Overheating and dehydration can negatively affect performance.
When a person starts to overheat, they can lose cognitive ability and reaction time; thus one would anticipate more errors and poorer performance.
When we start to get hot, our bodies perspire. As this perspiration on our skin evaporates, it helps to cool us down. In a race, your clothing may not allow the perspiration to evaporate properly, so your body gets hotter and produces more sweat, which then starts to create dehydration. You can quickly go from hot to spiralling into overheating and dehydration, which have been shown to negatively affect performance.
Your body temperature is an easy parameter to monitor.
But it's important to determine WHEN you are getting warmer. We've observed that in some instances, athletes started getting hot before the race even launched! Once you start to get warm, the heat never stops building. Seeing the early warning signs can help you manage your temperature before it's too late.