Overheating and dehydration will negatively affect a driver's performance.
When a person starts to overheat, they can lose cognitive ability and reaction time; thus one would anticipate more driver errors and poorer performance.
When we start to get hot, our bodies perspire (sweat). As this perspiration on our skin evaporates, it helps to cool our bodies. In a race vehicle the driver is in a suit that does not allow the perspiration to evaporate. The body gets hotter and produces more sweat, which then starts to create dehydration.
A driver can quickly go from hot to spiralling into overheating and dehydration all which have been shown to negatively affect racing performance.
So the driver's body temperature is an important parameter to monitor.
We have discovered it is important to determine WHEN they are getting warmer. We found that in some instances the driver started to get hot before the track session even started! Once a driver starts to get warm, the heat never stops building. A few simple procedures to keep drivers cooler on the dummy grid could have excellent results.
CAMS (Confederation of Australian Motorsport) has put published a Hydration Awareness Program
to help combat the effects of overheating.