Running in the heat presents specific challenges. Addressing these can improve your performance and safety.
Problems with Heat Running
Basically, heat running has two problems. Your body has to work harder and expend more energy to cool you down through sweat. This drains energy the longer a run goes on. Your muscles generate heat when you run through normal mechanisms.
The burn you feel in muscles is the heat getting too much, and the muscle will fail. It cannot continue past a certain temperature. To help thermal regulation, so your muscles can continue to work, the heat normally dissipates through your skin into the atmosphere. This is absolutely fine when your body temperature is 37.5 degrees and the air temperature is much lower. But if you’re in Hong Kong and the humidity makes the air temperature much closer to your body temperature, you have very little room for reducing muscle heat.
The key is to make sure that your muscles never produce “too much heat” unless we want them to. You do this by never pushing your muscles past a point where they become incredibly inefficient. You make sure to work within your capabilities.
Acclimatization Stages
Luckily, this situation doesn’t last forever. Your body does have several ways to acclimatize to hotter conditions. It will acclimatize in stages. This varies by body type, body fat %, gender, fitness, muscle size, sweat capacity, electrolyte balance, and recently a lot of evidence has come out that actually overall diet can have an impact. Although, I wouldn’t say enough research has been done for conclusive findings.
Stage 1: Initial Reaction
In 3-6 days, your HR and core body temperature spike massively because of heat stress. Between 7-10 days, this comes down. This is because your body increases the amount of water in your blood. Then your body can dissipate muscle heat into your blood and send it to parts of your body that aren’t as hot.
You might have heard this as “increasing blood plasma volume.” The issue with this is people don’t realize the body has retained more water. They change nothing about their diet. However, more water means more salt is needed. If you run with low salt, your body sweats out more water than necessary to try and maintain good salt levels. This thickens the blood, and it’s harder for your heart to pump the blood around. You’ll then have a higher heart rate as your heart has to work harder.
Being proactive about your hydration is the single best thing you can do to help. You can’t catch up mid-run on salt intake. However, you can maintain levels.
Stage 2: Sweat Gland Fatigue
Sweat glands get fatigued. They take 1-4 weeks to build up enough resilience to do more than 90 mins of exercise.
Stage 3: Heat Stress Perception
Recently more research has come out about this. It was previously very underappreciated. The longer you spend in hotter conditions, the more you just accept it’s a way of life. Your perception helps to reduce the stress you want to put on your body.
Conclusion
Understanding the challenges of running in the heat and the body’s acclimatization process can enhance your running experience and safety.
