When its hot, we sweat. Blood flow to the skin shunts heat from the body’s core. We are cooled by evaporation of sweat. That is why downwind legs on hot days are so hellacious and the beats a relief. The cooling apparent wind does not change the fact that it is hot. The heat will wear you down.
Heat has the following effects on performance.
- Heat and Humidity increase sweating, thus dehydration, which decreases performance.
- Heat increases heart rate for a given task and decreases endurance during the day
- Heat increase metabolism: blood is shunted to the skin, so less energy is available for working muscles
- A body’s ability to tolerate heat are worsened by alchohol, drugs, betablockers, diuretics ( used for high blood pressure), antihistamines, and sedatives
Fluid Loss
In conditions of high heat and humidity, at high exertion levels, a body may lose up to a gallon of water an hour. Dinghy Sailing is stressful but its not climbing a peak on the Tour de France. That said consider this. A regular person cycling for about two hours, drinking two 16 oz bottles of water during the ride can expect to lose 3 lbs during the ride. The equivalent of three more 16oz bottle of water. An average tennis player, on a hot day, diligently drinking, can expect to lose 4-5 pounds of water. Finally, a sailor, in hot conditions, drinking diligently, can expect to lose 3-5 lbs of water during the day. The sensation of thirst means you are already dehydrated!
Heat Illnesses
Heat Cramps: Caused by an imbalance in the body’s fluids and electrolytes, and over exertion of muscles. Treatment: Fluids, salt, rest, and get to a cool place.
Heat Exhaustion: Weak rapid pulse, low blood pressure, headache, dizziness, and weakness. Sweating might be reduced. Body temp not elevated to dangerous levels. Treatment: Stop activity. Move to a cooler location. Sponge with cool water or ice. Take a cool shower or bath. Drink!
Exertional Heat Injury: Gooseflesh, sensation of chilling, throbbing headache, weakness, perhaps dry skin, vomiting, unsteady gait, incoherent speech, loss of consciousness. Treatment: Dial 911! Stop activity. Move to a cooler location. Sponge with cool water or ice. Cool shower or bath. Fans for cooling breeze. Drink!
Heat Stroke: Mental confusion, convulsions, loss of consciousness, increased body temp, sweating may have stopped, skin may feel hot. Untreated it can lead to death! Treatment: Dial 911! Emergency treatment required. Move indoors to air conditioning. Cold Shower or ice bath. Fans. Chilled IV fluids.
Heat Index
Humidity slows evaporation making temperatures seem hotter. Heat Index number of 90 to 105 are associated with heat cramps. Heat Index number of 105 to 130 indicate that heat cramps and heat exhaustion are likely and exertional heat injury and heat stroke are possible. 130 and above indicate that heat stroke is a definite risk, extreme caution required, and or don’t sail.
Coping with Heat and Humidity
Hydrate with fluids with electrolytes before, during, and after sailing
While sailing drink at timed intervals, say every 20 minutes
Sponge, spray, or pour water over neck, head, ears, clothing and body. Bring a spritz bottle on the boat for spraying face, neck and ears.
Wear light colored clothing, that is well ventilated. Loosen PFD.
Use suncreen but avoid sunscreens which are water proof non-breathing types.
Set Your Heat Limits
Check weather forecast for heat index for race day. You would not consider racing in 35 kts of wind, why would you sail in a heat index of 120. Hang a small thermometer on your PFD. Make an agreement in advance between captain and crew on the maximum limit for temperature for sailing. If the temp goes that high, sailing is over. Set a limit and respect the limit and live to sail another day.