acid supplements were recognized as beneficial for strength performance. Through the years, many of ACSM's position papers on exercise, fluid replacement, anabolic steroids and creatine have become guidelines for individuals in the sports nutrition field. This year, more than 3,000 ACSM members met in Indianapolis to present some 1,800 new studies and seminar presentations. The following are some of the most compelling.

HMB Decreases Body Fat in Athletes
Beta-hydroxy-beta-methyl butyrate (HMB) is a metabolite of the amino acid leucine. The first study of HMB was published in 1996 by Steven Nissen, Ph.D., and colleagues at Iowa State University in Ames. They showed that HMB prevented protein breakdown and promoted increased muscle growth in weight-trained subjects. Since then, HMB has become a popular supplement for strength trainers.

Although you cannot adequately evaluate a supplement after just a few trials, a second study of HMB presented this year at ACSM also has promising results. Researchers at Armstrong Atlantic State University in Savannah, Ga., showed that giving 35 weight-trained football players 3 g/day of HMB for 28 days increased lean muscle mass and decreased fat weight by 7.3 percent. This study provides further evidence that HMB is a viable supplement for bodybuilders, weight lifters and strength-speed athletes.

Phosphatidylserine Protects from Muscle Damage
A study conducted at the Human Performance Laboratory at St. Cloud State University, St Cloud, Minn., shows that phosphatidylserine (PS) has a positive effect on muscular stress following moderately intense aerobic exercise by trained runners.

"It is generally accepted that the enzyme creatine kinase is an indicator of cell membrane damage and necrosis of the muscle fibers," says John Seifert, a principal investigator at St. Cloud. "Our work shows that PS supplementation results in significantly lower amounts of creatine kinase (CK) levels 24 hours after exercise. This implies that PS can help minimize muscle fiber damage caused by muscular stress."

In Seifert's study, 12 trained runners took either 600 or 300 mg PS/day or a placebo for 15 days, then performed a 90-minute run on the 15th day in this double-blind, crossover study. Blood samples were collected at 30-minute intervals throughout the performance tests as well as 24 hours afterward.

There was a significant difference in CK blood levels between the three trials. Twenty-four hours after the 90-minute runs, those receiving the placebo showed the highest average CK value of 247 U/L. Those receiving PS supplements had CK levels less than half as high—the 600-mg group had levels at 98 U/L, and the 300-mg group had 87 U/L. These results suggest that lesser amounts of PS may be more effective than higher amounts. Further studies are needed.

Ribose May Quicken Repeated Sprint Performance
The aim of this project was to investigate whether short-term, oral ribose supplementation improved anaerobic power in young men during strenuous exercise. Ribose is a simple five-carbon sugar used by muscle cells to help rebuild stores of adenosine triphosphate (ATP), which produces energy. Eight male subjects (mean age 20 years, weight 165 pounds and body fat 8.9 percent) performed a series of six 10-second cycle sprints punctuated with 60-second rest periods. The team used a counterbalanced design in which half the subjects took four 8 g ribose doses over a 36-hour time period prior to exercise, while the other half took placebo. After a five-day washout, they switched.

In four out of six sprints, peak power was 2.2­7.0 percent higher, and mean power was 2.0­10 percent higher in the ribose-supplemented participants. Although these values themselves are not statistically significant, sprint two of the six did achieve statistical significance. Lead researcher Tim Zigenfuss, Ph.D., of Eastern Michigan State University, Ypsilanti, Mich., noted that within the framework of the present experiment, these data suggest that supplementation may affect peak and mean power in men during repeated cycle sprints.

Ephedrine and Caffeine Effects on a 10-k Run
Strength athletes and individuals trying to lose weight are familiar with both ephedrine and caffeine as weight-loss supplements. These stimulants have been shown to depress appetite and cause mild increases in body temperature, which can help burn fat. One researcher hypothesized they may also improve endurance performance by stimulating the central nervous system.

A study by researchers at the Defense and Civil Institute of Environmental Medicine, Toronto, showed that ephedrine (0.8 mg/kg) and a mixture of 0.8 mg/kg ephedrine and 4 mg/kg caffeine improved performance by 1 to 1.3 minutes in a 10-kilometer run. This improvement is considered a very large performance increase for well-trained athletes in a race lasting slightly more than 30 minutes and was statistically significant compared to the results of the placebo group.

Sidebars:
Creatine Stands Its Ground

Edmund R. Burke, Ph.D., is an exercise physiologist at the University of Colorado, Colorado Springs.