During the summer months, many people like to break free of their stuffy gym and take their training outdoors.
And while outdoor workouts can be a fun way to change up your training, exercising in the sun is uniquely challenging.
Unlike with gym workouts, when you exercise outdoors you may contend with direct sunlight and high temperatures (depending on where you live), which can become dangerous if you don’t take precautions.
In this article you’ll learn everything you need to know about outdoor exercise, so you can enjoy exercising in the heat safely.
How Does Exercising in the Heat Affect Your Body?
One of the main ways doing exercise in the heat impacts your body has to do with blood flow.
During exercise your cardiovascular system works hard to pump blood around your body, clear waste products from your muscles, and provide your muscles with oxygen. When you exercise in the heat, your body also has to shift blood flow toward the surface of your skin to cool your body down.
These competing demands place a unique strain on your cardiovascular system, which makes exercising in the heat feel considerably more challenging and hastens the point at which you feel exhausted (basically, you’ll feel a higher rating of perceived exertion, or RPE).
This is compounded by the fact your body also relies more heavily on glycogen (carbohydrates stored in your muscles) for fuel when you train in the heat, which causes a greater accumulation of waste products in your muscles that make it harder to continue exercising.
To deal with the increased blood flow demands in your muscles and near the surface of your skin, your body also reduces blood flow in your brain. When less oxygen makes its way to your brain, central neural drive (your central nervous system’s ability to send signals to your muscles) decreases, which impairs your ability to produce force. This is exacerbated by an increase in brain temperature, which inhibits motor activity (your ability to move).
What’s more, exercising in the heat causes mental fatigue, which limits your attention span and can decrease your resilience.
Basically, working out in high temps frazzles your nerves and causes you to flag faster than you would otherwise.
Find the Perfect Supplements for You in Just 60 Seconds
You don’t need supplements to build muscle, lose fat, and get healthy. But the right ones can help. Take this quiz to learn which ones are best for you.
Take the Quiz
Is Outdoor Exercise Dangerous?
Doing outdoor exercise in hot conditions can be dangerous because it increases your risk of suffering a heat-related illness.
Heat-related illness refers to a spectrum of conditions that occur when your body produces more heat than it dissipates. As body temperature increases, so too do the severity of the conditions you can experience.
Everyone has a different tolerance to heat, which means the risk of experiencing heat-related illness is different for everyone.
Mild symptoms include heavy sweating, general feelings of discomfort, fatigue, cramps, dizziness, nausea, headache, and weakness. Signs of more serious conditions such as heat exhaustion or heat stroke include confusion, altered speech, loss of consciousness, seizures, and very high body temperature.
If you want to do outdoor workouts, you must understand how well you tolerate heat and learn to recognize signs that you’re approaching your limit. You can acclimate to hotter conditions to some degree, but until you do, you shouldn’t push your boundaries.
Maintaining a healthy body weight can also help reduce your risk of heat-related illness, as the more fat you have, the harder it is for your body to release heat and cool itself. (Basically, as you strip away insulation—fat—your body is less susceptible to heat-related illness.)
How to Enjoy Outdoor Workouts Safely
1. Protect your skin
The most effective way to protect your skin from the sun’s rays is to wear clothing.
While that sounds bad, many brands now make lightweight clothing designed to reflect and block UV rays. Some companies also claim wearing their products will help you stay even cooler than you would without them (usually allegedly through “wicking” the sweat off your skin faster so it can more quickly evaporate).
Frankly, the scientific justification for this idea doesn’t hold water (harhar), since every layer of clothing will slow the evaporation of sweat on your skin. That said, this effect is miniscule and unlikely to make you feel much hotter, and is usually worth the added sun protection.
One good option is to pick up a pair of sun sleeves, like these or a thin long sleeve sun shirt, like this, and a lightweight baseball hat (which tend to stay on better than sun hats while working out). I also recommend lighter colors, which reflect heat better than darker colors.
If you really don’t want to wear long sleeves and a hat in the sun, sunscreen is your next best bet (especially in humid conditions where more clothing simply isn’t an option). Go for something with an SPF of about 30-to-50. While many companies will sell you 70+ SPF creams, you get rapidly diminishing returns with anything over 30. SPF 30 blocks nearly 97% of UVB radiation, SPF 50 blocks about 98%, and SPF 100 blocks about 99%, for instance.
Finally, limit your exposure to harsh sunlight. Try to avoid working out between 10 a.m. and 4 p.m. when the sun’s rays are at their strongest and most likely to do harm. If you have to train during this time, try to stay in the shade as much as possible.
Find the Best Diet for You in Just 60 Seconds
How many calories should you eat? What about “macros?” What foods should you eat? Take our 60-second quiz to get science-based answers to these questions and more.
Take the Quiz
2. Stay adequately hydrated (but don’t overhydrate)
Many people think you have to drink specially formulated drinks such as electrolytes to stay hydrated, especially when you exercise in the heat.
This simply isn’t true, though.
Electrolytes are completely unnecessary and forcing yourself to drink more than your thirst dictates can actually lead to overhydration, where your fluid intake dilutes the sodium concentration of your blood. There’s nothing wrong with drinking electrolytes if you like them, but they don’t help you hydrate more than plain water.
The best way to stay hydrated is to drink water, to thirst, and no more. Check out this article to learn why.
3. If you feel unwell, stop and cool down.
If you feel dizzy or sick, immediately reduce your exercise intensity or stop altogether.
To cool down . . .
- Get into a cooler environment, ideally an air-conditioned room, but if that’s not available, find shade.
- Cool the largest areas of your body, such as your torso or legs, by dowsing yourself with (or immersing yourself in) cold water and fanning. Despite having small surface areas, cooling your head, face, and neck can disproportionately affect body temperature because they contain a large number of thermoreceptors that help regulate body temperature.
- Drink iced water to thirst (don’t force yourself to chug fluids—it’s not helpful and can be harmful when taken to extremes).
+ Scientific References
- Rowell, L. B. (1974). Human cardiovascular adjustments to exercise and thermal stress. Physiological Reviews, 54(1), 75–159. https://doi.org/10.1152/PHYSREV.19126.96.36.199
- Charkoudian, N. (2010). Mechanisms and modifiers of reflex induced cutaneous vasodilation and vasoconstriction in humans. Journal of Applied Physiology (Bethesda, Md. : 1985), 109(4), 1221–1228. https://doi.org/10.1152/JAPPLPHYSIOL.00298.2010
- Johnson, J. M., & Kellogg, D. L. (2010). Local thermal control of the human cutaneous circulation. Journal of Applied Physiology (Bethesda, Md. : 1985), 109(4), 1229–1238. https://doi.org/10.1152/JAPPLPHYSIOL.00407.2010
- Kenney, W. L., Stanhewicz, A. E., Bruning, R. S., & Alexander, L. M. (2014). Blood pressure regulation III: what happens when one system must serve two masters: temperature and pressure regulation? European Journal of Applied Physiology, 114(3), 467–479. https://doi.org/10.1007/S00421-013-2652-5
- Galloway, S. D. R., & Maughan, R. J. (1997). Effects of ambient temperature on the capacity to perform prolonged cycle exercise in man. Medicine and Science in Sports and Exercise, 29(9), 1240–1249. https://doi.org/10.1097/00005768-199709000-00018
- Maughan, R. J., Otani, H., & Watson, P. (2012). Influence of relative humidity on prolonged exercise capacity in a warm environment. European Journal of Applied Physiology, 112(6), 2313–2321. https://doi.org/10.1007/S00421-011-2206-7
- Febbraio, M. A., Snow, R. J., Stathis, C. G., Hargreaves, M., & Carey, M. F. (1994). Effect of heat stress on muscle energy metabolism during exercise. Journal of Applied Physiology (Bethesda, Md. : 1985), 77(6), 2827–2831. https://doi.org/10.1152/JAPPL.19188.8.131.5227
- Febbraio, M. A., Carey, M. F., Snow, R. J., Stathis, C. G., & Hargreaves, M. (1996). Influence of elevated muscle temperature on metabolism during intense, dynamic exercise. The American Journal of Physiology, 271(5 Pt 2). https://doi.org/10.1152/AJPREGU.1996.271.5.R1251
- Fink, W. J., Costill, D. L., & Van Handel, P. J. (1975). Leg muscle metabolism during exercise in the heat and cold. European Journal of Applied Physiology and Occupational Physiology, 34(3), 183–190. https://doi.org/10.1007/BF00999931
- Parkin, J. M., Carey, M. F., Zhao, S., & Febbraio, M. A. (1999). Effect of ambient temperature on human skeletal muscle metabolism during fatiguing submaximal exercise. Journal of Applied Physiology (Bethesda, Md. : 1985), 86(3), 902–908. https://doi.org/10.1152/JAPPL.19184.108.40.2062
- Nybo, L., & Nielsen, B. (2001). Middle cerebral artery blood velocity is reduced with hyperthermia during prolonged exercise in humans. The Journal of Physiology, 534(Pt 1), 279–286. https://doi.org/10.1111/J.1469-7793.2001.T01-1-00279.X
- Nybo, L., & Rasmussen, P. (2007). Inadequate cerebral oxygen delivery and central fatigue during strenuous exercise. Exercise and Sport Sciences Reviews, 35(3), 110–118. https://doi.org/10.1097/JES.0B013E3180A031EC
- Nybo, L., & Nielsen, B. (2001). Hyperthermia and central fatigue during prolonged exercise in humans. Journal of Applied Physiology (Bethesda, Md. : 1985), 91(3), 1055–1060. https://doi.org/10.1152/JAPPL.2001.91.3.1055
- Périard, J. D., Christian, R. J., Knez, W. L., & Racinais, S. (2014). Voluntary muscle and motor cortical activation during progressive exercise and passively induced hyperthermia. Experimental Physiology, 99(1), 136–148. https://doi.org/10.1113/EXPPHYSIOL.2013.074583
- Morrison, S. A., Sleivert, G. G., & Cheung, S. S. (2006). Aerobic influence on neuromuscular function and tolerance during passive hyperthermia. Medicine and Science in Sports and Exercise, 38(10), 1754–1761. https://doi.org/10.1249/01.MSS.0000230120.83641.98
- Nielsen, B., & Nybo, L. (2003). Cerebral changes during exercise in the heat. Sports Medicine (Auckland, N.Z.), 33(1), 1–11. https://doi.org/10.2165/00007256-200333010-00001
- Nybo, L. (2012). Brain temperature and exercise performance. Experimental Physiology, 97(3), 333–339. https://doi.org/10.1113/EXPPHYSIOL.2011.062273
- Robert, G., & Hockey, J. (1997). Compensatory control in the regulation of human performance under stress and high workload; a cognitive-energetical framework. Biological Psychology, 45(1–3), 73–93. https://doi.org/10.1016/S0301-0511(96)05223-4
- Cabanac, M. (n.d.). Sensory pleasure optimizes muscular work – PubMed. Retrieved July 13, 2022, from https://pubmed.ncbi.nlm.nih.gov/16737087/
- Armstrong, L. E., Casa, D. J., Millard-Stafford, M., Moran, D. S., Pyne, S. W., & Roberts, W. O. (2007). American College of Sports Medicine position stand. Exertional heat illness during training and competition. Medicine and Science in Sports and Exercise, 39(3), 556–572. https://doi.org/10.1249/MSS.0B013E31802FA199
- Westwood, C. S., Fallowfield, J. L., Delves, S. K., Nunns, M., Ogden, H. B., & Layden, J. D. (2021). Individual risk factors associated with exertional heat illness: A systematic review. Experimental Physiology, 106(1), 191–199. https://doi.org/10.1113/EP088458
- Veltmeijer, M. T. W., Thijssen, D. H. J., Hopman, M. T. E., & Eijsvogels, T. M. H. (2015). Within-subject Variation of Thermoregulatory Responses during Repeated Exercise Bouts. International Journal of Sports Medicine, 36(8), 631–635. https://doi.org/10.1055/S-0034-1398676
- Racinais, S., Alonso, J. M., Coutts, A. J., Flouris, A. D., Girard, O., González-Alonso, J., Hausswirth, C., Jay, O., Lee, J. K. W., Mitchell, N., Nassis, G. P., Nybo, L., Pluim, B. M., Roelands, B., Sawka, M. N., Wingo, J., & Périard, J. D. (2015). Consensus Recommendations on Training and Competing in the Heat. Sports Medicine (Auckland, N.Z.), 45(7), 925–938. https://doi.org/10.1007/S40279-015-0343-6
- Linos, E., Keiser, E., Fu, T., Colditz, G., Chen, S., & Tang, J. Y. (2011). Hat, shade, long sleeves, or sunscreen? Rethinking US sun protection messages based on their relative effectiveness. Cancer Causes & Control : CCC, 22(7), 1067–1071. https://doi.org/10.1007/S10552-011-9780-1
- Guerra KC, & Crane JS. (n.d.). Sunburn – StatPearls – NCBI Bookshelf. Retrieved July 13, 2022, from https://www.ncbi.nlm.nih.gov/books/NBK534837/
- Noakes, T. (2002). Hyponatremia in distance runners: fluid and sodium balance during exercise. Current Sports Medicine Reports, 1(4), 197–207. https://doi.org/10.1249/00149619-200208000-00003
- Noakes, T. D., Sharwood, K., Speedy, D., Hew, T., Reid, S., Dugas, J., Almond, C., Wharam, P., & Weschler, L. (2005). Three independent biological mechanisms cause exercise-associated hyponatremia: evidence from 2,135 weighed competitive athletic performances. Proceedings of the National Academy of Sciences of the United States of America, 102(51), 18550–18555. https://doi.org/10.1073/PNAS.0509096102
- Bongers, C. C. W. G., Hopman, M. T. E., & Eijsvogels, T. M. H. (2017). Cooling interventions for athletes: An overview of effectiveness, physiological mechanisms, and practical considerations. Temperature (Austin, Tex.), 4(1), 60–78. https://doi.org/10.1080/23328940.2016.1277003
- Saunders, A. G., Dugas, J. P., Tucker, R., Lambert, M. I., & Noakes, T. D. (2005). The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment. Acta Physiologica Scandinavica, 183(3), 241–255. https://doi.org/10.1111/J.1365-201X.2004.01400.X
- Cotter, J. D., & Taylor, N. A. S. (2005). The distribution of cutaneous sudomotor and alliesthesial thermosensitivity in mildly heat-stressed humans: an open-loop approach. The Journal of Physiology, 565(Pt 1), 335. https://doi.org/10.1113/JPHYSIOL.2004.081562
- Tan, P. M. S., & Lee, J. K. W. (2015). The role of fluid temperature and form on endurance performance in the heat. Scandinavian Journal of Medicine & Science in Sports, 25 Suppl 1(S1), 39–51. https://doi.org/10.1111/SMS.12366