Researchers conducted a study to determine whether specialized athletic training (training in only 1 sport year-round) in youth athletes leads to increased injury. Injured athletes aged 7 to 18 years were recruited from 2 hospital-based sports medicine clinics and compared with healthy controls from affiliated primary care clinics undergoing sports physicals (2010-2013). The nurse asked participants about hours per week spent in organized sports, physical education class, and free play. Injury details were obtained from athlete surveys and electronic medical record.

What kind of research design was used in this study? is there a risk of bias?