Journal Title (Medline/Pubmed accepted abbreviation):J. Sports Med. Phys. Fitness
Page numbers: 151-157
Summary of background and research design
Background: Ingestion of a beverage with carbohydrates (CHO) and protein (PRO) during exercise has been shown to attenuate exercise-induced muscle damage by increasing the amount of muscle protein being built (mostly attributed to PRO) and decreasing the amount of muscle protein being broken down (mostly attributed to CHO). However, the optimal ratio of CHO:PRO has not yet been established.
Serum creatine kinase is a parameter that is directly proportional to muscle damage. Myoglobin is released from damaged muscle tissue, and therefore is also directly proportional to muscle damage.
Goal: To provide beverages with different CHO:PRO ratios to untrained men during resistance training and compare post-exercise muscle soreness, serum creatine kinase, and myoglobin during the recovery period.
Subjects: 28 males that had not been involved in regular exercise in the prior 6 months, age 24.4 ± 2.9 y
Experimental design: randomized, blinded, placebo-controlled, parallel groups
Treatments: All beverages were 9% solids (90 g of each carbohydrate/protein blend per liter). The protein source was whey protein and the carbohydrate source was glucose.
a) 4:1 CHO:PRO
b) 3:1 CHO:PRO
c) 2:1 CHO:PRO
d) Placebo- water + salt, artificial sweetener, and lemon juice
Protocol: Before the exercise protocol, the participants were familiarized with the equipment and assessed for height, weight, and body composition. One repetition maxima (1RM) were determined for 7 resistance exercises that included the major muscle groups (ex. leg press and bench press). On the day of testing, the participants first provided a baseline blood sample. They ingested 2.5 mL per kg body weight of their assigned test beverage, and then began the exercise sessions. Equivalent beverages were consumed at 15 min intervals to equal 4 beverages and 10 mL/kg body weight total. After exercise, they rested for 1 hr, and a second blood sample was acquired. A third blood sample was collected 24 hrs after exercise. Perceived muscle soreness was reported 1 hr, 24 hr, and 48 hr after exercise. Blood was assessed for plasma creatine kinase concentration and plasma myoglobin concentration.
Summary of research findings
- Creatine kinase concentrations were slightly elevated 1 hr after exercise in all groups (p > 0.05 compared to baseline). After 24 hrs, creatine kinase concentration increased from about 150 IU/L at baseline to about 300-400 IU/L all the CHO:PRO groups and almost 900 IU/L in the placebo group (p < 0.05). This suggests that all the CHO:PRO beverages attenuated muscle damage to a similar degree.
- One hour post-exercise, concentrations of myoglobin were elevated in all groups, with the concentrations in the placebo group the highest. The next day, myoglobin concentrations had returned to baseline for all participants who had consumed a CHO:PRO beverage, though concentrations remained elevated in participants who consumed to placebo beverage.
- On a scale of 1-9 with 1 being no soreness and 9 being unbearable, soreness went from 1 at baseline to about 2-2.5 at 1 hr post-exercise then to 2.5-3 at 1 day post-exercise and about 2-3 at 2 days post-exercise. There were no significant differences between groups.
Key practice applications
Consumption of the CHO:PRO beverages during resistance training significantly attenuated markers of protein damage that incurred during the following 24 hrs compared to a low calorie control. However, the protocol did not distinguish between the different ratios of CHO:PRO. Beverages with 2:1, 3:1, or 4:1 CHO:PRO all provided similar protection from muscle damage.
The authors did not provide the standard deviations/errors for their data, so it is impossible to know the inter-individual variability among their participants or gauge the practical relevance in the differences.