What the experts say
Nigel Hetherington reviews the latest research material relating to coaching, exercise physiology and athletic development.
This month I reviewed recent scientific research on nutrition and the first thing that struck me was a 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, may be what is required. For example, while the aerobic energy system requirements for glycogen arising from 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 in order 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'.
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, 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, just consume the right nutritional supplement. This, of course, is the short-cut 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 there are key nutritional elements missing - begging the question 'who is right - the athlete or the expert?'
A Canadian Study based on over 450 university students both athletes and controls, identified that 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 are able to 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.
Carbohydrate-electrolyte (C-E) consumption during continuous exercise in the heat was studied using 10 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 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 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 a 24-hour period of diet and exercise control. The outcome may prove startling to many, but the fact was that absolutely no difference was measurable in performance between the two groups in either distance covered or power output. The study conclude 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 true in this case i.e. eat properly and rest! In a specific applied situation one study 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.
Moving on to review the consumption of some selective supplements one paper revisited the chronic taking of the vital amino acid-based substance, arginine aspartate as a potential nutritional ergogenic covered in an earlier paper. 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 looked at the ingestion of another amino acid; tyrosine (150mg/kg taken 30min prior to 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 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 despite the fact that the iron dosage ranged from between one to five times the RDA over a period of 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 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
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 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 a number of 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 clearly need to have a higher profile.
A study looked at 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!
A study 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 really get it wrong?" Heaven help us if they are right - these athletes are quick enough as it is!
Class 1 - Proven benefits
Class 2 - Well evidenced benefits
However, if we consider the 'class 1' substances, as we have termed them, 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!"
In conclusion, aside from training, nutrition may be the most important influence on athletic performance. 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.
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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 10 years' experience as 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' experience in scientific research and publishing.
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