Rehydration between workouts
You already know that you can lose a lot of fluid and sodium after a long and/or hard run. And you know that pre-exercise hydration is important for optimal performance. So naturally you would think that during high-volume training or racing periods, in addition to thinking about proper recovery nutrition, you should pay particular attention to post-exercise rehydration in order to replenish lost body water and ensure proper hydration heading into the next workout. And you’re right! You’re so smart.
How much fluid do you need?
If you have a digital scale, weigh yourself before and after your more strenuous run workouts (long runs, interval sessions, etc). Aim to drink enough fluid after exercise to replace 100-150% of the weight you lost (1kg weight loss = ~1L fluid loss). If the scale said 85kg when you left, and 84kg when you got back, you lost 1 litre of body water, and you want to drink 1-1.5 litres of fluid to rehydrate.
Not a chugging contest
Don’t worry; you don’t have to drink it all at once. In fact, you should ensure that you rehydrate gradually so you don’t end up simply peeing a lot of the fluid out (or getting a stomach ache). Drinking your required amount over a few hours after exercise is your best bet. Some athletes will find they don’t have to pee for a few hours after a hard session. This is okay! It means your body is using that fluid for rehydration. However, if this persists, you may want to consult a doctor.
Pass the salt
Sodium plays a big role in rehydration, helping your body hold onto the fluid you take in. My favourite source of post-exercise sodium is a frozen pizza (after it’s been baked in the oven of course). Some frozen pizzas contain more than 5,000mg of sodium in one pizza! How much sodium you need does depend on how much you lose, and as you know, your number can range from 500 to 2000mg per litre of sweat. Officially, you want to replace 100-150% of the sodium you lost (to go along with 100-150% of fluid losses). If you’re not sure how much you lose, you can find out, or you can simply add extra sodium to your post-exercise fluid or meal. It’s all about balance: you don’t want to drink lots of fluid with no sodium, nor do you want to take in lots of sodium with a small amount of fluid.
In a recent position paper, the American College of Sports Medicine indicated that “many athletes will require more than the Tolerable Upper Intake Level for sodium (2.3 g/day).” So while they don’t want to tell you to eat a frozen pizza’s worth of sodium every day, it is important to note that depending on how active you are and how much sodium you lose in your sweat, you may actually require more daily sodium than the average person.
Carbs help too
In addition to replacing used glycogen, carbohydrate in your drink can help with rehydration. A recent study found that athletes retained more fluid when they drank a 10% carbohydrate solution, compared to when they drank plain water.
References
Evans GH, Shirreffs SM, Maughan RJ. Postexercise rehydration in man: the effects of carbohydrate content and osmolality of drinks ingested ad libitum. Appl Physiol Nutr Metab. 2009;34(4):785-93.
Rodriguez NR, DiMarco NM, Langley S. Position of the American Dietetic Association, Dieticians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Diet Assoc. 2009;109(3):509-27.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement.Med Sci Sports Exerc. 2007;39(2):377-90.
How much fluid do you need?
If you have a digital scale, weigh yourself before and after your more strenuous run workouts (long runs, interval sessions, etc). Aim to drink enough fluid after exercise to replace 100-150% of the weight you lost (1kg weight loss = ~1L fluid loss). If the scale said 85kg when you left, and 84kg when you got back, you lost 1 litre of body water, and you want to drink 1-1.5 litres of fluid to rehydrate.
Not a chugging contest
Don’t worry; you don’t have to drink it all at once. In fact, you should ensure that you rehydrate gradually so you don’t end up simply peeing a lot of the fluid out (or getting a stomach ache). Drinking your required amount over a few hours after exercise is your best bet. Some athletes will find they don’t have to pee for a few hours after a hard session. This is okay! It means your body is using that fluid for rehydration. However, if this persists, you may want to consult a doctor.
Pass the salt
Sodium plays a big role in rehydration, helping your body hold onto the fluid you take in. My favourite source of post-exercise sodium is a frozen pizza (after it’s been baked in the oven of course). Some frozen pizzas contain more than 5,000mg of sodium in one pizza! How much sodium you need does depend on how much you lose, and as you know, your number can range from 500 to 2000mg per litre of sweat. Officially, you want to replace 100-150% of the sodium you lost (to go along with 100-150% of fluid losses). If you’re not sure how much you lose, you can find out, or you can simply add extra sodium to your post-exercise fluid or meal. It’s all about balance: you don’t want to drink lots of fluid with no sodium, nor do you want to take in lots of sodium with a small amount of fluid.
In a recent position paper, the American College of Sports Medicine indicated that “many athletes will require more than the Tolerable Upper Intake Level for sodium (2.3 g/day).” So while they don’t want to tell you to eat a frozen pizza’s worth of sodium every day, it is important to note that depending on how active you are and how much sodium you lose in your sweat, you may actually require more daily sodium than the average person.
Carbs help too
In addition to replacing used glycogen, carbohydrate in your drink can help with rehydration. A recent study found that athletes retained more fluid when they drank a 10% carbohydrate solution, compared to when they drank plain water.
References
Evans GH, Shirreffs SM, Maughan RJ. Postexercise rehydration in man: the effects of carbohydrate content and osmolality of drinks ingested ad libitum. Appl Physiol Nutr Metab. 2009;34(4):785-93.
Rodriguez NR, DiMarco NM, Langley S. Position of the American Dietetic Association, Dieticians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. J Am Diet Assoc. 2009;109(3):509-27.
Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. American College of Sports Medicine position stand. Exercise and fluid replacement.Med Sci Sports Exerc. 2007;39(2):377-90.
