VIGILANCE IS THE KEY TO MAINTAINING WATER BALANCE DURING PRE-SEASON TRAINING

Even at rest adults lose 2 to 3 litres of fluids daily through the skin, waste products and by breathing air out of the lungs. ---- During exercise there is a dramatic increase in water losses from breathing due to increased respiration rates and sweating as the body seeks to dissipate the excess heat. Most of this must be replenished by intake of food and liquids to achieve water balance and avoid the effects of dehydration. A fluid loss as low as 2% of body weight can have an effect on- - performance. Thirst is often not an adequate indicator as thirst, cues begin when body water loss is about 1% of body weight but even then most athletes learn to override them and only start to notice them when we are well on our way to more deleterious levels of dehydration.

Staying in water balance as an athlete is a challenge throughout the year, but during intense pre-season conditioning, the degree to which an athlete succeeds at hydration can make or break the effectiveness of his or her efforts.

IMPORTANCE OF ADEQUATE HYDRATION
Researchers and endurance athletes have known for a long time that body water losses of 3-4% of body weight, decrease endurance and muscular strength during prolonged exercise performance. Recent research shows that modestly reduced body water attenuates strength (by approximately 2%), power (by approximately 3%), and high intensity endurance (maximal activities lasting >30 seconds but <2 minutes; by approximately 10%) (I). Skills performance (such as cricket bowling accuracy, football/soccer skills performance) (2,3), and related cognitive functioning (such as headache, tiredness, reduced alertness, and greater difficulty concentrating) have been shown to be impacted at water losses of approximately 2% of body weight (4).

Environmental temperature matters. For many athletes training or competing in a cold or temperate environment (~22°C), a less than 2% loss of body water is tolerated without significant risk to well-being or exercise endurance. However, if the ambient temperature is hot (30°C or more), the same levels of dehydration impairs performance and increases the danger of experiencing a heat injury (5).

PROBLEMS ASSOCIATED WITH CHRONIC LOW-LEVEL DEHYDRATION
Signs of chronic dehydration include morning headaches, darkly coloured concentrated urine, and infrequent urination or low urine volume. A recent review article reported that maintaining good hydration status can reduce the risk of urinary tract infections, constipation, dental disease, gallstones and glaucoma. In addition, good hydration status has been shown to be useful in the treatment or management of various heart and vascular diseases including high blood pressure, coronary heart disease and stroke (6).

WATER BALANCE
Even at rest, adults lose 2-3 litres of fluids daily through the skin (~750 mls via insensible sweating), in the faeces (~200 mls), in the urine (~l500 mls) and by breathing air out of the lungs (~350 mls). A small amount of water is contributed to the body from metabolism (~300 mls) and the rest must be consumed in food and liquids (~2.5 L) to achieve water balance and avoid the effects of dehydration (7). In an exercising individual, water losses from breathing due to increased respiration rates and water losses through sweat, increase dramatically in order to dissipate the excess heat created in the body due to physical activity.

The body is remarkably inefficient at metabolic transfer of stored energy into muscular work meaning that about 75% of the energy generated by the burning of carbohydrates, fats and protein for exercise is liberated as heat (8). During exercise several powerful methods of heat loss from the body kick into gear to prevent an excessive rise in core temperature: increased blood flow to the body's surface; increase sweating to dissipate heat through evaporation; and a decrease in urinary output to conserve water for temperature regulation.

Exercising indoors and in hot environments and especially hot and humid environments, significantly add to the challenge of dissipating the excess heat generated during exercise and increase the chances of dehydration, serious decreases in performance, and heat-related illness. Heat acclimatization and optimising hydration status through the consistent and well-timed use of fluid replacement beverages containing modest amounts of sodium and glucose are effective interventions. The former lowers temperature thresholds for vasodilation at the body surface and the onset of sweating. The latter improves water absorption and retention (8).

VIGILANCE IS THE KEY
Thirst is often not an adequate indicator. While thirst cues begin when body water loss is about 1% of body weight, most of us are so accustomed to over-riding thirst cues that we only start to notice them when we are well on our way to more deleterious levels of dehydration. However, if you are thirsty, by all means drink to replenish lost fluids. Most athletes during intense training periods and, certainly when exercising indoors or in warm or hot humid outdoor conditions need to consciously drink fluids to replenish losses.

START WORKOUTS FULLY HYDRATED
It's important not only to replace the water used and lost during your workouts, but also to consume adequate fluids to replace water used throughout your day for metabolism, expiration, waste removal and perspiration. Average water needs throughout the day for time spent in sedentary or light active pursuits is between 8 and 9 cups for women and between 11 to 13 cups for men. It's important to fit these fluids in throughout the day so that you start your workouts fully hydrated. The last 2 cups or 16 ounces can be consumed 1 to 2 hours before the workout.

HYDRATION KEY FACTS Water loss of 3-4% of body weight can affect performance equaling a: 2% loss of strength 3% loss of power 10% drop in short high intensity activity levels 2% loss affects skill levels. At rest adults lose 2-3 litres a day via sweat, waste products and breathing. To replace, men need 11-I3 cups of water per day, women 8-9 cup (cup = 250mls) During exercise drink: 150-300mls every 20 minutes 500mls for every 1lb weight loss Adults approx 1.5 litres urine per day. Water loss of 1% of body weight occurs before you feel thirsty.

 

FLUID INTAKE DURING ACTIVITY
The amount of fluid needed during activity will vary with the temperature, humidity and the type of activity. A good rule of thumb is to drink about 150 to 300 mls every 10 to 20 minutes - taking care not to drink more than is needed to counter water losses due to the activity (9). When the workout has ended, athletes need to replace water lost at a rate of 2 cups (500 mls) for every pound of weight lost during activity. To this end, it is helpful for athletes in pre-season training to weigh him or herself before and after practice to learn to estimate the amount of additional fluid he or she needs to drink to get back into water balance.

In addition some athletes find it helpful to slightly hyperhydrate right before activity with plain cold water, diluted fruit juice or a glucose-electrolyte drink. For most athletes it is safe to drink up to 20 ounces of one of these fluids in the last 15 minutes before your workout and if the body's glycogen stores are low or the workout is extended the carbohydrate in a diluted fruit juice or sports drink may improve exercise endurance. Pre-exercise hyperhydration is not necessary and may not be appropriate for some athletes, but for others it lessens the need for vigilance during exercise.

WHAT SHOULD I DRINK?
The best fluid replacement beverage is still plain cool or cold water. During and after exercise, fluid and electrolyte replacement beverages (diluted sports drinks such as Gatorade) are also good choices which can help to replace sodium and other minerals lost in sweat and for bouts of activity over 60 minutes can help to keep blood glucose at healthy levels. Diluted fruit juices or juice drinks may also be used during or after exercise to nearly the same effect. Sweetened beverages, as long as they are not too concentrated, may help some athletes achieve adequate hydration as they are sometimes preferred. Young athletes in particular are more likely to achieve hydration goals if the beverage offered is considered tasty.

Alcohol and caffeine containing beverages may be enjoyed in moderation by adult athletes for various other reasons but should not be counted among good fluid replacement choices as both caffeine and alcohol increase water loss from the body.

Throughout the recovery periods of the day and week, fluids from any non-caffeine or alcohol containing beverage and watery foods such as soups, fruits, and vegetables contribute significantly to fluid replacement and water balance.

KEEPING WATER LOSS IN CHECK
As noted above, the simplest way to determine whether an athlete is drinking enough before and during activity to maintain water balance is to weigh them before and after each workout. That way the amount of fluid needed to reset blood volume can be determined on a daily basis. An alternative method or a way to check whether an athlete's fluid replacement efforts have been successful is to monitor urine colour and/or volume. The urine of a fully hydrated person should be pale yellow (provided he or she is not taking vitamins or medications that effect urine colour). Urine volume can also be monitored but this is a bit more cumbersome. Urine volume should be about 1.5 litres per day.

A NOTE ABOUT HYPERHYDRATlON
Hyponatremia, or low body sodium concentration, is very dangerous and can cause collapse and even death. Generally it is caused by overconsumption of fluids, particularly water, and amateur endurance athletes or first time long distance racers are more at risk because they are often encouraged to drink "as much as possible" to prevent dehydration. However racing long distances at a more modest pace it is possible to replace more fluids than are being lost, thereby diluting the salt concentration in the blood. A better approach for these participants is to drink ad libitum (as influenced by thirst) at a rate of no more than 400 to 800 mllhour (10).

THE BOTTOM LINE
Staying on top of hydration before, during, and after workouts is an important aspect of maximising training and performance potential. Because sweating rates and fluid and electrolyte losses vary with individuals, environmental conditions, intensity of training and customised fluid replacement programmes are recommended. (11) The recommendations outlined here will help athletes, coaches and trainers to determine the fluid replacement programme appropriate to each person

References

1. Judelson DA, Maresh CM, Anderson JM, Armstronq LE, Casa DJ, Kraemer WJ, Volek JS. Hydration and muscular performance: does fluid balance affect strength, power, and high intensity endurance? Sports Medicine 2007;37:907-21
2. McGregor S, Nicholas C, Lakomy H, Williams C. The influence of intermittent high-intensity shuttle running and fluid ingestion on the performance of a soccer skill. Journal of Sports Science 1999;17: 895-903
3. Devlin LH, Fraser SF, Barras NS, Hawley JA Moderate levels of hypohydration impairs bowling accuracy but not bowling velocity in skilled cricket players. Journal of Science and Medicine in Sport 2001;4:179-87
4. Shirreffs SM, Merson SJ, Fraser SM, Archer DT. The effects of fluid restriction on hydration status and subjective feelinqs in man. British Journal of Nutrition 2004;91:951-8
5. Shirreffs SM. The importance of good hydration for work and exercise performance Nutritional Revue 2005;63:~14-S~I
6. Manz F. Hydration and disease Journal of the American College of Nutrition 2007;26:535S-41s
7. Pivarnik JM Water and electrolytes during exercise In Nutrition in Exercise and Sport. Hickson JF, Wolinsky I, eds CRC Press, 1989:185-200
8. Wendt D, van Loon LJ, Lichenbelt WD Thermoregulation during exercise in the heat: strategies for maintaining health and performance. Sports Medicine 2007;37:669-82
9. Ganio MS, Casa DJ, Armstronq LE, Maresh CM. Evidence-based approach to lingerinq hydration questions. Clinical Journal of Sports Medicine 2007;26:1-16
10. Noakes T, IMMDA Fluid replacement during marathon running. Clinical Journal of Sports
    Medicine 2003;13:309-18
11. Am College of Sports Medicine, Sawka MN, Burke LM, Eichner ER, Mauqhan RJ, Montain SJ, Stachenfeld NS American College of Sports Medicine position stand. Exercise and fluid replacement. Medicine and Science in Sports and Exercise 2007;39:377-90

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Title	VIGILANCE IS THE KEY TO MAINTAINING WATER BALANCE DURING PRE-SEASON TRAINING.
Author	Lanou, Amy Joy
Source	SportEx dynamics
Publisher	Centor Publishing Ltd.
Issue	16
Date	April 2008
Pages	p.12-14
SIRC ID#	S-1077747

 

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