We’re in the middle of a July heat wave that’s very typical of our Baltimore summer weather. When the temperatures reach the 90s, our deck thermometer can register 100 degrees or more by late afternoon. The heat is one thing; it’s the humidity that makes many Marylanders feel miserable. When I moved here in my early 20s, it was the first time I remember hearing “dew point” mentioned during a weather report. It’s the temperature that water vapor in the air becomes saturated and "dew" or water droplets begin to form.
The Baltimore Inner Harbor temperature is 97 degrees right now with a dew point of 68 degrees and a heat index of 102 degrees. Any time the dew point level is above the mid-60s there’s a high level of moisture in the air and it feels uncomfortable and sticky outside. Heat index, or how humans perceive temperature, can easily be calculated using air temperature and relative humidity...
The Baltimore Inner Harbor temperature is 97 degrees right now with a dew point of 68 degrees and a heat index of 102 degrees. Any time the dew point level is above the mid-60s there’s a high level of moisture in the air and it feels uncomfortable and sticky outside. Heat index, or how humans perceive temperature, can easily be calculated using air temperature and relative humidity...
When I began graduate studies at the University of Maryland during an August heat wave I was amazed at how physically active students were despite the intense heat and humidity. Although we’re all warm-weather creatures, living in Upstate New York didn’t prepare me for the sweltering College Park temperatures. I was grateful that our exercise physiology professors shared advice on how to acclimate to the hot weather environment. The basic approach is to get outside in the heat and be active.
With prolonged exposure to high temperatures I eventually became more efficient at keeping cool, although at times I still feel less able to handle the heat compared to native Marylanders. In fact natives in hot environments are observed to have more active sweat glands than those born in more temperate climates. At least I was moving in the right direction (i.e., south) because humans adapt easier to the heat than the cold. Now whenever I return to my childhood hometown for summertime family visits, the Syracuse heat and humidity are very tolerable.
You can think of skin as your body’s air conditioning unit. In hot environments, blood is rerouted to the skin for cooling. Your skin is a human organ that provides a wonderfully large surface area for heat exchange. The problem is that pumping extra blood to the skin’s surface makes the heart work harder and many people feel lethargic as a result.
We’re the only mammals that shed most of our heat by sweating. All fur-covered creatures cool themselves by panting which is rather limiting compared to having millions of sweat glands. Humans are the best air-cooled engines that ever evolved. Because we’re able to lose heat on the run through sweating, our ancestors survived by persistence hunting (i.e., chasing fur-covered animals to their demise who were unable to stop during the pursuit and cool themselves by panting).
If the body's temperature regulation mechanisms are not adjusted to the dual challenge of exercise and heat, heat-related illness can result. During exercise your body temperature increases due to the heat that muscles produce; sweating becomes the main protection against overheating. When sweat comes in contact with the skin it is cooled as the sweat evaporates. The cooled skin in turn serves to cool the blood that has been shunted from the core to the surface. This balance can become upset if your body gains too much heat from the environment, or is unable to evaporate enough sweat to get rid of the heat.
If the environmental temperature is higher than skin temperature (90 degrees F), heat is gained from the environment rather than lost to it. In addition, a high relative humidity reduces an individual's ability to evaporate sweat, making it more difficult to lose heat from the body. During exercise in a hot, humid environment, the evaporation of sweat becomes impaired, raising the exercise heart rate and lowering performance ability.
Acclimatization is the physiological and psychological adaptation to a new environment such as moving from a cool to a hot climate, or from sea level to high altitude. It can also describe the adjustments made from spring to summer when you're exposed to warmer temperatures, although this only occurs if you avoid continuous indoor air-conditioned environments.
Some simple steps you can take that will help you adapt to working out in a hot environment include:
During acclimatization, the sweat rate increases, nearly doubling its capacity. Sweating begins earlier and is more dilute (i.e., less salt is lost). Thus there is a greater need for fluid replacement during and after exercising in a hot environment and there's no need for salt tablets. The physiologic adjustments that occur during acclimatization allow a person to exercise with a lower core temperature and heart rate than the unacclimatized person. After returning to a more temperate environment, the major benefits of acclimatization are lost within 2-3 weeks. This detraining concept is described in my training principles blog post. The only way to tolerate the heat is to continue working out in it.
With prolonged exposure to high temperatures I eventually became more efficient at keeping cool, although at times I still feel less able to handle the heat compared to native Marylanders. In fact natives in hot environments are observed to have more active sweat glands than those born in more temperate climates. At least I was moving in the right direction (i.e., south) because humans adapt easier to the heat than the cold. Now whenever I return to my childhood hometown for summertime family visits, the Syracuse heat and humidity are very tolerable.
You can think of skin as your body’s air conditioning unit. In hot environments, blood is rerouted to the skin for cooling. Your skin is a human organ that provides a wonderfully large surface area for heat exchange. The problem is that pumping extra blood to the skin’s surface makes the heart work harder and many people feel lethargic as a result.
We’re the only mammals that shed most of our heat by sweating. All fur-covered creatures cool themselves by panting which is rather limiting compared to having millions of sweat glands. Humans are the best air-cooled engines that ever evolved. Because we’re able to lose heat on the run through sweating, our ancestors survived by persistence hunting (i.e., chasing fur-covered animals to their demise who were unable to stop during the pursuit and cool themselves by panting).
If the body's temperature regulation mechanisms are not adjusted to the dual challenge of exercise and heat, heat-related illness can result. During exercise your body temperature increases due to the heat that muscles produce; sweating becomes the main protection against overheating. When sweat comes in contact with the skin it is cooled as the sweat evaporates. The cooled skin in turn serves to cool the blood that has been shunted from the core to the surface. This balance can become upset if your body gains too much heat from the environment, or is unable to evaporate enough sweat to get rid of the heat.
If the environmental temperature is higher than skin temperature (90 degrees F), heat is gained from the environment rather than lost to it. In addition, a high relative humidity reduces an individual's ability to evaporate sweat, making it more difficult to lose heat from the body. During exercise in a hot, humid environment, the evaporation of sweat becomes impaired, raising the exercise heart rate and lowering performance ability.
Acclimatization is the physiological and psychological adaptation to a new environment such as moving from a cool to a hot climate, or from sea level to high altitude. It can also describe the adjustments made from spring to summer when you're exposed to warmer temperatures, although this only occurs if you avoid continuous indoor air-conditioned environments.
Some simple steps you can take that will help you adapt to working out in a hot environment include:
- Allowing yourself to adjust gradually to the heat and humidity by reducing the intensity of your workouts for several days. Monitor your target heart rate, it's the best indicator of combined heat and exercise load, and stay within your training zone.
- Reducing the duration of your first sessions to 15-20 minutes (or less depending on your current workout) and lengthen your workouts to normal over the next 7 to 10 sessions. Acclimatization requires 10-14 days in the hot environment, although 75% of the adaptation is believed to occur within the first 5 days.
- Drinking WATER before, during, and after exercise. Fluid intake is essential because the acclimatization process is delayed if you're not well hydrated.
- Easing into your fitness program during the coolest part of the day if you are just starting to workout, and gradually shifting to warmer temperature workouts.
During acclimatization, the sweat rate increases, nearly doubling its capacity. Sweating begins earlier and is more dilute (i.e., less salt is lost). Thus there is a greater need for fluid replacement during and after exercising in a hot environment and there's no need for salt tablets. The physiologic adjustments that occur during acclimatization allow a person to exercise with a lower core temperature and heart rate than the unacclimatized person. After returning to a more temperate environment, the major benefits of acclimatization are lost within 2-3 weeks. This detraining concept is described in my training principles blog post. The only way to tolerate the heat is to continue working out in it.
This morning I heard a meteorologist remind everyone that heat waves are the leading cause of death among U.S. natural disasters. The elderly are especially at risk due to underlying heart problems and medication side effects. Overweight and obese individuals are also compromised because added fat insulates their body and interferes with heat elimination. Extreme heat conditions are especially dangerous during power outages such as those experienced in Maryland last summer.
If you visit Baltimore's Inner Harbor during a heat wave, head over to the Walter Sondheim Fountain. It’s an easy way to cool off outdoors without visiting a swimming pool and it's great fun to see all of the spontaneous physical activity in and around the fountain:
If you visit Baltimore's Inner Harbor during a heat wave, head over to the Walter Sondheim Fountain. It’s an easy way to cool off outdoors without visiting a swimming pool and it's great fun to see all of the spontaneous physical activity in and around the fountain:
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