The Control Group (CG) were healthy, had neither surgery/trauma in their lower extremities, nor history of hamstring injury, and there were no abnormal findings in their physical examination. The exclusion criteria included participants who: (1) had metal implants or pace makers, (2) weighted more than 200 kg (MRI table limitations), and (3) were unable to complete testing. In the Injured Group, patients were also excluded if their previous injury was originated from a non-muscular source (e.g., inguinal or femoral hernia, nerve entrapment, lumbosacral pathology), or if still had symptoms, had not returned to practice and had not been participating in track and field since their last injury.