Heat, Humidity and Hydration

The main benefit of this switch to an evening race, is in relation to Heat & Humidity!

The average daytime temperature in Singapore in December, ranges from 25 to 34O Centigrade. The humidity can range from 60% to above 90%. The peak temperatures are usually in late morning to mid-afternoon, so an evening start will reduce the risk of heat related injuries. I said reduce, not eliminate as it is critically important to remember that a heat injury is still high-risk, as the temperature may still be higher than 30 CO with a high humidity level >90%.

One of the riskiest times for direct sun and heat exposure is before the race even begins. The time taken to reach the race venue, drop your bag at the bag drop facility and make your way to the start pens is during the late afternoon sun. Simple steps to reduce this risk include applying sunscreen, wearing a hat, using appropriate sportswear that is lightweight, made of a breathable fabric and by avoiding dark coloured clothing. During this immediate pre-race period it is important to maintain good hydration practices to avoid beginning the race in the dehydrated state. Drink small amounts of water to maintain hydration prior to the start.

During the race, listen to your body!

Once the race starts the main risk of you not safely finishing your race or achieving your goal, is probably related to a heat injury. As you run, your core temperature will naturally rise and you will begin to sweat to try to maintain your core body temperature in a safe zone. The main mechanism to dissipate heat is through evaporation of sweat form the surface of the skin. This is more difficult with higher humidity levels. As you continue to run your body will try to radiate and evaporate more heat by diverting blood flow to your skin and away from other essential areas. The blood flow will be prioritised and maintained to your heart, lungs and brain but may be diverted from your gastro-intestinal, urinary system and eventually your skin!

During the race, there are several cooling strategies that will help you to continue safely. Hydration is critical, so it is important to drink to thirst, with a combination of water and sports drinks (with carbohydrates/electrolytes). It is also critical not to over-hydrate as the risk of drinking too much water can lead to a low sodium level (hyponatraemia), which is also dangerous. Pouring cold water over your head and neck can also assist in cooling.

Recognising signs of early heat injuries is very important as this should prevent progression into a more dangerous heat exhaustion or heat stroke scenario.

The most common initial sign of an heat injury, is muscle cramping. If this happens, listen to your body.

Slow down, even if this means stopping to stretch, rehydrate slowly and to restart at a slower pace.

If it persists, then don’t be shy – ASK FOR HELP!

There are over 400 medical staff, including nurses, first aid officers, paramedics and doctors on duty along the course who are there for the sole purpose of your safety.

If they advise you to withdraw, this is for your safety, so please listen to them.

If you spot one of your fellow runners in difficulty, please take the time to check on them, assist them if needed, and alert the nearest medical team member who can provide appropriate treatment.

Once you cross the finish line, Congratulations and enjoy the moment!

Slow to a walk and try to keep slowly moving towards the athletes recovery area. Start slowly rehydrating with water, sports drinks and salty foods. Try to get into a cool area with some good air-flow or a breeze or ideally an air-conditioned environment to help you cool down.

If you don’t feel well, then let the medical team members at the finish line or at the athlete’s village area know!

Dr. Cormac O’Muircheartaigh

Chief Physician SCSM 2019

Specialist Sports Physician