The thermal base layer - Your secret to staying warm while out riding your bike this winter

With the winter months now upon us morning rides are now being greeted with cold temperatures.  Cyclists have to contend with an even great threat to keeping warm than many other athletes manly due to two reasons. Much of our training is done out in the elements and this combined with the high speeds in which we travel at leads ourselves exposed to dangerous levels of wind chill.

Wind chill is defined as the "felt air temperature on exposed skin due to wind"... "The human body loses heat through convection, evaporation, conduction, and radiation. The rate of heat loss by a surface through convection depends on the wind speed above that surface: the faster the wind speed, the more readily the surface cools…"

When I use to ride in the 1980’s I would stick an old newspaper up the front of my cycling jersey to help reduce the effects of wind chill. These days the wind vest is a cycling garment that is commonly used to combat wind chill. The wind vest acts in the same way by producing a barrier and reduces the amount of air that penetrates the fabrics of our cycling clothing taking with it valuable trapped heat that is being used to keep us warm.  Like the wind vest, Windtex® has become a popular fabric for cycling. Windtex® is a membrane that is sewn into garments to help them become more wind proof.

But as the ambient temperatures drop below 10 degrees celsius a cycling jersey and a wind vest is not efficient enough to keep you warm while riding, especially downhill. Hence the need to a thermal base layer to help you maintain a trapped layer of warm air between you, your cycling jerseys and the cool environment.

Base layers are made out of several types of materials:

Cotton and nylon blend - Garments made from this material provide some degree of insulation and are commonly worn during the spring and autumn months. When wet it loses much of it's insulation properties. I use this garment when riding in temperatures above 12 degrees.

Polypropylene – Garments from this material exhibit much better insulation properties than the cotton and nylon counterparts. When wet it performs very well and it dries very quickly. Polypropylene is prone to becoming smelly from use due to the synthetic nature of it's fabric. Also, polypropylene seems to have a little bit of difficulty in managing fluctuations in temperature so you can suffer from the occasional heat flush when riding hard.

Merino Wool – Back in the 80’s I use to wear a “long john” woollen undergarment under my cycling jerseys during the cooler months. It was a little scratchy but kept me warm. Wool has come a long way since then with the introduction of merino wool. Merino wool is wool but without the scratch. Garments made from this material exhibit the best thermo regulation of all the fabrics. It is as warm or warmer than polypropylene but stays slightly warmer when wet. It however takes longer to dry out than polypropylene and doesn’t suffer from becoming smelly with use. I have been using merino wool since it came onto the market, not only for cycling, but for my outdoor adventures and as my casual wear. I prefer this garment over all others as a base layer when the temperature drops below 12 degrees.

Merino wool base layers can be brought from adventure shops. It is more expensive than polypropylene but costs around the same as a specialised cycling specific cotton and nylon blend garment brought from a cycling shop. It’s important to purchased one that is fitted. For cycling I purchase the women’s size to get a good “snug but not tight fit” as the men’s sizing is usually a loser fit. It's important to wash it on a wool wash with a degetent that is suitable for wool. If you do Merino wool will last you around five or more years.