The Retest Reliability of Common Tests to Assess Physical Qualities in Adolescent Rugby League Players.

Purpose: Rigorous evidence concerning the reliability of physical tests among young athletes is lacking. Therefore, this study aimed to comprehensively determine the retest reliability of the most commonly used tests to assess physical qualities in adolescent rugby league players, and to provide the standard error of measurement and minimal detectable change for each test to support objective athlete monitoring.

Method: A repeated-measures design was employed with 50 adolescent, schoolboy rugby league players (16.2 [1.3] y) completing the same testing battery across 2 consecutive weeks. Within each week, stature, body mass, and ∑4 skinfold thickness assessments, as well as countermovement jump, medicine ball throw, and 1-repetition maximum bench press, back squat, and prone row tests were conducted on the first testing day. Forty-eight hours later, a second testing day contained the 10- and 20-m linear sprints, 505-Agility Test, L-run Test, and Multistage Fitness Test.

Results: Nonsignificant (P > .05), trivial differences (dav = 0.00-0.16) were evident between trials in all tests. The coefficient of variation ranged from 0.05% to 4.02% across tests. The intraclass correlation ranged from .704 to .999. All tests presented relatively low standard error of measurement, with accompanying minimal detectable change provided.

Conclusion: These data can help inform decision making among end-users when implementing tests in a repeated manner and interpreting testing data.