Tightness right below sterum

When I play roller in 80 degree + weather after about 40 minutes in the net I start feeling uncomfortable and tight in the area right below my sterum. Either my C/A protector is too tight or I am just out of shape? When the weather is cooler I don't notice.

Dehydration is most likely one of the biggest issues here. I sweat 2-4 lbs off playing on ice. When you jump to 80+ degree weather your are going to really sweat more fluids then you can possibly bring in. This is one of the reasons I stopped playing roller years ago.

You're starting to cramp. Drink more water before during and after competition. Have a banana about an hour before playing. Chances are you also need to replace and restore your electrolyte balance. There are all sorts of drinks out there that can help you or you can mix up your own.

Ohh avoid overly sweet and caffeine laden sports drinks. They might give you more perceived energy but they dry you out faster. You lose water and may cramp sooner.

Other than that talk to a trainer or a doctor about it..