(5) RELIABILITY OF USING ISOKINETIC DYNAMOMETER-BASED PEAK TORQUE IN A LONG-TERM STUDY

Isokinetic dynamometer-based peak torque (PT) is a commonly evaluated and reported variable in research and clinical settings. Although its reliability has been widely reported it has been overwhelmingly so using a short-term (< ~10 day) inter-trial testing time frame. However, many studies and programs utilize a long-term (several weeks to months) inter-trial testing period. Also, the methods by which the PT value is selected and reported from a multiple rep testing scheme have not been well investigated for both reliability and PT absolute performance comparisons.

Purpose: The purpose of this study was to investigate the long-term reliability of isokinetic and isometric PT of the leg extensors with an emphasis on the differences among several PT score selection methods.

Methods: Thirteen men and women underwent two testing trials separated by 28.8 (± 1.8) days. Testing included maximal voluntary contractions of three sets of three reps for two isokinetic contraction conditions of 60 (Isok60) and 240 (Isok240) deg/s velocities, and three sets of one rep of isometric contractions for the leg extensors. The PT score was derived from seven different methods.

Results: Table 1 presents the statistical findings including ICC, SEM, and MD. Reliability varied widely across contraction conditions and PT score selection parameter. Isok60 overall had lower reliability than Isok240, and the set one PT score selection parameters were generally lower than those that involved sets two and three. Systematic error was shown for six out of the 17 PT selection variables.

Conclusion: On a subjective interpretation basis, when taking everything into account the best overall combination of time/trial efficiency, reliability, best/highest PT score parameter, and reduced risk of systematic bias appears to be the variable that uses the average of the highest two reps of the first two sets of three reps – i.e., averaging the highest two values of the six total reps from the first two sets. PRACTICAL APPLICATION: When measuring isokinetic peak torque as a variable for a long-term study, the most reliable measure may involve the highest two values of the six total reps from the first two sets and averaging them.




Acknowledgements: None