When ‘just doing it’ is not enough: Assessing the fidelity of player performance of an injury prevention exercise program Lauren V. Fortington, Alex Donaldson, Tim Lathlean, Warren B. Young, Belinda J. Gabbe, David Lloyd, Caroline F. Finchemail address Received 26 February 2014; received in revised form 8 April 2014; accepted 8 May 2014. published online 16 June 2014. Abstract Objectives To obtain benefits from sports injury prevention programs, players are instructed to perform the exercises as prescribed. We developed an observational checklist to measure the quality of exercise performance by players participating in FootyFirst, a coach-led, exercise-based, lower-limb injury prevention program in community Australian Football (AF). Design Observational. Methods The essential performance criteria for each FootyFirst exercise were described in terms of the technique, volume and intensity required to perform each exercise. An observational checklist was developed to evaluate each criterion through direct visual observation of players at training. The checklist was trialled by two independent raters who observed the same 70 players completing the exercises at eight clubs. Agreement between observers was assessed by Kappa-statistics. Exercise fidelity was defined as the proportion of observed players who performed all aspects of their exercises correctly. Results The raters agreed on 61/70 observations (87%) (Kappa=0.72, 95% CI: 0.55; 0.89). Of the observations with agreed ratings, 41 (67%) players were judged as performing the exercises as prescribed. Conclusions The observational checklist demonstrated high inter-rater reliability. Many players observed did not perform the exercises as prescribed, raising concern as to whether they would be receiving anticipated program benefits. Where quality of exercise performance is important, evaluation and reporting of program fidelity should include direct observations of participants.