by Thomas Incledon, PhD(c), RD, LD/LN, RPT, NSCA-CPT, CSCS
The Start of A New Era
Sports supplementation has really undergone an incredible overhaul. Remember the days when coaches would criticize their athletes for drinking water during physical activity? Later researchers demonstrated that dehydration would impair physical and mental performance and that drinking water before, during and after sports and exercise was actually a good thing. Then for some time the only advice most practitioners would offer was to drink more water. After additional research it was shown that ingesting carbohydrate-containing beverages before and during exercise would help maintain blood glucose levels and could delay fatigue and maintain or improve performance, depending on the activity and duration. Ingesting carbohydrate-containing foods and drinks after activity allowed glycogen to be resynthesized more rapidly. While most researchers and healthcare practitioners would accept that the ingestion of carbohydrate drinks and/or water could maintain or improve performance during activity, they often dismiss the use of other supplements. The reasons cited might include lack of: sufficient research for a given population, acute safety data, longitudinal research, and negligible or minimal performance benefits. However, these are the same issues that can be raised for water and carbohydrate drinks. For example, how many ten or twenty year studies have their been on water or carbohydrate drink consumption during activity? Hopefully this will have you thinking about some of the double standards that exist and open you up to the possible applications that other supplements may have. This article will cover a variety of different categories of supplements that have the potential to impact physical performance.
ATP Enhancers
This category of supplements includes agents that can increase or maintain ATP (adenosine 5’-triphosphate) levels. ATP is a purine nucleotide that is found in every mammalian cell. Most people are aware of its role in cellular energy metabolism. However, extracellular ATP (and its breakdown product adenosine) can affect a variety of biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation, and liver glycogen metabolism. The rationale to increase ATP levels in order to improve performance is based on the assumption that declining ATP levels may be rate limiting for performance. While there is some research evidence that ATP levels are reduced during activity, it would be unlikely that reduced ATP levels represent the sole reason for fatigue. The effect of physical exertion on intramuscular ATP levels depends on the intensity and duration of the activity.
Adenosine Triphosphate
Clinical studies have demonstrated that ATP may have potential therapeutic potential for patients with neuropathic pain, ischaemic pain, haemorrhagic shock, pulmonary hypertension, tachycardia, cystic fibrosis, lung cancer, radiation tissue damage, and coronary artery disease [1]. However, these studies administered ATP via injection. Studies documenting the effects of ATP on exercise performance have also used clinical populations and delivered the agent via injection. Oral doses of 40 to 300 mg daily appear to be well tolerated in patients [2, 3].
Various products have appeared in the supplement market claiming to contain ATP. The methods of delivery include oral tablet or capsule, liposomal (spheres of phosphorylated fatty acids), intraoral (sublingual sprays), and transdermal (creams, gels, or sprays applied to skin). Based on clinical studies, it appears that both oral and liposomal ATP exert physiological effects. Oral ATP is usually a salt and appears fairly stable. The use of liposomes as a delivery method for supplements has been questioned due to the unstable nature of liposomes. Intraoral delivery of ATP may not be ideal because the buccal cavity contains enzymes that breakdown ATP [4]. Transdermal delivery is also not ideal because ATP causes a dose-related pain response in human skin [5].
Given the lack of exercise-related data in healthy people, using ATP at this point would be premature. The areas of concern include dose-response effects and physiological adaptations to elevated ATP levels.
Creatine
Creatine is an amino acid that can be used by the body to make creatine phosphate and ATP. Numerous studies have been conducted on the effects of oral creatine monohydrate on physical performance. While some acute studies have shown no benefit of creatine on anaerobic performance, the majority of studies do show an improvement. Long-term studies indicate that creatine ingestion increases the gains in strength and lean body mass provided by resistance exercise [6-8]. The ingestion of substances that can elevate insulin appears to improve the acute ergogenic effects of creatine [9]. In practice, this is often accomplished by ingesting creatine with a protein/carbohydrate drink after exercise.
Various forms of creatine have appeared on the market. Most of the research has been done using creatine monohydrate ingested either as capsules or powder. Other creatine products include suspensions, liquids, and candy. Different labs have tested a liquid creatine product and found no evidence of creatine. Given the instability of current liquid products, creatine powders appear a more prudent choice. It is thought that creatine provides its ergogenic benefits by increasing the total intramuscular pool of creatine, thereby increasing the ability to make ATP. There is some debate over the mechanisms of action of creatine, however there is general agreement among research studies that creatine is chronically safe when ingested in doses of 10 grams or less per day [10, 11].
Ribose
Ribose is a five-carbon sugar that can be used by the body to make ATP via the pentose-phosphate pathway. This pathway is of interest to researchers because it does not require oxygen for ATP production and therefore may be of use during conditions of impaired or inadequate blood flow. Exercise studies using patients with cardiovascular disease indicates it can improve performance [12]. Oral does as high 50-60 grams per day were well tolerated without side effects [13]. However this was administered in smaller amounts of four grams each. Doses at 10 grams or more may cause hypoglycemia.
While several studies have been conducted on ribose in healthy subjects, thus far the information has appeared primarily as abstracts presented at scientific conferences. The results overall appear to support the theoretical strategy that ribose supplementation before and during exercise may improve physical performance. Of critical importance is the timing of administration at dose. Unpublished observations indicate that approximately five grams should be ingested every 30-45 minutes of activity. At this point in time it appears that ribose has potential to improve performance in healthy subjects, but lacks sufficient research published in peer-reviewed journals.
Neurotransmitter Precursors
This category of supplements includes agents that can serve as the starting point for synthesizing neurotransmitters such as acetylcholine and epinephrine. These neurotransmitters are responsible for communicating signals between neurons and other cells. Stress can deplete brain norepinephrine and dopamine, catecholaminergic neurotransmitters. When this happens, mental and physical performance will be hindered. Neurotransmitter precursors can help maintain normal levels of neurotransmitters. They can also stimulate different regions of the brain resulting in altered hormonal responses and improved function of the central nervous system. The traditional neurotransmitter precursor used to improve performance was choline. Research indicates that an eight gram dose of choline citrate has no effect on fatigue [14]. This has led researchers to investigate the effects of other agents.
Alpha-GPC
Alpha-glycerylphosphorylcholine is a choline-containing compound that is believed to serve as a precursor for acetylcholine and/or membrane phospholipids. Animal studies indicate that it improves both learning and memory in a dose dependent fashion. Studies on humans indicate that it can prevent drug induced memory deficits and offer therapeutic application for protecting the brain and other neural tissues. Recent interest in alpha-GPC has focused on its ability to augment growth hormone release when combined with other stimuli. Administration of alpha-GPC and growth hormone releasing hormone results in significantly greater growth hormone release [15]. A recent abstract presented at the American Society of Exercise Physiologists’ Annual Meeting lends additional support to the previous findings. A product containing 100 mg of alpha-GPC stimulated a greater increase in exercise-induced growth hormone release compared to placebo.
Clinical studies have generally used doses between 400 and 1200 mg per day. Most products on the market offer substantially less than this (ie 100 mg or less). So far the overall evidence for choline-containing compounds to improve physical performance is weak. However, there appears to be sufficient evidence on alpha-GPC to warrant further investigation into its potential ergogenic value.
Tyrosine
Research suggests that tyrosine, a precursor of the neurotransmitter norepinephrine, may be useful in counteracting stress-related performance decrements and mood deterioration. Various forms of stress can induce depletion of brain catecholamines, especially norepinephrine, in animals. Reduced brain norepinephrine levels are closely related to stress-induced performance decrements in animals. Tyrosine administration minimizes or reverses stress-induced performance decrements by increasing brain norepinephrine levels. Studies on humans indicate that tyrosine can improve cognitive performance during stressful conditions and reduce the effects of environmental stress [16-18].
Products marketed towards increasing neurotransmitter levels often provide less than 3000 mg of tyrosine. The actual doses used in studies vary from two gram doses ingested five times per day (a total of 10 grams ingested) to single servings providing up to 15 grams in one dose. Most studies showing a benefit of tyrosine use 100 mg/kg for a single dose.
Agents Influencing Protein Synthesis
Amino Acid/Carbohydrate Drinks
Previous research indicated that muscle protein turnover and amino acid transport are increased after resistance exercise in humans [19]. Ingesting amino acid solutions after exercise protein metabolism could be skewed favorably to net protein synthesis [20]. The amino acid solutions do not need to contain non-essential amino acids [21]. During this time, additional research on insulin demonstrated that it stimulates protein synthesis and enhances the transport of selected amino acids into human skeletal muscle at rest [22]. After exercise, insulin significantly reduces protein degradation [23]. Since the effects of insulin may be limited by the availability of amino acids, the logical extension of the previous research would be to elevate amino acid and insulin levels in the blood simultaneously after exercise. This was accomplished by providing a solution containing six grams of essential amino acids and 35 grams of sucrose [24]. The combination of resistance exercise, amino acids, and insulin (stimulated by the carbohydrate amino acid drink) resulted in an increase of protein synthesis by ~400% [24]. This is a substantial increase in protein synthesis rates. Research from the same lab also indicates that this number can be elevated higher if the same solution is ingested immediately before training.
Most post-workout products on the market provide whole proteins, not amino acids. The significance of this is that additional calories in the form of nonessential amino acids are ingested when it is now known that only essential amino acids are needed. Many of these products also contain a low carbohydrate-to-protein ratio. Previous studies are using ratios of carbohydrate-to-protein of about 6:1 and provide only about 164 calories. Athletes choosing to follow these guidelines may stimulate increases in lean body mass and minimize gains in body fat.
A Sample Strategy
It’s not uncommon for athletes to want to take everything at once, with the thought process that if one thing works, then taking everything should really boost performance. Unfortunately, this is seldom the case and even if it were true, it would still not be the ideal strategy. In order to evaluate the effectiveness of a given supplement for a given client, it has to be administered in a controlled fashion. A prudent strategy first involves determining if the individual is following the right diet. A poor diet with lots of supplements is still a poor diet. Rather than using supplementation to mask dietary weakness, it would be better to use supplementation to augment a sound diet. Typically this means monitoring a client while he/she follows a diet for a four-to-eight week period. The dietary regimen should have been manipulated by that point in time to achieve the client’s goals. Next, each supplement is introduced one at a time with an appropriate evaluation period. Using this systematic approach, an individualized and unique diet and supplement strategy is developed. Assuming this process has taken place, a sample strategy would look like:
7:00 AM Meal 1
10:00 AM Meal 2
1:00 PM Meal 3
3:30 PM Pre-Workout Drink #1: 100 mg/kg tyrosine mixed in carbohydrate beverage like CeraSport or Gatorade. (Ingested about 30-45 minutes before training)
4:10 PM Pre-Workout Drink #2: Six grams of essential amino acids, 35 grams of sucrose, and five grams of ribose. (Ingested immediately before training)
5:30 PM Post-Workout Drink: Six grams of essential amino acids, 35 grams of sucrose, five grams of ribose, and five grams of creatine.
7:00 PM Meal 4
10:00 PM Meal 5
This strategy can be applied to both the athlete desiring to lose weight as well as the athlete desiring to gain weight, providing the appropriate calorie and macronutrient adjustments are made. It should not be mistaken for a template to copy and hand out to clients. Rather it is simply an example of one possible strategy that can be developed utilizing the latest research on supplementation with an emphasis on improving performance. While this article certainly doesn’t cover all the supplements currently on the market, it hopefully offers some insight to the potential use of some products.
References:
1. Agteresch, H.J., et al., Adenosine triphosphate. Established and potential clinical applications. Drugs, 1999. 58(2): p. 211-232.
2. Wang, J. and G. Bu, Clinical observation of oral adenosine triphosphate in treating rhinitis medicamentosa. Chinese Medical Journal, 2000. 113(4): p. 349.
3. Mizukoshi, K., et al., Clinical evaluation of medical treatment for Meniere’s disease, using a double-blind controlled study. American Journal of Otology, 1988. 9(5): p. 418-422.
4. Dabelsteen, E. and S. Kirkeby, ATP-ase positive cells in human oral mucosa transplanted to nude mice. Scandinavian Journal of Dental Research, 1981. 89(5): p. 433-5.
5. Hamilton, S.G., et al., ATP in human skin elicits a dose-related pain response which is potentiated under conditions of hyperalgesia. Brain, 2000. 123(Pt 6): p. 1238-46.
6. Becque, M.D., J.D. Lochmann, and D.R. Melrose, Effects of oral creatine supplementation on muscular strength and body composition. Medicine & Science in Sports & Exercise, 2000. 32(3): p. 654-8.
7. Volek, J.S., et al., Performance and muscle fiber adaptations to creatine supplementation and heavy resistance training. Medicine & Science in Sports & Exercise, 1999. 31(8): p. 1147-56.
8. Vandenberghe, K., et al., Long-term creatine intake is beneficial to muscle performance during resistance training. Journal of Applied Physiology, 1997. 83(6): p. 2055-63.
9. Green, A.L., et al., Carbohydrate ingestion augments creatine retention during creatine feeding in humans. Acta Physiologica Scandinavica, 1996. 158(2): p. 195-202.
10. Poortmans, J.R. and M. Francaux, Long-term oral creatine supplementation does not impair renal function in healthy athletes. Medicine & Science in Sports & Exercise, 1999. 31(8): p. 1108-10.
11. Schilling, B.K., et al., Creatine supplementation and health variables: a retrospective study. Medicine & Science in Sports & Exercise, 2001. 33(2): p. 183-8.
12. Pliml, W., et al., Effects of ribose on exercise-induced ischaemia in stable coronary artery disease. Lancet, 1992. 340(8818): p. 507-510.
13. Zollner, N., et al., Myoadenylate deaminase deficiency: successful symptomatic therapy by high dose oral administration of ribose. Klinische Wochenschrift, 1986. 64(24): p. 1281-1290.
14. Warber, J.P., et al., The effects of choline supplementation on physical performance. International Journal of Sport Nutrition & Exercise Metabolism, 2000. 10(2): p. 170-81.
15. Ceda, G.P., et al., alpha-Glycerylphosphorylcholine administration increases the GH responses to GHRH of young and elderly subjects. Hormone & Metabolic Research, 1992. 24(3): p. 119-21.
16. Deijen, J.B., et al., Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course. Brain Research Bulletin, 1999. 48(2): p. 203-9.
17. Deijen, J.B. and J.F. Orlebeke, Effect of tyrosine on cognitive function and blood pressure under stress. Brain Research Bulletin, 1994. 33(3): p. 319-323.
18. Banderet, L.E. and H.R. Lieberman, Treatment with tyrosine, a neurotransmitter precursor, reduces environmental stress in humans. Brain Research Bulletin, 1989. 22(4): p. 759-62.
19. Biolo, G., et al., Increased rates of muscle protein turnover and amino acid transport after resistance exercise in humans. American Journal of Physiology: Endocrinology and Metabolism, 1995. 268(3 Pt 1): p. E514-E520.
20. Tipton, K.D., et al., Postexercise net protein synthesis in human muscle from orally administered amino acids. American Journal of Physiology: Endocrinology and Metabolism, 1999. 276(4): p. E628-E206.
21. Tipton, K.D., et al., Nonessential amino acids are not necessary to stimulate net muscle protein synthesis in healthy volunteers. Journal of Nutritional Biochemistry, 1999. 10(2): p. 89-95.
22. Biolo, G., R.Y. Declan Fleming, and R.R. Wolfe, Physiologic hyperinsulinemia stimulates protein synthesis and enhances transport of selected amino acids in human skeletal muscle. Journal of Clinical Investigation, 1995. 95(2): p. 811-819.
23. iolo, G., et al., Insulin action on muscle protein kinetics and amino acid transport during recovery after resistance exercise. Diabetes, 1999. 48(5): p. 949-957.
24. asmussen, B.B., et al., An oral essential amino acid-carbohydrate supplement enhances muscle protein anabolism after resistance exercise. Journal of Applied Physiology, 2000. 88(2): p. 386-92.
|
Resource Library HTML 
