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New Studies From the ISSN

Some studies presented at the seventh annual meeting of the International Society of Sports Nutrition, held in Clearwater, Florida, last June, have pertinence to bodybuilding. Here is an overview:

PS helps maintain training focus. Phosphatidylserine is a supplement often touted for its ability to reduce elevated cortisol, which is an adrenal steroid hormone that produces catabolic effects in muscle. Various studies show that taking a PS supplement can reduce cortisol by an average of 30 percent, although precisely how it does that is still a matter of speculation. PS has been shown to increase athletic performance in such disparate sports as running, golf and cycling, as well as aiding exercise performance.

The study presented at the ISSN conference described the effects of PS on brain reactions in 18 men aged 18 to 30.1 The subjects took either 400 milligrams of PS or a placebo every day for two weeks, then did two things: engaged in a weight-training session and took a test that measured calculation time. Those who got the PS supplement had increased ability to do faster calculations, which demonstrated that PS aided mental function prior to training. That would translate into increased mental focus and concentration when it’s taken prior to training.

Do branched-chain amino acids reduce muscle damage? This study involved nine men, aged 20 to 35, who had at least a year of training experience.2 They worked out an average of four times a week and received either a branched-chain amino acid supplement or a placebo 30 minutes prior to a weight session, immediately afterward and 30 minutes after that. The five-gram BCAA supplement was formulated with 2.5 grams of leucine, 1.25 grams of isoleucine and 1.25 grams of valine.

The researchers measured blood creatinine to identify the extent of training-induced muscle damage. Creatinine is the primary breakdown product of creatine, which is stored in muscle, and when muscle is damaged, as through exercise, creatinine is released into the blood. The measurements revealed that the subjects taking BCAAs had decreased blood creatinine by 27 percent, pointing to significantly less muscle damage with BCAAs.

High-protein diets help retain lean mass during dieting. Most studies examine the effects of dieting on obese or sedentary people. This one, presented at the ISSN conference, analyzed the effects of different nutrient combinations on the body composition of active men.3 The subjects were soldiers, average age 25, who had average bodyfat counts of 15 percent, which is considered lean. They were competing for a place on the Army Combatives team and participated in a six-week training camp that included 10 hours of supervised physical activity each week. During the training, the soldiers went on one of three diets:

1) High-protein diet: 30 percent protein, 40 percent carb, 30 percent fat, which is identical in makeup to the popular Zone diet, espoused by biochemist Barry Sears.

2) High-carb diet: 65 percent carb, 15 percent protein, 20 percent fat.

3) Control: No particular combination of macronutrients, but subjects on this plan engaged in the same activity as groups 1 and 2.

At the end of six weeks, 13 men had completed the study. While the carb group lost the most weight, those in the higher-protein group lost the most fat, followed by the carb group, then the control group. Both the control and protein groups gained lean mass, a.k.a. muscle, while those in the high-carb group lost it. The study shows that a higher protein intake helps retain more muscle during a diet in athletic people.

Does the type of protein supplement affect performance? Seventy-four collegiate football players were assigned to one of four supplement groups:

1) 40 grams of a whey-and-casein protein blend

2) Whey protein

3) Casein protein

4) Glucose control—no protein

The players trained with weights five days a week and took the supplements after workouts. At the end of eight weeks they were given body-composition and a number of performance tests. While all the groups had similar performance increases, particularly in strength, none of the supplements proved superior. The casein protein, however, generated greater fat loss than the whey and carb groups.

Does tribulus work? Tribulus is a combination of herbs that has frequently been touted as a testosterone booster. Most of its positive effects have been reported from Bulgaria but have not been replicated in Western studies. In fact, some studies have shown that tribulus is more effective at raising estrogen than upping testosterone.

In the latest study presented at the conference, 28 men, age range 18 to 30, were randomly assigned to take either a placebo or a tribulus fruit extract containing 40 percent saponins, thought to be the active factors in tribulus. The study had a double-blind design, meaning that neither researchers nor subjects could initially tell the real tribulus from the placebo. The subjects trained four days a week on a split routine. They were tested at the start of the study and at the four- and eight-week marks for body composition, strength, endurance and anaerobic power. Testosterone, cortisol and insulin were also measured.

The researchers found that engaging in weight training produced significant muscular adaptations in the subjects. The supplement, however, offered no additional benefits over the training alone. Nor were there changes in testosterone or cortisol, although the tribulus group experienced a minor change in insulin counts. The good news: no side effects were observed.

Effects of one week of a NO-boosting supplement. Most supplements that are sold to boost nitric oxide in the body contain some form of arginine as the primary ingredient. That makes sense, since the amino acid L-arginine is the primary nutritional precursor of NO synthesis in the body. On the other hand, NO production is not determined by the availability of arginine but rather by enzymes that dictate the synthesis of NO from arginine. NO is said to help build muscle by increasing muscle blood flow, while also boosting oxygen delivery to working muscles.

A new study examined the effects of a popular bodybuilding supplement containing arginine-alpha-ketoglutarate on arterial blood flow, circulating arginine, NO and NO synthesizing enzyme. Twenty-four men, aged 18 to 25 took either an NO supplement or a placebo for one week. Before and after taking the supplement, they engaged in a weight-training session. Immediately before, immediately after and 30 minutes after training they were tested for arterial blood flow.

Blood arginine decreased by 0.89 percent in the placebo group, while it increased by 84.67 percent in those who got the actual supplement. Arterial blood flow increased significantly in both groups right after training but didn’t differ between the supplement and placebo groups. NO also increased in both groups, with no significant differences, as was the case with the NO-synthesizing enzyme. So while the supplement did boost blood arginine, all effects related to NO production were the result of the actual exercise rather than the supplement.

—Jerry Brainum


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1 Parker, A., et al. (2010). The effects of phosphatidylserine supplementation on cognitive functioning prior to and following an acute bout of resistance training in young males. J Int J Sports Nutr. 7: P2.

2 Marangon , A., et al. (2010). Effect of supplementation of branched-chain amino acids in muscle damage induced by resistance training. J Int Soc Sports Nutr. 7: P3.

3 Case, J., et al. (2010). Use of higher protein diets for body composition improvement in nonobese, active individuals. Int Soc of Sports Nutr J. 7: P6.


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