Why Your Body Overheats During Exercise — And How It Cools Itself Down

Exertional heat stroke is one of the top three leading causes of death in sports, right up there with cardiac conditions and traumatic injuries. It’s sudden, dangerous, and often preventable — but to understand how, you need to first understand why your body overheats in the first place.

This post breaks down the surprising inefficiency of human movement, how your body generates and manages heat, and what you can do to support this process — especially during intense training or extreme heat.

You’re Inefficient — and That’s the Problem

Humans are surprisingly inefficient when it comes to converting energy into movement. In fact, over 80% of the energy your body uses during most physical activities is converted into heat, not motion.

Here are some examples of how energy efficiency breaks down:

• Climbing stairs: ~24% efficient

• Lifting weights: ~15% efficient

• Shoveling: ~7% efficient

That means up to 93% of your effort during something like shoveling is spent generating heat, not getting the job done.

To make matters more intense, elite athletes can produce massive amounts of heat. For instance, world-class distance runner Kenenisa Bekele generates over 1500 watts of heat during a 10k — that’s more heat than your average hair dryer.

If your body didn’t have a cooling system in place, core temperatures could reach dangerous levels — like 104°F (40°C) — in just 12 minutes of hard running. That’s life-threatening heat, fast.

Your Body’s Heat Management System: Blood Flow and Sweat

Luckily, your body has evolved an incredibly effective system for keeping internal temperatures in check — a process known as thermoregulation.

Here’s how it works:

1. Heat is generated in your muscles during activity.

2. Blood acts as a transporter, picking up heat from your working muscles.

3. The heated blood is sent to the skin, where heat is released through sweat and evaporation.

This cycle — generate → move → release — is the foundation of how you stay cool during exercise.

The Hidden Challenge: Blood Pressure Drops During Exercise

Exercise places strain on your cardiovascular system. One effect is a drop in blood pressure, which may be good for long-term heart health, but it reduces your body's ability to circulate heat efficiently in the moment.

This makes your natural cooling process less effective — just when you need it most.

Nitric Oxide: Your Body’s Secret Cooling Aid

To combat this, your body releases a powerful compound: nitric oxide.

Nitric oxide helps dilate blood vessels, increasing circulation and allowing more heat to escape the body. This is a critical part of your heat defense mechanism, especially during long or intense training sessions.

Certain ingredients have been shown to support nitric oxide production, including:

• L-Citrulline

• L-Arginine

• Beet Root Extract

• Arugula

These compounds help boost nitric oxide and improve heat transfer through increased blood flow. Some hydration and performance products include these ingredients — including Heat Hydration, formulated specifically to support performance in hot, demanding conditions.

Stay Ahead of the Heat

Your body’s heat response is an incredible system — but it has limits. By understanding how heat is generated and how it’s managed, you can train smarter and stay safer.

Support your thermoregulation system with proper hydration, smart nutrition, and nitric oxide–boosting ingredients — especially in the heat.