Sports Performance and Nutrition


Part IV – Hydration and Supplements for Athletes
Part I – Energy Requirements  |  Part II – Nutritional Guidelines  |  Part III – Food Choices


Everybody knows that water is a necessity of life.  Water is fundamental to nearly every physiologic process in the body that makes physical activity even possible.  It maintains blood volume to allow oxygen and nutrient delivery to the muscle, lubricates our joints and lungs, and keeps us from overheating.  Yet, the majority of athletes are not getting enough of it before, during, or after exercise (1).  It is so vital to physical activity that even a seemingly insignificant drop in water volume can seriously hamper performance.  With as little as a 2% reduction in water, our physiologic capacity to exercise is impeded, as cardiovascular output and body temperature regulation systems weaken (2).  Obviously, the level of decline intensifies with the magnitude of dehydration.

The issue with dehydration in athletics stems from our lack of a long-term water storage system, and a misunderstanding of the thirst sensation.  Feeling thirsty is not a sign of pending dehydration, as commonly believed, but rather a sign of actual dehydration.  Receptors gather bodily information, such as a drop in blood pressure from a declining blood volume, which is interpreted as dehydration, and triggers the brain to release a ‘thirsty signal.’ Since athletes expend water stores at a much higher rate than at rest, by the time they feel thirsty, they may not be able to fully rehydrate themselves without stopping.  Athletes need to practice their water intake such that they never have too much or too little water during competition.  Actual water requirements depend largely on the needs of the individual and the sport they are participating in, making it difficult to establish general hydration guidelines.  However, all athletes should consume a large fluid volume about 1.5 hours prior to competition to fully hydrate, consume fluids at the same rate as water loss during play, then rehydrate with 500-600 ml of water for every pound lost during exercise (3).

The most contentious subject in sports nutrition is surely the use of supplements, or ergogenic aids, to increase performance capacity in athletes.  A lot of money is spent by the supplement industry to convince athletes to use their product.  The actual level of evidence for supplementation in sport is much poorer than the industry would have us believe, with a lot of the benefit attributed to the fact that athletes under consume calories (4), and supplements simply allow them to operate at an energy level closer to ideal.  Needless to say, there are much cheaper options to fulfill energy requirements than expensive supplement regimes.

Some ergogenic aids do have a clearly demonstrated benefits:

  1. Carbohydrates and Electrolytes – During exhaustive exercise, such as during a triathlon or marathon, the energy stores are used up, and electrolytes are lost in the sweat.  Athletes need to replace these losses during activity to maintain performance.  There is a clear benefit of carbohydrate and electrolyte ingestion with delayed progression of fatigue, and maintenance of energy stores (5).
  2.  Essential Fatty Acids – Omega 3 fats have a well-documented anti-inflammatory ability, and have been shown to reduce inflammatory processes in the body (6).  Since high intensity training causes continual bodily trauma, athletes tend to have a high inflammatory load, which can impact performance, increase injury susceptibility, and lead to the development of chronic disease (7).  Taking 2 grams of 2:1 EPA to DHA is recommended for athletes to offset this risk.
  3.  Branched Chain Amino Acids (BCAA’s) – BCAA’s were once thought to decrease fatigue by increasing blood levels of tryptophan, however studies have since shown this to not be the case (8).  However, they have been shown to reduce muscle damage during activity and improve muscle recovery after exercise (9).
  4.  L-Carnitine – In endurance events, athletes who can utilize a larger portion of their energy stores will have an increased capacity to perform.  L-carnitine has been shown to aid athletic ability by making fats a more readily available energy substrate (10).  Further benefits include improved muscle recovery and immune function (11).


Read more in this four-part Sports Nutrition series:
Part I – Energy Requirements for Athletes
Part II – Nutritional Guidelines for Athletes
Part III – Food Choices for Athletes
Part IV – Hydration and Supplements for Athletes

1. Burke L. Fluid balance during team sports. Journal of Sports Sciences. 1997; 15(3): p. 287-295.

2. Murray R. Dehydration, Hyperthermia, and Athletes: Science and Practice. Journal of Athletic Training. 1996 September; 31(3): p. 248-252.

3. Benardot D. Advanced Sports Nutrition. 2nd ed. Windsor: Human Kinetics; 2012.

4. Costill D, Flynn M, Kirwan J, Houmard J, Mitchell J, Thomas R, et al. Effects of repeated days of intensified training on muscle glycogen and swimming performance. Med Sci Sports Exerc. 1988 June; 20(3): p. 249-254.

5. Coyle E, Coggan A, Hemmert M, Ivy J. Muscle glycogen utilization during prolonged, strenuous exercise when fed carbohydrates. Journal of Applied Physiology. 1986; 61: p. 165-172.

6. Wall R, Ross P, Fitzgerald G, Stanton C. Fatty acids from fish: the anti-inflammatory potential of long-chain omega-3 fatty acids. Nutrition Reviews. 2010 May; 68(5): p. 280-289.

7. Simopoulous A. Omega-3 fatty acids and athletic. Sports Medicine Reports. 2007 August; 6(4): p. 230-236.

8. van Hall G, Raaymakers J, Saris W, Wagenmakers A. Ingestion of branched-chain amino acids and tryptophan during sustained exercise in man: failure to affect performance. The Journal of Physiology. 1995 August;(486): p. 789-794.

9. Negro M, Giardina S, Marzani B, Marzatico F. Branched-chain amino acid supplementation does not enhance athletic performance but affects muscle recovery and the immune system. The Journal of Sports Medicine and Physical Fitness. 2008; 48(3): p. 347-351.

10. Siliprandi N, Di Lisa F, Memabo R. Clinical use of carnitine. Past, present, and future. Adv Exp med Biol. 1990; 272.

11. Karlic H, Lohninger A. Supplementation of L-carnitine in athletes: Does it make sense? Nutrition. 2004; 20: p. 709-715.