With the range of sports drinks out on supermarket shelves, you may have wondered if it is good enough to just be drinking water after workouts.
Are these sports drinks a gimmick, or do you really need them?
If they are beneficial, when should you have sports drinks and when is just drinking water after workouts sufficient? How much should you be having?
In this article, I’ll first highlight the importance of hydration when exercising (for more detail, click check out this link). Then, we’ll go through the goals of drinking before, during, and after exercise. In the process, we will discuss the amount and types of fluid you should choose at each of those stages.
The importance of adequate hydration during exercise
The amount of water in our body averages at about 60% of our body mass. The role of water in our body is crucial as it maintains our blood volume for circulation. It also helps with nutrient transfer, waste removal, joint lubrication, and maintenance of body temperature.
The balance of water in our body depends on the daily net difference between water gain and water loss. We gain water by consuming food and drink, and as a by-product of metabolism. We lose water when we breathe, defecate, urinate, vomit, and sweat.
When we exercise, we mainly lose fluid through sweat. Sweat contains electrolytes such as sodium, potassium, magnesium, calcium, and chloride. They are involved in muscle contraction and nerve function. Therefore, when we sweat during exercise, we lose electrolytes, especially sodium chloride, followed by potassium. Failure to replenish fluid and electrolyte losses through sweat during exercise leads to dehydration. Dehydration of >2% compromises aerobic exercise as well as cognitive and mental performance.
Therefore, the goal of drinking during exercise is to prevent >2% body weight loss from water loss and excessive changes in electrolyte balance that can affect performance.
Before Exercise
Goal: To begin physical activity in a state of euhydration with normal plasma electrolyte levels.
You should be in a state of euhydration if you’ve had a prolonged recovery period (8-12 hours) since you last exercised and had enough fluids with meals. If not, pre-hydrate yourself! This involves slowly drinking beverages at least 4 hours before exercise. You should aim to have 5-7ml/kg body weight. If your urine is still dark or concentrated, drink another 3-5ml/kg roughly 2 hours before exercise.
Often, this amount of fluid may be difficult to consume. If this is the case, it may help to adjust the temperature, sodium content, and flavour of the drink. An ideal temperature is 15-21°C and a sodium concentration of 460-1150mg/L. Also, you may consume small amounts of sodium-containing foods with your drink. They stimulate your body’s thirst reflex and encourage fluid retention.
Note of caution: Do not over hydrate (or hyperhydrate) as it may increase the need to void in the middle of exercise. This is not ideal in the case of a competition. More importantly, excessively replacing fluid during exercise may lower plasma sodium levels and increase risk of hyponatremia. This may have detrimental effects on physiological outcomes and/or performance.
During Exercise
Goal: To prevent excessive dehydration (>2% body weight loss) and large fluctuations in electrolyte balance.
The amount and rate at which you should replace fluids depend on your sweating rate, exercise duration, and opportunity to drink. You should drink periodically during exercise whenever you can.
Your sweating rate and sweat electrolyte concentrations are influenced by:
- Type of exercise
- Weather condition
- Genetic predisposition
- Heat acclimatisation
- Training status
Therefore, fluid replacement varies from person to person. You may estimate your sweat loss during a particular activity by monitoring your change in body weight during exercise.
For endurance exercise, it is recommended that fluid be replaced at a rate of 0.4-0.8L/hour, varying depending on weight, exercise intensity, and environment. However, individuals engaging in different types of physical activity under more intense conditions may have greater needs. Fluid should be consumed frequently (every 5-20 minutes) in small amounts (150-200mls).
Generally, for low intensity exercise and/or short duration exercise (<1 hour), water is an effective fluid replacement.
For moderate/high intensity exercise of >1 hour or endurance sports, sports drinks may be used as fluid replacement. You should look for a sports drink with the following composition:
- 20-30mEQ/L sodium (460-690mg/L)
- 2-5mEQ/L potassium (78-195mg/L)
- 5-10% carbohydrate
Sodium and potassium help to replace sweat electrolyte losses. Sodium additionally stimulates thirst, as well as sugar and water uptake in the small intestines. It also decreases urine production for fluid retention.
Carbohydrate provides energy and helps sustain exercise intensity by maintaining blood glucose levels during high intensity exercise of 1 hour or longer. It is recommended to consume 30-60g of carbohydrates per hour, consisting of a mix of sugars (glucose, sucrose, fructose, maltodextrine).
Unsuitable forms of fluid replacement include:
- Soft drinks and fruit juices, as they do not provide sufficient electrolytes. They are also more slowly absorbed due to their high carbohydrate content. However, you may improve the nutrition profile of fruit juices by diluting them with water in a 1:1 ratio and adding sodium.
- Energy drinks, as they contain high amounts of carbohydrates. This makes them more slowly absorbed, which can worsen dehydration
After Exercise
Goal: To fully replace any fluid and electrolyte deficit.
What about drinking water after workouts? If time is not a factor, consuming normal meals and snacks with sufficient plain water will restore euhydration. Ensure food is well salted. Extra salt may be added to meals or recovery fluids if sweat sodium losses are high. If time is limited, for rapid recovery from dehydration, drink 1.5L of fluids for each kilogram loss of body weight. Spread this fluid intake out as much as possible for maximum fluid retention.
To answer the question of whether drinking water after workouts is enough, it really depends on the type, intensity, and duration of exercise you’re engaged in. Beyond that, it is important to also consider how else you may optimise your fluid intake before and during exercise. With these measures in place, dehydration may be avoided and exercise performance improved. Lastly, the recommendations in this article are general. Your needs may be more specific depending on the exercise you’re engaged in or health conditions you have. Do seek personalised advice if you require.
Reference:
American College of Sports Medicine, Sawka MN, Burke LM, et al. American College of Sports Medicine position stand. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377-390. doi:10.1249/mss.0b013e31802ca597
