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RELIABILITY OF PORTABLE STRENGTH TESTING FOR ASSESSING MAXIMAL AND RAPID ISOMETRIC TORQUE CHARACTERISTICS IN FRAIL, ELDERLY ADULTS

Abstract

Ty B. Palmer, Ryan M. Thiele, Eric C. Conchola & Douglas B. Smith

Oklahoma State University, Stillwater, Oklahoma

PURPOSE: To determine the reliability for maximal and rapid isometric torque characteristics of the leg extensors and flexors in frail, elderly adults using portable strength testing. METHODS: Fifteen frail, elderly adults (mean±SD age=88±6yr; mass=69±11kg; height=157±8cm) volunteered for this investigation on 2 non-consecutive days at the same time of day (±2h). During each visit, participants performed 2 isometric maximal voluntary contractions (MVCs) of the leg extensors and flexors. All MVCs were performed in a seated position on the right leg at a knee joint angle of 90°. Participants were instructed during each MVC to push or pull “as hard and fast as possible” against a load cell attached immediately posterior to the heel for 3-4 s. Isometric MVC peak torque (PT; Nm) was determined as the highest mean 500 ms epoch during the entire 3-4 s MVC plateau. Rate of torque development (RTD; Nm·s-1) was determined from the linear slope of the torque-time curve over the time intervals of 0-30, 0-50, 0-100, 0-200, and 100-200 ms relative to the onset of torque production (7.5 Nm for the leg extensors; 4 Nm for the leg flexors). Reliability for PT and the RTD variables were determined using the intraclass correlation coefficient (ICC, model 2,1) and standard error of measurement (SEM). Systematic variability was examined using separate one-way repeated measures analyses of variance (ANOVAs). RESULTS: The ANOVAs indicated no systematic variability in any of the dependent variables (P>0.05). The ICCs and SEM values expressed as a percentage of the mean ranged from 0.504-0.847 and 23.619-55.189% for the leg extensors and 0.716-0.826 and 15.408-32.356% for the leg flexors, respectively (Table 1). CONCLUSION: These findings demonstrate that portable strength testing may be a highly consistent and equally reliable assessment technique for measuring maximal and later (>100ms) but not early (≤100ms) rapid torque characteristics of the leg extensors and flexors in frail elderly adults.

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Table 1.docx (446 kB)
Table 1

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