How many 10-year old athletes participated in the Gymnastics Men's Parallel Bars, Teams event?
10-year old athletes refer to competitor_id where age = 10; Gymnastics Men's Parallel Bars, Teams refer to event_name = 'Gymnastics Men''s Parallel Bars, Teams';
SELECT COUNT(T2.person_id) FROM competitor_event AS T1 INNER JOIN games_competitor AS T2 ON T1.competitor_id = T2.id INNER JOIN event AS T3 ON T1.event_id = T3.id WHERE T3.event_name LIKE 'Gymnastics Men%s Parallel Bars, Teams' AND T2.age = 10