Last week I shared a stage in Chicago with Michael Sokolove, the genial but sharp-eyed author of a compelling new book called Warrior Girls.It explores the same terrain that I look at in the Sports chapter of Under Presure, but in greater depth (it’s a whole book on the subject, after all) and with the focus on girls. Our insistence on treating children like professional athletes, with punishing training regimes, long seasons, win-at-all-costs competition and early specialization is taking a heavy toll, but in some ways the damage is worse for girls because their bodies are simply not as robust. Less testosterone means less muscle and more oestrogen means laxer ligaments. That makes girls more prone to chronic knee pain; shin splints; stress fractures; ankle sprains; concussions; hip and back pain. They are five times more likely than are boys to rupture an anterior cruciate ligament (ACL). Just look at the roll call of female athletes hobbled by over-training in their youth. Katharine Merry, the fastest girl in the world at 14, was laid low by a series of knee, achilles and foot injuries. Martina Hingis hit the pro tennis tour at 14 but was forced by foot and angle injuries to retire at 22. Foot trouble ended Anna Kournikova’s tennis career at the same age. Of course, sports are wonderful for girls and we should be encouraging more of them to take part. But this needs to be done in the right spirit – that means without turning sports into a fight to the death. Like boys, girls need to learn to push themselves hard without pushing themselves over the edge.