HYDRATION, DEHYDRATION & PERFORMANCE - by GLEN TITHER

GLEN TITHER HEALTH & FITNESS ARTICLES
Website: www.gtpersonaltrainer.co.uk
Email: glen@gtpersonaltrainer.co.uk

HYDRATION, DEHYDRATION & PERFORMANCE

Whether it’s optimum effort during gym sessions, or playing a full 80/90 minutes to the best of your ability, hydration plays a huge part. Gym sessions and competitive games are hard enough without suffering a drop in your performance simply because you’re not hydrated enough.
A drop of just 2% in hydration equates to a serious depletion in performance, as your body struggles to cope with the decrease in blood volume and the increase in body temperature, not to mention the increase in lactic acid build up and muscle cramps.
Get hydration right once and for all and your training, and playing, will reap the rewards.

·         For your body to function properly, both physically and mentally - dehydration also affects the amount of blood getting to your brain - it is dependent on you taking onboard adequate amounts of water throughout the day.

·         Just to maintain your body in a resting state requires 1 - 1½ litres of water every day. Therefore, you need to ensure hydration by drinking 2 - 2½ litres of water every day, and increase this daily amount when you exercise intensely, or in warm conditions, to take into account the additional demands on your body to keep hydrated.

·         During any form of physical activity, if you do not keep adequately hydrated then you will slowly reduce your ability to perform tasks to your full potential.

·         When exercising we build up heat in the working muscles causing our internal temperatures to rise. We cool ourselves by perspiring. It is this evaporation of sweat from our skin that helps us maintain a lower core body temperature. However, when there is a lot of moisture in the air, evaporation isn’t an effective cooling means and we keep sweating and losing fluids in order to try and stay comfortable. As a result, we have to drink more water to replenish this lost fluid. With less blood flowing to the skin, the body stores more heat; with more heat being stored, the body tries to sweat more to compensate, but ultimately the body’s core temperature increases; the brain senses the increase in temperature directly, and the exercise starts to feel harder and performance starts to decrease.

·         The water lost through sweating comes from blood plasma. Plasma is the vehicle for red blood cells, which contain the oxygen that muscles need in order to perform. As you become dehydrated, your total blood volume is reduced, and the oxygen-carrying capability of your blood decreases. If you continue to exercise without proper fluid intake, you may experience a drop in blood pressure; feel faint, dizzy or nauseous. These are the symptoms of heat exhaustion. If you keep going, your body's ability to dissipate heat is further impaired and you may suffer heat stroke.

If you continue to dehydrate during exercise:
·         Eventually your body will struggle to deliver blood to the muscles.
·         Your heart will pump less blood per beat.
·         Your heart rate will increase to compensate for the decreased blood flow - performance starts to decrease further.

Whether it is during game play or an exercise session, essentially, keeping hydrated and preventing a decline in blood volume will help prevent a decline in performance.

Drinking 2 or more litres of water every day might sound like a lot, but I’m not asking you do drink it all at once! Spread it out over the course of your day by drinking a glass approximately every 30 minutes.

It is extremely important to keep hydrated during your workouts. Therefore, try to drink ‘little and often’ with an aim of 250mL every 10 minutes.

Even though hydration is very individual, you can use the following guidelines as a starting point, and modify your fluid needs accordingly.

Hydration before exercise
Drink approximately 500mL 2 - 3 hours before exercise.
Drink 250mL 10 - 15 minutes before exercise.

Don't wait until you're thirsty to start drinking! The sensation of thirst is triggered by the hypothalamus in the brain. It measures the concentration of salts in your blood. As blood volume decreases due to sweating, your concentration of salts goes up, and the hypothalamus sends the signal to start drinking. By the time you feel thirsty, you are already dehydrated.

A good visual indication of your hydration levels is the colour of your urine. When your urine is a very pale yellow colour, sometimes called straw coloured, you are sufficiently hydrated. As a rule the darker your urine the more dehydrated your body. However, clear urine sometimes signals over-hydration, known as hyponatremia; this is also harmful to the body as you risk washing out vital nutrients, in very severe cases of hyponatremia the blood can become too diluted which can lead to death.

Players should aim to start their matches well hydrated.  The day before and on match day, having fluids with all main meals, and having access to fluids in between meals, serves as a useful strategy to help ensure this goal is met.  During matches, players should look for opportunities to consume fluids at regular intervals to minimise the fluid deficit incurred e.g. pauses in play after one team/player has scored, penalties, free-kicks, half time etc.

While water is a suitable option, sports drinks afford players the opportunity to contribute towards their fuel and fluid needs simultaneously.

Measuring fluid loss.
Because everyone sweats at different rates, losses and hydration levels it is nearly impossible to provide an exact calculation, which everyone can use, which will determine their dehydration/rehydration needs. However, it is widely recognised that 1 litre of sweat = 1 kilogram of body mass. Therefore, if you weigh yourself before and after exercise, the recorded change in body mass will reflect your change in body fluid (for combined sweat and urine). It is simply a balance between what you put into your body (fluid) and what your body loses (sweat and urine).  As long as you know these two parts of the equation you can calculate your individual fluid balance (see below equation).

Sweat loss (Litre) = Pre-exercise body mass (Kilograms) – Post-exercise body mass (Kilograms) + Volume of fluid consumed (Litre) – Volume of urine lost (Litre).

Equation example: If an athlete weighs 85kg (pre exercise); weighs 84kg (post exercise); has drank 1000ml (1Litre) of fluid during exercise and estimates to have lost 500mL during urination.

85kg – 84kg + 1000ml (1 Litre) – 500mL = 1.5 (Litres).
Therefore, this individual requires a further 1.5 Litres during exercise to ensure fluid balance.

Pre-exercise body mass.
You can use either your own bathroom scales at home; or ask a member of staff at your gym, most gyms will have weighing facilities available. You’ll need to obtain as accurate weight as possible, both pre and post exercise. Therefore, if you can weigh yourself naked, or just in your underwear, on both occasions then it will eliminate the weight of sweat sodden clothing. Remember, you want your body mass, not your body mass plus shoes, plus hat, plus clothing mass.  Make sure to weigh yourself in kilograms to 1 decimal place (0.1 kilogram = 100 millilitres). Another point to keep in mind is that any weight gain could mean that you are consuming more fluid than you need.

Calculating the ‘Volume of fluid consumed’.
If you drinking a sports drink, or bottle of water, then this part is easy because the volume is listed on the label (eg. 500mL). If you are using a refillable bottle, you will need to know the content volume beforehand eg check the capacity of the refillable bottle and make a note of the point at which you fill it up to; the majority of refillable bottles are sized 500ml, 750ml or 1000ml (1 litre).

Calculating the ‘Volume of urine lost’.
This part is a bit trickier; unless you have a measuring cup on hand you will have to guess.  Luckily the body does not usually produce much urine during exercise. Urine losses are typically 200 - 300 mL, and will rarely be greater than 500 - 600 mL. Use your judgment.