I ran elementary school cross country for the first time when I was in third grade. The main thing I remember about our practices was that we spent a lot of time trying to touch our toes, and I was terrible at it. Years later, that would become a reassuring memory, because as a teen and adult runner I spent hours each week stretching and yet remained absurdly inflexible. I even have a kindergarten class photo where all the other kids are sitting happily cross-legged while I’m clearly uncomfortable, my knees nearly touching my chin. This is a fitness affliction shaped by my genetics, not a reflection of my laziness and hate of stretching.
So it’s no shock to me that a new study finds that, of all fitness domains, flexibility is the one most determined by your genes. The study, which is published in Medicine & Science in Sports & Exercise, uses data from twin pairs to tease out the respective contributions of genes and environment—talent and training, you might say—for fifteen different fitness tests. Overall, the results support the notion that picking your parents well is a crucial step on the road to athletic…
