Hot Weather Training

The summer months are upon us, energy levels are high, daylight hours are long.  This is the time for walking relays, downtown races and other outdoor activities. But this is also the time for heat, which can get you into trouble if you are not careful. Walkers and runners, especially enthusiastic novices, are particularly vulnerable to heat illness. Participants may attempt to finish an event by exceeding their training levels, or walking/running too fast for their level of fitness.  Heat and humidity put extra stress on the body during a workout. See heat index chart chart

During an exotic fitness travel, muscle activity produces heat which raises your body temperature.  As the body temperature rises, blood flows to the surface capillaries of the skin to release the heat.  The primary means for the body to cool during exercise is perspiration (“sweat”) and evaporation of perspiration. The amount of evaporation and heat loss depend on the air temperature, humidity, and wind speed. When humidity is high and the air is still, evaporation will diminish or cease completely.

Your heart rate increases as the heart must beat harder in an attempt to provide blood to both the skin surface and the exercising muscles.  Another factor affecting heart rate is the loss of water through your sweat glands. As the blood volume decreases, the heart has less blood to work with which forces it to beat harder still.
Anyone who exercises in the heat runs the risk for heat illness. Injuries from heat occur in three forms, heat cramps, heat exhaustion, and heat stroke.
Heat cramps.  The mildest heat illness occurs during or after strenuous physical activity. This disorder is characterized by painful muscle spasm affecting those muscles worked the hardest.  Treatment, usually, consist of drinking a commercially available electrolyte solution and massaging the affected muscles.
Heat exhaustion.  The most common heat illness for athletes. The primary cause is dehydration. The symptoms include sweating profusely, chills, light-headedness, dizziness, headache, and nausea. Other signs are decreased coordination and staggering, tachycardia (heart rate more than 100) and fainting. Treatment should include rest and fluid replacement. Move the individual to a cool shaded area to reduce further sweating, administer fluids and seek medical advice.
Heat stroke.  The least common but most serious heat illness. A true medical emergency which may be fatal. It initially appears similar to heat exhaustion but progresses to manifest more serious symptoms: increased body temperature, disorientation, loss of consciousness and seizures. Treatment is rapid medical attention.

It is best to exercise during the coolest part of the day. This is usually early in the morning. Although the evening hours feel cooler, the ground continues to radiate heat. Walking in the early morning or evening will also help avoid direct sunlight, cancerous UV waves.  Fortunately,  as the need arises to compete in the heat,  your body can acclimate to the heat. Acclimatization refers to the body’s ability to adapt to heat stress over time, resulting in increased capacity to work in hot and/or humid conditions. Studies have shown that heat training increases both sweating and skin blood flow, lower temperature sweat point and a decreased sweat salt content. These adjustments or acclimatization usually take about 10 days of  heat training.  A safe method for acclimation when the heat arrives is to walk at an easy, comfortable pace for 25 to 30 minutes. Each following day, lengthen these easy walks by 7 to 14 minutes, until you can walk comfortably for 60 to 70 minutes. (Monitor your heart rate). Switch to walking more intensely (at about 85% of maximum heart rate) for 45 minutes for three or four days. Let your body be your guide. You should now be pretty well adapted to the heat. Remember to drink water before, during and after these workouts.
Guidelines to avoid the risk of heat stress injury:

  •  Avoid exercising in extreme heat and humidity.
  •  Wear sensible, porous, light-colored, loose-fitting clothing while exercising in the heat.
  •  Train for competition in heat by acclimating slowly, increasing intensity and duration of exercise over eight to ten days. Gradually building up tolerance for walking in warmer weather.
  • Maintain a high level of fitness and don’t overestimate your level of fitness.
  • Hydrate. Drink adequate water before, during and for 24 hours after vigorous exercise. Drink fluid 30-45 minutes before exercise and then  every 10-15 minutes while exercising. After exercise drink more than you think you need. The thirst mechanism is a poor indicator of when your body needs fluids, especially as you age.
  • Recognize early symptoms of heat stress-dizziness, cramps, clammy skin, extreme weakness and don’t be too proud to quit if these should occur.
  • Watch your health. Make sure you are aware of both medical conditions and medications that can affect your tolerance for exercise in the heat. The information provided is not intended as a substitute for the medical recommendations of physicians or other health-care providers.

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