Yikes, I'm thinking it must be off. My Polar chest strap is the only monitor that hasn't messed up from sweat. Wrist ones don't work for me. What is your normal average? At 183BPM, it gets hard to say more than a word or two. My wife will be next to me and tries to ask me a question when mine is upper 170s. I just turn to her with a "are you serious?" look. lol