Which start and call room rules are different for U16 athletes?

Athletics Canada varies the World Athletics technical rules for U16 athletes in two ways:

• Starting blocks: in races up to and including 400m (including the first leg of the 4x200m, medley relay and 4x400m), a crouch start and starting blocks are compulsory, except for U16, where blocks are optional.
• Call room: an athlete who is not in the call room at the published time is excluded from that event and shown as DNS. A U16 athlete is not excluded from the rest of the competition for a first violation: they are shown as DNS for that event and may compete in later events if they report on time. A second violation excludes the athlete from all remaining events, including relays.

False starts are not treated differently: any athlete responsible for a false start is disqualified by the Starter, including U16 (except in combined events).

Source: Athletics Canada Technical Rules, December 2025 (variations to World Athletics Technical Rules 4.5 and 16).