sport, too. The results show that something other than “the relative-age effect” – the greater maturity of those born early in the school year – is at work, especially as the fittest children were not the tallest or heaviest, he added. The authors believe that autumn-born children’s greater exposure over the summer months, towards the end of pregnancy, to vitamin D – the “sunshine vitamin” linked to a range of health benefits – is the most likely explanation. “Seasonal differences in intrauterine vitamin D concentrations seem most plausible,” they say. John Steele, chief executive of the Youth Sport Trust, said the quality of a young person’s introduction to PE and sport at school can be “a major factor” in their sporting development. “Children that get a high-quality first experience, which develops their physical literacy, are those that will have greater agility, balance and coordination, and are more likely to develop an enjoyment of physical activity and excel in sport as they grow up”, he said. UK Sport could not say if a disproportionately high number of the 1,300 athletes across 47 sports it funds were born in November and October. Natalie Dunman, its head of performance pathways, said that, while the differences highlighted in the new findings were borne out by teenagers competing in junior-level competitions, they had disappeared by