Welcome! › Forums › Running Forum › Heat and humidity: Physical impact or is it mostly mental? › Re: Significant physical impact
I would love to have a talk with this person who told you it’s all mental. This person obviously does not know a whole lot about physiology.
The fact is heat has a significant impact on our bodies. Among the physical changes, our body temperatures rise which creates inefficiency and our body sends more blood to our periphery to aid cooling which takes away from the amount of blood we can send to our working muscles. Of course dehydration is a factor but it is far from the only factor and dehydration is a factor to some extent regardless of weather.
I did a quick Google search and came across this page, which references many studies related to temperature and performance. Among the ones you might find interesting are the following: