title: Identification of intrinsic and reflexive contributions to low-back stiffness: medium-term reliability and construct validity.
abstract: This study aimed at testing the reliability and construct validity of a trunk perturbation protocol (TPP) that estimates the intrinsic and reflexive contributions to low-back stiffness. The TPP consists of a series of pseudorandom position-controlled trunk perturbations in an apparatus measuring forces and displacements at the harness surrounding the thorax. Intrinsic and reflexive contributions to low-back stiffness were estimated using a system identification procedure, leading to 12 parameters. Study 1 methods (reliability): 30 subjects performed five 75-s trials, on each of two separate days (eight weeks apart). Reliability was assessed using the generalizability theory, which allowed computing indexes of dependability (ϕ, analogous to intraclass correlation coefficient) and standard errors of measurement (SEM). Study 2 methods (validity): 20 healthy subjects performed three 75-s trials for each of five experimental conditions assumed to provide different lumbar stiffness; testing the construct validity of the TPP using four conditions with different lumbar belt designs and one control condition without. Study 1 results (reliability): Learning was seen between the first and following trials. Consequently, reliability analyses were performed without the first trial. Simulations showed that averaging the scores of three trials can lead to acceptable reliability results for some TPP parameters. Study 2 results (validity): All lumbar belt designs increased low-back intrinsic stiffness, while only some of them decreased reflex stiffness, which support the construct validity of the TPP. Overall, these findings support the use of the TPP to test the effect of rehabilitation or between-groups differences with regards to trunk stiffness.
authors.affiliation: Occupational Health and Safety Research Institute Robert-Sauvé, Montreal, Quebec, Canada; Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, Canada. Electronic address: larchr@irsst.qc.ca.
authors.forename: Christian
authors.initials: C
authors.lastname: Larivière
authors.affiliation: Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL, USA; Department of Physical Medicine & Rehabilitation, Northwestern University, Chicago, IL, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Ludvig
authors.affiliation: Biomedical Engineering Department, McGill University, Montreal, Canada.
authors.forename: Robert
authors.initials: R
authors.lastname: Kearney
authors.affiliation: Occupational Health and Safety Research Institute Robert-Sauvé, Montreal, Quebec, Canada; Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, Canada.
authors.forename: Hakim
authors.initials: H
authors.lastname: Mecheri
authors.affiliation: School of Physiotherapy and Occupational Therapy, McGill University, Montreal, Canada; Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, Canada.
authors.forename: Jean-Maxime
authors.initials: JM
authors.lastname: Caron
authors.affiliation: School of Physiotherapy and Occupational Therapy, McGill University, Montreal, Canada; Centre for Interdisciplinary Research in Rehabilitation of Greater Montreal (CRIR), Montreal Rehabilitation Institute, Montreal, Canada.
authors.forename: Richard
authors.initials: R
authors.lastname: Preuss
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001415:Back / Q000502:physiology*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000379:methods*; D055595:Mechanical Phenomena; D008875:Middle Aged; D012018:Reflex; D015203:Reproducibility of Results; D013909:Thorax; D055815:Young Adult
keywords: Low back pain; Reflex; Rehabilitation; Reproducibility; Trunk stiffness