Ears popping while running

Patient: My 16 year old healthy daughter is conditioning for her High School Field Hockey Team. She is running 7minute 30 second miles, calisthenics and sprints continuously for 2 hours each morning for the last two weeks. About three days ago she started complaining about her ears popping and very slight pain in her ears. She only has spring allergies and currently shows no signs of Sinus headache, pressure or infection. Why do her ears pop when she runs fast like that?