I’m getting into HEMA (longsword fighting) and need advice on dealing with overheating

I’m doing really well. HEMA is really helping my body. But I overdid it around Halloween and everything is flaring. Including the POTS. I’ve been to several classes and today was the first time I got overheated. My heart rate went out of control and I started to feel the pre-syncope. I couldn’t get the mask off fast enough. My sparring partner noticed too before I said anything. Everyone was very cool about it thankfully, and just let me do my thing (while demonstrating stuff so I didn’t miss out), it wasn’t a big deal to my classmates or instructor which helped a lot tbh.

But I used to ride horses competitively and I’d like to be able to compete with HEMA someday. I’ve been unable to ride due to my health, because of the heat issue. But I’m determined to do HEMA. I love it so much already.

For tournaments or sparring with steel you wear the mask, plastic throat, shoulder and chest protection. Shin pads. And a very thickly padded jacket overtop to protect you. So it wouldn’t be something feasible to wear unless I figured out how to deal with it.