Identifying Heat Illness & Cardiac Stress

Pacers spend hours running next to the same runners. That makes you one of the best-placed people on the course to notice when something is wrong. In tropical races, such as those in Vietnam, heat and humidity are the biggest risk (see pacing in heat and humidity). You are not expected to diagnose anyone. You are expected to notice warning signs early, act quickly and call for help.

Heat exhaustion vs heat stroke#

Both are caused by the body struggling to get rid of heat, but they are very different in danger.

Heat exhaustion is the body being overloaded. The runner is usually still clear in the head. Signs include heavy sweating, pale and clammy skin, feeling faint or dizzy, headache, nausea, weakness, muscle cramps and a fast heartbeat.

Heat stroke (also called exertional heat stroke) is a medical emergency. The body's core temperature is dangerously high and the brain is affected. It can kill if not treated fast. Signs include:

• Confusion or strange behaviour, such as not knowing where they are or running in the wrong direction
• Unsteady gait (ataxia), meaning stumbling, weaving or running as if drunk
• Slurred speech
• Very hot skin; sweating may have stopped, but many runners with heat stroke are still sweating, so do not rely on dry skin
• Collapse, fainting or seizure

The key difference: any change in mental state means you treat it as heat stroke. Do not wait for other signs.

Cardiac stress#

Heart problems in races are rare but serious. Watch for:

• Chest pain, pressure or tightness, sometimes spreading to the arm, jaw, neck or back
• Unusual breathlessness that is out of proportion to the pace
• A very irregular or racing heartbeat the runner mentions
• Sudden dizziness, grey or sweaty skin, or feeling "something is very wrong"
• Sudden collapse, which may be cardiac arrest

A runner with chest pain must stop running immediately. Never encourage them to "push through it".

Hyponatremia (over-drinking)#

Hyponatremia means the salt level in the blood becomes too low, often because a runner has drunk much more water than they lose, usually in long races. Signs can look like heat illness: nausea, headache, bloating, swollen hands, confusion and, in severe cases, seizures or collapse. This is why runners should drink regularly but not force down large amounts at every station. Never make a confused runner drink large amounts of water; let the medical team decide.

Recognize → Act → Escalate#

Use this simple structure, the same one used on the CDPP crisis cheat sheets.

When in doubt, escalate. Calling medics for a runner who turns out to be fine costs nothing. Waiting can cost a life. Lesson 4.2 explains exactly what to do when a runner collapses.

Key takeaways#

• Heat exhaustion: runner is clear-headed. Heat stroke: confusion, ataxia, slurred speech or collapse, a medical emergency.
• Any change in mental state means stop, cool and call medics immediately.
• Chest pain or unusual breathlessness means stop running and alert medics; never "push through it".
• Over-drinking can cause hyponatremia; do not force water on a confused runner.
• Use Recognize → Act → Escalate, and take a certified first-aid and CPR course.