What's too much? It may be different for different women. If you are a hard-core exerciser and are still getting your period regularly, your exercise regimen is most likely not a problem, he says. But, Goldfarb adds, your menstrual period is not the first thing to go if you are exercising too heavily. "The first thing that happens is that you have a shorter second half of your cycle. You should have a period 14 days after you ovulate, but too much exercise can shorten this phase." This would be the first hint that you need to curtail your fitness regimen. He suggests tracking how long it takes you to get a period after you ovulate as the best way to know for sure.