The inability to maintain core body temperature during prolonged exposure to wet and cool conditions can make a marathon uncomfortable and put you at risk of hypothermia. Remember that all rain starts as snow high up and is often still pretty cool water when it touches down, especially in winter. In my experience, wet days always lead to more medical encounters due to runners’ lowered body temperatures.
This all revolves around heat balance: Can you produce enough heat to keep your body temperature up when the conditions are ripe for body heat loss? In the heat, we rely on sweat evaporation to remove heat from the body. In cold, wet conditions, body heat can be rapidly transferred away from the body by conduction and convection into the surrounding air. This will be most noticeable if it is windy as you will experience the effects of “windchill” on top of the cooling rain water. And if you slow down or stop, you reduce your heat production. Heat production will also decrease as you run out of fuel to produce metabolic heat.
Clothing can make a difference. For cold and wet conditions, cotton is rotten. High-tech materials wick moisture away from your body and maintain a layer of air next to the skin to give an insulation layer and help preserve heat. So wearing the right clothes and appropriate number of layers can help. A hat and pair of gloves or mittens also helps preserve heat. Faster runners who will spend less time on the course, and therefore will experience less exposure to the elements and will maintain a higher body temperature may require less outerwear than someone who will be out there for four to six hours.
The finish line is always a bugger in a cool, wet race. As soon as you stop running, your heat production tails off rapidly. The cool air, continued rain, and wind start to take their toll. Your warm clothes are not sitting there waiting for you. This is where the “space blankets” play a role. Over the years, they have evolved from the silver Mylar or white plastic sheets to the product called Heatsheets. The technology behind this product is great for both hot and cold races as the silver side reflects heat. So on a cold or cold wet day, you put the silver side facing in toward your body – reflecting your body heat back toward you. An on a hot day the silver side is out – reflecting the sun’s heat away from you. It also acts as a windbreaker.
On a wet race day, your clothing bag should be packed to fit the conditions. Ideally, you want to find an area where you can take off your wet clothes, towel off, and change into dry clothes as soon as possible. If you can’t do that, putting on a fleece top and pants and a windproof outer shell over your race gear will draw the water and sweat away from your skin and provide air layers to allow your body heat to rewarm you. Fluids and carbohydrates will fuel the body to also help with heat production. Then you need to trek back to your lodging where you can dry off and warm up in a shower or bath before you change into dry clothing. If you are light headed or dizzy, the warm shower may not be advisable until you replace fluid volume losses and feel able to stand without feeling faint. Stopping for a warm beverage on the way to your hotel may help a bit, but the heat exchange to the body will be small from a cup of soup, coffee, or hot chocolate – getting into the dry warm space of the café may do more to help warm you.
When you are running, remember the volunteers who are also out in the elements for many hours helping improve your race experience.
