Last week we explained why exercise in the heat is such a problem and the physiological process of keeping cool. In this week’s blog, I’ll explain how you can acclimatise before you travel, the physiological changes that take place as a consequence of acclimatisation and simple tips to ensure you stay hydrated and perform at your best.
It’s a bit cold up North, so acclimatising might be difficult!!
Okay, if you live in the North of the UK and you’re traveling abroad to race, then you might be struggling to understand how you can possibly acclimatise. In simple terms, to acclimatise before traveling, you need to make yourself hot and encourage sweating when you train. There are really easy ways to do this:
- Wear extra clothing
- Run on a treadmill or cycle indoors and turn up the heat
- Spend time in a sauna or steam room on a daily basis
I’d recommend you start doing this from 2 weeks out, but you need to do it consistently. Ideally it should be on a daily basis. There’s plenty of evidence to suggest that the above methods can help acclimatise you before travelling to warmer climates.
What are the physiological changes that take place?
There are a couple of key changes that take place when you are forced to sweat at a high rate:
1. The first is an expansion of plasma volume, this refers to an increase in the amount of blood plasma. Last week we explained that blood is made up of plasma (the fluid part) and cells. As you sweat, you lose plasma, which then thickens the blood. Part of the acclimatisation process in as increase in plasma, which means your blood is thinner.
2. The second key change is a reduction in salt loss. Early in the acclimatisation process, your sweat contains a high amount of sodium. As the acclimatisation process progresses, your body retains sodium by reducing the amount lost in sweat. In simple terms, your sweat becomes less salty.
How much should I drink during exercise?
Most guides will recommend somewhere between 0.75 – 1.5 litres per hour depending upon individual sweat rates, but it is unlikely that very high amounts can actually be absorbed when you are exercising. If it's warm, aim for 750ml per hour as a minimum and drink to thirst. The common advice 20 years ago was "If you get thirsty it's too late, you're already dehydrated". This is bad advice, drink 750ml and if you're still thirsty, drink some more.
How much salt should I take?
The more common advice is that 'you can get enough salt from your normal diet and don't need any more'. However, if you are running/cycling in warm weather, you will need to get salt from somewhere as your daily diet and water alone is just not enough.
Just to clarify, when we talk 'SALT', the key one is 'SODIUM'. Table salt is 40% sodium, so 100g of table salt equates to 40g of sodium.
Steady running on a warm day, you can very easily lose 500mg per hour of sodium (generally it's more for many people) and that impacts significantly upon fluid balance in your body. To be correctly hydrated, you need salt with your water.
Just to give you an idea, a product such as High5 Zero Electrolyte Tabs (the kind which can be dissolved in water) have 200mg of sodium per tablet. SaltSticks capsules have 250mg per capsule. So you'd need 2/2.5 tablets per hour as a minimum to replace lost sodium.
There are other salts, not just sodium!
I always get one comment or email pointing out that sodium is not the ONLY salt. That's right, there are 3 other salts/electrolytes, and they are calcium, potassium and magnesium. These are important too but sodium is far more important in the role of hydration and is lost in much greater amounts in sweat.
Isn't there salt in my energy products, such as gels, bars etc ?
It depends on which brand you use, but generally salt content is low. There are specific electrolyte drinks, but often you have to take a lot. Powerbar products are generally pretty good, but it can be a minefield.
If you are racing in warm weather, fluid intake and salt intake need to be considered in some detail as it could be the difference between a great result and a DNF. If you do need advice, call in store and speak to us, we'll be happy to help.
The Endurance Store