It's time to take a look at some pertinent research studies that have surfaced over the last few years.
In the past few years, sports nutritionists have been concentrating a lot on figuring out what makes the best post-workout snack or meal to help muscles regenerate. Most recommend that athletes ingest a combination of carbohydrates and protein, and a recent study backs up this advice.
The goal of this investigation was to determine the individual and combined effects of amino acids (AA), the building blocks of protein, and carbohydrate (CHO) on muscle protein synthesis.
Subjects completed a 40-minute resistance training bout. One hour post-exercise, subjects ingested a CHO-only drink (0.5g CHO/kg bodyweight), a CHO-AA drink (0.5g CHO + 0.087 g/kg AA), or an AA-only drink (0.087g/kg AA). For a 150-pound individual, this is the equivalent of approximately 35g of CHO and 6 g of AA. It was found that CHO alone positively affected moderate anabolism, but did not affect muscle protein synthesis, which should be a goal of post-recovery nutrition.
When the AA was taken alone there was an increase in protein synthesis. However, when the AAs were combined with CHO, there was an interactive effect between the two nutrients. In simple terms, when taken together, the insulin from the CHO facilitated the action of the AA to cause a greater muscle protein response and thus better recovery.
Take-home message: Carbohydrates and protein, together, are ideal for optimizing recovery, which will ultimately lead to enhanced performance. Some suggestions?
Fat-free chocolate milk makes a wonderful post-exercise recovery drink, as it contains approximately 35g of CHO and approximately 10g of protein. (The exact serving size needs to be determined on an individual basis according to the athlete's bodyweight.) If solid food is an option, anything that contains about 3/4 carbohydrate and 1/4 protein is good, such as lowfat yogurt.
To date, there are over 700 research studies that have been conducted on creatine. However, confusion, misinformation, and rumors about creatine still abound.
Scientific and anecdotal evidence has demonstrated creatine supplementation is beneficial for making gains during short-duration, high-intensity exercise such as weightlifting and sprinting in most individuals. It has also been shown to produce weight gain in those who use it.
A 2002 study wanted to look more closely at why weight gain occurs with creatine supplementation. Specifically, it wanted to see if using creatine results in more carbohydrates or more fat being "burned" for energy. The trial, which lasted 12 weeks and was double-blind, looked at substrate oxidation in individuals (i.e., what food the body is metabolizing: carbohydrates, proteins, or fats).
The method researchers use to determine substrate utilization is the measurement of the respiratory exchange ratio (RER). Values typically range from 0.70 to 1.00. The higher the value, the more carbohydrates are being metabolized. A lower value means fat is the primary fuel.
All 10 subjects participated in a pre-determined strength-training program throughout the study. In addition, the same meals were consumed 12 hours prior to RER testing to reduce potential confounders, and no other food was consumed until post-measurement.
The researchers found that carbohydrate oxidation increased during creatine supplementation (there was a trend for an increase in RER), and thus fat metabolism decreased. In addition, while fat mass did not change with creatine supplementation, it did decrease significantly in those taking the placebo.
The important take-home message from these results is that individuals who supplement with creatine may decrease their ability to lose fat after exercise training, potentially due to the RER increase. According to the results from this study only, those attempting to reduce body fat may want to steer away from supplementing with creatine as it may work against them in that regard. (However, as this was the first study of its kind, more research is clearly necessary.)
Another concern with creatine is whether excess supplementation may put undue stress on both the liver and kidneys. Several small studies in the past have shown that creatine does not harm these vital organs, and this more recent one had similar results.
In a retrospective study of athletes' self-reported previous (and voluntary) creatine use, it was determined that the 23 volunteers from an NCAA Division II college football team supplemented with an average of 13.9 grams a day. Several analyses were utilized to determine the effects on current kidney and liver function. It was determined that there were no significant differences between kidney or liver function in creatine- and non-creatine-supplemented groups.
We can thus infer that creatine use does not result in any detrimental acute or cumulative effects on liver or kidney function when supplementing for this length of time (average of 2.9 years) and with this amount of creatine (average 13.9g/day).
Exercise & Fat Loss
Many nutritionists tell athletes that cardiovascular exercise is better for weight loss than resistance training. However, much of the advice is based on anecdotal evidence rather than actual research. Therefore, the primary aim of a study by Edward Melanson, et al., was to compare the effects of aerobic vs. anaerobic training on energy expenditure (EE) and substrate oxidation.
This study measured energy expenditure in 10 non-obese male subjects on four separate occasions using different exercise protocols. Aerobic training was done on an exercise bike while circuit training was used for anaerobic exercise. Subjects expended similar amounts of energy for both types of exercise with no significant differences between exercise conditions.
The results? There were no differences in fat oxidation over 24 hours, but there was an increase in the amount of carbohydrates oxidized during aerobic exercise.
The take-home message from this study: If an athlete's goal is weight loss, aerobic exercise should be the cornerstone of his or her regimen. This is bad news for the football player attempting to lose weight during preseason workouts, but good news for the long-distance track athlete, for example.
Therefore, athletes whose workouts are primarily anaerobic in nature may want to concentrate any weight-loss efforts in the off-season, when it may be more acceptable to incorporate a significant amount of aerobic activities.