Exercise in the good old summertime

By MORT MALKIN

Exercise—not too little and not too much—is a significant part of healthy lifestyle. Exercise as preventive medicine must be year round, not just during pleasant weather days of spring and autumn.

Exercise in summer bears potential risk factors, but sensible precautions will protect you from anything serious. Sweating, in and of itself, is not serious.

Lets review the threats of summer and the shields you can employ:

• Repeated exposure to the sun’s rays increases the risk of the three types of skin cancer: basal cell CA, epidermoid (squamous cell) CA and malignant melanoma. Basal cell CA is a slow growing, locally invasive tumor that doesn’t spread to other parts of the body. Epidermoid CA grows faster and can spread to regional lymph glands and then to further sites. Malignant melanoma is very dangerous and can spread rapidly to distant parts of the body. It’s better to prevent skin cancers than to have to treat them.
• Outdoor exercise can finesse this risk with the right timing—before 10:00 a.m. or after 4:00 p.m. When outdoors in the sun during high-risk times, use sun block, cover up with light colored clothing, and wear a broad-brimmed hat.
• The sun presents single-exposure risk as well—sunburn. The same precautions are in order. Water sports may be deceiving because we feel cool in or on the water. When swimming or snorkeling in tropical latitudes, its a good idea to wear a t-shirt and tights. Canoeists, kayakers and sailors are exposed to both the sun’s direct rays and the reflected rays from the water’s surface. Use extra vigilance.
• The temperature of the air, especially in this time of global heating, is also a single-time exposure risk. When exercising, body temperature rises. Our bodies rely on several physiological strategies to moderate temperature during exercise. Two principal mechanisms are: passing off some of the heat to the lower temperature surrounding air, and evaporating sweat from our skin to produce a cooling effect. A 98.6 degree day with close to 100 percent humidity eliminates these protections. Runners, aerobic walkers, skaters and skiers (cross-country skis can be fitted with wheels for summer), should work out at cooler times of day, find a shaded track or trail, wear clothing made with breathable fabric and drink plenty of fluids. Cutting back on distance and pace also helps. Under adverse conditions, temperature can rise rapidly during exercise and reach dangerous levels. Body temperature of 103° to 104° is not uncommon. Body temperatures of 105° to 106° results in heat injury—heat exhaustion, heat stroke and perhaps brain damage. Heat injury may cause symptoms of confusion, cessation of sweating, dizziness, nausea, inability to walk a straight line and even unconsciousness—none of which can be mistaken for health and fitness.

One solution to the risks of summertime exercise is to work out in an air-conditioned gym. Yes, that avoids the usual risks, but it also avoids the benefits of sunlight: production of vitamin D from the skin, mood elevation and the stability of melatonin cycles. Regarding exercise effectiveness—motorized treadmills do not provide the resistance required for a high-grade aerobic effect and stationary bicycles are not weight bearing (on your feet). Working against the inertia of the earth is still the gold standard for aerobic exercise.

Rocking back and forth in a rocking chair on a shaded porch with a tall glass of iced tea (gin & tonic?) does not satisfy our body’s need for exercise. Summertime is not a time to stop exercising, just a time to be careful.

[Dr. Mort Malkin is a specialist in primary preventive medicine.]