But at the senior or adult-sports level, the impacts of specialisation flip-flopped, the data showed. (Most senior athletes are in their 20s or 30s, although each sport sets its own age cut-off for junior and senior divisions.) The world’s best adult athletes, including Olympic and world champions, typically took up competitive sports of any kind a year or two later than other players, and practiced fewer hours throughout their careers. Most also dabbled with multiple sports, usually three or four a year, often not settling on a primary activity until their mid-teens or so, several years after most of their later competitors. And few garnered much immediate attention or acclaim from coaches and officials, rarely joining select teams at the start of their careers.