Hydration is a huge topic in the summer, when big increases in sweat rates during training can make it tough to keep fluid levels balanced.
However, increased amounts of indoor training, wearing more layers and exercising in colder, drier air mean that the good hydration practices should definitely not be forgotten during winter.
Before your session
When training indoors in the winter, we often do shorter but more intensive sessions. So, showing up to them adequately hydrated is a sound plan if want to perform at your best and recover quickly afterwards.
Sweat losses can be heavy if you're working hard and it's no good just aiming to drink lots when you're on the turbo or treadmill. That's the classic 'shut the door when the horse has already bolted' approach.
Instead, work at your hydration in the last few hours before your workout by sipping 500 - 750ml (c.16-25oz) water, or an electrolyte drink, so that your body has time to process and absorb what it needs, and to eliminate any excess. Any fluid you take in immediately before the session is likely to simply sit in your stomach and do you very little good, especially if you're doing something intense, like interval work (where most of the blood flow is directly away from your gut and to the working muscles), further reducing the chance of it being absorbed quickly.
During your session
If you're outside doing longer sessions in cold, dry air, you might find that you benefit from drinking a stronger electrolyte drink than normal, as there is a tendency for your body to want to pee more in the cold (a well documented but not fully understood phenomenon called 'Cold Diuresis').
Adding more electrolytes (mainly sodium) to your water encourages your body to hold on to fluids more effectively. This keeps your blood sodium balance in check, and therefore you should lose less water as a result. You may also sweat quite a lot even in colder temperatures if you wear a lot of extra clothing layers.
After your session
Recovery from any training session can be improved by restoring fluid balance relatively quickly. Once again, adding some sodium to your post session drinks can help.
Sodium helps the body replace what was lost in sweat and also increase the percentage of water that is actually absorbed.
One thing to remember is that your body can only take in a certain amount of fluid, usually somewhere between about 400ml and 1000ml per hour (approximately 15 to 36oz), so drinking any more than that is probably futile.
Pace your rehydration out over a few hours post session, using thirst and urine colour/volume as the main indicators of when you are back to where you should be. Ideally your pee should be a relatively pale, straw like colour, not dark (indicating possible dehydration) or totally clear (probably indicating over-hydration).
Don't drink too much
In the past, when it came to hydration, 'more is better' was the most frequent advice. It's actually a balancing act.
Your body has fantastic self regulatory mechanisms in place to keep your fluid and electrolyte levels in homeostasis. If you give it roughly the right amount of each, that is.
Things tend to go wrong when people override natural instincts and become convinced of the need to just drink lots and lots regardless, because dehydration is the perceived consequence of not doing so.
At first if you drink too much fluid your body will do a good job of getting rid of the excess by simply making you pee more. Keep doing so and you'll begin to dilute the level of electrolytes in your blood, as well as put on unnecessary water weight, neither of which is good for your health or performance.
That's why learning to listen to your body and to read the early signs of thirst is actually the best way to keep your fluid levels balanced.
1. Don't neglect hydration in the winter, especially if large amounts of your training is done indoors or in cold, dry conditions where fluid loss can be surprisingly high.
2. Turn up as hydrated as possible. Don't just drink loads right before you get started.
3. Listen to your body (and keep an eye on urine colour) to monitor your hydration level. Dark pee means you probably need to increase fluid intake. If it's completely clear and you are peeing alot, you're probably drinking too much, which can be as bad than not drinking enough.
4. Drink to thirst rather than setting arbitrary targets for how much you think you 'should' be consuming.
5. Add electrolytes (sodium is the key one) to drinks if sessions are particularly long, arduous or if you have an especially high sweat rate.