Aashish Contractor -- run and sports medicine expert who is the advisory on board with Bisleri, the official hydration partner for TATA Mumbai Marathon 2018, and Vijay Alva, Founder, Vijay Alva's Fitness Academy (VAFA), suggest
‘It is recommended to consume about 500 ml of fluid, 2-3 hours before the event and another 250 ml, 15 minutes before the event.’
* Fluids before exercise:
Ideally, your body should be in a state of 'euhydration' before exercise, which is a perfect balance of fluid in your system -- neither deficit or in excess. Sometimes, athletes tend to take excessive fluid before an event, which should be avoided, since it can lead to bloating. It's a good idea to consume about 500 ml of fluid, 2-3 hours before the event and another 250 ml, 15 minutes before the event.
* Fluids during exercise:
An ideal plan is to drink sufficient fluids to replace sweat losses. As mentioned earlier, the best way to do this is to calculate your sweat rate. Do keep in mind that the sweat rate, will vary depending on the weather. However, if you do not know your sweat rate, a good rule of thumb is to consume between 0.5 - 1 litre of fluid for every hour of exercise. You could split this amount into four parts, and drink every 15 minutes.
* What should you drink:
For exercise lasting less than an hour, plain water is an effective fluid replacement. For exercise, lasting more than an hour, the body needs approximately 30-60 gm of carbohydrates per hour. This can be achieved by mixing it in your water, in a range of 6-8 per cent carbohydrate concentration, or could be obtained separately too.
It is also essential to have a little sodium and potassium as part of your fluid replacement in longer runs, such as the half and full marathon. This fluid mixture could be obtained from a sports drink, or you could make your own sports drink, such as home-made lemon water, with sugar and a pinch of salt.
* Fluids after exercise:
After prolonged exercise, most runners tend to be in a slightly dehydrated state, so it is important to replace the fluids within two hours of exercise. Often sweat loss and urine loss continues in the recovery phase, so it is advised to consume 1.25 to 1.5 litre of fluid for every litre of sweat lost (every kg of body weight lost immediately post-exercise).
* Quantity is important:
A runner should have at least 160 to 200ml of water 2 hours prior to a long run and keep having fluids every 15 to 20 minutes during the run. It is important to hydrate post the run as all the lost water from the body due to sweating needs to be made up for.
Keeping oneself hydrated means avoiding muscle cramps dizziness and drop in energy levels which is very important for good performance.