Up to 60% of Human body is made of water and an optimal state of body hydration is necessary for adequate cardiovascular, thermoregulatory, and mental function during exercise. Young athletes may lose copious amounts of body fluid in sweat during training and competition in sports, especially in hot and humid environments. In addition to starting exercise in a state of fluid deficit, young athletes do not replace enough of the fluid lost through sweat when drinking water ad libitum. The mismatch between the sweat produced and the fluid ingested leads to dehydration, which may result in decrements in sports performance and heat illness.
Within athletic populations, large sweat rates during exercise challenge fluid balance and additional fluid consumption is required to stay hydrated.
Intermittent intensity sports such as tennis and team sports like basketball, soccer, American football, and ice hockey are stop and go in nature with high intensity exercise bouts and periods of low intensity or no activity. Young athletes participating in these sports show higher sweat rates and dehydration levels during competition than during training, due to the higher intensities of exercise and less focus on hydration.
How Dehydration affects athletes?
Dehydration levels as low as 1% exacerbate the rise in core temperature and impact negatively on sports performance especially in endurance events .In adult athletes, the consensus is that dehydration levels >2% lead to premature fatigue and impairment in exercise performance.
It is not uncommon for athletes to commence exercise in a state of fluid deficit. Failure to rehydrate between sessions or aggressive weight making strategies makes dehydration a real risk within athletic populations. Negative effects of dehydration on exercise performance include: increased cardiovascular strain (increased heart rate (HR)), core temperature, muscle cramping, perception of effort and result in significant increases in plasma cortisol levels compared to exercise in a well hydrated state.
Dehydration also affects sleep, therefore reduces recovery, and in turn affect performance, increased cognitive errors, impaired decision making, reduced maximal power and increased fatigued during exercise.
Sodium and chloride are the main electrolytes lost in sweat with other electrolytes like potassium, calcium, and magnesium present in low concentrations. Sodium helps regulate body water distribution and blood volume and is important for normal transmission of nerve impulses and skeletal muscle contraction.
How to track hydration levels?
Thirst is the most common indicator of dehydration. Athletes should monitor body mass before and after competition to measure amount of body weight lost during activity. (Through sweat). Reported sweat rate values are in the range of 0.5–2.0 L/h in young male athletes and 0.4–1.0 L/h in young female athletes.
Monitoring urine volume and colour can help estimate hydration state. Decreased urine volume, reduced frequency of urination, attenuated urge to urinate, and darker than normal urine colour might all indicate dehydration (acute) or hypo hydration (chronic). Urine colour should be straw to lemonade in colour and can easily be assessed using a field-expedient urine colour chart. Urine colour akin to apple juice or darker is suggestive of dehydration.
Some athletes might leave white sweat marks on their clothing post exercise indicating high losses of sodium (and other electrolytes) through sweat.
How to hydrate effectively?
There is evidence that when young athletes are offered drinks that are flavoured and contain carbohydrates and electrolytes (sports drinks), hydration status is better maintained and thermal stress and deterioration in sports skills are minimized. The effects have been attributed to increased palatability due to flavour, sodium, and carbohydrates and to the water-retaining qualities of sodium.
The pre competition meal helps provide fluid to maintain adequate hydration and carbohydrate to maximize blood glucose and stored glycogen levels while also keeping hunger pangs at bay. Glycogen is the main form of energy used during high-intensity (>70% VO2 max) exercise. Consuming carbohydrate–electrolyte drinks will help replace fluid and glycogen loses and delay fatigue. Consuming a 6%, carbohydrate– electrolyte drink (5 min before and at 15 min intervals) can increase high-intensity endurance capacity in young team sport players.
- 4 hours before activity consume approximately 5-7 ml of water or a sports drink per kilogram body weight and 1-4 g carbohydrate per kilogram body weight.
- 2 hours before prolonged activity in hot weather, they should consume a sports drink containing 20 to 30 mEq of sodium (460-690 mg with chloride as the anion) per liter, 2 to 5 mEq of potassium (78-195 mg) per liter, and carbohydrate in a concentration of 5% to 10%. If not adequately hydrated, sip on 3-5 ml (0.10-0.17 oz.) of fluid per kilogram body weight with 1 g carbohydrate per kilogram body weight.
- 1 hour before activity, consume 0.5 g carbohydrate per kilogram body weight with 8 oz. fluid.
Nutrition is an important factor during aerobic endurance events lasting greater than 45 minutes, intermittent-activity sports, or when an athlete has multiple events in one day. Fluids and carbohydrates can affect performance, while the provision of amino acids may minimize muscle damage.
Due to large variations in sweat rates and electrolyte concentrations, athletes should measure weight changes during training and competition in specific weather conditions and develop individualized hydration strategies based on this information.
- During prolonged activity in hot weather, the Institute of Medicine recommends sports drinks containing 20 to 30 mEq of sodium (460-690 mg with chloride as the anion) per liter, 2 to 5 mEq of potassium (78-195 mg) per liter, and carbohydrate in a concentration of 5% to 10%.
- Children weighing 40 kg (88 pounds) should drink 5 ounces (148 ml) of cold water or a flavored salted beverage every 20 minutes during practice.
- Adolescents weighing 60 kg (132 pounds) should drink 9 ounces (256 ml) every 20 minutes even if they do not feel thirsty.
- Aerobic endurance athletes should consume 30 to 90 g of multiple types of carbohydrates together, such as sucrose, fructose, and glucose, or maltodextrin, each hour during prolonged aerobic endurance activity.
- Tennis players should aim for approximately 200 to 400 ml fluid per changeover and have some of this fluid from a carbohydrate-electrolyte sports drink.
After competition, athletes should replace fluid and electrolyte losses. Therefore, what they consume in the time period soon after training or competition helps prepare their body for the next bout of activity. Athletes must consume 150% of the lost weight to achieve normal hydration within 6 hours after exercise.
- The recommendation is to ingest 20 to 24 ounces (600 to 720 ml) of fluids for every pound of body weight lost during training. More salt can be added to foods when sweat sodium losses are substantial.
Athletes can choose a carbohydrate-electrolyte sports drink or plain water alongside foods that contain sodium chloride.
It is important to understand that the nutritional requirements for each athlete are unique. It is recommended that you consult your sports nutritionist and coach while developing a tailor made diet plan for the athlete to maximize performance and keep the athlete safe.
Essentials of strength training and conditioning / National Strength and Conditioning Association ; G. Gregory Haff, N. Travis Triplett,Fourth edition. Nutrition Strategies for Maximizing Performance.
Fluid Balance, Hydration, and Athletic Performance, Edited by Flavia Meyer Zbigniew Szygula Boguslaw Wilk.
Nutrition and Hydration Implications For trained Athletes, Sophie Charlotte Killer.
NSCA’s Guide to Sport and Exercise Nutrition,Bill I. Campbell, Marie A.Spano.
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ABOUT THE AUTHOR
Dion Soares is the Head Fitness Coach at Aditya Chougule Tennis Academy. He has worked with athletes from different sports such as Football,Swimming,Badminton etc. His goal is to have the most positive impact on his athletes, helping them with performance, mindset, motivation and lifestyle. He enjoys learning and educating others with evidence-based recommendations about performance, cardiovascular health, mental health and diabetes.