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Advice from the experts: It's hotting up

Riding a Wattbike offers many advantages when compared to riding outdoors. You can cycle any time of the day, there’s no traffic and intervals can be performed with absolute precision. Further, with the advent of apps such as VirtuGO, you can team up with friends anywhere in the world and complete a training session; all from the relative comfort of your home.

However, that term ‘relative comfort’ is pointed at the one obvious disadvantage of training indoors: it’s hot. We all know the feeling of being covered in sweat from head-to-toe after riding inside. But sweat is just one by-product of a complex series of bodily processes that respond to exercising in a hot environment. Understanding some of the body’s other regulatory systems and their limits is a step in the right direction to making your next indoor workout more efficient and more comfortable. In this first part of a two-blog series, VirtuGO gave us their insight into why things heat up on the Wattbike.


To understand how a cyclist copes with training in a hot environment, it’s worthwhile looking at the limits of body temperature and how they are regulated under normal conditions. Not all areas of the body maintain the same temperature. Core temperature is kept at 37 degrees while skin temperature can be as low as 20 degrees if a cyclist has bare skin exposed in a cold room.

However while riding indoors the temperature inside muscles can reach as high as 41 degrees while core temperature will remain within tight limits and possibly only increase a degree or two. 

As the room you’re in gets hotter the longer you exercise, and the temperature inside exercising muscles increases, the brain detects this stress and sweat production is accelerated. Simultaneously, blood vessels in the skin dilate while blood flow is directed away from internal organs towards the skin. This heat that is carried by blood is what drives the evaporation of water released from sweat glands to achieve evaporative cooling. Think of this system as a slightly more sophisticated version of a car engine-cooling unit. The human heart replaces the pump, skin functions as the radiator and blood is the coolant.


Evaporative cooling is very important for cyclists when training outdoors. Holding threshold-level power for over an hour is common in elite riders under race conditions. However, when these same cyclists are required to exercise in a laboratory setting they are often surprised that they cannot perform at the same level. 

This is because the headwind generated on the road is continuously removing the air layer next to their skin, which in turn accelerates evaporative cooling. But when riding indoor this process is dramatically reduced and the heat loss from the rider is significantly less. The humidity inside a lab or your own indoor training space is also a factor in limiting performance. If humidity is 75% or higher the sweat coming off your skin will remain a liquid and drip onto the floor. In such cases sweating only causes dehydration and any evaporative cooling effect will be lost.

Find out more from the experts at VirtuGO in our next instalment. For more training insights, visit our blog.