Arginine supplementation is known to increase the body’s capacity to produce nitric oxide, a biochemical that causes the blood vessels to dilate, increasing blood flow during exercise. Because of this effect, arginine supplementation is potentially beneficial to endurance performance. Researchers from Cal State University-Fresno recently investigated the effects of arginine supplementation on VO2max and ventilatory threshold in trained cyclists. Eighteen male cyclists completed graded exercise tests before and after a 28-day period during which half received arginine and the other half placebo. Arginine supplementation was found to have no effect on either VO2max or ventilatory threshold as measured in the graded exercise test. So it would appear that arginine supplementation is useless for cyclists.

The amino acids cystine and theanine are involved in the body’s immune and inflammatory processes. Japanese researchers recently invetigated whether supplementation with these amino acids would reduce markers of immune suppression and inflammation in high-level runners engaging in heavy training. Sixteen runners received either daily theanine and cystine supplementation or placebo for the week preceding a nine-day training camp and throughout the training camp. The runners averaged 12.3 miles of running per day before the camp and 17.7 miles per day during the camp. The researchers found that supplementation attenuated both the inflammatory and immune responses to the increased training load on the first day of the training camp, but not on the last day. These findings suggest that cystine and theanine helped the runners to better handle the initial stress of the camp, but that adaptations occurred during the camp that made supplementation unnecessary.

There is some evidence that antioxidant supplementation can have a positive effect on endurance performance. Swiss researchers recently studied whether three weeks of supplementation with antioxidant-rich green tea extract would enhance time trial performance in trained cyclists. Nine male subjects completed a test consisting of a two-hour ride at moderate intensity immediately followed by a 30-minute time trial on two occasions separated by three weeks. Between the tests the subjects were randomly assigned to receive either green tea extract or placebo daily. After the second time trial and a washout period, the entire experiment was repeated, with those subjects who had received the supplement the first time getting placebo the second time and those having received placebo the first time getting green tea extract the second time. The researchers found that green tea extract had no effect on time trial performance or on any of the metabolic measures taken. It did, however, reduce blood levels of the inflammatory marker C-reactive protein after exercise. For what that’s worth.

Citrulline malate had become a popular nutritional supplement among athletes due to purported beneficial effects on aerobic performance. One possible mechanism for this effect is the prevention of arginine depletion during prolonged exercise. The amino acid arginine plays an important role in nitric oxide release, and nitric oxide in turn help dilate the blood vessels and increase blood flow to working muscles. In a new study, Spanish researchers studied the effects of citrulline malate supplementation on the metabolism of amino acids, including arginine, during cycling exercise. They found that citrulline malate did indeed significantly increase the use of amino acids, and especially the branched chain amino acids, which include arginine, during exercise compared to placebo. This increase was also associated with an increase in metabolites of amino acid breakdown, including nitrite, which indicates the possibility of higher nitric oxide levels.

N-acetylcysteine (NAC) is an altered form of the amino acid l-cysteine. It is used in medicine to treat diverse conditions including Tylenol overdose and infant nasal blockage. There is also some evidence that it enhances exercise performance, possibly by increasing the body’s antioxidant capacity. Polish researchers recently studied the effects of NAC supplementation on antioxidant capacity and exercise performance in 15 healthy men. These subjects were randomly assigned to take an NAC supplement or placebo daily for nine days. Before the first day and again on the last day of the intervention, all of the subjects completed an incremental exercise test to exhaustion. NAC supplementation was found to significantly increase both resting and post-exercise levels of glutathione, the body’s master antioxidant. It also significantly reduced markers of muscle damage after exercise. However, NAC had no effect on performance in the exercise test.

Rhodiola rosea is a plant, extracts of which have become popular nutritional supplements among endurance athletes because of their purported ability to promote fatty acids utilisation, to enhance antioxidant function, and to improve the body’s tolerance for physical strenuous efforts. Researchers recently tested the physiological and performance effect of four weeks of rhodiola rosea supplementation in trained endurance athletes. While supplementation was found to reduce lactate levels and markers of muscle damage after an exhaustive endurance test, it had no effect on performance in that test. Does anyone really need a supplement that enables us only to achieve the same level of performance by slightly different physiological means?

The International Society of Sports Nutrition has published a new position on the use and effectiveness of caffeine as an ergogenic aid to exercise performance. Jointly authored by a veritable Who’s-Who of sports nutrition experts, the paper reaches the following conclusions:

“1.) Caffeine is effective for enhancing sport performance in trained athletes when consumed in low-to-moderate dosages (~3-6 mg/kg) and overall does not result in further enhancement in performance when consumed in higher dosages (>/= 9 mg/kg). 2.) Caffeine exerts a greater ergogenic effect when consumed in an anhydrous state as compared to coffee. 3.) It has been shown that caffeine can enhance vigilance during bouts of extended exhaustive exercise, as well as periods of sustained sleep deprivation. 4.) Caffeine is ergogenic for sustained maximal endurance exercise, and has been shown to be highly effective for time-trial performance. 5.) Caffeine supplementation is beneficial for high-intensity exercise, including team sports such as soccer and rugby, both of which are categorized by intermittent activity within a period of prolonged duration. 6.) The literature is equivocal when considering the effects of caffeine supplementation on strength-power performance, and additional research in this area is warranted. 7.) The scientific literature does not support caffeine-induced diuresis during exercise, or any harmful change in fluid balance that would negatively affect performance.”

Quercetin is a plant nutrient in the “flavanoid” class that functions as an antioxidant, anti-inflammatory, and stimulus for mitochondrial biogenesis in the human body. Researchers at the University of South Carolina recently investigated whether quercetin supplementation increases maximal aerobic capacity and endurance in untrained subjects. Twelve subjects received either 1000 mg of quercetin daily or placebo for seven days. All subjects performed indoor cycling tests before and after the supplementation period. The whole study design was then repeated with the treatments reversed. On average, the subjects exhibited a 3.9 percent increase in VO2max and a 13.2 percent increase in time to exhaustion after quercetin supplementation.

The authors of the study, which was published in the International Journal of Sports Nutrition and Exercise Metabolism, concluded, “These data suggest that as little as 7 days of quercetin supplementation can increase endurance without exercise training in untrained participants. These benefits of quercetin may have important implications for enhancement of athletic and military performance. This apparent increase in fitness without exercise training may have implications beyond that of performance enhancement to health promotion and disease prevention.”

Overtraining syndrome is an athletic disorder that involves immune system dysfunction. Elevated levels of cytokines, a class of immune cells, is a known marker of overtraining in athletes. There is some evidence that increased carbohydrate intake may offer some protection against immune system stress during periods of heavy training. Researchers from England’s University of Newcastle recently tested this notion in a group of cyclists and triathletes. The subjects were divided into two groups, one of which was placed on a high-carb diet and the other on a moderate-carb diet for 28 days. At the end of this period all of the subjects performed a challenging test workout on indoor bikes.

The researchers measured the cytokine response to this workout and found no difference in the overall response. However, they did find that the anti-inflammatory cytokine response to exercise was reduced by 30-50 percent in members of the moderate-carb group compared to members of the high-carb group. The researchers concluded that the effect was not enough to warrant the high level of carbohydrate intake used in the study.

Researchers from Appalachian State University recently investigated the effects of independent and combined supplementation with omega-3 essential fatty acids and antioxidant vitamins on exercise-induced oxidative stress (i.e. free radical damage) in the muscles of competitive cyclists. The subjects were divided into four groups. For a period of six weeks, each cyclist received either omega-3, antioxidant vitamins, both, or placebo daily. At the end of the supplementation period, markers of oxidative stress were measured over three days of training. The authors of the study, which was published in Medicine & Science in Sports & Exercise, found that omega-3 supplementation alone significantly increased post-exercise levels of F2-isoprostanes, which are a biomarker of oxidative stress. Supplementation with antioxidant vitamins only slightly reduced the increase associated with omega-3 supplementation. So, while omega-3 fats do a lot of good things in the body, reducing exercise-related oxidative stress appears not to be one of them!