Fitness is hugely important in motorsport. Even in a 15min clubbie saloon race you can experience extreme conditions, especially mid summer when its 30 degrees and you’ve sealed up all the windows for better aero. Keeping yourself fit can be the key to winning or loosing.
As you tire your concentration slips and that’s when your pace drops or mistakes happen.
I’m not advocating you train like an Olympic athlete, tailor your training to your racing: if you are driving an LMP at Le Mans then you will need to train harder than for a 15 minute clubbie saloon race.
A bit of a jog a couple of times a week and you will not only feel fresher in the car but you’ll save a couple of kilos too. How much does that carbon bonnet cost that’ll save you a couple of kilos?