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Exercise and Sport in Diabetes, 2nd Ed.: Fluid and Hydration

Elaine Hibbert-Jones and Gill Regan

Exercise_and_Sport_In_Diabetes

 

 

 

 

The following excerpt covers fluid replacement before, during and after energy expenditure while exercising.

Most exercise sessions result in some degree of sweating leading to a loss of water and salts. Fluid replacement is required to maintain hydration and allow the athlete to perform and limit fatigue. Inadequate fluid intake will adversely affect temperature regulation, cardiovascular function and muscle metabolism.
 
Fluid requirements

Sweat rates during exercise are typically 0.5-1.51 h-1 23 but can increase in trained individuals up to 3 1 h -1 in hot and humid conditions. During exercise it is important to limit dehydration by drinking fluids at a rate that most closely matches sweating rate. However, because sweat rates vary greatly between individuals and the fluid requirements will also be influenced by fitness levels and duration of exercise, the best advice is to measure body weight loss by weighing the athlete before and after exercise.

  • a weight loss of greater than 2 per cent, especially when exercising in a hot and humid environment (>30 DC), is likely to impair exercise performance;
  • 2 per cent weight loss equates to 1 kg for a 50 kg person, 1.5 kg for a 75 kg person and 2 kg for a 100 kg person.

Fluid intake should be sufficient to replace total sweat losses. Avoid excess fluid intake during exercise to prevent an increase in body weight. Fluid lost is estimated at 1.2-1.5 times the actual fluid lost during exercise to allow for
obligatory losses e.g. continued sweating and urine production.

When it is not possible to weigh before and after exercise, another good indicator of fluid loss is to determine the volume and color of urine produced. Pale and plentiful urine generally indicates the athlete is hydrated; dark and sparse urine is an indication that more fluid is required.

Key point

  • Dehydration can lead to a rise in body temperature, light-headedness, nausea, fatigue or heatstroke and must not be confused with symptoms of hypoglycemia.
Fluid intake and exercise

Drinking plenty of fluids to avoid compromising health as well as to improve exercise performance is essential. To succeed, it is important to plan drinking strategies for the athlete and to recommend they practice drinking during exercise so that the body can adapt to the necessary fluid intake required for the planned level of exercise.

Guidelines for fluid replacement before, during and after exercise

Before exercise

Blood glucose should be monitored before exercise.  
  • Always start an exercise session fully hydrated. Thirst is a poor indicator of hydration status.
  • Drinking 400-600 ml water in the 2 h before exercise will help hydrate the body24. Sports drinks containing carbohydrate need to be used with caution because of the effect they may have on the pre-exercise blood glucose level. However, they may be useful to maintain blood glucose levels within the target range during exercise. This range needs to be agreed with the diabetes team.
  • Water, no-added-sugar squash, regular squash and isotonic sports drinks can all be useful, depending upon the intensity and duration of the exercise, the blood glucose level and the environmental conditions in which it takes place.
  • Sports drinks containing carbohydrate may also be useful for the correction of hypoglycemia.
During exercise  

Blood glucose levels should be monitored during exercise where possible.

  • Aim to drink enough fluid to limit losses as sweat. Drinking small volumes frequently will minimize gastric discomfort.
  • During exercise lasting more than 1 h athletes are advised to drink 150-200 ml. fluid every 15-20 mins (30-60 g carbohydrate/h) to offset fluid losses. The choice of fluid will depend on the athlete’s strategy for maintaining blood glucose levels within the target range during exercise.
  • Sports drinks containing 6-8 g carbohydrate 100 ml-1 may be useful in providing both carbohydrate and fluid to maintain both blood glucose levels and hydration during the  
  • Sodium should be included in fluids consumed during exercise for more than 2 h. Isotonic sports drinks generally contain added electrolytes.
  • Complete restoration of fluid balance after exercise is an important part of the recovery process.
  • Fluid replacement will be dependent on how much fluid has been lost during exercise.
  • The volume of fluid taken should be greater than the volume of fluid lost to allow for the ongoing obligatory losses, e.g. sweat and urine.
  • Research shows that athletes drink larger volumes when the drink is flavored.
  • Isotonic sports drinks containing 4-8 per cent (4-8 g 100 ml-1) carbohydrate
    may be useful for maintaining post-exercise blood glucose levels and refueling
    glycogen stores after exercise. Sufficient insulin must be available for the
    refueling process.
  • Rehydration after exercise requires not only the replacement of volume losses
    but also the replacement of electrolytes, primarily sodium lost in sweat. This
    can be achieved by adding salt to food or eating salty snacks. Salt supplements
    are not normally necessary.
  • Drinking excessively during exercise resulting in weight gain is not recommended.
  • Caffeine taken during the later stages of exercise when taken in quantities 1.5 mg kg-1 has been found to be ergogenic.
  • No benefit is gained from the ingestion of glycerol and amino acid supplementation during exercise.
After exercise
 
Blood glucose levels should be monitored after exercise.
  • Complete restoration of fluid balance after exercise is an important part of the recovery process.
  • Fluid replacement will be dependent on how much fluid has been lost during exercise.
  • The volume of fluid taken should be greater than the volume of fluid lost to allow for the ongoing obligatory losses, e.g. sweat and urine.
  • Research shows that athletes drink larger volumes when the drink is flavored.
  • Isotonic sports drinks containing 4-8 per cent (4-8 g 100 ml-1) carbohydrate may be useful for maintaining post-exercise blood glucose levels and refueling glycogen stores after exercise. Sufficient insulin must be available for the refueling process.
  • Rehydration after exercise requires not only the replacement of volume losses but also the replacement of electrolytes, primarily sodium lost in sweat. This can be achieved by adding salt to food or eating salty snacks. Salt supplements are not normally necessary. 
Sports drinks

The composition of sports drinks is a key factor for consideration in terms of beverage choice when used for fluid replacement before, during and after exercise. Most sports drinks aim to influence performance by providing the athlete with both a fluid and energy source from carbohydrate. The carbohydrate is generally derived from sugars (glucose, sucrose and fructose), maltodextrins or other rapidly absorbed carbohydrates.

The formulation of sports drinks is generally classified as hypotonic, isotonic or hypertonic. The rate of fluid delivery to the body depends on the composition of the drink, which influences, how much is drunk, how quickly it is emptied from the stomach and how quickly it is absorbed from the intestine. Studies have shown that sports drinks are an efficient way to supply both fluid and fuel. The choice of sports drink used will depend on the athlete’s priority for fluid or fuel and the maintenance of blood glucose levels within the target range before, during and after exercise.

Water vs. sports drinks

The choice between water and sports drinks, as fluid replacement, will be dependent on the following factors:

  • pre- and post-exercise blood glucose levels;
  • timing and availability of circulating insulin;
  • duration and intensity of exercise;
  • environmental conditions, e.g. heat, humidity and cold;
  • training status, i.e. fitness;
  • strategies for fluid replacement before, during and after exercise need to be made with the athlete in consultation with their diabetes team, taking into account the type and duration of exercise that is to be undertaken.
Key points
  • Fluid intake is essential during exercise.
  • Start exercise fully hydrated.
  • Athletes tend to drink too little rather than too much.
  • Thirst is a poor indicator of hydration status. Athletes should drink before they are thirsty to ensure adequate fluid intake.
  • Flavored drinks may encourage greater fluid intake than plain water. Ensure availability of palatable drinks.
  • Avoid carbonated drinks which may cause gastric disturbances.
  • Start rehydration immediately after exercise.
  • Ensure a high-carbohydrate drink is always available for treatment and correction of hypoglycemia.
3.13 Pulling It All Together  

A number of factors need to be considered when developing a nutritional strategy for sport and exercise:

  • Is the exercise planned or unplanned? Unplanned exercise usually requires additional carbohydrate. Adjustments can be made to insulin prior to planned exercise which may reduce the amount of additional carbohydrate which needs to be consumed.
  • Type of exercise – different types of exercise will have different nutritional requirements and different effects on the blood glucose level, e.g. resistance training such as weight-lifting, endurance exercise such as running, high-intensity exercise such as sprinting, intermittent, high intensity exercise such as ball games.
  • Timing of exercise in relation to timing of both insulin and carbohydrate intake.
  • Duration and intensity of exercise.
  • Pre-exercise blood glucose level and the athlete’s usual response to different types of exercise
  • Training status, e.g. fitness level.
  • Hydration status – the perceived effort will be greater in an athlete who is poorly hydrated.
  • Team sports – position played, strength of opposition.
  • Frequency and length of time between exercise sessions.
  • Competitive athletes will need a different nutritional strategy prior to competition. This needs to be tried and tested in -low-key events.
  • Environmental factors, e.g. humidity, temperature (hot and cold).
  • Clothing – additional clothing worn for exercise may cause an Increase in sweating rates.
Key points  
  • Monitor blood glucose levels before, during and after exercise.
  • Avoid exercise if blood glucose levels before exercise are > 250mg/dL.(14 mmol.) with ketones and use caution if levels are >300mg/dL.(17mmol.) without ketones. Take extra carbohydrate if blood glucose level is <99mg/dL.(5.5 rnmol).
  • Encourage people with diabetes to learn their own blood glucose response to different types of exercise.
  • Identify when changes in insulin and/or carbohydrate intake are necessary.
  • People with diabetes who regularly participate in sport may find it useful to keep a record of carbohydrate intake, details of exercise sessions, insulin doses and blood glucose levels.
  • Ensure an adequate fluid intake.
  • Keep a hypo remedy readily available at all times.
  • It is essential that people with diabetes are encouraged to discuss the their individual insulin regimens and dietary requirements with their diabetic team.
Additional Information  

The rigid recommendation to use carbohydrate supplementation, calculated from the planned intensity and duration of physical activity, without regard to the glycemic level at the start of the activity, the previous metabolic response and the patient’s insulin therapy, is no longer appropriate.

Recently Grimm et al. have proposed a table of carbohydrate supplementation to prevent hypoglycemia, for physical activity of different intensity and duration. However, it is designed for patients who have good metabolic control during the hours before exercise12. More research is needed in this area.

References:
  1. International Olympic Committee. Sports nutrition. J Sports Sci 2004; 22(1): 1-146.
  2. Diabetes UK. The implementation of nutritional advice for people with diabetes. Diab Med 2003; 20: 786-807.
  3. Colberg S. The Diabetic Athlete. Leeds: Human Kinetics, 2001.
  4. Loucks AB. Energy balance and body composition in sports and exercise. J Sports Sci 2004; 22: 1-14.
  5. Devlin JT, Williams C (eds). Final consensus statement: foods, nutrition and sports performance. J Sports Sci 1991; 9 (suppl.): iii.
  6. Burke LM, Cox GR, Cummings NK, Desbrow B. Guidelines for daily carbohydrate intake: do athletes achieve them? Sports Med 2001; 31: 267-299.
  7. Burke LM, Kiens B, Ivy JL. Carbohydrates and fat for training and recovery. J Sports Sci 2004; 22: 15-30.
  8. Stear S. Fuelling training and recovery. In Fuelling Fitness for Sports Performance. The Sugar Bureau, 2004; 33-51.
  9. DAFNE Study Group. Training in flexible intensive insulin management to enable dietary freedom in people with type 1 diabetes: Dose Adjustment for Normal Eating (DAFNE) randomised controlled trial. Br Med J 2002; 325: 746-749.
  10. Everett J, Jenkins E, Ken D, Cavan DA. Implementation of an effective outpatient intensive education programme for patients with type 1 diabetes. Pract Diabet lilt 2003; 20(2): 51-55.
  11. Burke LM, Collier GR, Hargreaves M. Muscle glycogen storage after prolonged exercise: the effect of glycaemic index of carbohydrate feedings. J Appl Physioll993; 75: 1019-1023.
  12. Grimm JJ, Ybarra J, Berne C, Muchnick S, Golay A. A new table for prevention of hypoglycaemia during physical activity in type 1 diabetic patients. Diabetes Metab 2004; 30: 465-470.
  13. Ivy JL, Gosforth HW, Damon BD, McCauley TR, Parsons EC, Price TB. Early post-exercise muscle glycogen recovery is enhanced with a carbohydrate-protein supplement. J Appl Physioi 2002; 93: 1337-1344.
  14. Tipton KD, Wolfe RR. Protein and amino acids for athletes. J Sports Sci 2003; 22(1): 65-79.
  15. Ha TKK, Lean MEJ. Technical review. Recommendations for the nutritional management of patients with diabetes mellitus. Eur J Clin Nutr 1998; 52: 467-481.
  16. American Diabetes Association. Evidence-based nutritional principles and recommenda- tions for the treatment and prevention of diabetes and related complications. Diabetes Care 2003; 26: S51-S61.
  17. Lemon PW. Effect of exercise on protein requirements. J Sports Sci 1991; 9: S3-S70.
  18. Stear S. The protein question. In Fuelling Fitness for Sports Performance. The Sugar Bureau,
    2004; 53-65.
  19. Watt MJ, Heigenhauser GJF, Spriet LL. IMTG utilisation in human skeletal muscle during exercise: is there a controversy? J Appl Physiol 2002; 93: ]]85-]]95.
  20. Spriet LL, Gibala MJ. Nutritional strategies to influence adaptations to training. J Sports Sci 2004; 22: 127-141.
  21. UK Sport, British Olympic Association (BOA), British Paralympic Association (BPA), National Sports Medicine Institute (NSMI) and Home Country Sports Councils (HCSC). Position statement. Advice to UK athletes on the use of supplements, 2003; www.mpagb. org.uklnotices/supplements.pdf (accessed September 2004).
  22. Maughan RJ, King DS, Lea T. Dietary supplements. J Sports Sci 2004; 22: 95-113.
  23. Maughan R. Eating for exercise. Nutr Pract 2004; 5(2): 1-3.
  24. Shirreffs SM, Armstrong LE, Cheuuvront SN. Fluid and electrolyte needs for preparation and recovery from training and competition. J Sports Sci 2004; 22: 57-63.
  25. Coyle EF. Fluid and fuel intake during exercise. J Sports Sci 2004; 22: 39-55.

 

The new edition of this acclaimed title provides a practical guide to the risks and benefits of undertaking sport and general exercise for patients with diabetes.

Fully updated to reflect the progress and understanding in the field, the book features new chapters and material on insulin pump therapy and exercise, physical activity and prevention of type 2 diabetes, dietary advice for exercise and sport in type 1 diabetes, and fluid and electrolyte replacement.

For more information on this book and how to get a copy, just follow this link to Amazon.com, Exercise and Sport in Diabetes (Practical Diabetes)alt, Dinesh Nagi 2nd Edition.

Copyright © 2010 by Blackwell Publishing Ltd, UK