Sports nutrition.

Continuing education and the APD program

This quiz is an ideal activity for APD members to include in your CPD log, where it relates to personal learning goals. Record the time taken, to the nearest hour, to complete the quiz and any associated research.

INTRODUCTION

Australians love their sport and enjoy the successes of our athletes at Commonwealth Games, Olympics Games and World Championships. Nutrition advice from a qualified sports dietitian can help an athlete perform at their best--whether this is on the world stage or as a weekend warrior. Sports nutrition strategies are dependent on the energy systems used in sport, individual characteristics of the athlete, competition and training schedules, environmental conditions, accessibility to food and fluids and practicality of applying guidelines.

The following questions have been designed to highlight the range of skills and technical expertise required to ensure that state-of-the-art advice is provided to athletes undertaking regular exercise.

1. Which is the LEAST ACCURATE statement regarding fat oxidation, exercise intensity and loss of body fat?

a. To lose body fat it is best to exercise at low-moderate intensities (i.e. 45% of V[O.sub.2]max) because fat oxidation is proportionally greatest at these intensities

b. The highest rates of fat oxidation (g/min) probably occur at moderately high work intensities (i.e. 65% V[O.sub.2]max)

c. People who wish to exercise to lose body fat should choose the highest exercise intensity that they can comfortably maintain during the time that they have allocated to exercise, so that caloric expenditure during exercise is maximised

d. There is a decline in rates of fat oxidation at high exercise intensities, due to the reduction in blood flow from adipose tissue to the exercising muscle, which acts to reduce the provision of plasma free fatty acids as a muscle fuel

2. When counselling an athlete about their training diet, which of the following macronutrient to energy ratios should be set as a standard, with energy coming from protein, carbohydrate and fat in the following ratios?

a. 20%, 70%, 10%

b. 30%, 40%, 30%

c. 15%, 55%, 30%

d. 15%, 60%, 25%

e. None of the above

3. Which of the following statements is MOST ACCURATE regarding carbohydrate intake and post-exercise glycogen synthesis?

a. High glycaemic index (GI) carbohydrate-rich foods appear to be most effective in promoting muscle glycogen synthesis; however, low GI carbohydrate-rich foods can be included within the menu if they are favourite foods of the athlete

b. Low GI foods are not suitable for glycogen synthesis and should not be included on the athletes recovery menu

c. A dietary intake providing 70% carbohydrate will ensure optimum glycogen synthesis for all athletes

d. An athlete should always eat carbohydrate foods immediately after exercise to maximise post-exercise glycogen synthesis

4. Which of the following athletes is likely to have the HIGHEST daily protein requirement, estimated in grams per kg body mass?

a. A resistance training athlete who is starting a new program

b. An experienced resistance training athlete

c. A recreational endurance athlete training five times a week for 45 minutes

d. An elite cyclist undertaking a gruelling stage race

e. (a) and (d) have similarly elevated requirements

5. Liquid meal supplements are used by some athletes as a pre-event meal. Which of the following BEST describes the benefit of these meals?

a. They enhance performance significantly more than pre-competition solid meals

b. They are useful for athletes who are too nervous to eat solid meals before competition

c. They contain glucose polymers that are more efficiently converted to muscle glycogen compared with solid foods

d. They contain vitamins and minerals in amounts that are not adequate in solid foods

e. They contain whey protein which is the ideal protein source

6. Which of the following statements is most ACCURATE with regard to sports drinks?

a. They should be diluted to 1/2 strength as they are too concentrated and salty for consumption during exercise

b. They work better for elite athletes than recreational athletes

c. Athletes need to be educated about the best use of sports drinks during and after exercise

d. Sports water is better than a standard sports drink because it has fewer kilojoules

7. Risk of hyperthermia in children is higher than in adults. Which of the following statements BEST explains this finding:

a. Lower body weight in children

b. Children have a lower sweat rate than adults, due to lower sweat production by each gland

c. The sweating threshold is higher in children than in adults

d. The sweat response is more efficient in children

e. Both (b) and (c)

8. A middle distance runner comes to you, complaining of tiredness and fatigue during training. He has recently resumed heavy training after months of injury and anti-inflammatory treatment. Blood tests show him to be iron-deficient. Over the past few years, previous blood tests have always been indicative of good iron status. He has been a lacto-ovo-vegetarian for eight years. Which of the following is likely to be most important in contributing to his present status?

a. Increased iron losses through sweat and footstrike haemolysis 

b. Gastrointestinal blood loss through anti-inflammatory drug use

c. Low dietary intake haem iron

d. Both (a) and (b)

ANSWERS

1. a.

For any physical activity to be beneficial it must contribute to energy imbalance in the form of an overall daily energy deficit over time. Low-intensity physical activity (25-45% V[O.sub.2]max) is often promoted as advantageous for fat-burning. This is a confusing message based on the relatively high percentage of fatty acid oxidation in relation to total energy expenditure at this intensity. (2) In fact, the amount in kilo-joules of fat being oxidised reaches its peak at moderate intensity (~65% V[O.sub.2]max), (2) but with total energy expenditure increasing more, the percentage of fat oxidation reduces. As the overall energy expended and creation and maintenance of an energy deficit is the key to promoting long-term fat loss, low-intensity physical activity may not be the most efficient means to achieving fat loss goals. People who wish to exercise to lose body fat should choose the highest exercise intensity that they can comfortably maintain during the time that they have allocated to exercise, so that caloric expenditure during exercise is maximised. Readers are referred to Hawley and Burke (3) and O'Connor et al. (4) for further reading.

2. e.

Individual athletes usually have specific macronutrient requirements, including carbohydrate (for muscle fuel) (5-8) and protein (for growth and repair). (9) These requirements are in absolute terms relative to muscle or body mass rather than being proportional to energy needs, and will vary according to fuel requirements of the training/competition program and the athlete's goals for performance and recovery. New carbohydrate intake guidelines are scaled to volume and intensity of the exercise program and range from moderate intakes for athletes with lower fuel requirements for training to higher intakes for athletes undertaking heavy training/competition workloads. (5) Of course it should be realised that these recommendations are a 'starting point' and need to be fine-tuned in consideration of the athlete's other nutrition goals and with feedback from training and competition performance (Table 1).

Once gram and kilojoule amounts are determined for carbohydrate and protein, these can be expressed as a percentage value with the number being dependent on the energy budget of the individual. However, requirements for macronutrients expressed in terms of percentage values are difficult for athletes to translate, whereas requirements expressed in terms of gram amounts can be supported using ready reckoners, commercially available food counters and label-reading advice. Therefore, the use of energy percentage terminology to translate the dietary needs of athletes is discouraged. (5) Readers are also referred to question 4 for specific protein recommendations for athletes and to Burke et al., (5-7) Maughan, (8) Tarnopolsky (9) and Hawley and Burke (3) for further reading on the carbohydrate, protein and fat requirements for athletes.

3. a.

There is now a considerable body of research that points to the gram amount of carbohydrate intake as being the most important factor in glycogen resynthesis. (7) Maximal glycogen storage occurs over 24 hours with intake of 7-12 g/kg of carbohydrate, although some athletes may need more. (10-13) Specific attention to timing of carbohydrate intake immediately post exercise (within 30 minutes) is required if the athlete needs to perform again within eight hours. (14) However, a delay in carbohydrate intake of up to two hours post exercise does not appear to be detrimental to muscle glycogen resynthesis if the recovery period is longer. (15) There is some evidence that higher GI foods may enhance glycogen recovery. (16) However, in order to satisfy the requirement to consume large amounts of carbohydrate as well as other nutritional requirements, athletes are encouraged to consume a variety of carbohydrate-rich foods. Readers are referred to Burke for further reading. (7)

4. e.

Nitrogen balance studies on athletes undertaking different stages and types of training have updated our knowledge of their requirements. These are listed in Table 2.

Readers are referred to the study by Tarnopolsky for a review on this topic. (9) Untrained athletes who begin a new resistance training program require extra protein for myofibrillar protein accretion in the first few months. Thereafter, protein requirements reduce. Athletes undertaking extended daily training sessions may also need extra protein, which is likely to be due to increased amino acid oxidation. Therefore a resistance training athlete starting a new program, and an elite cyclist in a grueling race stage are likely to have similarly elevated requirements. Some athletes on energy-restricted diets may not meet protein recommendations and so dietary intake must be specifically tailored to meet needs. However, most athletes will achieve the increased protein requirements without specific dietary change due to increased food intake with their overall increased energy requirement.

5. b.

According to Hawley and Burke, (17) the goals of the pre-event meal are to:

* Continue to fuel muscle glycogen stores if they have not fully stored or loaded since the last exercise session

* Restore liver glycogen content, especially for events undertaken in the morning where liver stores are depleted by overnight fast

* Ensure that the athlete is well hydrated 

* Prevent hunger, yet avoid the gastrointestinal discomfort and upset often experienced during exercise, and

* Include foods and practices that are important to the athlete's psychology or superstitions

If a liquid meal supplements is chosen as the pre-event meal, it should be carbohydrate-rich to supply energy needs and low in fat and fibre to reduce potential for gastrointestinal discomfort. (18) They do not supply any specific performance benefit over solid meal alternatives, but may be beneficial for the nervous athlete or for those who report reflux or gastrointestinal discomfort. (18) The general view on pre-exercise carbohydrate is that the amount is more important than type. (6) Micronutrient intake is a lower priority in the pre-event meal than in everyday training nutrition. There is new evidence that consuming protein prior to a resistance training session offers benefits to post-training protein balance; (19) therefore, there is a good reason to include high-quality protein in the meals eaten before some exercise sessions. Readers are referred to Burke for further reading. (6)

6. c.

Sports drinks are specially formulated to deliver carbohydrates, fluids and electrolytes in a 'best fit' profile to suit a range of sports and environmental conditions, and do not need to be diluted. The addition of flavour (20-23) enhances palatability, which may enhance voluntary consumption of fluids. Research has demonstrated that fluids obtained via sports drinks are better retained than via water or soft drink. (24) In theory, the benefits of sports drinks should be evident for recreational and elite athletes alike; however, it is worth noting that most research has been conducted on recreational to sub-elite groups. Sports drinks are not the same as 'energy drinks', which generally contain more carbohydrate and substantial amounts of caffeine. There are many misconceptions about the use of sports drinks, and athletes need to be educated on their best and most appropriate use. Readers are referred to Maughan for further reading. (8)

7. e.

Children need to be carefully monitored when exercising in extreme weather conditions. The body surface area to volume rather than body weight is of importance in considering thermoregulatory capacity in children. They have higher surface area to volume ratio, which means they absorb heat from the environment more quickly than adults, (25) and while heat production per kilogram is greater, (26) heat transfer from core to skin is less efficient. Children have a less efficient sweat response than adults. (26) Their sweat glands produce less sweat (26) and sweating threshold appears to be higher in children than adults. (27) Fluid intake in physically active children should be carefully planned and monitored, especially in the heat. Readers are referred to Bass and Inge for further reading. (28)

8. d.

Deakin has outlined the physiological and dietary factors associated with iron deficiency. (29) Although inadequate intake of iron-rich foods and/or foods with low iron bioavailability can contribute to iron deficiency, this particular athlete has always had good iron status. Assuming no dietary change, a dietary cause for iron depletion appears unlikely. However, athletes may lose iron via sweat, (30,31) gastrointestinal losses, (32,33) red blood cell destruction due to physical trauma, (34) or blood loss associated with injury. (29) Anti-inflammatory drugs may also contribute to gastrointestinal blood losses. (29) The resumption of a heavy training load may also place added stress on iron stores with the increase in red blood cell mass that will be occurring at that time. In the scenario given, increased losses via sweat, footstrike and/or gastrointestinal losses due to anti-inflammatory usage seem the most likely answer. Readers are referred to Deakin (29) and Cox (35) for further reading.

REFERENCES

1 Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006.

2 Romijn JA, Coyle EF, Sidossis LS et al. Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. Am J Physiol Endocrinol Metab 1993; 265: E380-91.

3 Hawley J, Burke L. Nutritional strategies to enhance fat oxidation during aerobic exercise. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 455-83.

4 O'Connor H, Sullivan T, Caterson I. Weight loss and the athlete. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 135-73.

5 Burke L, Kiens B, Ivy J. Carbohydrates and fat for training and recovery. J Sports Sci 2004; 22: 15-30.

6 Burke L. Preparation for competition. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 355-84.

7 Burke L. Nutrition for recovery after competition and training. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 415-53.

8 Maughan R. Fluid and carbohydrate intake during exercise. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 385-414.

9 Tarnopolsky M. Protein and amino acid needs for training and bulking up. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 73-111.

10 Costill D, Sherman W, Fink W, Maresh C, Witten M, Miller J. The role of dietary carbohydrates in muscle glycogen resynthesis after strenuous running. Am J Clin Nutr 1981; 34: 1831-6.

11 Burke LM, Collier GR, Beasley SK et al. Effect of coingestion of fat and protein with carbohydrate feedings on muscle glycogen storage. J Appl Physiol 1995; 78: 2187-92.

12 Coyle EF, Jeukendrup AE, Oseto MC, Hodgkinson BJ, Zderic TW. Low-fat diet alters intramuscular substrates and reduces lipolysis and fat oxidation during exercise. Am J Physiol Endocrinol Metab 2001; 280: E391-8.

13 Saris W, Van Erp-Baart M, Brouns F, Westerterp K, ten Hoor F. Study on food intake and energy expenditure during extreme sustained exercise: the Tour de France. Int J Sports Med 1989; 10 (Suppl. 1): S26-31.

14 Ivy JL, Katz AL, Cutler CL, Sherman WM, Coyle EF. Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion. J Appl Physiol 1988; 64: 1480-85.

15 Parkin J, Carey M, Martin I, Stojanovska L, Febbraio M. Muscle glycogen storage following prolonged exercise: effect of timing of ingestion of high glycemic index food. Med Sci Sports Exerc 1997; 29: 220-24.

16 Burke LM, Collier GR, Hargreaves M. Muscle glycogen storage after prolonged exercise: effect of the glycemic index of carbohydrate feedings. J Appl Physiol 1993; 75: 1019-23.

17 Hawley J, Burke L. Peak Performance. Sydney: Allen and Unwin, 1998.

18 Garden L. Practice tips: fuelling for competition. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 376-80.

19 Tipton KD, Rasmussen BB, Miller SL et al. Timing of amino acid-carbohydrate ingestion alters anabolic response of muscle to resistance exercise. Am J Physiol Endocrinol Metab 2001; 281: E197-206.

20 Minehan M, Riley M, Burke L. Effect of flavour and awareness of kilojoule content of drinks on preference and fluid balance in team sports. Int J Sport Nutr Exerc Metab 2002; 12: 81-92.

21 Bar-Or O, Wilk B. Water and electrolyte replacement in the exercising child. Int J Sport Nutr 1996; 6: 93-9.

22 Hubbard RW, Sandick BL, Matthew WT et al. Voluntary dehydration and alliesthesia for water. J Appl Physiol 1984; 57: 868-73.

23 Szlyk P, Sils I, Francesconi R, Hubbard R, Armstrong L. Effects of water temperature and flavoring on voluntary dehydration in men. Physiol Behav 1989; 45: 639-47.

24 Gonzalez-Alonso J, Heaps C, Coyle E. Rehydration after exercise with common beverages and water. Int J Sports Med 1992; 13: 399-406.

25 Bar-Or O, Dotan R, Inbar O, Rotshtein A, Zonder H. Voluntary hypohydration in 10- to 12-year-old boys. J Appl Physiol 1980; 48: 104-8.

26 Bar-Or O. Temperature regulation during exercise in children and adolescents. In: Gisolfi C, Lamb D, eds. Perspectives in Exercise Science and Sports Medicine: Youth, Exercise and Sport. Indianapolis: Benchmark Press, 1989; 335-67.

27 Falk B. Effects of thermal stress during rest and exercise in the pediatric population. Sports Med 1998; 25: 221-40.

28 Bass S, Inge K. Nutrition for special populations: children and young athletes. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 589-625.

29 Deakin V. Iron depletion in athletes. In: Burke L, Deakin V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 263-312.

30 LaManca J, Haymes E, Daly J, Moffatt R, Waller M. Sweat iron loss of male and female runners during exercise. Int J Sports Med 1988; 9: 52-5.

31 Waller M, Haymes E. The effects of heat and exercise on sweat iron loss. Med Sci Sports Exerc 1996; 28: 197-203.

32 Lampe J, Ellefson M, Slavin J, Schwartz S, Apple F. The effect of marathon running on gastrointestinal transit time and fecal blood loss in women runners. Med Sci Sports Exerc 1987; 19: S21.

33 Nachtigall D, Neilson R, Fischer R, Engelhardt R, Gabbe E. Iron deficiency in distance runners: a reinvestigation 99Fe labeling and non invasive liver iron quantification. Int J Sports Med 1996; 17: 473-9.

34 Miller B, Pate R, Burgess W. Foot impact force and intra-vascular haemolysis during distance running. Int J Sports Med 1988; 9: 56-60.

35 Cox G. Special needs: the vegetarian athlete. In: Burke L, Deakin, V, eds. Clinical Sports Nutrition, 3rd edn. Sydney: McGraw-Hill Book Company Australia Pty Limited, 2006; 699-719.

This quiz has been prepared by Louise Burke, Anthony Meade, Janelle Barnard, Greg Shaw and Greg Cox on behalf of Sports Dietitians Australia. Correct answers follow the questions to allow readers to carry out self-assessment. For further reading on each topic, more comprehensive reviews from the latest edition of Clinical Sports Nutrition (1) are cited. Correspondence should be directed to Janelle Barnard at [e-mail]

Table 1 Recommended intakes of carbohydrate for athletes in training (5)

Athletes should aim to achieve carbohydrate intakes to meet the fuel
requirements of their training program and to optimise restoration of
muscle glycogen stores between workouts. General recommendations can be
provided, but should be fine-tuned with individual consideration of
total energy needs, specific training needs and feedback from training
performance
* Immediate recovery after exercise (zero to four hours): 1-1.2 g/kg/
  hour consumed at frequent intervals
* Daily recovery: moderate-duration/low-intensity training: 5-7 g/kg/day
* Daily recovery: moderate-heavy endurance training: 7-12 g/kg/day
* Daily recovery: extreme exercise program (four to six hours or more
  per day): 10-12+ g/kg/day

Table 2 Estimated protein requirements for athletes

                                      Protein intake
Group                                 (g/kg/day)

Sedentary men and women               0.8-1.0
Elite male endurance athletes         1.6
Moderate-intensity endurance          1.2
  athletes (a)
Recreational endurance athletes (b)   0.8-1.0
Football, power sports                1.4-1.7
Resistance athletes (early training)  1.5-1.7
Resistance athletes (steady state)    1.0-1.2
Female athletes                       ~15% lower than male athletes

(a) Exercising approximately four to five times per week for 45-60
minutes.
(b) Exercising four to five times per week for 30 minutes at <55%
V[O.sub.2peak].
Adapted from Tarnopolsky (1999, 2004) cited in Tarnopolsky (page 95).
(9) Reprinted with permission from McGraw-Hill Australia