Title

An examination of the true reliability of lower limb stiffness measures during overground hopping

Document Type

Article

Publication Date

6-1-2016

Abstract

Evidence suggests reports describing the reliability of leg-spring (k ) and joint stiffness (k ) measures are contaminated by artifacts originating from digital filtering procedures. In addition, the intraday reliability of k and k requires investigation. This study examined the effects of experimental procedures on the inter- and intraday reliability of k and k . Thirty-two participants completed 2 trials of single-legged hopping at 1.5, 2.2, and 3.0 Hz at the same time of day across 3 days. On the final test day a fourth experimental bout took place 6 hours before or after participants' typical testing time. Kinematic and kinetic data were collected throughout. Stiffness was calculated using models of k and k . Classifications of measurement agreement were established using thresholds for absolute and relative reliability statistics. Results illustrated that k and k exhibited strong agreement. In contrast, k and k demonstrated weak-to-moderate consistency. Results suggest limits in k reliability persist despite employment of appropriate filtering procedures. Furthermore, diurnal fluctuations in lower-limb muscle-tendon stiffness exhibit little effect on intraday reliability. The present findings support the existence of k as an attractor state during hopping, achieved through fluctuations in k variables. Limits to k reliability appear to represent biological function rather than measurement artifact. leg joint leg joint leg joint leg joint leg ankle knee hip joint leg joint joint

Publication Name

Journal of Applied Biomechanics

Volume Number

32

First Page

278

Last Page

286

Issue Number

3

DOI

10.1123/jab.2015-0210

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