Grouping young tennis players according to their physical maturity rather than their chronological age could help us develop tennis champions, suggests new research. Boys and girls vary in their rates of growth and maturity during adolescence. Those who mature early are taller, quicker and stronger, giving them a significant advantage over those maturing late. “Tennis is a sport that favours youth who are taller and mature earlier than their peers. Our data show that this selection bias impacts girls from the age of 10 and boys from the age of 12,” said a senior lecturer.