Not Fun in the SummertimePosted by hclibrary on Jul 22, 2013 in Fitness, Health, Safety | 0 comments
The humidity and heat of summer in Columbia, Maryland, have descended, and I’ve been reminding myself to lift my feet when I walk. I first realized on day three of 90-plus temperatures that I was shuffling around as if I were wearing bedroom slippers. This was about the same time I felt I needed to concentrate on keeping my eyes open since my eyelids seemed to be at half-mast. Dazed and dragging, I found myself thinking about absolutely nothing and wondering why I just wanted to crawl back into bed.
Living in the DC-Baltimore corridor, I expect wet sauna conditions every year. I know I should wait to shower until after I walk the dog if I want to avoid feeling sweaty on my way to work. We don’t get many breezy, warm spring days before heavy, wet air envelops us, yet every summer is an adjustment. Friendly people ask, “How are you?” and rather than the bland, positive response that is expected, I want to answer, “Hot and tired.”
Although the connection between hot, humid conditions and mental fatigue are less easy to define, the physiological factors are well studied. In hotter temperatures, the body produces more sweat. As the body sweats, salt loss increases, which can lead to an electrolyte imbalance. Symptoms of electrolyte imbalance include fatigue, dizziness, muscle cramps, thirst, nausea, and headache. When the relative humidity rises, sweat evaporation slows down. The evaporation of perspiration has a cooling effect on the body, so in high humidity, body temperature rises. Our skin flushes in hot conditions because surface blood vessels are dilating to carry more blood and allow heat to escape from the body. Muscle fatigue occurs sooner in the heat because blood flow is being shifted away from the muscle and out to the skin to help lower body temperature.
So what can a person do to acclimate to the heat and get back in the groove? The National Institute for Occupation Safety and Health (NIOSH) has guidelines for workers in hot environments. Recommendations include wearing loose-fitting clothing in breathable fabrics, drinking more water, and taking additional breaks. They advise against drinking alcohol or beverages with high sugar or caffeine content. The NIOSH website also describes the symptoms of heat stress and its more serious consequences, heat stroke and heat exhaustion. Those who exercise regularly acclimate most quickly to a hotter environment, but studies have shown that this adaptation takes up to 14 days to complete. Even if I were to “prepare” for the heat by spending time in an actual sauna in advance of the onset of increased temperatures, it takes up to 5 days for the physiological adaptation to begin. These changes include salt conservation, resulting in less salty sweat; increased blood supply, resulting in a lowered heart rate; increased blood flow to the skin, resulting in increased heat dissipation; and lowered resting core body temperature. Longer, less intense exposure to heat seems to help athletes acclimate faster than shorter, more intense exposures. Gradually increasing time spent in the heat is helpful to limiting heat stress symptoms. Time spent in a cooler climate will require another period of acclimation when returning to the heat.
For now, I have summer resolutions. I will be careful to drink water throughout the day and wear cool, comfortable clothes. I will gradually increase the time I spend exercising in the heat. Most importantly perhaps, I will maintain a regular sleep-wake schedule so that I can reassure myself I have had enough sleep, even if it doesn’t always feel that way.