Reliability and smallest worthwhile difference of the NFL-225 test in NCAA Division I football players

Abstract

The NFL-225 test is widely used to assess the strength level and evaluate the progress of college football players during resistance training. Despite the studies evaluating the validity of this test, there are no reports assessing its reliability. The purpose of this study was to determine the reliability and smallest worthwhile difference (SWD) of the NFL-225 test in Division I college football players. Seventy-two players were assessed for more than 3 weeks for the number of repetitions completed with a constant load of 102.3 kg (225 lbs) during winter conditioning. Test sessions occurred on the same day and at the same time 1 week apart. Intraclass correlation coefficients (ICCs) between weeks 1 and 2 (ICC = 0.987), weeks 2 and 3 (ICC = 0.981), and across weeks 1, 2, and 3 (ICC = 0.988) indicated high relative reliability. A small technical error (TE) (TE = 0.5 repetitions) provided strong absolute reliability. The SWD suggests that a change in performance of 3 repetitions or more after training would indicate a meaningful improvement in performance for this test. © 2014 National Strength and Conditioning Association.