By Christopher Mohr
Christopher Mohr, MS, RD, LDN, is a doctoral student in Exercise Physiology at the University of Pittsburgh. He is a registered and licensed dietitian and was a Sports Nutritionist at the University of Massachusetts for two years.
Training & Conditioning, 14.6, September 2004, http://www.momentummedia.com/articles/tc/tc1406/nutritionroundup.htm
Conference Review
This summer, the International Society of Sports Nutrition held its first conference, which it plans to continue to do annually. I had the opportunity to attend this conference and will highlight some of the more pertinent research findings for those working with competitive athletes.
Adding Protein Post-Exercise
"Early Post Exercise Carbohydrate + Protein Ingestion Enhances Exercise Performance Six Hours Later" was presented by John Berardi, Eric Noreen, and Peter Lemon.
We know that glycogen (the storage form of carbohydrate) is necessary for optimal performance, and that carbohydrate should be the primary source of fuel ingested post-exercise. But protein has also shown some benefits during exercise recovery. Typically the research showing an improvement with the addition of protein comes from the increase in protein synthesis. However, few studies have compared the actual performance outcomes from an isocaloric carbohydrate-only drink to a carbohydrate-protein drink. This study did just that.
In this short, 24-hour study, 22 participants completed a 60-minute cycling time trial. One and two hours post exercise, subjects received a carbohydrate beverage (1.2 g carbohydrate/kg bodyweight), carbohydrate/protein beverage (0.8 g carbohydrate and 0.4 g protein/kg bodyweight), or placebo. Four hours later, each participant consumed a solid meal which was identical to their breakfast. This was to ensure that the total calories consumed were identical among subjects and allowed researchers to focus on the macronutrient differences in the recovery drinks rather than the caloric differences throughout the day.
After recovery from the meal, participants repeated the earlier cycling and measurement protocols. It turned out that those consuming the carbohydrate-protein supplements improved total cycling distance and power when compared to the groups consuming carbohydrate alone or a placebo.
Take home message: A carbohydrate/protein supplement is better than carbohydrate alone post-exercise after cycling. Moreover, enough research is available to suggest a similar beverage for enhanced recovery during all activities. My current recommendation: one to two cups of fat-free chocolate milk, which provides both carbohydrate and protein, and is inexpensive.
A Close Look at NO2
"Effects of Arginine-Alpha-Ketoglutarate Supplementation on Body Composition and Training Adaptations" was presented by Bill Campbell, et al.
Arginine-alpha-ketoglutarate (AKG) has recently grown in popularity in the dietary supplement world. It is more commonly known as NO2 and is purported to increase nitric oxide synthesis, thereby enhancing blood flow, oxygen delivery, and glucose uptake. All could lead to enhanced muscle mass and strength during training. While sales have recently surged, it has not really undergone scientific scrutiny—until now.
The purpose of this study was to examine how an AKG supplement would affect muscle strength and overall muscle mass during training. Thirty-five resistance-trained males were matched for fat free mass and assigned to either take an NO2 supplement or a placebo. Subjects ingested 12 grams of the product per day for eight weeks during standardized training. At 0, 4, and 8 weeks, body composition was measured and subjects performed one repetition maximum (RM) bench press, an isokinetic endurance test, a cycling anaerobic capacity test, and a max cardiopulmonary exercise test on a treadmill.
There were no significant differences between groups in body mass, fat free mass, or percent body fat. There were also no significant differences in average power or total work. On the other hand, changes in 1 RM bench press, sprint peak power, time to peak power, and rate to fatigue were all significantly greater in those taking the NO2 supplement than in those taking the placebo. However, no mechanism was suggested and this is the only study on NO2 to date.
Take home message: NO2 supplementation (AKG) did not effect body composition, but did change 1 RM strength and sprint power in response to training. However, I suggest athletes wait for more studies of this supplement before taking it since one study does not make a truth.
Caffeine and Metabolic Rate
"Effect of JavaFit Extreme on Metabolic Rate, Substrate Utilization, and Cardiovascular Safety" was presented by Ron Mendel, Jennifer Hofheins, and Tim Ziegenfuss.
This study was conducted to examine a new "designer" coffee, JavaFit Extreme, on metabolic rate, substrate oxidation (how fuels are used in the body), and cardiovascular hemodynamics. JavaFit Extreme contains 4.4 grams of Arabica beans, with a total of 670 mg composed of garcinia cambogia extract, citrus aurantium extract, caffeine USP, and chromium polynicotinate.
After baseline testing of metabolic rate, substrate oxidation and heart rate, blood pressure, and ECG, subjects were provided brewed JavaFit Extreme of different amounts. All measurements were again conducted over a three-hour timespan to see how the coffee affected them. No negative effects were found for heart rate, blood pressure, or ECG. However, metabolic rate increased by 8.9 percent and 25.6 percent with 1.5 and 2.0 tablespoons, respectively, of coffee provided. These data indicate JavaFit extreme has dose-dependent thermogenic properties in healthy subjects.
In my humble opinion, it would have been nice to see another group who consumed plain old coffee, to see if there were any differences among subjects in either group. Moreover, since this was an acute trial, it would be interesting to see if these changes carried over to a change in body composition with chronic use.
Take home message: JavaFit Extreme (and plain old coffee) does increase metabolic rate because of the caffeine. Of course when you load it up with sugar and cream, any positive attributes will be negated. In addition, too much caffeine is banned by the NCAA, so overloading on the stimulant is not a good idea.
Zinc And Magnesium Supplementation
"Effects Of ZMA Supplementation on the Relationship of Zinc and Magnesium to Body Composition, Strength, Sprint Performance, and Metabolic and Hormone Profiles" was presented by Colin Wilborn, et al.
Zinc and magnesium deficiencies negatively affect serum testosterone levels, impair immune function, and subsequently decrease strength in athletes. Therefore, because of smart marketing, a supplement by the name of ZMA (zinc and magnesium aspartate) has grown in popularity.
The purpose of this study was to assess plasma zinc and magnesium status on strength, body composition, and markers of anabolic/catabolic status and to determine if ZMA influences these relationships. Twenty-six males participated in this study and were assigned to either a ZMA supplement or a placebo.
Blood tests revealed that the experienced weight lifters in this study had normal zinc and magnesium status. Not surprisingly, ZMA supplementation non-significantly increased plasma zinc levels and did not affect magnesium levels. In addition, zinc levels did not correlate to body composition, hormone profiles, strength, or sprint performance variables.
Take home message: Zinc and magnesium deficiencies are rare in an otherwise healthy population. Despite the popularity of this supplement, ZMA supplementation appears to have limited value on body composition, hormonal profiles, and performance in athletes with normal zinc and magnesium status.