Red rash above armpits after gymnastics rings exercises

sethbrandeis

I did a set of exercises on the gymnastics rings, which included inverted hangs into forward leaver, backward leaver, and then the move where one holds themselves up on the rings (palms pushing down, elbows/arms locked out).

I noticed there is a really red rash on the underside of my right arm. It looks like a bunch of crimson lines, like cracked ground. The left arm has a tiny bit but not as much as the right.

I have not felt any pain yet--what is this rash and should I be worried?