title: Age-related differences in trunk intrinsic stiffness.
abstract: Age-related differences in trunk intrinsic stiffness, as an important potential contributor to spinal stability, were investigated here because of: (1) the role of spinal instability in low back pain (LBP) development; (2) the increasing prevalence of LBP with age, and (3) the increasing population of older people in the workforce. Sixty individuals aged 20-70 years, in five equal-size age groups, completed a series of displacement-controlled perturbation tests in an upright standing posture while holding four different levels of trunk extension efforts. In addition to examining any age-related difference in trunk intrinsic stiffness, the current design assessed the effects of gender, level of effort, and any differences in lower back neuromuscular patterns on trunk intrinsic stiffness. No significant differences in trunk intrinsic stiffness were found between the age groups. However, stiffness was significantly larger among males and increased with the level of extension effort. No influences of differences in neuromuscular pattern were observed. Since the passive contribution of trunk tissues in the upright standing posture is minimal, our values of estimated trunk intrinsic stiffness primarily represent the volitional contribution of the lower back musculoskeletal system to spinal stability. Therefore, it seems unlikely that the alterations in volitional behavior of the lower back musculature, caused by aging (e.g., as reflected in reduced strength), diminish their contributions to the spinal stability.
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514E Robotic and Manufacturing Building, Lexington, KY 40506, USA.
authors.forename: Milad
authors.initials: M
authors.lastname: Vazirian
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514E Robotic and Manufacturing Building, Lexington, KY 40506, USA.
authors.forename: Iman
authors.initials: I
authors.lastname: Shojaei
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514E Robotic and Manufacturing Building, Lexington, KY 40506, USA.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Tromp
authors.affiliation: Department of Industrial and Systems Engineering, Virginia Tech, Blacksburg, VA 24061, USA.
authors.forename: Maury A
authors.initials: MA
authors.lastname: Nussbaum
authors.affiliation: Department of Biomedical Engineering, University of Kentucky, 514E Robotic and Manufacturing Building, Lexington, KY 40506, USA. Electronic address: babak.bazrgari@uky.edu.
authors.forename: Babak
authors.initials: B
authors.lastname: Bazrgari
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D001415:Back / Q000503:physiopathology; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000150:complications / Q000453:epidemiology*; D017116:Low Back Pain / Q000453:epidemiology / Q000209:etiology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D011187:Posture; D016059:Range of Motion, Articular; D055815:Young Adult
keywords: Aging; Perturbation test; Spinal stability; Trunk apparent mass; Trunk intrinsic stiffness