Getting hydration right in the heat
We have had our share of hot days during our summer of lockdown in 2020 and hopefully, we can return to racing in exotic climes of our choosing in the future. When training or racing in the heat how much attention have you paid to your hydration? In this article coach Jon takes a look at some key things you can do to stay hydrated when the temperature starts to rise.
Firstly, what happens when you start exercising in the heat?
Your working muscles give off a lot of heat when you are exercising, this increases your core body temperature (CBT), once your CBT reaches a certain point, your body diverts blood to your skin and you begin to sweat in an attempt to expel as much heat as possible. In hot environments, your CBT will rise quickly leading to higher rates of sweat production. In particularly humid environments, that sweat will not evaporate as easily into the atmosphere so your body will produce even more sweat to try and keep you cool.
The more you sweat the more sodium you will lose, how much, depends on your individual sweat rate and sweat sodium concentration. When sodium concentration in the blood plasma drops, water is pushed out of the blood and into the surrounding tissue. This decreases your blood volume meaning your cardiovascular system has to work harder to pump oxygen to the muscles and expel heat away from the body. Therefore, decreased blood sodium concentration can lead to degraded performance in endurance events and is one of the leading theories behind the cause of cramp suffered by athletes late on in events.
Drinking too little can lead to dehydration and overheating, causing a drop in performance. However drinking too much water can dilute sodium concentration content in the blood further, in extreme cases, causing hyponatremia. So how do we give our bodies the best chance of staying adequately hydrated and keep our sodium levels balanced in the heat?
Hydration advice during endurance events has changed many times over the years, in the 60s it was frowned upon to drink anything at all, in the 90s advice changed to - drink as much as you can tolerate. More recently Tim Noakes has advised athletes to drink to thirst during endurance events to prevent overhydration and potential hyponatremia. If training or racing in the heat Tri Training Harder recommends formulating a hydration strategy for endurance events rather than simply drinking to thirst.
Hydration strategies work best if they are individualised. Sweat rates and sweat sodium concentration vary from person to person. To calculate your sweat rate, you can follow this procedure. The second thing to be ascertained is your individual sweat sodium concentration, the most accurate method is through an advanced sweat test, a one time test performed by Precision Hydration. This will give you the amount of sodium in every litre of sweat, this is genetic and rarely changes despite changes in diet or heat acclimatisation. Most athletes have a sodium sweat concentration of between 300-500mg per litre. If you often suffer from cramps, have red or stinging eyes if sweat drips into your eyes or find salt residue on your skin or clothes after sweating you may well be a ‘salty sweater’ (I suffer from all of these traits, after taking the PH advanced sweat test I discovered am an extremely salty sweater with a sodium concentration of 1924mg per litre!). If you are a salty sweater or have a very high sweat rate it is especially important you formulate a hydration strategy including adequate sodium for hot races by way of electrolyte products.
Once you have your sweat rate and sweat sodium concentration you can use these figures to guide your hydration in hot races. The aim is not to completely replace all of the fluid you will sweat out (a nearly impossible task), but to use your personal sweat characteristics to guide you in your choice of electrolyte product to replace enough sodium to keep your blood plasma volume up and keep you performing at your best.
Before
For any length of race or session in the heat, the most important thing you can do to get your hydration right is to ‘preload’. Precision Hydration, recommend preloading with a strong isotonic drink (the strength depends on the characteristics of your sweat) the night before a big event or training event, then repeat the process a few hours before the event. Make sure you stop drinking 45 minutes before the start to give your body time to absorb the fluid. It is important not to drink any extra plain water, to avoid overhydration.
During
The longer and hotter your event or session the more you will sweat and the more important your hydration strategy becomes. For events lasting less than 90 minutes, providing you preload your hydration you do not require a hydration plan as you are unlikely to sweat a sufficient amount in that time to affect sodium concentration. Drinking to thirst will suffice.
Longer duration races or days where you will have two hard training sessions in the same day require a proper hydration strategy, especially if you are not used to exercising in the heat. Athletes who have many hot races under their belt have the opportunity to fine-tune their hydration strategy with experience. Read next week’s blog for a guide on how to plan a hydration strategy for an Ironman.
How do we know if we’ve got it right? If you feel thirsty, have a dry mouth and don’t need to pee at least once during a long endurance event you may be under hydrating. However, if you feel bloated, can feel fluid sloshing around in your stomach and need to pee more than 3 times in a long event you may be drinking too much. Don’t over-do it!
After
Post-exercise, if you have another event or session within 24 hours then rehydration becomes very important to ensure your fluid levels are topped up and you don’t start the next event dehydrated. You will need to proactively replace fluids and drink 1.5 times the amount you lost in the first session or event. Sipping a strong electrolyte product is the most efficient way to do this.
There is no fixed formula to get hydration right in the heat, we are all different and it takes a lot of trial and error to get right, however, taking some of the tips from Precision Hydration regarding preloading and working out the make-up of your sweat can guide you in the right direction to make solid choices around your hydration going forwards. If you would like any further information on sweat testing your TTH coach can help you organise testing with Precision Hydration.
We’re here to help
Tri Training Harder are one of the leading Triathlon coaching providers in the UK, using our wealth of experience to unite scientific and technological research with already well-established and successful best practices, to create a formula for triathlon and endurance coaching that works.
The result is an honest, dynamic, yet simple new way of constructing an athlete’s training to allow them to reach their potential.
If you’re planning your next season, just starting out in the sport or are looking for extra guidance at the very top end of the field, we are here to help, and our coaches would be delighted to hear from you. You can contact us via the website, and one of the team will be in touch.