Here is an important article from Dr. Gordon Blackburn (Director of Cardiac Rehabilitation, Preventive Cardiology and Rehabilitation Program) at the Cleveland Clinic.
Exercising in the summer should be approached with some caution and planning
The added thermal load of the bright, warm sunshine also increases the stress on the heart, especially during activity. As the heart works to provide blood and oxygen to the exercising muscles, it must also shunt blood the skin where it can be cooled by the evaporation of our sweat. In addition, for every degree the body’s internal temperature rises the heart beats approximately 10 bpm faster. Exercise plus higher body temperatures and the added work of shunting blood for cooling can dramatically increase the stress on the heart during an exercise session in the heat of summer.
When exercising in the summer, it is wise to exercise in the cooler morning or evening hours to minimize the thermal stress. On hot, humid days it is best to slow your normal exercise pace too. Monitoring of your exercise heart rate and staying within the ranges prescribed by your exercise physiologist or rehabilitation staff will help you adjust your exercise level for the added thermal load and avoid overtaxing the heart. If the temperature is above 80° F and the humidity above 80%, it’s best to postpone outside activity until things cool off.
If your exercise session will be longer than 30 minutes, maintenance of hydration (fluid) is also important. Drink 8 – 12 oz. of water 20 – 30 minutes prior to exercise plus 6 –10 oz. additional every 30 minutes of exercise to help prevent dehydration. For most individuals, water is an acceptable fluid replacement. Unless your exercise sessions exceed an hour and your fluid and electrolyte loss is extensive and chronic, sports drinks add unnecessary sodium and calories.
Remember too to dress for the temperature and the activity. Rubber suits or long sleeved sweat-suits, that prevent evaporation of sweat, interfere with the body’s ability to cool itself and can raise body temperatures to dangerously high levels. Wear loose fitting cotton t-shirts, shorts and a brimmed hat when exercising outside in the summer.
Be heart-smart, stay active and reap the benefits of regular exercise all year round.