An Isometric Strength Testing Device for Use with the Elderly: Validation Compared with Isokinetic Measures

Objective: To estimate the concurrent validity of a new isometric strength-testing device, the Leg Press Sled (LPS), using a criterion measure of isokinetic strength among a frail elderly population. Design: Prospective validation study. Setting: University of Houston. Participants: Eleven elderly subjects (81.7 ± 7.0 yrs) from an assisted-living facility. Measurements: Measurements of isometric leg strength using the LPS were compared with measurements of isokinetic leg strength using the Biodex System 3, as a reference standard. For isometric measures, a sample of elderly subjects (mean 81.7 ± 7.0 yrs) was measured at knee angles 60° and 90°. Results: Significant relationships (R2 > 0.50, P < 0.05) between lower-limb-strength measures performed using the LPS and the Biodex System 3 were observed at both angles measured. Conclusion: The LPS is a valid measure of leg strength in elderly populations. The device is portable, inexpensive, easy to use, and specifically suited for special-needs populations such as the home-bound elderly due to its supine mode of operation.