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

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

Timing of reactive stepping among individuals with sub-acute stroke: effects of ‘single-task’ and ‘dual-task’ conditions

AbstractPerformance decrements in balance tasks are often observed when a secondary cognitive task is performed simultaneously. This study aimed to determine whether increased cognitive load resulted in altered reactive stepping in individuals with sub-acute stroke, compared to a reactive stepping trial with no secondary task. The secondary purpose was to determine whether differences existed between the first usual-response trial, subsequent usual-response trials, and the dual-task condition. Individuals with sub-acute stroke were exposed to external perturbations to elicit reactive steps. Perturbations were performed under a usual-response (single-task) and dual-task condition. Measures of step timing and number of steps were based on force plate and video data, respectively; these measures were compared between the usual-response and dual-task trials, and between the first usual-response trial, later usual-response trials (trials 2–5) and a dual-task trial. A longer time of unloading onset and greater number of steps were identified for the first usual-response trial compared to later usual-response trials. No significant differences were identified between usual-response and dual-task trials. Although improvements were observed from the first to subsequent usual-response lean-and-release trials, performance then tended to decrease with the introduction of the dual-task condition. These findings suggest that when introduced after usual-response trials, the dual-task trial may represent the first trial of a new condition, which may be beneficial in reducing the potential for adaptation that may occur after multiple repetitions of a reactive stepping task. Therefore, these findings may lend support to the introduction of a new condition (i.e. a dual-task trial) in addition to usual-response trials when assessing reactive balance in individuals with stroke

Assessing The Feasibility Of Pedometers For Quantifying The Volume Of Impacts During Varsity Athletic Practices

The purpose of the current investigation was to test the feasibility of utilizing pedometer data collected during game-like practices to quantify the number of impacts experienced by varsity athletes. Forty-four varsity basketball and soccer athletes wore pedometers and the total number of steps and practice time were recorded during two different practices of similar intensity. The normalized step count, calculated as the total numbers of steps divided by the practice time, was obtained from the first practice and was used to estimate the step count for the second practice. The estimated step count was then compared to the actual step count, as determined from the pedometers. The mean percent difference between actual and estimated step counts was under 25% for approximately 75% of all athletes with no significant difference between the estimated and actual number of steps. The presented results suggest that the pedometer-based method presented here is a feasible method for estimating the number of steps experienced by university varsity athletes

Lower limb muscle activity underlying temporal gait asymmetry post-stroke

Objective: Asymmetric walking after stroke is common, detrimental, and difficult to treat, but current knowledge of underlying physiological mechanisms is limited. This study investigated electromyographic (EMG) features of temporal gait asymmetry (TGA). Methods: Participants post-stroke with or without TGA and control adults (n=27, 8, and 9, respectively) performed self-paced overground gait trials. EMG, force plate, and motion capture data were collected. Lower limb muscle activity was compared across groups and sides (more/less affected). Results: Significant group by side interaction effects were found: more affected plantarflexor stance activity ended early (p=.0006) and less affected dorsiflexor on/off time was delayed (p<.01) in persons with asymmetry compared to symmetric and normative controls. The TGA group exhibited fewer dorsiflexor bursts during swing (p=.0009). Conclusions: Temporal patterns of muscular activation, particularly about the ankle around the stance to-swing transition period, are associated with TGA. The results may reflect specific impairments or compensations that affect locomotor coordination. Significance: Neuromuscular underpinnings of spatiotemporal asymmetry have not been previously characterized. These novel findings may inform targeted therapeutic strategies to improve gait qualityafter stroke.This work was supported by a Collaborative Health Research Projects Grant from the Canadian Institutes of Health Research and the National Science Engineering Research Council the Heart and Stroke Foundation [#337523]; Canadian Institutes of Health Research [MOP 133577]. The authors also acknowledge the support of the Toronto Rehabilitation Institute; equipment and space have been funded with grants from the Canada Foundation for Innovation, Ontario Innovation Trust, and Ministry of Research and Innovation. AM holds a New Investigator Award from the Canadian Institutes of Health Research (MSH 141983) and KP holds a salary award from the Heart and Stroke Foundation. Sponsors were not involved in study design and execution or article preparation