Exercise in Hot Weather Safely

Physical activity accelerates weight loss and improves every aspect of health. But exercising in tropical heat without proper precautions risks heat-related illness that can range from uncomfortable to life-threatening. This guide ensures you can stay active safely year-round.

How Your Body Handles Exercise Heat

During exercise, your muscles generate heat as a byproduct of energy production. Your body must dissipate this heat to maintain safe core temperature. It accomplishes this primarily through sweating—water evaporating from skin carries heat away.

This cooling system works efficiently in moderate conditions. In hot, humid environments, two problems emerge. First, when air temperature approaches body temperature, heat dissipation slows. Second, high humidity prevents sweat from evaporating—it just drips off without cooling you. This combination makes tropical exercise particularly challenging.

Heat Acclimatisation

People who regularly exercise in heat develop physiological adaptations that improve heat tolerance. These include earlier onset of sweating, increased sweat volume, reduced sodium loss in sweat, and improved cardiovascular efficiency. Full acclimatisation takes 10-14 days of consistent heat exposure.

If you have not exercised regularly in heat, begin cautiously. Start with shorter sessions at lower intensity, gradually increasing both as your body adapts. Long-term tropical residents have usually acclimatised but may lose this adaptation during extended periods indoors with air conditioning.

Timing Your Workouts

Dawn: The Optimal Window

The hours between first light and 8 AM offer the coolest temperatures and lowest UV radiation. Ground surfaces have cooled overnight, radiating less heat. Air quality is often best before traffic peaks and thermal activity stirs dust and pollution.

Early exercise also provides psychological benefits. Completing your workout before daily demands begin eliminates the "I'll exercise later" excuses that often fail. Early exercisers report better consistency than those who plan afternoon workouts.

Evening: The Second-Best Option

After 5 PM, temperatures begin falling though they remain higher than morning. UV exposure decreases as the sun lowers. If morning exercise is impossible, evening provides a reasonable alternative.

Caution: intense evening exercise can interfere with sleep. Finish workouts at least two hours before bedtime to allow your body temperature and stress hormones to normalise.

Midday: Indoor Only

Between 10 AM and 4 PM, outdoor exercise in tropical heat creates unnecessary risk. Reserve this period for air-conditioned gyms, indoor swimming, or rest. Even if you feel capable, the long-term health costs of repeated heat stress are not worth the convenience.

Hydration Protocols

Before Exercise

Drink 400-600ml of water 2-3 hours before exercise, then another 200-300ml 15-20 minutes before starting. This ensures you begin hydrated without feeling uncomfortably full.

Check urine colour: pale yellow indicates adequate hydration. Dark urine means you need more fluids before starting.

During Exercise

Aim for 150-250ml every 15-20 minutes during activity. Do not wait for thirst—by the time you feel thirsty, dehydration has already begun affecting performance. Set a timer if needed to remind yourself to drink.

For exercise lasting over one hour, electrolyte replacement becomes important. Options include commercial sports drinks (choose low-sugar versions), coconut water, or water with a pinch of salt and splash of fruit juice.

After Exercise

Replace 150% of weight lost during exercise over the following 2-4 hours. A person who loses 1kg during a workout should drink at least 1.5 litres afterward. Weighing yourself before and after exercise provides exact loss figures.

Appropriate Exercise Choices

Swimming

Perhaps the ideal hot-climate exercise. Water continuously cools your body, preventing overheating regardless of intensity. Swimming provides full-body workout with no joint impact. Even treading water burns significant calories.

Pool chlorine can dry skin—rinse off promptly after swimming. Outdoor pools during midday still expose you to UV radiation; swimming earlier or later minimises sun damage.

Walking

Lower intensity means less heat generation, making walking more heat-tolerant than running. Early morning walks provide exercise with minimal risk. Seek shaded routes through parks or tree-lined streets.

Walking in shopping malls offers air-conditioned exercise without gym memberships. Many malls open early specifically for mall walkers.

Indoor Cycling and Gym Equipment

Stationary bikes, ellipticals, and treadmills in air-conditioned facilities allow high-intensity exercise without heat concerns. Many gyms offer classes that provide motivation and structure.

Yoga and Indoor Classes

Yoga, pilates, and similar activities in ventilated indoor spaces provide flexibility and strength benefits with minimal heat stress. Note: "hot yoga" intentionally adds heat stress—proceed cautiously and consider whether this is appropriate in an already-hot climate.

Clothing and Gear

Fabric choices: Lightweight, loose-fitting, moisture-wicking synthetic fabrics outperform cotton, which absorbs sweat and stays wet. Light colours reflect heat better than dark colours.

Sun protection: A hat with brim protects your face and neck. Sunglasses with UV protection prevent eye damage. Apply water-resistant sunscreen to exposed skin 30 minutes before exercise.

Footwear: Well-ventilated shoes with moisture-wicking socks prevent blisters from sweaty feet. Some people exercise in sandals or barefoot where terrain permits.

Recognising Heat Illness

Heat Cramps

Painful muscle spasms, usually in legs or abdomen, often occurring after exercise. Caused by electrolyte imbalances from sweating. Treatment: stop activity, stretch gently, drink electrolyte-containing fluids. Prevention: adequate pre-exercise hydration and electrolyte replacement.

Heat Exhaustion

Symptoms: heavy sweating, weakness, cold or clammy skin, nausea or vomiting, dizziness, headache, fainting. Body temperature may be elevated but below 40°C.

Treatment: stop exercise immediately, move to cool area, lie down with legs elevated, remove excess clothing, apply cool water to skin (especially neck, armpits, groin), drink cool fluids if conscious and not vomiting. Seek medical attention if symptoms do not improve within 30 minutes.

Heat Stroke

Medical emergency. Symptoms: body temperature above 40°C, hot dry skin (sweating may have stopped), rapid strong pulse, confusion, altered consciousness, possible seizures.

Treatment: call emergency services immediately. While waiting, cool the person aggressively—cold water immersion is ideal, or apply ice packs to neck, armpits, and groin while fanning wet skin. Do not give fluids to unconscious person.

GLP-1 Medications and Heat Exercise

GLP-1 medications do not directly affect heat tolerance, but two considerations apply:

Gastrointestinal effects: If you experience nausea as a medication side effect, exercise in heat may worsen it. Exercise during your best-feeling times of day, and ensure you are well-hydrated before starting.

Reduced eating: If medication significantly reduces your food intake, ensure you have adequate fuel for exercise. A small carbohydrate snack 30-60 minutes before activity provides energy without requiring large volume.