Between-day reliability of pedal forces for cyclists during an incremental cycling test to exhaustion

BACKGROUND: Reliability of pedal forces during cycling specific tests needs to be established if pedal forces are to be used in longitudinal studies evaluating performance improvements. METHOD: We assessed the reliability of pedal force measures during two incremental cycling tests to exhaustion separated by two to seven days. The number of competitive cyclists completing each workload increment varied (n = 10 for 100 W to 250W; n = 8 for 300W; n = 6 for 350 W). Pedal forces were measured via strain gauge instrumented pedals and pedal-to-crank angles via angular potentiometers attached to the pedal spindles. Mean and standard deviations, typical error of measurement percentage (TE%) and effect sizes (ES) between days across workloads for oxygen uptake (VO2), peak normal force (PNF), peak anterior-posterior force (PAPF), average total force on the pedal (ATF) and index of effectiveness percentage (IE) for right and left pedals were calculated. RESULTS: Averages across all workloads showed high reliability and trivial differences between two to seven days of testing for all variables (TE%, ICC, ES; VO2 = 4%, 0.94, 0.1; PNFright = 6%, 0.98, 0.1; PNFleft = 12%, 0.98, 0.1; PAPFright = 13%, 0.95, 0.2; PAPFleft = 14%, 0.96, 0.1; ATFright = 5%, 0.98, 0.1; ATFleft = 11%, 0.97, 0.1; IEright = 10%, 0.94, 0.2; IEleft = 14%, 0.91, 0.1). CONCLUSION: Pedal force measures during incremental cycling tests to exhaustion can be used to assess changes in performance given the high reliability reported in our study.