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From The March 2000 Issue of Nutrition Science News
Ergogenics for Endurance Athletes
by Alan Christianson, N.D.
Athletes, by their very nature, constantly seek to improve their performance. They know training is the most effective way to excel, but they also know it is the hardest. The search for an extra edge makes nearly any purported performance booster alluring. There are plenty of ergogenics—substances that promise to improve physical performance—on the market to tempt both weekend warriors and competitive athletes.
Ergogenics, through a variety of mechanisms, improve strength and endurance. They are typically used by endurance athletes who participate in sports that last more than three hours. Marathoners, ultramarathoners, triathletes and stage bicycle racers fall into this category. This information will help you explain to customers which supplements are scientifically proven to help increase endurance and which ones are still at the starting line.
Amino Acids
The group of branched chain amino acids appear to help endurance athletes, while carnitine and creatine do not.
Branched Chain Amino Acids (BCAAs), including leucine, isoleucine and valine, are essential to aerobic metabolism. During aerobic activity, BCAA levels decrease as they are taken up by skeletal muscle, causing the ratio of serum BCAAs to tryptophan to skew in favor of tryptophan, an amino acid that contributes to serotonin formation. Increased serotonin production during exercise enhances the perception of fatigue, but maintaining adequate BCAA levels in the bloodstream keeps serotonin production in check. BCAA decline parallels the onset of fatigue and may decrease efficiency of glycogen metabolism, the breakdown of stored sugar.1 Simply put, lower levels of BCAAs mean less available fuel; more tryptophan means more perceived fatigue.
Edward Blomstrand, Ph.D., of Research Laboratories, Stockholm, Sweden, observed seven trained cyclists given one 3-g dose of BCAAs. The athletes, who had exercised to exhaustion the night before to produce low levels of muscle glycogen, exercised for an hour. During the activity they were given either BCAAs or placebo. The group taking BCAAs perceived less exertion than the placebo group. Physical performance was the same for both groups.2
These results are consistent with other studies that have shown BCAAs tend to reduce perceived exertion but do not affect actual performance in events lasting less than three hours.3
Carnitine is a conditionally essential amino acid, meaning the body can make it in most, but not all, circumstances. Its prime role is shuttling free fatty acids—those available in the bloodstream for use as fuel—into the mitochondria, the part of the cell where energy is made, for adenosine triphosphate (ATP) synthesis. Skeletal and cardiac muscle cells are especially dependent on adequate carnitine for their energy metabolism. Carbohydrates, fats and proteins all contribute to ATP production. Trained athletes can use a higher proportion of stored fat to carbohydrates for energy than the untrained. Because more calories are stored as body fat than as carbohydrates, being able to use more fat means that more energy is available. Many researchers have speculated that supplemental carnitine may help improve the ability of cells to use fats; however, research reviewed at the Cape Town Medical School, South Africa, showed that chronic carnitine ingestion had no effect on fat metabolism.4
Physiologist Petro Colombani of Zurich, Switzerland, and colleagues studied the effects of carnitine on trained endurance athletes during and after a marathon. In this double-blind study, seven men took 2 g carnitine two hours before the 26.2-mile run and the same dose after 13.1 miles, while seven men took placebo. Supplementing with carnitine increased plasma carnitine but did not significantly change running time or serum metabolites—markers that indicate physical fatigue level. The morning after the run, a submaximal performance test was done on both groups. This test evaluates athletes at levels lower than their maximum heart rate. Carnitine did not alter the athletes' performance, metabolic efficiency or recovery5 and seems to have no benefit for endurance athletes.
Creatine, or creatine monohydrate, is an amino acid that helps skeletal muscles produce ATP and increases muscle mass via hydration. Although it has been shown to benefit strength-training athletes,6 studies show it decreases endurance. William Cook, Ph.D., of Texas A&M University, College Station, gave 20 g creatine per day to 12 cyclists for five days. Supplementation resulted in a 1.58 percent decline in peak power (maximum pedaling force) in the creatine group.7
Considering the threat to fluid stores and research suggesting impaired performance, creatine is not recommended for endurance athletes. For more on creatine and its applications, see NSN 1999 Oct;4(10):472-80.
Hormones
Despite the hype about androstenedione a year or so ago, neither it nor androgens have been proven to enhance performance.
Androgens are hormones that impart male secondary sexual properties including voice deepening, genital maturation, semen production and nonhead hair growth. Androgens used to increase sports performance are primarily testosterones and their precursors. These hormones can help strength athletes by increasing lean body mass, but for endurance athletes extra mass is an impediment. Endurance athletes would be wise to steer clear of androgens in general.
Androstenedione, technically a hormone precursor, is converted in the body to testosterone and estrogens. Some data show androstenedione to increase serum testosterone within 1.5 hours of taking the supplement, whereas other reports show no increase in serum testosterone levels but an increase in estrogenic compounds. These variations can be attributed to the subjects' current hormone levels. For that reason, androstenedione is not recommended for young athletes.8
No studies have evaluated androstenedione as an endurance aid. Since more powerful androgens such as testosterone and synthetic testosterone do not affect endurance, there is little chance androstenedione will either. In addition, the International Olympic Committee includes androstenedione on its list of banned substances.
There is no data, researched or hypothetical, supporting androstenedione as an ergogenic supplement.
Botanicals
Despite herbal lore to the contrary, the ginsengs have yet to stand up to scientific scrutiny as performance enhancers.
Chinese Ginseng (Panax ginseng), also called Ren Shen, has certainly captured the hopes of those seeking more energy. The roots of 3- to 7-year-old plants contain the active constituent ginsenoside.9 In animals, panax has been shown to increase swimming endurance and stress resistance.10 In humans, ginseng has been shown to alter endocrine function, specifically by elevating testosterone and adrenocorticotropic hormone (ACTH), which stimulates cortisol release.11,12 Caution customers against using ginseng with steroid drugs such as prednisone because ginseng can enhance the effects of the drug.
Although several studies have evaluated ginseng as an ergogenic, results have been equivocal or negative.13 In a representative study, Calvin Meyer, M.D., a neuroendocrinologist in Detriot, Mich., and colleagues studied physiologic and psychological effects of ginseng on aerobic exertion. They evaluated 36 healthy men who took ginseng for eight weeks. Nine took 200 mg/day, nine took 400 mg/day and 18 took placebo. Submaximal and maximal aerobic studies were done before and after the trial to evaluate aerobic performance. At either dose, ginseng provided no significant change in perceived exertion, oxygen consumption or other markers of exertion.14
Siberian Ginseng (Eleutherococcus senticosus), also called Ci Wu Jia, is not a true ginseng but is called one because of its use as a general tonic. Clinically, its most authenticated effect is lowering the risk of infection during stressful times.9 As with panax, animal studies have shown an increase in maximal swim times. However, human studies on endurance have shown no benefit. For example, 20 distance runners participated in a study at Old Dominion University, Norfolk, Va., in which 10 were given eleutherococcus extract and 10 placebo. Initially and during the eight-week study, the runners completed trials of a 10-minute treadmill run at their 10-km race pace and a maximal treadmill test. Researchers measured heart rate, oxygen consumption and perceived exertion. No significant differences were seen in perceived exertion, measured parameters or time to exhaustion.15
Hydration Aids
Water itself is an endurance aid, and sound hydration strategies are essential in long events.
Glycerol is a 3-carbon nonintoxicating alcohol. It is a product of triacylglycerol (free fatty acids), which is used in the body's citric acid cycle of aerobic energy metabolism. Glycerol increases water in muscles, enhancing hydration. Eight athletes supplementing with 1 g glycerol/kg body weight were able to increase their total body water by nearly 1 L—about 2.5 percent—which helped them adapt to heat during prolonged exercise.16
Although this phenomenon has been demonstrated in only a small number of studies, the benefits have been consistent, especially in hot weather.17 For example, researchers at the Department of Medicine, Veterans Affairs Medical Center, Albuquerque, N.M., studied the effects of glycerol on the hydration and performance of 11 athletes exercising in the heat. Before riding to exhaustion, they were given 1.2 g/kg glycerol or placebo. During the same levels of intensity, those given glycerol showed lower heart rates than those given placebo. Elevated heart rate is a marker of poor hydration. Additionally, the riders given glycerol ran longer before exhaustion.18
During events lasting longer than three hours, glycerol replacement during exercise may also be of benefit. In addition to taking straight glycerol, athletes may choose from several hydration formulas that now contain this ingredient. At effective dosages, straight glycerol is more economical than formulas.
Phosphate and bicarbonate salts are the body's main pH buffers. Fatigue is related to a decline in muscle pH, which also inhibits aerobic and anaerobic energy production. Based on this, scientists have theorized that buffering metabolic acids with phosphate might enhance endurance and help maintain hydration.
In a double-blind study, researchers evaluated the effects of phosphate loading (4-60 g/day) on the performance of six trained triatheletes. They took either 4 g/day of sodium phosphate in four divided doses or placebo for three days before performing both maximal cycling tests and a 40-kilometer time trial. They continued the doses for an extra day and were retested to evaluate recovery. All tests were repeated after a 17-day washout period. Phosphate enhanced cycling endurance and raised aerobic threshold (maximum level of intensity at metabolic efficiency).19
Considering the low cost of sodium phosphate solution, its lack of side effects and proven efficacy, it is a worthwhile ergogenic for endurance.
Neuroregulators
Exertion affects the body at a chemical level. Some researchers have speculated that replenishing chemicals depleted can circumvent exhaustion.
Choline is used to make acetylcholine, which aids nerve impulses. Prolonged exercise causes a decline in acetylcholine, which may reduce the ability of nerves to transmit impulses to exercising muscles. Marathon runners have been shown to lose 40 percent of plasma choline during the course of a race. This level of decline has compromised nerve junction activity in vivo.20 Although a potential for benefit exists, actual benefit from choline supplementation is theoretical because there have been no clinical trials.
Supplements for the Long Haul
As discussed, hydration is one of the most critical variables that endurance athletes can control. The longer the event and the hotter the day, the more important it is. To improve hydration, athletes can load for one week with 2 oz glycerol and 1 oz phosphate daily. During events longer than three hours, athletes should take fluid replacement formulas that contain glycerol. Until more is known, the most effective ergogenic will remain diligent training.
Sidebars:
A Cuppa Joe - To Go
Alan Christianson, N.D., has a private practice in Scottsdale, Ariz.
References
1. Conlay LA, et al. Exercise and neuromodulators: choline and acetylcholine in marathon runners. Int J Sports Med 1992 Oct;13 Suppl 1:S141-2.
2. Blomstrand E, et al. Administration of branched-chain amino acids during sustained exercise—effects on performance and on plasma concentration of some amino acids. Eur J Appl Physiol 1991;63(2):83-8.
3. Blomstrand E, et al. Influence of ingesting a solution of branched-chain amino acids on perceived exertion during exercise. Acta Physiol Scand 1997 Jan;159(1):41-9.
4. Hawley JA. Strategies to enhance fat utilization during exercise. Sports Med 1998 Apr;25(4):241-57.
5. Colombani P, et al. Effects of L-carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double-blind crossover field study. Eur J Appl Physiol 1996;73(5):434-9.
6. Earnest CP, et al. The effect of creatine monohydrate ingestion on aerobic power indices, muscular strength and body composition. Acta Physiol Scand 1995;153:207-9.
7. Cooke WH, et al. Effect of oral creatine supplementation on power output and fatigue during bicycle ergometry. J Appl Physiol 1995;78:670-3.
8. Dyment PG, et al. The adolescent athlete and ergogenic aids. J Adolesc Health Care 1987 Jan; 8(1):68-73.
9. Gruenwald J, et al. PDR of Herbal Medicines. Hackensack (NJ): Medical Economics; 1998. p 1009.
10. Saito H, et al. Effect of Panax ginseng root on exhaustive exercise in mice. Jpn J Pharmacol 1974;24:119-27.
11. Hiai S, et al. Stimulation of pituitary-adrenocortical system by ginseng saponin. Endocrinol Jpn 1979;26:661-5.
12. Salvati G, et al. Effects of Panax ginseng saponins on male fertility. Panminerva Med 1996;38:249-54.
13. Morris AC. No ergogenic effect of ginseng ingestion. Int J Sport Nutr 1996 Sep;6(3):263-71.
14. Engels HJ, et al. No ergogenic effects of ginseng (Panax ginseng C.A. Meyer) during graded maximal aerobic exercise. J Am Diet Assoc 1997 Oct;97(10):1110-5.
15. Dowling EA, et al. Effect of Eleutherococcus senticosus on submaximal and maximal exercise performance. Med Sci Sports Exerc 1996 Apr;28(4):482-9.
16. Robergs RA, et al. Glycerol biochemistry, pharmacokinetics: clinical and practical applications. Sports Med 1998 Sep;26(3):145-67.
17. Inder WJ, et al. The effect of glycerol and desmopressin on exercise performance and hydration in triathletes. J Med Sci Sports Exerc 1998 Aug;30(8):1263-9.
18. Montner P, et al. Pre-exercise glycerol hydration improves cycling endurance time. Int J Sports Med, 1996 Jan;17(1):27-33.
19. Kreider RB, et al. Effects of phosphate loading on metabolic and myocardial responses to maximal and endurance exercise. Int J Sport Nutr 1992 Mar;2(1):20-47.
20. Kanter MM, et al. Antioxidants, carnitine, and choline as putative ergogenic aids. Int J Sport Nutr 1995 Jun;5 Suppl:S120-31.
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