Abstract
This study assessed the measurement reliability and validity of the Hydra-Fitness
Omnitron, a microprocessor-controlled isokinetic ergometer that provides concentric
resistance for dynamic extension and flexion movements as well as resistance for isometric
contractions. Maximal peak torque output measured by the Omnitron and strain gauge
devices connected to the apparatus were compared in 26 physically active males who
were tested over 3 days for isometric knee extension and isokinetic knee flexion/extension
at two resistance levels. Maximal torque outputs remained stable on days 2 and 3 (p
< 0.05), and in-traclass reliability yielded r = 0.94 to 0.98. There was no difference
between the slopes of the regression lines for the different experimental conditions
(p > 0.05). There was significant improvement between day 1 and days 2 and 3 that
corresponded to a combination of a training and learning effect. Thus, one practice
session was necessary to obtain reliable individual differences. The validity correlations
between peak torque output measured from the Omnitron and strain gauges were greater
than r = 0.94. There was a small discrepancy (0.44 to 0.88 Nm) between the two measuring
devices that can be explained by the difference in shank pad positioning that accomodates
for different segment lengths. We conclude that reliability and validity were excellent
over a wide range of torque outputs measured during maximal isometric and maximal
dynamic double concentric flexion and extension movements.
Key words
knee extension - knee flexion - peak torque - validity - reliability - exercise testing
- fitness evaluation - muscle strength
