Abstract

The purpose of this study was to assess reliability of both indoor and outdoor 40 km time-trial cycling performance. Eight trained cyclists completed three indoor 40 km time-trials on an air-braked ergometer (KingcycleTM) and three outdoor 40 km time-trials on a local course. Power output was measured for all trials using the SRM™ powermeter. Mean performance time across three indoor trials was 54.21 ± 2.59 (min : sec) and was significantly different (P < 0.05) to mean time across three outdoor trials (57.29 ± 3.22 min : sec). However, there was no significant difference (P = 0.34) for mean power across three indoor trials (303 ± 35 W) when compared to outdoor performances (312 ± 23 W). Within-subject variation for mean power output expressed as a coefficient of variation (CV) improved in both indoors and outdoors for trials 2 and 3 (CV = 1.9 %, 95 % CI 1.0 - 3.4 and CV = 2.1 %, 95 % CI 1.1 - 3.8) when compared to trials 1 and 2 (CV = 2.1 %, 95 % CI 1.2 - 3.8 and CV = 2.4 %, 95 % CI 1.3 - 4.3). These findings indicate that power output measured using the SRM powermeter is highly reproducible for both laboratory-based and actual 40 km time-trial cycling performance.