Hydration in Sport: Part 2

Now that we know why water is needed in the body, this week we're looking at how to calculate your own fluid replacement after exercise and what the best method is.
 
During exercise, we sweat to regulate our body temperature and to stop us from overheating. This results in a loss of water and minerals that must be replaced to aid in performance and recovery.
 
                So, how do you know how much to drink to replace what you lose through sweat?
                                    
Without getting too scientific, here’s an example!
 
EG.
Central forward soccer player participating in high intensity 90min training:
Pre-training weight                               = 75kg
Fluid consumed during training     = 1.5L
Post Training Weight                            = 73kg
Activity duration                                     = 90min
 
To avoid dehydration or overhydration after the training session, how much fluid should the athlete consume?
**As mentioned last week, we want to keep weight lost during exercise to 1 kg or a maximum of 2% body weight to maintain performance.
 
Weight Loss 
= 75kg - 73kg = 2kg (or 2L)
 
% Weight Loss
= 2kg/75kg = 2.7% (Dehydrated! we want no more than 2% loss of body weight for maintaining                                                      performance)
 
Total Sweat Loss 
= 2L weight loss + 1.5L consumed during training = 3.5L
 
Allowable Sweat Loss 
= 2% x 75kg = 1.5L   (again, we only want to allow for a 2% loss of body weight)
 
Minimum Fluid Replacement 
= 3.5L total sweat loss – 1.5L consumed = 2L over 90mins of training
= 2000ml / 6
= 330mls per 15mins of training
 
Maximum Fluid Replacement = 3.5L
= 3.5L total sweat loss over 90mins of training
= 3500ml / 6
= 580mls / 15mins
 
So the minimum amount the athlete should be consuming post 90min training to avoid dehydration is
2000ml (2L)
The maximum amount the athlete should be consuming post 90min training to avoid dehydration, but also to avoid over hydration is 3500ml (3.5L)

*Note that this can be consumed over a few hours, not downed immediately after training!
 
RECOVERY:
What is the best thing to drink to replace fluids? Water or Sports drinks?
It’s important to consider the intensity and duration of the activity when choosing what to rehydrate with.
 
Water:
Water is the best option for exercise that is less than 1 hour and low intensity as it:
- Relieves thirst
- Rehydrates
- Maintains body processes

It is not as effective for high intensity, long duration exercise due to:
- Causing bloating and suppressing thirst, reducing the will to drink more to rehydrate
- Contains no carbohydrates, electrolytes or sodium, therefore cannot replace what is lost during exercise
- Empties from stomach faster, so is not absorbed as efficiently
- Dilutes sodium content in body, therefore you don’t feel thirsty and don’t drink more to rehydrate
  
Sports Drinks:
Sports drinks are best used for prolonged exercise with a higher intensity.
- They contain carbohydrates, electrolytes and sodium, all of which are lost during heavy exercise
- They promote thirst as they contain minerals (sodium), so you feel thirsty and drink more to rehydrate
- Sports drinks are absorbed faster into the body compared to water, meaning faster rehydration
 
However, if drinking frequently when not required, consumption may lead to health implications and weight gain. Remember that Sports drinks are to be used short term. Once you have rehydrated as per your Fluid Replacement plan, you still need to consume water for daily body processes.

Types of Sports Drinks:
​There are heaps of different types of sports drinks out there is can be pretty confusing to know what the differences are and when to use them. So I'm making it easy for you!

​ISOTONIC
Contains electrolytes and carbohydrates (6-8%)
Replaces carbohydrates and fluids equally
Most effective choice for team/individual sports
Best consumed during or after event
EG. Powerade, Gatorade, Maximus

HYPOTONIC
​Contains fluids, electrolytes and low levels of carbohydrates (less than 6%)
Replaces more fluids than carbohydrates
Great for gymnasts/jockeys
Best consumed before events to replace fluids, not carbs
EG. Powerade Zero

HYPERTONIC
High levels of carbohydrates (more than 8%)
Replaces more carbohydrates than fluids
Best used post exercise
Used for high intensity activities: Cross country skiing, ultra-marathon, distance cycling events
EG: Powerade Energy, "Endurance" or "Performance" labelled drinks, Fruit juices​

So when planning your next ride, game or training session, take into consideration your hydration for recovery and performance. It's easy to work out your own fluid replacement plan, just substitute your figures in to the formula!
Choose your fluids wisely when rehydrating, keeping in mind the type, duration and intensity of your exercise.