Being laid up certainly has many disadvantages. One advantage that sticks out is that I’ll get to work a lot on my sports nutrition classes and keep up with my blog. With the recent heat and humidity increases all over the East Coast, athletes are begging for a break. In my athlete’s diaries I’ll read how a run pace has increased :30/mile or someone had to bag a bike as they couldn’t breathe the humidity was so great. These are all very typical of the summertime or of all the time if you live in the tropics.
Take a warm temp, but certainly not scorching temp of 75 degrees. At 20% humidity, it isn’t bad at all, at 70% humidity, it can feel like 90 degrees. So when going out for a workout, look at both the temperature and the humidity.
There are many different fields of study just in heat and body temperature regulation. I’m going to focus on 4 areas. Cooling before, cooling during, cooling after and fluid temperature/composition and how that relates to your performance and core body temp.
Pre-exercise cooling is the area that seems to have the most room to help us as athletes.
How: If you can pre-cool your body prior to exercise in a hot/humid environment, you’ll give yourself a larger window before you reach your critical limiting temperature (when you have to stop). So it’s a larger margin. They will also increase your stroke volume and decrease your heart rate.
Pre-exercise cooling modalities
- Cold air exposure- you’ll need to spend a minimum of 2 hours in a cold environment (think winter)
- Cold water exposure- you’ll need to spend a minimum of 1 hour in a cold water environment
- Cooling vest-you’ll need to wear a cooling vest (cold enough to be uncomfortable) prior to exercise
So, looking at those three choices, you’re probably like me and no thank you. All three of these modalities work, however they are impractical.
Drinking fluid prior:
This is a much more practical way of cooling your body prior to exercise. While drink temperature has no effect on skin temperature, drinking a cool (40 degree F) fluid will decrease your heart rate, and reduce other physiological strains that heat and humidity bring. A study done by Lee et al in 2008 actually showed that drinking cold fluids prior to exercise both reduced a person’s core body temperature and increased their endurance capacity once the exercise began. The increase was 23% improvement over a warm fluid.
During Exercise Cooling:
As it turns out, this was an interesting find. You know when you come upon an aid station and they hand you a cup of warm sports drink, you needn’t worry about anything other than the taste. The temperature of the fluid you ingest, doesn’t significantly effect your core body temp. One study showed a small increase in performance from drinking the cool fluid, however this could also be because it is more palatable, and they increased their performance by getting the needed calories, carbs and electrolytes.
Post Exercise Cooling:
If you drink a cold fluid vs a warm fluid post exercise, you’ll actually see a greater reduction in body temperature. There seems to be by a peripheral vascular constriction by drinking the cold fluid. So this is a good thing, and important. Especially if you are playing a sport like soccer where you come on and off the field getting short amounts of rest, swimmers between events and track athletes between events. The reason that drinking a cold fluid after reduces your body temp, while drinking it during exercise does not, is because at rest, you have a lower cardiac output and this reduces the time to equilibrium of body temperature.
Type of Fluid/Composition:
So now we know that drinking cold fluids before and after exercise will reduce your core body temperature. Also, they might potentially give a slight benefit during exercise. If we look at a fluid vs an ice slushy we see an even greater reduction in core body temperature.
- Drinking an ice slushy will reduce your body temperature .7 degrees C vs fluid alone
- Studies showed drinking an ice slushy before or during exercise will also increase your endurance capacity by 7-19%
- An interesting fact found in one of the studies was that drinking a slushy will also help to keep your brain temperature down, or reduce your brain’s temperature.
- Drinking an ice slushy 30min before exercise will reduce your core temperature, skin temperature, heart rate and will help to attenuate hyperthermia.
- It may also be beneficial to drink an ice slushy post exercise to reduce your body temperature post exercise and decrease your recovery time
- The only negative side effect of a slushy would be a brain freeze
In summary, it isn’t necessary to drink a cold fluid during exercise. It might be more palatable, but there is no need to worry if handed a warm drink. Here are some tips for better performance in the heat
1. Drink either a cold fluid or ice slushy 30 min prior to exercising in the heat. This will pre-cool your body and increase your endurance
2. Drink a slushy during exercise to try to reduce your core body temp. The studies didn’t specifically look at this, but when you’re in a IM or marathon, taking in ice chips or adding ice to your sports drink can help.
3. Post exercise, drink either a cold drink, or an ice slushy to reduce your core body temperature and increase recovery.
Stay cool out there!