I wonder could endorphins play their role. Production of endorphins are triggered by pain in the muscles when excercising, and athlete becomes accustomed to it

I wonder could endorphins play their role. Production of endorphins are triggered by pain in the muscles when excercising, and athlete becomes accustomed to it and (as I heard) even addicted to a physical activity. When athlete stops her sports career, physical activity levels suddenly drops, so no more cheap endorphins. At the same time she face a problem of resocialization into "normal" lifestyle. Patterns in her mind know the only way to be happy, to work hard, to excercise and to win. I suppose it can be hard, very hard. Especially a first year after retirement. But Twigg's case seems more complicated for me than that. Her lifestyle suspiciously in harmony with her mother kicked her out of home when she was just 16.