Quantification and Evaluation of the Biomechanical Behaviour of the Trunk During Fundamental Tasks: Should the Thoracic Spine be Considered?

Thoracic spine research is sparse relative to the lumbar spine. A better understanding of thoracic spine mechanics may provide insight into pain mechanisms in both spine regions. This dissertation quantified and evaluated the biomechanical behaviour of the thoracic spine during fundamental tasks, to determine if monitoring the thoracic spine is necessary in the investigation of spine mechanics. The number of trials required for repeatable and reliable trunk kinematic and muscle activation measures across maximal ranges-of-motion (ROM) were determined (Study #1). Thirty participants performed 10 trials of upright standing and maximal trunk ROM. Most measures demonstrated high repeatability, with two to five trials required. The head and arm positions enabling maximal spinal ROM were determined in Study #2 using 24 participants, as relationships have been shown in head, arm, and upper back motion. The greatest angles were produced with the active head–loose arm, active head–crossed arm, and active head–abducted arm positions for maximum flexion, bending, and twisting, respectively. Studies #3 and #4 determined the segments and superficial muscles that were necessary to quantify the motion and muscle activation characteristics of the trunk, specifically the thoracic spine. Thirty participants performed upright standing, maximum trunk ROM, and thoracic ROM. A four-cluster marker set quantified motion for most movement tasks. Of the 16 muscles tested, 10–14 were necessary to evaluate trunk muscle activation. These studies provided insight into thoracic function in relation to the lumbar spine. Lumbar co-contraction was quantified during thoracic movements in Study #5. Thirty participants performed upright standing, maximum trunk ROM, and thoracic ROM. Thoracic flexion, bending, and twisting elicited 67%, 45%, and 55% greater co-contraction in the lumbar region than upright standing, demonstrating that the thoracic spine impacts the muscular response of the lumbar spine. These studies quantified and characterized the biomechanical behaviour of the thoracic spine during fundamental tasks. As the thoracic spine demonstrated differences in motion and muscle activation characteristics along its length and compared to the lumbar spine, knowledge of thoracic spine behaviour and interactions may aid in clarifying the behaviour of and elucidating pain mechanisms within the thoracic and lumbar spine regions

Characteristics of voluntary-induced stepping response in persons with stroke compared with those of healthy young and older adults

Background: Impairment of protective steps to recover balance from external perturbation is evident after stroke. Voluntary-induced stepping response (VSR) can be used to practice protective steps by instructing an individual to voluntarily lean their whole body forward until they perceive a loss of balance and automatically induce a step. However, to improve protective stepping performance, detailed characteristics of VSR in healthy persons are required. Research question: What is the difference in VSR between healthy and persons with stroke? Methods: An observational study was conducted in 30 participants, (10 young, 10 older, and 10 persons with stroke). All participants performed VSR for 10 trials. Step length, step width, step duration, CoM position, CoM velocity, trunk-hip displacement, and strategies of response were recorded using a motion capture system and analysed using Matlab software. Statistical analysis was performed using One-way ANOVA and Chi-square. Results: On average, participants with stroke had shorter step lengths and step durations than young and older adults. Step width of older adults and participants with stroke was wider than that of young adults (p<0.05). While multiple steps and losing balance were reported more frequently in participants with stroke than the others, the percentage of trials in which participants grasped the handrails was not significantly different between older adults and participants with stroke. CoM position, CoM velocity, and trunk-hip displacement at foot liftoff were significantly smaller in older adults and participants with stroke than young adults (p<0.05). Participants with stroke tended to use trunk bending rather than trunk leaning strategies to generate VSR in contrast to healthy participant. The prevalence of the trunk bending strategy was also greater in older adults than young adults. Significance: Values obtained from healthy groups can be used as guidelines to set realistic goals during VSR training to improve protective steps in patients with stroke

High-Density Electromyography Provides New Insights into the Flexion Relaxation Phenomenon in Individuals with Low Back Pain.

Recent research using high-density electromyography (HDEMG) has provided a more precise understanding of the behaviour of the paraspinal muscles in people with low back pain (LBP); but so far, HDEMG has not been used to investigate the flexion relaxation phenomenon (FRP). To evaluate this, HDEMG signals were detected with grids of electrodes (13 × 5) placed bilaterally over the lumbar paraspinal muscles in individuals with and without LBP as they performed repetitions of full trunk flexion. The root mean square of the HDEMG signals was computed to generate the average normalized amplitude; and the spatial FRP onset was determined and expressed as percentage of trunk flexion. Smoothing spline analysis of variance models and the contrast cycle difference approach using the Bayesian interpretation were used to determine statistical inference. All pain-free controls and 64.3% of the individuals with LBP exhibited the FRP. Individuals with LBP and the FRP exhibited a delay of its onset compared to pain-free controls (significant mean difference of 13.3% of trunk flexion).  They also showed reduced normalized amplitude compared to those without the FRP, but still greater than pain-free controls (significant mean difference of 27.4% and 11.6% respectively). This study provides novel insights into changes in lumbar muscle behavior in individuals with LBP

Quantifying segmental contributions to center-of-mass motion during dynamic continuous support surface perturbations using simplified estimation models

Investigating balance reactions following continuous, multidirectional, support surface perturbations is essential for improving our understanding of balance control in moving environments. Segmental motions are often incorporated into rapid balance reactions following external perturbations to balance, although the effects of these motions during complex, continuous perturbations have not been assessed. This study aimed to quantify the contributions of body segments (ie, trunk, head, upper extremity, and lower extremity) to the control of center-of-mass (COM) movement during continuous, multidirectional, support surface perturbations. Three-dimensional, whole-body kinematics were captured while 10 participants experienced 5 minutes of perturbations. Anteroposterior, mediolateral, and vertical COM position and velocity were calculated using a full-body model and 7 models with reduced numbers of segments, which were compared with the full-body model. With removal of body segments, errors relative to the full-body model increased, while relationship strength decreased. The inclusion of body segments appeared to affect COM measures, particularly COM velocity. Findings suggest that the body segments may provide a means of improving the control of COM motion, primarily its velocity, during continuous, multidirectional perturbations, and constitute a step toward improving our understanding of how the limbs contribute to balance control in moving environments

Leg Tissue Mass Composition Affects Tibial Acceleration Response Following Impact

To date, there has not been a direct examination of the effect that tissue composition (lean mass/muscle, fat mass, bone mineral content) differences between males and females has on how the tibia responds to impacts similar to those seen during running. To evaluate this, controlled heel impacts were imparted to 36 participants (6 M and 6 F in each of low, medium and high percent body fat [BF] groups) using a human pendulum. A skin-mounted accelerometer medial to the tibial tuberosity was used to determine the tibial response parameters (peak acceleration, acceleration slope and time to peak acceleration). There were no consistent effects of BF or specific tissue masses on the un-normalized tibial response parameters. However, females experienced 25% greater peak acceleration than males. When normalized to lean mass, wobbling mass, and bone mineral content, females experienced 50%, 62% and 70% greater peak acceleration, respectively, per gram of tissue than males. Higher magnitudes of lean mass and bone mass significantly contributed to decreased acceleration responses in general

Factors Contributing to Unexpected Retirement and Unemployment in Adults Over 50 Years Old in Ireland

Older adults are increasingly important to maintaining stable workforces. As such, factors contributing to early workforce exit must be identified. This study aimed to identify predictors of unexpected retirement and unemployment at older age, with respect to psychological constructs, resulting adverse behaviors, and health-related factors reflecting functional status. Data were extracted from The Irish Longitudinal Study on Ageing (TILDA) to predict unexpected retirement and unemployment in older adults in Ireland. Increasing age, increasing number of impairments in activities of daily living, and frailty status of “pre-frail/frail” (relative to non-frail) increased the likelihood of unexpected retirement; while greater numbers of physical limitations and “pre-frail/frail” status significantly predicted unemployment at older age. Pre-frail/frail status or reduced physical capability for everyday tasks may adversely affect older individuals’ ability to obtain and/or maintain employment. These findings advance the current understanding of factors associated with unexpected retirement and unemployment at older ages. Findings may aid in identifying strategies to extend working life and to aid at-risk older adults, and may inform components of care on which to focus to minimize loss of function and mobility, and maintain independence, with aging