NEW YORK (Reuters Health) – The best strategy for keeping up your exercise routine as the temperature climbs is, in a nutshell, acclimatisation, the National Athletic Trainers' Association (NATA) advises.

On the first hot days of spring or summer, exercisers should cut back on the intensity of their outdoor workout, Brendon McDermott, an athletic trainer at the University of Connecticut, told Reuters Health. Once they've gotten used to the heat, they can gradually begin to exercise more strenuously. "Somebody who's in shape will acclimatise more easily," McDermott added in an interview. "But if somebody is in shape, it doesn't necessarily make them immune" to heat-related problems.

NATA urges proper hydration before and during outside activity, and says that dark urine is a quick indicator of dehydration. Not getting enough rest between bouts of exercise can increase the risk of conditions like heat exhaustion, McDermott noted, while new research shows that getting enough sleep is also key to coping with hot weather. Lack of sleep stresses the body's thermoregulatory systems, he explained, making it more difficult for people to handle the heat.

Heat exhaustion is the most common type of heat-related ailment that occurs among exercisers, he said, and it occurs when a person loses too much fluid or sodium in the heat. Symptoms of heat exhaustion include dizziness and loss of coordination; pale skin; profuse sweating; nausea, vomiting, stomach and intestinal cramps, and diarrhoea; and muscle cramps that don't go away.

Heat exhaustion can progress to exertional heat stroke, which can be fatal. People with symptoms of heat exhaustion should lie down with their feet up in a cool, shady spot and drink fluids.

The symptoms of exertional heat stroke are similar, but also include a very high body temperature (typically above 104 degrees F) and confusion, mental instability, or even irrational behaviour and combativeness. A person's heart rate and breathing may speed up, while their blood pressure can drop.

It's important to know that while heat exhaustion can precede exertional heat stroke, heat stroke can also occur on its own, McDermott said. Anyone suffering from heat stroke should undergo whole-body cooling immediately, ideally by immersion in cool water, and should receive emergency medical treatment, according to NATA. Listening to your body is just as important as paying attention to acclimatisation, advised McDermott. "If you're not feeling good and you feel as though you need a break or rest...do it."