My 5-year-old daughter looks at me and asks in an unusually quiet voice: "Mummy, am I going to do that?"
We are standing in a basement gym in Daikanyama, rap music blaring, as adults with cartoon-perfect muscles crouch to the ground before springing to their feet and, with a sharp intake of breath, wobble poles of heavy weights above their heads.
"Um, no, I don't think so," I reply — although to be honest, I have no idea what exactly my daughters will be doing. We're waiting for a CrossFit Kids class to begin and — full disclosure — it's not only my children who are apparently out of their comfort zone, as it's not often that I find myself in the confines of a gym.