I often get asked "does dehydration actually affect me and my performance that much?". Unfortunately the answer is "Yes, it affects you more than you think".
Essentially electrolytes optimise the function and contraction of each nerve and muscle unit. So you need enough sodium, potassium, calcium, chloride and magnesium (amongst others) to send nerve impulses to your muscles and contract them. If you don't have enough, your nerve and muscle unit can't operate normally.
During exercise, these electrolytes are easily lost through sweat, along with water. This is the process of becoming dehydrated. So how does dehydration impact on performance?
Reduced power output: The body always prioritises delivery of fluids to life-sustaining organs. So even at 2% dehydration, fewer electrolytes are delivered to your muscles. If you’re trying to perform, your power output suffers – you can’t run as fast, jump as high, or tackle as hard.
Thermoregulation becomes less efficient – your body tries to reduce sweating, and cannot cool itself. Other physical effects such as headache, dizziness, muscle cramps, and general fatigue are common. Your risk of injury also increases.
Reduced cognitive function: At 4% dehydration, concentration, memory, attention, reaction time, and decision-making all decrease. You may not remember the game plan under pressure, you may lose concentration and make a serious error, or react too slowly to your opponent.
Increased perception of effort: Imagine you are playing sport at moderate intensity. At 4% dehydration the effort felt during a run is approximately 30% higher than at 1% dehydration. At higher intensities, the difference is greater. You will feel you have worked much harder than you actually have.
Exhaustion: This starts around 6% dehydration. This is where your energy stores are depleted, your body cannot cool itself, and the body focuses on survival. Mental exhaustion means your brain uses fuel sparingly. Most athletes do not get to this point, but it can happen if you are poorly prepared and conditions are harsh.
In my experience it is good habits, and listening t o your body that gets this right.
- Replace what you have lost through sweat. Electrolytes are replaced easiest with sports drinks but best with electrolyte tablets.
- Start hydrating 24 hrs prior to your event. If you’re serious about your sport, you need to make good food and drink choices the night before.
- Regularly check the colour of your urine. Lighter straw colour is best, dark yellow or brown means you need to drink fluids, preferably with electrolytes. Red coloured urine means you should see your doctor. Remember – if you are using multivitamins, your urine colour may be bright yellow all the time and can’t be reliably used to monitor your hydration.
- Know what dehydrates you, and make the best choice for you: Coffee, alcohol, sugar-rich foods, salt-rich foods, and low carbohydrate diets all reduce the amount of water retained in the body.
- Keep drinking pre-game and during the game for optimal performance.
- Post-game / recovery rehydration is essential if you are training or competing the following day, for example for another club, or in a tournament.