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What the experts say

Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.

Food glorious food

This month I reviewed recent scientific research on nutrition, and the first thing that struck me was the question "Where is all this taking us?" The reason for this lies in the fact that many studies are becoming so single-stranded that they may be overlooking the obvious overall requirements of nutrition. Dietary supplements are increasingly being promoted, and their consumption studied. A more holistic, back to basics approach that takes account of the impact of diet as a whole, maybe what is required. For example, while the aerobic energy system requirements for glycogen arising from the digestion of carbohydrate are well understood, we seem to be arriving at the point whereby studies are trying to identify the optimum carbohydrate concentration for intake during exercise to yield ultimate performance. The reality is that performance is relative to, for example, the individual, other competitors and the event and is dependent on, exercise intensity, duration, diet, metabolism, biochemistry, physiology, the environment, hydration etc. Not surprisingly, therefore, the literature is churning up claims and counter-claims of the importance of several aspects of nutritional requirement while comparing apples with pears! The whole picture is undoubtedly being muddied by commercial pressures to 'prove' that 'product A' is the best for 'keeping you going' or that 'product B' will support 'unprecedented strength improvements'.

Staying on the right track

Thankfully, the balance is restored by some researchers who have looked at the overall dietary intake of large groups of athletes. They found that, on the whole, the diet was unbalanced. Simple nutritional measures would improve overall performance. This would appear to be the key to the argument; otherwise, the real danger is that athletes may start to believe that they do not need to train for their sport, consume the right nutritional supplement. This, of course, is the shortcut to disaster whereby they may take whatever substance is available, legal or illegal, to enable them to 'win'. Remember, in the immortal words of Beverly Sills, 'there are no shortcuts to anywhere worth going'. A paper to put the 'cat amongst the pigeons' looks at elite performers, i.e. proven world-beaters, and finds that key nutritional elements are missing - begging the question 'who is right - the athlete or the expert?'

What influences athletes to take supplements?

A Canadian study[1] based on over 450 university students, both athletes and controls, identified the fact that over 90% of the group consumed dietary supplements. Males consumed sports drinks and products including carbohydrate gels, protein powder and creatine more than women. The most common source of reference information was the Internet, and the main recommendation for actual consumption was from friends. Very little knowledge was apparent concerning benefits or side effects, and the study identified the overwhelming need for nutritional education. Students, on the whole not being renowned for healthy diets, but in a situation where they can learn, it seems would be the ideal starting point for raising levels of awareness and placing a focus on healthier eating while dealing with the pros and cons of dietary supplementation in an objective and digestible form.

Carbs might 'keep you going'!

Carbohydrate-electrolyte (C-E) consumption during continuous exercise in the heat was studied[2] using ten males to establish whether 8% C-E (weight in volume) concentration is optimal or whether a lower concentration should be used when comparing performance to the control placebo. In this study, performance levels were around 8% C-E higher with the intake of carbohydrate as compared to the placebo trial with a small advantage apparent at the 8% C-E level.

Just before you rush away and prepare your energy boost for your next tough session or competition, you may need to heed the words of the following study[3] that looked at gastrointestinal (GI) discomfort related to carbohydrate-electrolyte consumption when exercising at high-intensity. The study looked at thirty-six adult and adolescent athletes during circuit training and used the same regime as above, i.e. 8%, and 6% C-E and placebo.

Though discomfort levels were reported as modest throughout the study, the overall finding was that stomach upset, and side ache was highest in the 8% C-E. Finally, on carbohydrates this month, a study[4] looked at benefits from 6% C-E consumption, in the form of a recognized sports drink, during a 1-hour cycle time-trial versus placebo in a group of trained cyclists after 24 hours of diet and exercise control. The outcome may prove startling to many, but the fact was that no difference was measurable in performance between the two groups in either distance covered or power output. The study concludes that provided glucose availability is optimized through a carefully controlled diet (57.4 Calories/kg energy and 9.1g/kg carbohydrate) and exercise regime for 24 hours then there is no benefit from consuming this sports drink during exercise. The nutrition basics approach referred to at the beginning of this review holds in this case, i.e. eat properly and rest! In a specific applied situation, one study[5] looked at nutritional strategies used by competitors in two-day mountain marathons and found that the competitors in longer events were more conscious of the needs to carry less food mass that is more energy dense than competitors in shorter distance events held over the same two-day duration.

On the flip side, the study also established that the longer distance competitors attained a higher level of dehydration directly affecting performance. In conclusion, all competitors need to drink more fluids throughout such events, and those competitors in the shorter distance events should carry and consume more energy-dense foods.

A supplementary question

Moving on to review the consumption of some selective supplements one paper[6] revisited the chronic taking of the vital amino acid-based substance, arginine aspartate as a potential nutritional ergogenic covered in an earlier paper[7]. In the latest study 30 male endurance cyclists underwent a four-week study based on two different daily intakes. At the end of the period, no performance, metabolic or endocrine benefits could be determined. Similarly, a study[8] looked at the ingestion of another amino acid; tyrosine (150mg/kg taken 30min before exercise) thought to improve aerobic endurance, muscle strength and endurance. Based on a study of 20 men on a load-carriage treadmill activity against a placebo trial, no difference was found in endurance, muscle strength or aerobic power arising from the acute ingestion of tyrosine. Iron, often linked with under-performance, particularly in women was the subject of a study[9] on 42 swimmers, aged 12-17, half of whom were female. The study used a regime of dietary supplementation in one group, an iron-rich normal diet and a control group on a normal diet. At the end of a 6-month training period, although fluctuations in iron levels were recorded dependent on the stage in the training period, there were no significant differences between the groups in iron status at any one time or performance. This was even though the iron dosage ranged from between one to five times the RDA over six months. The conclusion is that normal healthy sportspeople do not require dietary supplementation with iron.

Dietary intake has been shown to affect serum levels of testosterone and free testosterone. In a study[10] that looked at a group of 8 strength athletes and 10 physically active non-athletes performing heavy resistance exercise, the findings were that the strength athletes only showed testosterone levels could be reduced through either excessive protein intake or reduced fat intake. Again, this stresses the importance of a balanced diet for athletes in training.

Don't be a dope

During the last few years to around 2001, there was an apparent surge in the number of athletes failing dope tests due to anabolic steroids, not least of all nandrolone. A survey[11] carried out between October 2000 and November 2001 of so-called non-hormonal nutritional supplements based on chemical analysis produced quite shocking results. Of the 634 products analysed 94 (14.8%) produced positive results for the presence of anabolic androgenic steroids not declared on the label. A further 66 samples had 'matrix effects' blocking the analysis for potentially banned substances.

The risks of taking steroids in terms of side-effects are well documented, and chronic use at medium to high levels can be fatal from several standpoints. Athletes are potentially gambling with their lives through ignorance while the nutritional science seems to be increasingly pointing to minimal benefit gains from supplementation and maximal benefit gains through a healthy diet. Communication, education and awareness need to have a higher profile.

One way to be better?

A study[12] looked at the dietary intake of 58 members of the Greek national swimming and water polo teams. It revealed that 71% of the males and 93% of the females did not meet the Dietary Reference Intakes for at least one of the antioxidant vitamins (due to a lack of fruit and vegetable intake) and that both male and female athletes consumed too much fat and too little carbohydrate. Eat a healthy diet!

One way to be worse?

A study[13] of elite Kenyan endurance runners was made to compare dietary intake with recommendations for endurance athletes. The main findings were that energy intake appeared to be below expenditure, creating a negative energy balance and that fluid intake was modest. The report questions if modifying these parameters will enhance performance. I would ask the question - "Are your sums correct! - do these elite performers get it wrong?" Heaven help us if they are right - these athletes are quick enough as it is!

A summary of benefits based on dietary supplementation

Class 1 - Proven benefits

Supplement Benefit
Creatine monohydrate high-intensity, short duration exercise or sports with alternating low- and high-intensity efforts
Multivitamin-mineral supplements if deficient
Vitamin C to reduce pain and speed muscle strength recovery after intense exercise

Class 2 - Well evidenced benefits

Supplement Benefit
Citrate high-intensity, short- to intermediate-duration exercise
Creatine monohydrate non-weight bearing endurance exercise
DHEA improving strength in older men only
Electrolyte replacement for ultra-endurance competition only
Glutamine for reducing the risk of post-exercise infection only
HMB improving body composition with strength training in untrained people only
Iron for iron deficiency only
Pyruvate exercise performance
Sodium bicarbonate performance enhancement in events of specific durations only
Soy exercise recovery only
Vitamin C deficiency only
Vitamin E exercise recovery and high-altitude exercise performance only

However, if we consider the 'class 1' substances, as we have termed them[14], we can quickly see that these are all very common substances found in food. So, the right diet, with some 'tweaking' for the specific activity, should provide all the basic ingredients. For example, for power athletes, creatine plays an important role. Is it coincidental that power athletes traditionally consumed healthy proportions of meat and fish, for example, these being an excellent source of creatine? As a very experienced Welsh colleague of mine once said to me, "People were lifting heavy weights and throwing things a long way before anyone knew creatine existed, boy!"

A warning and a way forward

In conclusion, aside from training, nutrition may be the most important influence on athletic performance[15]. However, in seeking a competitive edge, athletes are often susceptible to fad diets or supplements that have not been scientifically validated. Nevertheless, there is much useful research to guide the exerciser toward optimum health and performance.

Article Reference

This article first appeared in:

  • HETHERINGTON, N. (2005) What the experts say. Brian Mackenzie's Successful Coaching, (ISSN 1745-7513/ 24 / July-August), p. 13-16


  1. Kristiansen M et al. 'Dietary Supplement Use by Varsity Athletes at a Canadian University', IJSNEM, 15(2), April 2005
  2. Millard-Stafford ML 'Should Carbohydrate Concentration of a Sports Drink Be Less Than 8% During Exercise in the Heat?' IJSNEM, 15(2), April 2005
  3. Shi X et al. 'Gastrointestinal Discomfort During Intermittent High-Intensity Exercise: Effect of Carbohydrate-Electrolyte Beverage' IJSNEM, 14(6), December 2004
  4. Desbrow B et al. 'Carbohydrate-Electrolyte Feedings and 1h Time Trial Cycling Performance' IJSNEM, 14(5), October 2004
  5. Clark HR et al. 'Nutritional Strategies of Mountain Marathon Competitors - An Observational Study' IJSNEM, 15(2), April 2005
  6. Abel T et al. 'Influence of Chronic Supplementation of Arginine Aspartate in Endurance Athletes on Performance and Substrate Metabolism. A Randomized, Double-Blind, Placebo-Controlled Study' Int J Sports Med 2005; 26: 344-349
  7. Colombani PC 'Chronic arginine aspartate supplementation in runners reduces total plasma amino acid level at rest and during a marathon run' Eur J Nutr. 1999 Dec;38(6):263-70
  8. Sutton EE 'Ingestion of Tyrosine: Effects on Endurance, Muscle Strength, and Anaerobic Performance' IJSNEM, 15(2), April 2005
  9. Tsalis G 'Effects of Iron Intake Through Food or Supplement on Iron Status and Performance of Healthy Adolescent Swimmers During a Training Season' Int J Sports Med 2004; 25: 306-313
  10. Sallinene A 'Relationship Between Diet and Serum Anabolic Hormone Responses to Heavy-Resistance Exercise in Men' Int J Sports Med 2004; 25: 627-633
  11. Geyer H 'Analysis of Non-Hormonal Nutritional Supplements for Anabolic-Androgenic Steroids - Results of an International Study' Int J Sports Med 2004; 25: 124-1
  12. Farajian P et al. 'Dietary Intake and Nutritional Practices of Elite Greek Aquatic Athletes' IJSNEM, 14(5), October 2004
  13. Onywera VO et al. 'Food and Macronutrient Intake of Elite Kenyan Distance Runners' IJSNEM, 14(6), December 2004
  14. Internet
  15. American Dietetic Association. Position of the American Dietetic Association and the Canadian Dietetic Association: Nutrition for physical fitness and athletic performance for adults. J Am Diet Assoc 1993;93:691-6.

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About the Author

Nigel Hetherington was the Head Track & Field Coach at the internationally acclaimed Singapore Sports School. He is a former National Performance Development Manager for Scottish Athletics and National Sprints Coach for Wales. Qualified and highly active as a British Athletics level 4 performance coach in all events he has coached athletes to National and International honours in sprints, hurdles as well as a World Record holder in the Paralympic shot. He has ten years of experience as a senior coach educator and assessor trainer on behalf of British Athletics. Nigel is also an experienced athlete in sprint (World Masters Championship level) and endurance (3-hour marathon runner plus completed the 24 hour 'Bob Graham Round' ultra-endurance event up and down 42 mountain peaks in the English Lake District). He is a chartered chemist with 26 years of experience in scientific research and publishing.