TY - JOUR
T1 - An examination of the true reliability of lower limb stiffness measures during overground hopping
AU - Diggin, David
AU - Anderson, Ross
AU - Harrison, Andrew J.
N1 - Publisher Copyright:
© 2016 Human Kinetics, Inc.
PY - 2016/6
Y1 - 2016/6
N2 - Evidence suggests reports describing the reliability of leg-spring (kleg) and joint stiffness (kjoint) measures are contaminated by artifacts originating from digital filtering procedures. In addition, the intraday reliability of kleg and kjoint requires investigation. This study examined the effects of experimental procedures on the inter- and intraday reliability of kleg and kjoint. 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 kleg and kjoint. Classifications of measurement agreement were established using thresholds for absolute and relative reliability statistics. Results illustrated that kleg and kankle exhibited strong agreement. In contrast, kknee and khip demonstrated weak-to-moderate consistency. Results suggest limits in kjoint 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 kleg as an attractor state during hopping, achieved through fluctuations in kjoint variables. Limits to kjoint reliability appear to represent biological function rather than measurement artifact.
AB - Evidence suggests reports describing the reliability of leg-spring (kleg) and joint stiffness (kjoint) measures are contaminated by artifacts originating from digital filtering procedures. In addition, the intraday reliability of kleg and kjoint requires investigation. This study examined the effects of experimental procedures on the inter- and intraday reliability of kleg and kjoint. 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 kleg and kjoint. Classifications of measurement agreement were established using thresholds for absolute and relative reliability statistics. Results illustrated that kleg and kankle exhibited strong agreement. In contrast, kknee and khip demonstrated weak-to-moderate consistency. Results suggest limits in kjoint 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 kleg as an attractor state during hopping, achieved through fluctuations in kjoint variables. Limits to kjoint reliability appear to represent biological function rather than measurement artifact.
KW - Biological variability
KW - Diurnal
KW - Joint stiffness
KW - Leg-spring
KW - Measurement artifact
UR - http://www.scopus.com/inward/record.url?scp=84977661983&partnerID=8YFLogxK
U2 - 10.1123/jab.2015-0210
DO - 10.1123/jab.2015-0210
M3 - Article
C2 - 26745354
AN - SCOPUS:84977661983
SN - 1065-8483
VL - 32
SP - 278
EP - 286
JO - Journal of Applied Biomechanics
JF - Journal of Applied Biomechanics
IS - 3
ER -