Early Recognition of Heatstroke During Summer Training: 3 Stages of Warning Signs and Emergency Response

Medical Classification of Heat Illness

Exertional hyperthermia is divided into three stages, with core temperature as the gold standard:

Stage 1: Heat Cramps

Early Warning Signs

• Cramping in the calves, thighs, or abdomen (most common sites)
• Heavy sweating with noticeably salty sweat
• Increased thirst
• Heart rate 10-15 bpm higher than usual
• Unable to maintain pace, but fully conscious

Treatment Protocol

1. Stop training immediately and move to a shaded area
2. Passively stretch the cramped muscle (for calves, pull toes upward)
3. Consume 500ml of electrolyte drink containing sodium (do not drink plain water only)
4. Rest for 15-20 minutes; only consider resuming if symptoms subside
5. Reduce intensity or mileage by 50% for the remainder of the day’s training

Stage 2: Heat Exhaustion

Warning Signs (much more severe than heat cramps)

• Dizziness, headache, blurred vision or seeing flashes
• Nausea, feeling of vomiting
• Cool, clammy skin (not hot, not dry)
• Heart rate exceeding 90% of max HR, pace collapses
• Brief confusion but still able to converse
• General weakness, unable to run in a straight line

Emergency Treatment Protocol

1. Stop training immediately, lie flat, and elevate legs 30 cm
2. Move to a shaded area or air-conditioned room
3. Remove excess clothing and wipe the forehead, neck, armpits, and groin with cool water
4. Sip sports drinks slowly (avoid gulping large amounts of water at once)
5. If symptoms do not improve within 30 minutes → seek medical attention immediately
6. Complete rest from training that day; reassess after 48 hours

Stage 3: Heat Stroke (Life-Threatening)

Life-Threatening Warning Signs

• Loss of consciousness or incoherent speech
• Skin becomes dry and sweating stops (central thermoregulation fails)
• Rapid breathing, irregular heart rate
• Seizures, coma
• Skin feels like “red-hot iron” to the touch

First Aid Principle: “Cooling First”

1. Call 119 immediately (every minute of delay reduces survival rate by 5%)
2. Immerse in cold water or pour copious cold water over the entire body (most effective cooling method)
3. If no cold water bath is available: wrap the body in wet towels + use a fan at full blast
4. Cooling takes priority over transport to hospital; the goal is to lower core temperature below 38.5°C within 30 minutes
5. Continue cooling while waiting for the ambulance

Fatal Myth: “Don’t cool too fast” is wrong. Research shows that the faster the cooling, the higher the survival rate; cold water immersion is the gold standard.

High-Risk Groups

The following runners have a 3-5 times higher risk of developing heat illness:

• BMI > 27
• Alcohol consumption within 24 hours before training
• Less than 6 hours of sleep within 24 hours before training
• Taking diuretics, antihistamines, or antidepressants
• Recovering from a cold (even a mild one)
• First-time exposure to that intensity of heat environment

Prevention Principles: 5 Must-Dos

1. Check WBGT (Wet Bulb Globe Temperature) on a weather app

   • <28°C: normal training allowed
   • 28-30°C: reduce volume by 25%
   • 30-32°C: reduce volume by 50%
   • >32°C: suspend outdoor training

2. Buddy system: never run long distances alone above 30°C

3. Phone as a lifeline: enable location sharing and inform family of your route

4. Identify shaded points on the route: rest stops with shelter and water access every 3-5 km

5. Pre-training self-check: sleep, alcohol, cold symptoms, weight changes (a sudden 2kg drop may indicate dehydration)

Recovery After Heat Illness

Stage 1: return to normal training within 48 hours
Stage 2: 1 week of reduced training, full recovery in 2 weeks
Stage 3: at least 4 weeks off running + physician evaluation; liver, kidney, and heart muscle may be damaged

Emergency Kit

Recommended to carry during summer long runs:

• 5 salt candies
• 2 packets of electrolyte powder
• Cooling towel
• Phone (emergency contact + GPS)
• 100ml plain water (not sports drink; for pouring over the body to cool down)

Heat illness is not a matter of luck—it’s a matter of your ability to read your body’s signals. Memorize these 3 stages, and your summer training will have its first line of safety.

Related Reading

• Heat Stroke Warning Signs and Rescue: The Red Line Guide for Runners’ Summer Training
• Heat Exhaustion vs Heat Stroke: The Life-or-Death Distinction for Basketball Players’ Summer Training
• Complete Guide to Distinguishing Heat Exhaustion and Heat Stroke: Classification, On-Site Management, and Hospital Warning Signs You Must Not Delay
• Exertional Heat Exhaustion and Heat Stroke: Advanced Warning Signs from Core Temperature 38.5°C to 41°C