Researchers are finally starting to branch out with their hypotheses about creatine's functions, instead of just trying to determine if creatine supplementation increases lean body mass. To my knowledge, this was the only study of its kind to measure how creatine supplementation effects substrate utilization at rest.
The authors of this study hypothesized that creatine supplementation would result in a downward shift from fat, the typical resting substrate utilization, to an increase in carbohydrate utilization. Subjects participated in a 12-week resistance training program and in a double-blind, crossover design, were given creatine (20g/4 days, followed by 2g/day for 17 days) or placebo in two separate trials.
Each trial was separated by a 4-week washout period [research has shown it takes about 30 days for creatine stores to return back to normal after supplementation] and were then again given supplemental creatine or placebo.
Although the primary outcome of the study was to determine the effects of creatine on substrate utilization, what creatine study would be complete without measuring gains in strength? So, just to cover the study in its entirety, here is my brief summary. Strength (measured by 1-RM bench press) increased in the creatine group vs. placebo group and there were no significant differences in body composition.
As for substrate utilization, carbohydrate oxidation was increased during creatine supplementation (as there was a trend for an increase in respiratory exhange ratio (RER); a higher RER means more carbs are being "burned" and lower RER demonstrates greater fat utilization).
The exact mechanism is unclear, so more research is definitely warranted. The authors concluded that these results demonstrate individuals who supplement with creatine may decrease their ability to lose fat due to the RER increase.
The purpose of this study was to determine the effects of amino acid supplementation on muscular strength, power, and high-intensity endurance. Seventeen previously trained subjects were randomly assigned to either a placebo or amino acid supplement. Subjects underwent 4-weeks of a periodized resistance training program, designed to allow the researchers to effectively measure the outcomes of the study.
Subjects in the amino acid group received an amino acid supplement that provided 0.4g/kg body weight of amino acids divided into three daily doses. All subjects were instructed to follow a calculated isocaloric diet throughout the study (e.g., they at the same amount of calories), to reduce the confounding factor of energy differences between groups.
However, it was noted that those in the amino acid supplement group consumed an additional 25-55 g protein per day (remember that amino acids are the building blocks of protein).
There were no significant changes in any of the anthropometry variables measured, such as body fat, girth measurements, etc. There were some significant changes in outcome variables in the experimental group. For example, one repetition maximum squat and bench press increased significantly during the final 3 time points of the study.
There were also several other trends towards significance in other variables. The authors noted that this may be attributed to the fact that amino acid supplementation increases protein synthesis, enhances glycogen resynthesis, and reduces muscle damage.
Take home message: While the results of this study demonstrate that supplementing with amino acids may benefit individuals in very specific aspects of training, eating adequate amounts of protein should suffice.
Remember that those in the amino acid group consumed an extra 25-55g protein/day; if individuals were to consume this additional protein, without adding individual amino acids, more than likely they would receive the same benefit as with a supplement.
A study comparing the aforementioned amino acid supplement versus a group consuming the same amount of extra protein through foods would be interesting.
Carbohydrate drinks are often recommended for athletes as a means to replenish glycogen stores. The hope is that athletes will recover more quickly and perform well at their next practice or competition. However, current research is emerging to demonstrate that carbohydrate isn't the only nutrient necessary during recovery; protein may be just as important for optimal results.
Researchers compared a carbohydrate-electrolyte beverage to a carbohydrate-protein beverage. It was hypothesized that the addition of protein would enhance the insulin response that occurs with the consumption of carbohydrates, subsequently enhancing the restoration of muscle glycogen (insulin helps facilitate the storage of glycogen).
The entire study was broken up into two segments:
- The first part was to determine the actual outcome of supplementing with the two drinks
- And the second part was to determine why this outcome happens-only the first aspect will be covered in this brief review.
Eight male cyclists were recruited for this study and after initial testing, were asked to cycle for 2 hours at 65-75% VO2max on a cycle ergometer. This protocol was designed with the intention of depleting muscle glycogen. Subjects consumed either 355 mL of the carbohydrate only beverage or 355 mL of the carbohydrate-protein beverage immediately post-exercise and again 2 hours later.
Each subject then completed another exercise bout and their time to fatigue was determined. Time to fatigue was significantly greater when subjects consumed the carbohydrate-protein versus the carbohydrate-only supplement (31.1 3.2 and 20.0 2.0 minutes, respectively).
I do agree that protein should be added to a post-workout recovery food or beverage; however, the results of this particular study are difficult to interpret because the carbohydrate-protein drink also provided an additional 205 calories, 32 grams of carbohydrate, and 14 grams of protein in the 355 mL provided.
Considering the subjects ingested this twice before their "performance test," each in the carbohydrate-protein group consumed an additional 64 grams of carbohydrates, 28 grams of protein and 410 calories.
Although the design of this study does not fully explain the mechanism, the results support the notion that protein should be added to recovery drinks. Future studies should use isocaloric beverages to elucidate the mechanisms of the increased glycogen resynthesis.
Until next time, keep up the hard work!
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