This year, 4,000 members of the American College of Sports Medicine attended the organization's annual meeting in St. Louis, Mo., to share their latest discoveries. The conference's 250 seminars featured reports of the results of nearly 1,700 new sports science studies. It provided a snapshot of current developments in nutrition aimed at helping exercise enthusiasts and athletes reach peak performance and improve exercise recovery.
Some of these latest findings include discoveries on pre-exercise diet composition and supplemention as well as confirmation on the utility of amino acids and protein to improve exercise recovery.
Fat Beats Carbs
Some athletes consume a high-fat and high-protein diet, but many experts believe such a diet may have a negative effect on performance and health, including increased adiposity and risk of coronary artery disease.
Researchers at the Evolution Sports Science, Human Performance Center, Waltham, Mass., examined the effects of a high-fat diet (52 percent of total energy intake from fat, 30 percent carbohydrate) vs. a high-carbohydrate diet (16 percent of total energy from fat, 70 percent carbohydrate) on plasma lipid and lipoproteins, body fat, aerobic capacity, lean body mass and bone-mineral density in 28 endurance-trained triathletes over a 15-week period.
Plasma, total cholesterol, low-density lipoproteins, high-density lipoproteins, triglycerides, homocysteine, lipoprotein(a), aerobic capacity, bone-mineral density and body composition were measured at baseline and after five, 10 and 15 weeks. From baseline to week 15, there were no significant differences between each group in total and percent body fat, lean tissue mass, body weight and total body bone density. Changes in lipids and lipoproteins from baseline to week 15 did not differ between the two groups except in HDL, which decreased significantly, and in triglycerides, which increased significantly in the carbohydrate-rich diet.
Bottom line: During periods of endurance training when energy requirements are high, increasing the percentage of dietary fat in well-trained triathletes to approximately 52 percent of total energy did not increase body weight or adiposity. It also did not result in adverse changes to the lipoprotein profile, aerobic capacity, body composition or bone-mineral density.
Regulating Blood-sugar levels
Many people avoid sports drinks before exercising for fear they will cause a surge of insulin, which would then lower blood glucose levels during the initial stages of exercise. Researchers at the University of Birmingham, U.K., studied the effect of varying amounts of pre-exercise glucose intake on glucose and insulin levels during cycling exercise and a time-trial performance.
Nine male cyclists completed four exercise trials in random order. Forty-five minutes before the start of exercise subjects consumed 500 mL of a beverage containing either 0 g, 25 g, 75 g or 200 g glucose. The exercise trials consisted of 20 minutes of submaximal steady-state exercise at 65 percent of maximal power output immediately followed by a time trial.
Plasma insulin concentrations at the onset of exercise were significantly higher in 75 g and 200 g compared with 0 g and 25 g trials. Plasma glucose fell rapidly during submaximal exercise in all glucose trials, while plasma glucose remained stable in the 0 g group. There were no differences in plasma glucose concentration between the exercise trials at any time point. Hypoglycemia was observed in five subjects during submaximal exercise after pre-exercise glucose feeding, while none of the subjects developed hypoglycemia after the 0 g trial. However, there was no difference in time-trial performance between the four trials.
Bottom line: Ingesting 0 g, 25 g, 75 g or 200 g glucose 45 minutes before a 20-minute submaximal exercise did not affect subsequent time-trial performance. In addition, mild rebound hypoglycemia following pre-exercise glucose ingestion did not negatively affect time-trial performance.
Perils Of Pre-event Snacking
Because data on the effects of pre-event snacking among children during athletic events are limited, researchers at Stanford University, Palo Alto, Calif., compared the effects of two pre-event snacks (a raisins-and-peanuts mix or a bagel with lemonade) on blood levels of glucose, insulin and lactic acid following a standard soccer match.
Experienced soccer players ages 10 to 12 years ate a standard breakfast on two game days. Participants randomly consumed one of the two 350-calorie, pre-event snacks before the first match and the second snack choice before the second match.
Researchers analyzed blood samples for glucose, insulin and lactic acid using standard methods. Subjects wore heart rate and body motion monitors during the two matches to document activity levels. During the match, mean heart rate was similar for the two groups. Pre-event values (mg/dL) for glucose, insulin and lactic acid did not differ. Differences were significant for glucose (+13.0 mg/dL for raisin and peanuts mix, +24.2 mg/dL for bagel with lemonade), and insulin (-3.5 mg/dL for raisin and peanuts mix, +4.7 mg/dL for bagel with lemonade), but were not for lactic acid.
Bottom line: Differences in the glucose and insulin responses were probably due to the composition of the snack. The fiber in the raisins combined with the protein and fat of the peanuts appears to result in a more desirable insulin and glucose level after vigorous physical activity in young soccer players.
PC Is Physically Correct
Strength athletes often look for better ways to reduce muscle damage and preserve muscle mass during periods of hard resistance training. Researchers at the University of Connecticut at Storrs examined the influence of phosphatidylcholine on body composition and muscle damage related to repeated resistance training.
In a three-week double-blind placebo-controlled study, nine male subjects took supplements while doing resistance training. Researchers measured muscle damage (creatine kinase and malonaldehyde increases) for several days following exercise and discovered the group taking phosphatidycholine had no muscle damage on the day after the first exercise session, whereas the placebo group had increased muscle damage lasting for up to eight days. The group taking phosphatidycholine also had a significantly greater increase in lean body mass (0.74 kg vs. 0 .33 kg).
Bottom line: Phosphatidycholine had a favorable effect on lean body mass and recovery from resistance exercise, and the effect may become more pronounced over time.
Proteases Reduce Soreness
Both protease and nonsteroidal anti-inflammatory drug supplementation have been shown to attenuate the effects of delayed-onset muscle soreness resulting from intense exercise. Researchers at Elon University in North Carolina conducted a randomized double-blind study on males who ran downhill on a treadmill for 30 minutes at 80 percent predicted maximum heart rate. Subjects took either two protease tablets (325 mg pancreatic enzymes, 75 mg trypsin, 50 mg papain, 50 mg bromelain, 10mg amylase, 10 mg lipase, 10 mg lysozyme); 1,000 mg acetaminophen; or a placebo for four days after the run.
Study results showed that pain was lower in the back and front of the right leg in the placebo and acetaminophen groups compared with the protease group when measured 24 hours and 48 hours after running. However, leg strength was superior in the protease group compared with placebo and acetaminophen groups at 24, 48 and 72 hours after exercise.
Bottom line: Protease may facilitate the restoration of muscle function, possibly by minimizing inflammation and accelerating muscle healing.
Aminos Enhance Recovery
A growing number of endurance athletes are taking amino acids after strenuous exercise to prevent muscle damage and to aid in recovery. Researchers at the University of Tokyo examined the effects of an amino acid mixture on parameters related to recovery from distance running. They tested 13 well-trained male triathletes who ran two 30-km runs within 72 hours. Athletes were divided into two groups according to weekly running distance, age, height, weight and estimated 30-km running time.
In double-blind fashion, group A took an amino acid formula and group B, consumed a sports drink containing 26 g/L fructose, 61 g/L sodium chloride and flavoring. The amino acid formula taken by group A was the same drink as taken by group B but with added amino acids: 640 mg/L leucine, 520 mg/L isoleucine, 420 mg/L valine, 720 mg/L glutamine and 720 mg/L arginine, plus small amounts of threonine, lysine, proline, methionine, histidine, phenylalanine and tryptophan to total 3.6 g total amino acids per dose in a base of manitol.
Participants took 0.6 g amino acid mix or placebo 40 minutes before a run, and again at 5-, 10-, 15-, 20- and 25-km running distances.
During the 72-hour recovery period, group A took the amino acid mix five times (3.6 g with each morning and evening meal). Researchers monitored the subjects' heart rates and took blood samples (for glucose, lactate and ammonia analysis) at rest, run start, and at 10, 20 and 30 km. There were no consistent blood value differences between the groups.
An index of physiological running efficiency (distance run per heartbeat) showed that mean efficiency for group A was about 4 percent greater on the second run, whereas mean efficiency for group B declined by 0.4 percent during the second run. All subjects in group A, compared with one subject in group B, showed increased efficiency during the second run.
Bottom line: Supplementing with amino acids may enhance recovery between two 30-km runs within 72 hours, or more between two strenuous athletic performances spaced about 72 hours apart.
Use Protein In Recovery Drinks
The human body, which requires amino acids to grow new muscle cells and repair damaged ones, can obtain these nutrients only from the diet. Researchers from Virginia Tech University, Blacksburg, Va., compared the postexercise effects of milk with a carbohydrate caloric equivalent on body composition changes and strength gain resulting from resistance training. Nineteen untrained men ages 18 to 25 lifted weights three times a week for 10 weeks. Participants drank either milk (about 84 g carbohydrate, 19 g protein, 5 g fat) or the same amount of calories as pure carbohydrates after weight training.
Both groups reduced body fat significantly (-1.1 percent), but the milk group had a greater increase in lean body mass (1.6 kg vs. 0.8kg in the carbohydrate-only group). Both groups also increased body strength. The amount of amino acids in the blood was much greater after milk consumption than after carbohydrate-only consumption.
Bottom line: It would be best to consume a food or supplement that contains carbohydrate and protein, rather than carbohydrate alone, after hard exercise. Like the previously reported study from Japan, this research indicates the need for protein in an exercise-recovery drink.
Edmund R. Burke, Ph.D., is an exercise physiologist at the University of Colorado, Colorado Springs.
Natural Foods Merchandiser volume XXIII/number 11/p. 34, 40