As the weather heats up, you may find the same jog that was comfortable outdoors a few weeks ago now leaves you drenched in sweat.<\/p>\n
Sweating a lot can mean you\u2019re working hard, but sweat alone isn\u2019t necessarily a great indicator of workout intensity, said Mindy Millard-Stafford, an exercise physiologist. \u201cYou can\u2019t really compare one person\u2019s sweat rate to another and say, \u2018this person worked harder\u2019,\u201d she said.<\/p>\n
But understanding how much you sweat can help you stay hydrated and safe while working out in warmer conditions. We asked experts what to watch out for.<\/p>\n
Sweating cools you down<\/p>\n
Sweating is your body\u2019s way of trying to keep your temperature under control, said Dr Michael Fredericson, a sports medicine physician at Stanford University. When you exercise, or when it\u2019s hot outside, your brain sends chemical signals to your body that cause your sweat glands to produce and release sweat, which helps dissipate heat as it evaporates.<\/p>\n
When you sweat, you lose water and electrolytes. Studies have found that many athletes produce more than a litre of sweat per hour, particularly if it\u2019s very hot or during intense workouts. You may lose up to 2-6 per cent of your body weight if you\u2019re exercising for a long time. At about 2 per cent loss, both athletic and cognitive performance start to decline.<\/p>\n
How much you sweat<\/p>\n
In general, the more intense your workout is, the more your core temperature increases and the more you sweat. But sweat rates and even salt concentrations vary based on your genetics and other factors. \u201cEven among serious athletes, no two people sweat the same,\u201d Fredericson said.<\/p>\n
How much you sweat also depends on your clothing and the humidity, temperature, wind speed and strength of the sun in your environment. You will probably sweat more in a hot, humid spin class than you would biking outdoors in the shade, for example, but that doesn\u2019t necessarily mean you\u2019re working harder. Although you sweat more initially when it\u2019s humid, Millard-Stafford said, at some point you may sweat less because your skin is wet.<\/p>\n
If you work out consistently in the heat or improve your aerobic fitness, your sweating response will generally become more efficient. W Larry Kenney, a physiologist, said that as your body acclimates, you start to sweat sooner into a workout. Your sweat glands adapt to produce sweat that is diluted and evaporates more easily. Sweat can appear across more of your body, on your arms and legs rather than just your face, chest and back, he said.<\/p>\n
Conversely, as you age, sweat covers less of your body and each sweat gland produces less sweat. But even in older age, sweat rates vary and can be improved by acclimating to the heat or building your aerobic fitness, Kenney said.<\/p>\n
Sweating safely<\/p>\n
If you\u2019re exercising in a hotter environment than usual, be prepared to stop if you notice dizziness, headaches, an inability to urinate, nausea or chills, which can all be symptoms of heat exhaustion. You should also stop and seek emergency medical attention if you experience confusion, which can signal heat stroke.<\/p>\n
The American College of Sports Medicine recommends hydrating before starting a workout, which can mean consuming fluids several hours before exercise. During your workout, some experts recommend simply drinking when you\u2019re thirsty, but thirst can be delayed until after you\u2019ve already lost about 2 per cent of your body mass in fluid, and can be particularly delayed in older adults.<\/p>\n
Floris Wardenaar, a sports scientist who studies hydration and thermoregulation at the College of Health Solutions at Arizona State University, said it can be difficult to estimate how much fluid you lose during exercise. Weighing yourself before and after a workout can give you an idea. If you\u2019re 1lb lighter, for example, you should aim to drink about 3 cups of fluid to rehydrate, ideally over time rather than all at once. You can also check the colour of your urine, which should be closer to pale lemonade than straw when you\u2019re hydrated.<\/p>\n
In extreme cases, dehydration can decrease your blood pressure and blood flow to the heart, said Dr Sean Swearingen, a sports cardiologist. (Conversely, drinking too much can dilute the sodium in your blood and lead to a dangerous condition called hyponatremia, which is rare but can be a risk if you\u2019re exercising for a long time and replacing more fluid than you lose.)<\/p>\n
Your heart rate is typically a better gauge of intensity than sweating, and will generally be higher during exercise in warmer conditions. To avoid pushing yourself too hard, Swearingen recommended matching your heart rate to a typical workout, even if that means cutting back on pace or distance in the heat.<\/p>\n