Well since my max when I was in High School was 240 I'm not a believer in the formula. \

But back then in swimming we did pulse rate repeats and when your pulse was down to 150 it was time to go again.

I guess I should point out I'd hit the max after 100 yerd all out swims and that included finishing into the wall just as you would in a race, which meanst no breths when it seemed like your lungs would burst. Somehow I think that helps evevate heartrate as the body is trynig to get oxygen to the muscles.