Gotta Have Heart! - Patricia T. Tanenbaum

Eight-year-old Ella Riley doesn't like running in PE. The other kids call her Slo-Mo Ella. She's always the last one to finish laps around the track.

But now, with the help of her teacher, Mrs. Rose, Ella's class is putting together a relay race called Running for Rio-all designed to help her younger brother, Rio, who is five years old and who needs surgery to repair his heart. She's grateful for the help and proud of her friends, but how can Slo-Mo Ella possibly join in running relay races? Ella's determined not to quit. With a little bit of help and a lot of hard work and commitment, she's going to do her best for her beloved little brother. Failure isn't an option.

In this children's story, a girl who struggles with running gets involved in a set of relay races to raise funds for her brother's heart surgery and relies on her determination to succeed.