Ok so I had a vague idea of the answer but I went and looked it up to get the official wording and check I'm not spreading misinformation IASF split their countries in to "season 1" or "season 2" countries depending on when their competition season runs, so Canada is a season 1 country and the UK is a season 2. For season 2 countries, a minimum of 50% of the team must have been registered on the team during the season where the bid was won. From the official guidance "A minimum of 50% of the athletes participating on a team at The IASF Worlds must be a registered member of that team’s gym during the competition season in which the bid was received. On The IASF Cheerleading Worlds Roster, each athlete’s name of the 50% will have to be identified as an original participant of the team who competed on the floor where the bid was received, a substitute or an alternate. Names on the team rosters will be verified by the event producer who awarded the Worlds bid" There are a few competitions earlier in the season so teams usually start training around August/September time and you'd expect the Worlds teams to be putting out their Worlds ready routines at the competitions in February/March. Some of the Worlds teams might start training earlier than others but I wouldn't know. Most teams will only have competed their routines a handful of times before Worlds. The bid giving events in the UK take place in March, May, June and July.