On those dark, early mornings (or even at night after a long day at the office) I need extra help to get me going. Starting is hard. And that’s just for me, a person who generally likes a good sweat session. But research shows that many people don’t like aspects of exercise, in part because so many of us feel intimidated in the gym. Another reason: Some people are genetically predisposed to get less pleasure from working out, as one study found . Even pro athletes feel this way sometimes. Tennis star Serena Williams once told Star Magazine : “I hate working out more than anything, but I have to — when I’m running, I think about how much I want to win. That’s the only thing that keeps me going.”