Reliability, Validity, and Sensitivity of a Novel Smartphone-Based Eccentric Hamstring Strength Test in Professional Football Players.

Purpose: To evaluate the test-retest reliability, sensitivity, and concurrent validity of a smartphone-based method for assessing eccentric hamstring strength among male professional football players.

Methods: A total of 25 healthy male professional football players performed the Chinese University of Hong Kong (CUHK) Nordic break-point test, hamstring fatigue protocol, and isokinetic hamstring strength test. The CUHK Nordic break-point test is based on a Nordic hamstring exercise.