Heroic abilities won't trigger when a copy of a spell is created on the stack or when a spell's targets are changed to include a creature with a heroic ability.

Heroic abilities will resolve before the spell that caused them to trigger.

Heroic abilities will trigger only once per spell, even if that spell targets the creature with the heroic ability multiple times.

Resolving Arena Athlete's ability after a creature has blocked won't remove the blocking creature from combat or cause the creature it blocked to become unblocked.