Dr Sunita Kumari & Miss Layba Noor
People are gradually becoming more aware of the health benefits of exercise and agrowing number of people from all age groups are partaking in different types of exercise programs to improve their physical fitness.For those living in places that undergo seasonal climate changes, exercising outdoors can be particularly dangerous during the transition from spring to summer.In hot, humid summers, it becomes mandatory to modify the exercise intensity until the participating individual gradually adjusts to changed environmental conditions, else the participating individuals and even athletes may suffer from exertional heat illnesses due to long-duration or high-intensity workouts, and the result may be withdrawal from the workout or collapse during or soon after the workout. The present article is intended to reduce the morbidity and mortality of exertional heat-related illnesses during intense workouts.
In a healthy state, the normal temperature of the human body at rest ranges between 97.0 to 100.0 degrees Fahrenheit (36.1 to 37.8 degrees Celsius), and fluctuations are less than 1.8 degrees Fahrenheit, which reflects the balance between heat loss and heat production. During intense exercise, the metabolic rate can rise beyond 20-25 times the normal resting level, and consequently, there can be an increase in the core body temperature by about one degree C every 5 minutes.A hot, humid environment further accentuates the risk of an increase in core body temperature, which can be life-threatening in case the fluctuation is more than 1.8 degrees Fahrenheit.
The spectrum of heat-related illnesses includes, Heat rash and oedema,Heat Syncope,Heat Cramps, Heat Exhaustionand Heat Stroke.The most serious heat-related illnessis Heat Strokewhere core body temperaturerises beyond 104 degrees F with altered sensorium such as irritability, confusion,seizures and loss of consciousness. Exertional heat stroke can develop in a few hours. An important feature is the absence of sweating as because of markedly elevated body temperature, thermoregulatory mechanisms stop functioningand cannot initiate heat-loss mechanisms.The rate of metabolism increases as higher temperatures speed up the rate of all chemical reactions and the result is even greater heat production. Heat stroke is rapidly fatal if untreated. Even with treatment, the mortality rate is high. The rate of permanent disability in survivors is also high because of irreversible damage caused by the high internal heat.One more important thing is that althoughabsence of sweating is a sign of heat stroke, butinathletes, presence of sweating does not rule out stroke.Even non-exertional heat stroke may occur during prolonged, stifling heat waves in elderly and otherwise unwell individuals. In that case it tends to develop slowly over days.
How does sweating work?
It is not the wetness of the sweat that makes us cool but cooling occurs when sweat evaporates off the skin and carries away heat with it.In winters when body temperature is more than the environmental temperature body loses heat by conduction, convection, radiation and evaporation. But during summers when environmental temperature is greater than the body temperature, evaporation is the only means to remove extra heat.In dry summers, sweat evaporates fast and brings out a cooling effect. Therefore, comparatively lesser sweating is required to maintain normal body temperature. But in humid summers, evaporation of sweat occurs more slowly or sometimes may even stop as the surrounding air already contains a lot of moisture. Therefore, under such conditions body tries to get rid of extra heat by sweating even more. In an adult man, about 60% of body weight is water, out of which only 10% circulates in the bloodstream and can be excreted out through sweating. Intense workout in hot humid conditions can make us sweat up to three litres which is almost equivalent to all the water present in the blood stream.The person loses excessive body water through sweating, feels drenched and uncomfortably hot and becomes dehydrated. In that case in order to replace this lost water from blood stream body draws water from adjacent tissues or uses fluids that we drink during and after the exercise.At this time body struggles with three challenges, increased core body temperature, maintaining body temperature against the higher environmental temperature and decreased cooling efficiency of sweat due to high humidity.
Recommendations for Athletes and Exercise Partakers
Ensure acclimatization: Before stepping into intense workouts and competing in hot humid environments, acclimatization is recommended for umpires, volunteers, players, athletes and other officials especially if they are coming from temperate climate to hot humid conditions for competition. Repeated exercise training in hot humid conditions induces certain changes in the body that leads toenhancement of heat tolerance leading to improvement of performance under the similar environmental conditions.Composition of sweat also differs in trainedversus untrained people. After heat acclimatization, body retains more salt and sweat is more dilute. Heat acclimatization is an important and most effective performance enhancement approach, but despite the well-known benefits, it is an underutilized pre-competition intervention in athletes. Below are few suggestions regarding heat acclimatization:
- One hour acclimatization activity per day for one to two weeks with at least four sessions per week provides significant preparation for safe workout in the heat.Two sessions per week are recommended to maintain the acclimatization changes.
- Preferred method is training in an atmospheresimilar to the competition. Alternatively other strategies like overdressed training, passive heat exposure that increase the core and skin temperature can be used.
- Complete the acclimatization processaround1 to 3 weeks before the competition.
- Restrict acclimatization decline by intermittent exercise and exposure to heat and also re-acclimatization is recommended with 2 to 4 consecutive days of exercise heat training just before the competition.
Stay hydrated: Drink sufficient fluids orally before, during and after the exercise and replenish your electrolytes also. Hourly consumption of 16 to 24 hourly consumption of water is recommended but during endurance exercise in hot humid atmosphere fluids consumption needs to be increased to thrice. Fluid intake should be customized depending upon fluid losses (1 litre of fluid loss equals 1 kilogram weight loss). Light- or pale-yellow coloured urine indicates adequate hydration. Caffeine, alcohol and sugar containing drinks should be avoided as they can aggravate dehydration. Prefer low calorie options.
Wear appropriate clothing and use sunscreens regularly: Choose clothes that enhance sweat evaporation. Lose-fitting, light coloured wicking fabrics made up of natural fibres are good choice. Use sunscreen (SPF 30 or higher),sunglasses and hat if possible. Avoid direct sunlight. Protective clothing (leathers in mountain biking and motorcycling, protective equipment for hocky goalkeepers, softball and baseball umpires) should be worn only while training and competing. Immediately remove non-breathable clothing in case any participant or official feels unwell and start cooling the body.
Adopt cooling strategies: Listen to your body and reduce workout intensity in high temperatures. Prefer shady areas while walking. Cooling strategies include external (water immersion, fanning, application of iced garments) and internal (intake of cold water or ice-slurry) methods. Depending upon the type of activity, cooling strategies should be tested and customized during training sessions to minimize disruption to the athletes.
Recommendations for event organizers: Avoid the hottest part of the day. Ensure an adequate supply of palatable fluids. Encourage proactive monitoring of hydration status and behaviour of athletes. Beware of signs of heat illnesses.
Treatment of heat illnesses
The first critical step is to diagnose that the individual is in trouble. Heat illness may progress if this step is missed. The goal is to bring down core body temperature toan acceptable level (below 100.4 degrees F) as quickly as possible. Move the player into a shaded area away from direct sunlight, remove extra clothing and immediately start cooling the bodyvia cool spray, ventilation, wrapping in cold towels, applying ice packs and also make him ingest cold fluids or sports drink. Raise his legs above the heart level. Intravenous fluid therapy may be required in case he is not tolerating oral fluids. Altered sensorium indicates heatstroke and in that case the treatment strategy is altogether different and requires immediate medical attention with the aim of lowering body temperature below 104 degrees F within 30 minutes in order to protect the athlete’s brain and other vital organs. Immediately shift the patient to nearby hospital and meanwhile during the transit try to continue with the hydration and cooling of the body.
Return to play after exertional heat illness
After mild heat illness, athletes may return to play within 24 hours with adequate hydration. Prior to return to play, they should be evaluated by a physician. Recovery time mainly depends upon severity of illness. The athlete must be symptom-free, and laboratory tests should be normal. For successful and full participation after an exertional heat stroke, a gradual return-to-play strategy should be adapted under the direct supervision of an athletic trainer or physician.
(The Authors Dr. Sunita Kumari is an Assistant Professor in the Department of Physiology & Layba Noor is a second-semester MBBS student at AIIMS Vijaypur Jammu)