Purpose: Controversy exists as to whether adding protein (PROT) to a carbohydrate (CHO)-electrolyte beverages will reduce skeletal muscle damage. Some of the inconsistency in the literature appears to be due to the varied timing of ingestion. The present study is designed to determine whether the timing of a CHO-PROT beverage influences indirect indicators of exercise-induced muscle damage and running performance. Methods: Three trials were used in the present study. Across all trials, participants completed a 30 minute downhill run (-9.5% grade), followed by a 1.5 mile treadmill running time trial 24 hours later. Lower body muscle soreness was assessed before both runs. Nine aerobically trained subjects (6 males; 3 females) completed the protocol three times in a crossover design with 7 days in between trials. Subjects were given two familiarization trials in order to decrease the learning curve for the time trial. Either a CHO-PROT or non-caloric placebo beverage was given 30 min and 5 min prior to, at the 15 min mark during, immediately after, and 30 min after the downhill running protocol. In the first treatment (T1), a total of 360 kilocalories (72 grams CHO, 18 grams PROT) was given 30 min and 5 min prior to downhill running, as well as at the 15 min mark, with placebos used at other time points. In the second treatment (T2), the same caloric amount was given but only immediately after and 30 min after downhill running, with placebos used at other time points. In the placebo treatment (PL), a placebo was given at all time points. The total fluid volume consumed during all trials was similar (approximately 92 fluid ounces). Treatments were randomized as to eliminate the influence of a repeated bout effect on muscle damage or a learning curve for the next day time trial. Dietary intake (total energy, g CHO, g PROT, g fat) 3 days prior to, and 1 day after, the exercise trials was also examined. Data were analyzed using repeated measure ANOVA. Results: There were no significant differences in the 1.5 mile time trial between the T1 trial (648.11 ± 64.79 s), the T2 trial (660.00 ± 52.91 s), and the PL trial (654.00 ± 56.48 s) (p > 0.05). There were also no differences between T1, T2, and PL trials for 24-hour delayed onset muscle soreness (2.9 ± 1.8, 3.3 ± 1.7, 3.8 ± 2.0, respectively) (p > 0.05). However, there was an order effect (p < 0.05) in regards to muscle soreness. Dietary intake did not differ between trials (p > 0.05). Conclusions: CHO-PROT beverages had no significant effect on muscle soreness at 24-hours post downhill run or next-day 1.5 mile running performance as compared to a non-caloric placebo beverage. Practical Applications: The present study does not support the need for CHO-PROT beverage use before or after eccentrically biased aerobic exercise. As there was a significant order effect present, 7 days between trials was inadequate to prevent the repeated bout effect in regards to muscle soreness in aerobically trained individuals. Although other studies using similar methodology have not reported an order effect, future studies using eccentrically biased aerobic exercise may want to consider longer rest periods between trials to minimize this effect.
Available at: http://works.bepress.com/beau_greer/12/