The heat is the most difficult element for runners to train in. The effects of heat and humidity on training and racing are two- fold and impact performance both long-term and short-term. During a workout or a race in the heat, your performance suffers for three different reasons.
Why running in the heat is hard
First, you have an increase in your overall body temperature. Just like when you run a fever, the higher your core body temperature, the worse you are going to feel.
Second, as soon as the body starts to heat up, blood is diverted to the skin, where cooling takes place through sweating and evaporation. Therefore, less blood is available to transport oxygen to the working muscles. Less oxygen means you can’t run as fast or as hard and the effort to maintain or increase your pace dramatically increases. In this way, training and racing in the heat is somewhat similar to altitude training.
Finally, you become more easily dehydrated in hot and humid conditions. When fluid levels drop, your body’s cooling methods, mainly the ability to sweat, erode and you have a harder time controlling your body temperature. This in turn causes the core body temperature to rise faster, which creates a vicious cycle that severely limits performance.
How running in the heat effects recovery
Not only does heat and humidity make that one specific workout harder, it also hampers recovery and your ability to perform on subsequent workouts. After you exercise in hot conditions, your body needs to spend more energy on cooling itself rather than delivering nutrients to your battered muscles. When the muscles can’t get the nutrients they need to repair the damage caused by the workout, recovery is slower and you may not be fully prepared for your next hard workout like you normally would be.
Running in the Heat Trick #1 – Adjust Your Paces
As we can clearly see, performance suffers in the heat and humidity. I’ve worked with some runners who question the amount the heat and humidity actually affects their workout and race times, but it’s a scientific fact that even the most heat acclimatized runner will suffer performance loss in hot conditions.
Therefore, it’s important that you find ways to adjust your workout times and race paces to reflect how you’ll perform in hot conditions. Likewise, sometimes you need to know how much more effort a workout is taking in hot and humid conditions so you can better monitor fitness and progression.
How to adjust your running pace in the heat
Luckily for you, I’ve created a calculator that will estimate of how much harder you’re working in the heat and humidity. Download this calculator to find out how heat effects your running times here.
Running in the Heat Trick #2 – Proper Hydration
Hydration is a critical element to staying cool and performing your best in hot conditions. What makes hydrating so difficult is knowing exactly how much fluid you need to stay cool and replenish what you lose through sweating. Likewise, pre-hydrating and re-hydrating with the proper fluids is critical to maintaining fluid levels and performing at your best
Every runner sweats at a different rate relative to their conditioning, acclimatization and individual make-up. A study conducted by Jack Daniels found that runners with similar backgrounds, training regimens and under identical training conditions differed in sweat loss by as much as 2.5 liters per hour. This means that while I may only sweat at a rate of 1.5 liters per hour, you might sweat at rate of four liters per hour, making drinking and hydrating much more important for you.
How to measure sweat loss in the heat:
To help you out, I’ve created a simple calculator that will enable you to calculate your exact rate of fluid loss at given temperatures so that you know exactly how much you need to rehydrate before, during and after a run of any distance or temperature. You can use our sweat loss calculator here.
Sports Drinks vs Water
The critical factor in hydration is how rapidly fluids can be absorbed into the blood stream. As a general rule, the higher the carbohydrate content, the slower the absorption rate. Therefore, you should drink water of diluted sports drinks before and during running, and sports drinks or a recovery beverage after. Here’s a more in-depth analysis of sports drinks or water for runners.
How to hydrate before a run:
Research has demonstrated that beginning your run hyper-hydrated (of hydrating your body above its normal state before exercise ) will delay or eliminate the onset of dehydration, particularly if you fail to completely replace sweat loss during your run. The problem is that you will quickly urinate any excess fluids. Luckily, we have a simple trick using a product called glycerol that will help you retain this extra fluid and increase your performance by up to 6 percent in hot and humid conditions. Check out our article on hydrating before your run.
Running in the Heat Trick #3 – Racing in the Heat
The heat is the most difficult element for runners to compete in and race well. As mentioned previously, with the rise in core body temperature, a runner will have less oxygen available to working muscles, become dehydrated and suffer a decline in performance. However, we do have a few tricks up our sleeves to teach you how to race better in the heat.
Pre-cooling before a race:
Pre-cooling is a technique used to slightly lower a runner’s core body temperature before they start running, which in turn extends the amount of time they can run hard before hitting that critical temperature threshold. Learn how you can use pre-cooling to improve your racing times.
Racing a marathon in the heat:
Running a marathon or half marathon in the heat isn’t an exciting thought. However, you can’t change the weather, so the best strategy is to be prepared. The following is a brief list of some innovative strategies and tips that you can implement on race day should you have to run a marathon in the heat.