Run-Based Tests Performed on an Indoor and Outdoor Surface Are Comparable in Adolescent Rugby League Players

At non-professional levels of rugby league, run-based tests are commonly performed on outdoor turfed fields and on indoor multipurpose sport surfaces, and results are monitored to gauge player performance and progression. However, test–retest reliability has not been conducted on indoor surfaces in adolescent rugby league players, and no research has examined if results obtained on outdoor and indoor surfaces are comparable for practitioners. Adolescent, male, rugby league players (N = 15; age = 17.1 ± 0.7 years) completed a 20 m linear sprint test (10- and 20 m splits), 505-Agility Test, and Multistage Fitness Test (MSFT) weekly for three consecutive weeks. Absolute (coefficient of variation (CV)) and relative (intraclass correlation coefficient (ICC)) reliability of each run-based test performed on the indoor surface was quantified. Dependent t-tests, Hedges g, and 95% confidence intervals were used to examine if differences in performance occurred between indoor and outdoor surfaces. Effect size magnitudes were determined as Trivial: <0.20, Small: 0.20–0.49, Medium: 0.50–0.79, and Large: ≥0.80. All tests were considered reliable on the indoor surface (CV < 5.0%; ICCs = moderate-good) except for the 505-Agility Test (CV = 4.6–5.1%; ICCs = poor). Non-significant (p > 0.05), trivial differences were revealed between surface types for 10 (g = 0.15, 95% CI = −0.41 to 0.70) and 20 m (g = 0.06, 95% CI = −0.49 to 0.61) sprint tests, the 505-Agility Test (Right: g = −0.53, 95% CI = −1.12 to 0.06; Left: g = −0.40, 95% CI = −0.97 to 0.17), and the MSFT (g = 0.25, 95% CI = −0.31 to 0.81). The 10 and 20 m linear sprint test and MSFT have acceptable test–retest reliability on an indoor multipurpose sport surface, and practitioners may compare results of run-based tests obtained on an outdoor and indoor surface.