Colin Michie
Physically satisfying, a good sweat can be a pleasure after a workout, carnival or sauna. Gyms are putting up their temperatures and humidity – sizzling spin classes, hot Pilates, warm barre and hot, humid Bikram yoga – all to tempt clients into sweating more. Sweaty exercise is now another goal in athletic pursuits!
The body supports sweating by increasing the blood supply to the skin and its various glands. As you perspire, your heart and breathing rates rise; metabolic rates go up. All those microscopic powerhouses, the mitochondria, work harder and faster at higher temperatures, too, whether you are training or relaxing in a sauna. Sweat evaporates on the skin to cool us.
For millennia, Scandinavians have used saunas for relaxation, family gatherings, and healing. Spas are a mainstay of health resorts, where their warm waters, sometimes volcanic and full of sulphur, bring relief to painful joints, injuries, inflammation or poor circulation. Wellbeing from sauna heat extends to the heart, blood vessels and their linings. Heat can reduce blood pressures and risks from cardiovascular diseases. Sweating may help some people with acne, eczema or psoriasis, although for others it can irritate.
Healers in the past used high temperatures to treat tumours that could be seen on the skin. This same process is used today in oncology units for many different tumours. Cancers may be sensitive to high temperatures or hyperthermia that disrupts their structures. Hyperthermia can be created inside tumour in clinics using ultrasound. This process can be targeted in a precise, focused way so as to involve only cancerous tissues making them more sensitive to chemotherapy, radiotherapy and immunotherapies.
Dealing with heat is not the same for everyone. Each of us has differing numbers and types of sweat glands. Most sweat comes from 2-5 million eccrine glands. These secrete 99% water. Smaller numbers of apocrine sweat glands in the armpits and groin produce a different soup of secretions that include compounds that evaporate and cause some of our body odour. Apocrine glands respond to emotional or intimate situations, such as fear or happiness. This means they can share communications between us and others close by, sometimes subconsciously.
A third group of skin glands lubricate hair follicles with lipids and oils – the sebum glands. Their products increase with heat so as to moisturise and protect warm skin, adding a healthy glow, and some personalised odours too. Sweat is individualised and distinct to each of us. Forensic measurements can detect traces of metabolites, such as sugar and urea in sweat, and so may be used to identify our personal patterns of metabolites in the sweat of our fingerprints.
Sweating is not a route for getting rid of toxins because most of these are passed out in urine. Sweat rates vary depending on activity levels. Most sports (and saunas) cause sweating to increase to about a litre an hour, losing about a gram of sodium per litre (not a great deal). These are likely to go up further in endurance competitions or sports performed at high temperatures.
Should your temperature rise over 40 degrees, there is a risk of heatstroke. This is a life-threatening condition that can injure the kidneys, liver, brain (with confusion, seizures, coma) and the coagulation system. To head off heatstroke, you must keep hydrated, reduce physical activity and shelter from heat sources. A fan helps sweat evaporate from the skin until the room thermometer reads over 45 degrees. At that point, it is more effective to douse much of your skin with cool water, take foot baths in water of about 20 degrees, or indulge in a total body ice bath. Crushed ice in a damp towel applied to the chest, as well as cold drinks, are useful short-term approaches.
Heat can become an occupational or health hazard. This is an increasingly common situation as the planet warms. Last year (2024) was the warmest year on record, with an average global temperature 1.55°C above preindustrial levels. Extreme heat events are more frequent causes of death than the cold or other climatic disasters. Deaths are most common in those over 65 years with cardiovascular disease, particularly in marginalised communities.
Careful urban building and garden designs can reduce high temperatures in our environments. These strategies are particularly important to the elderly, in workplaces and schools. Individual cooling and the use of air conditioning where possible will improve safety and productivity. Mass gatherings require careful planning, with provisions of water and shade. At a recent T20 Cricket World Cup, 22 spectators were treated for heatstroke. In April this year, two athletes suffered heatstroke in Guadeloupe. Within our communities, it would be wise to find ways to support the elderly in particular during a heatwave. We are all likely to sweat more in the future, outside any gym!
Sources: nhs.uk/conditions/heat-exhaustion-heatstroke ~ who.int/news-room/fact-sheets/detail/climate-change-heat-and-health
