Heat Illness & Heat Stroke

Overview

Heat illness is a spectrum of conditions caused by the body's inability to regulate its core temperature during physical exertion, particularly in hot, humid or sun-exposed environments. It ranges from mild heat cramps and heat syncope, through heat exhaustion, to the life-threatening emergency of exertional heat stroke.

Heat illness can affect athletes of all fitness levels and is not limited to elite competitors. Outdoor events such as polo tournaments, cycling sportives, running races and public events in summer conditions present elevated risk. Early recognition and rapid cooling are the most important factors in preventing serious harm.

Common Causes

• Prolonged physical exertion in high ambient temperature or humidity
• Insufficient fluid intake before and during activity
• Heavy or poorly ventilated clothing or protective equipment
• Sudden exposure to hot weather without adequate acclimatisation
• Exercise on artificial or reflective surfaces that increase radiant heat
• Alcohol consumption before or during activity
• Illness, fever or recent gastrointestinal illness reducing heat tolerance
• Certain medications that impair sweating or increase heat production

Signs and Symptoms

Heat exhaustion:

• Heavy sweating
• Dizziness or fainting
• Headache
• Nausea
• Pale, cool, moist skin
• Fatigue or muscle weakness
• Fast, weak pulse
• Muscle cramps

Exertional heat stroke (medical emergency):

• Core body temperature above 40°C
• Hot skin — may be wet or dry
• Confusion, slurred speech or altered mental state
• Loss of consciousness or collapse
• Seizure
• Rapid, strong pulse progressing to weak pulse
• Absence of sweating (in classical heat stroke) or continued sweating

Immediate Actions

• Stop the activity immediately and move the athlete to a cool, shaded area
• Remove excess clothing, helmets and protective equipment
• Begin active cooling immediately — apply ice packs to neck, armpits and groin
• Use cool water and fanning to enhance evaporative cooling
• If conscious and able to swallow, encourage sipping cool water
• Lay the athlete down and elevate their legs if they feel faint
• Monitor temperature if a thermometer is available
• Continue cooling until the athlete's condition improves or emergency services arrive

When to Call Emergency Services

Event Environment Considerations

Outdoor sporting events held in warm weather require specific medical and operational planning to manage heat illness risk:

• Medical teams at outdoor events should carry ice packs, cooling sprays and fluids
• A designated cool, shaded treatment area should be established at events
• Hydration stations should be positioned throughout event venues
• At polo and equestrian events, both riders and horses are at risk of heat illness
• Cycling events in hot conditions require medical cover along the route, not just at the finish
• Event organisers should monitor weather forecasts and adapt schedules where necessary
• Staff and volunteers should be briefed on heat illness recognition and cooling protocols

Prevention Advice

• Begin hydrating well in advance — do not rely solely on thirst as a hydration cue
• Acclimatise gradually to hot conditions before competing — allow 7–14 days
• Wear light-coloured, breathable and well-ventilated clothing where possible
• Schedule intense activity during cooler parts of the day when possible
• Set up shaded rest areas at events, particularly for long-duration activities
• Athletes with a history of heat illness should seek medical advice before competing in hot conditions

When to Seek Medical Assessment

Any athlete who has experienced suspected heat stroke should be assessed in hospital. Athletes with heat exhaustion should be reviewed by a clinician if symptoms do not fully resolve with cooling and rehydration.

• Any episode of loss of consciousness or altered mental state
• Any suspected heat stroke episode
• Symptoms that persist beyond 1–2 hours despite cooling and hydration
• Athletes with underlying medical conditions including diabetes or cardiac disease
• A second heat illness episode within the same season