Intrarater reliability and agreement of linear encoder derived heel-rise endurance test outcome measures in healthy adults.

A linear encoder measuring vertical displacement during the heel-rise endurance test (HRET) enables the assessment of work and maximum height in addition to the traditional repetitions measure. We aimed to compare the test-retest reliability and agreement of these three outcome measures. Thirty-eight healthy participants (20 females, 18 males) performed the HRET on two occasions separated by a minimum of seven days. Reliability was assessed by the intraclass correlation coefficient (ICC) and agreement by a range of measures including the standard error of measurement (SEM), coefficient of variation (CV), and 95% limits of agreement (LoA). Reliability for repetitions (ICC=0.77 (0.66, 0.85)) was equivalent to work (ICC=0.84 (95% CI 0.76, 0.89)) and maximum height (ICC=0.85 (0.77, 0.90)). Agreement for repetitions (SEM=6.7 (5.8, 7.9); CV=13.9% (11.9, 16.8%); LoA=-1.9±37.2%) was equivalent to work (SEM=419J (361, 499J); CV=13.1% (11.2, 15.8%); LoA=0.1±34.8%) with maximum height superior (SEM=0.8cm (0.6, 1.0cm); CV=6.6% (5.7, 7.9%); LoA=1.3±17.1%). Work and maximum height demonstrated acceptable reliability and agreement that was at least equivalent to the traditional repetitions measure.