Trunk Angular Displacement Research Articles

Transhumeral prosthesis use affects upper body kinematics and kinetics

BackgroundTranshumeral (TH) limb loss leads to loss of body mass and reduced shoulder range of motion. Despite most owning a prosthesis, prosthesis abandonment is common. The consequence of TH limb loss and prosthesis use and disuse during gait may be compensation in the upper body, contributing to back pain or injury. Understanding the impact of not wearing a TH prosthesis on upper body asymmetries and spatial-temporal aspects of gait will inform how TH prosthesis use and disuse affects the body. Research questionDoes TH limb loss alter upper body asymmetries and spatial-temporal parameters during gait when wearing and not wearing a prosthesis compared to able-bodied controls? MethodsEight male TH limb loss participants and eight male control participants completed three gait trials at self-selected speeds. The TH limb loss group performed trials with and without their prosthesis. Arm swing, trunk angular displacement, trunk-pelvis moment, and spatial-temporal aspects were compared using non-parametric statistical analyses. ResultsBoth TH walking conditions showed greater arm swing in the intact limb compared to the residual (p≤0.001), resulting in increased asymmetry compared to the control group (p≤0.001). Without the prosthesis, there was less trunk flexion and lateral flexion compared to the control group (p≤0.001). Maximum moments between the trunk and pelvis were higher in the TH group than the control group (p≤0.05). Spatial-temporal parameters of gait did not differ between the control group and either TH limb loss condition. SignificanceProsthesis use affects upper body kinematics and kinetics, but does not significantly impact spatial-temporal aspects of gait, suggesting these are compensatory actions. Wearing a prosthesis helps achieve more normative upper body kinematics and kinetics than not wearing a prosthesis, which may help limit back pain. These findings emphasize the importance of encouraging at least passive use of prostheses for individuals with TH limb loss.

Extended physiological proprioception is affected by transhumeral Socket-Suspended prosthesis use

The objective of this study was to define targeted reaching performance without visual information for transhumeral (TH) prosthesis users, establishing baseline information about extended physiological proprioception (EPP) in this population. Subjects completed a seated proprioceptive targeting task under simultaneous motion capture, using their prosthesis and intact limb. Eight male subjects, median age of 58 years (range 29–77 years), were selected from an ongoing screening study to participate. Five subjects had a left-side TH amputation, and three a right-side TH amputation. Median time since amputation was 9 years (range 3–54 years). Four subjects used a body-powered prosthetic hook, three a myoelectric hand, and one a myoelectric hook. The outcome measures were precision and accuracy, motion of the targeting hand, and joint angular displacement. Subjects demonstrated better precision when targeting with their intact limb compared to targeting with their prosthesis, 1.9 cm2 (0.8–3.0) v. 7.1 cm2 (1.3–12.8), respectively, p = 0.008. Subjects achieved a more direct reach path ratio when targeting with the intact limb compared to with the prosthesis, 1.2 (1.1–1.3) v. 1.3 (1.3–1.4), respectively, p = 0.039 The acceleration, deceleration, and corrective phase durations were consistent between conditions. Trunk angular displacement increased in flexion, lateral flexion, and axial rotation while shoulder flexion decreased when subjects targeted with their prosthesis compared to the intact limb. The differences in targeting precision, reach patio ratio, and joint angular displacements while completing the targeting task indicate diminished EPP. These findings establish baseline information about EPP in TH prosthesis users for comparison as novel prosthesis suspension systems become more available to be tested.

Gait Deviations Identified During the Six-Minute Walk Test Using Inertial Measurement Units in Patients with Multiple Sclerosis

PURPOSE Gait deviations are common in patients with multiple sclerosis (MS) and can increase the risk of falls and potential for musculoskeletal pain. This study evaluated relationships between fatigue-induced changes in lower extremity kinematics and spatiotemporal measures during a Six-Minute Walk Test (6MWT). METHODS Baseline data from 29 participants ((age 49±12 years, 21F, Expanded Disability Status Scale 1-5.0) with MS completed the 6MWT. Gait parameters were recorded continuously via inertial measurement units (Xsens MVN, Enschede, Netherlands). Peak joint angles (knee flexion, hip adduction, trunk angular displacement) and spatiotemporal measures (gait speed, stance time, stride length) were calculated and analyzed for each walking stride during the first and last minute of the test. Pearson correlations were used to evaluate 1) relationships between the Distance Walked Index (DWI, difference in distance between first and last minute) and changes in involved (i) and uninvolved (u) limb peak joint angles and 2) relationships between changes in gait parameters, spatiotemporal measures, and 6MWT DWI. Paired t-tests evaluated differences in peak joint angles between the first and last minute of the 6MWT. RESULTS Participants demonstrated a 7.0% decline on the DWI (4.3 ± 6.4m reduction in walking distance) and gait speed declined by 8.5% (0.07 ± 0.11 m/s) between the first and last minute of the 6MWT. A weak, negative correlation was observed between change in frontal trunk angular displacement and DWI (R= -.501, p= .009). There were no changes in stance timei or stance timeu. Stride length decreased on both limbs over time (Mean Difference (MD)i: 3.2cm, p <.001; MDu: 3.2cm, p<.001). Within-limb peak knee flexion angle decreased on both limbs over time (MDi: -6.7±14.1°, p=.021; MDu: -8.11±14.7°, p=.008). CONCLUSION Gait deviations presented as decreased stride length and bilateral reduced peak knee flexion angle during the 6MWT. Greater DWI was associated with reduced trunk angular displacement. Interventions targeting hip and knee joint-specific dysfunction may be advantageous for mitigating gait deviations in patients with MS. Gait deviations are common in patients with multiple sclerosis (MS) and can increase the risk of falls and potential for musculoskeletal pain. This study evaluated relationships between fatigue-induced changes in lower extremity kinematics and spatiotemporal measures during a Six-Minute Walk Test (6MWT). Baseline data from 29 participants ((age 49±12 years, 21F, Expanded Disability Status Scale 1-5.0) with MS completed the 6MWT. Gait parameters were recorded continuously via inertial measurement units (Xsens MVN, Enschede, Netherlands). Peak joint angles (knee flexion, hip adduction, trunk angular displacement) and spatiotemporal measures (gait speed, stance time, stride length) were calculated and analyzed for each walking stride during the first and last minute of the test. Pearson correlations were used to evaluate 1) relationships between the Distance Walked Index (DWI, difference in distance between first and last minute) and changes in involved (i) and uninvolved (u) limb peak joint angles and 2) relationships between changes in gait parameters, spatiotemporal measures, and 6MWT DWI. Paired t-tests evaluated differences in peak joint angles between the first and last minute of the 6MWT. Participants demonstrated a 7.0% decline on the DWI (4.3 ± 6.4m reduction in walking distance) and gait speed declined by 8.5% (0.07 ± 0.11 m/s) between the first and last minute of the 6MWT. A weak, negative correlation was observed between change in frontal trunk angular displacement and DWI (R= -.501, p= .009). There were no changes in stance timei or stance timeu. Stride length decreased on both limbs over time (Mean Difference (MD)i: 3.2cm, p <.001; MDu: 3.2cm, p<.001). Within-limb peak knee flexion angle decreased on both limbs over time (MDi: -6.7±14.1°, p=.021; MDu: -8.11±14.7°, p=.008). Gait deviations presented as decreased stride length and bilateral reduced peak knee flexion angle during the 6MWT. Greater DWI was associated with reduced trunk angular displacement. Interventions targeting hip and knee joint-specific dysfunction may be advantageous for mitigating gait deviations in patients with MS.

Effect of Handrail Height and Age on Trunk and Shoulder Kinematics Following Perturbation-Evoked Grasping Reactions During Gait.

To characterize the effect of handrail height and age on trunk and shoulder kinematics, and concomitant handrail forces, on balance recovery reactions during gait. Falls are the leading cause of unintentional injury in adults in North America. Handrails can significantly enhance balance recovery and help individuals to avoid falls, provided that their design allows users across the lifespan to reach and grasp the rail after balance loss, and control their trunk by applying hand-contact forces to the rail. However, the effect of handrail height and age on trunk and shoulder kinematics when recovering from perturbations during gait is unknown. Fourteen younger and 13 older adults experienced balance loss (sudden platform translations) while walking beside a height-adjustable handrail. Handrail height was varied from 30 to 44 inches (76 to 112 cm). Trunk and shoulder kinematics were measured via 3D motion capture; applied handrail forces were collected from load cells mounted to the rail. As handrail height increased (up to 42 inches/107 cm), peak trunk angular displacement and velocity generally decreased, while shoulder elevation angles during reaching and peak handrail forces did not differ significantly between 36 and 42 inches (91 and 107 cm). Age was associated with reduced peak trunk angular displacements, but did not affect applied handrail forces. Higher handrails (up to 42 inches) may be advantageous for trunk control when recovering from destabilizations during gait. Our results can inform building codes, workplace safety standards, and accessibility standards, for safer handrail design.

Feasibility study of inertia sensor technology on the pelvic and trunk kinematics during horseback riding in children

Inertial sensors technology (IMU) has been utilized to determine kinematic data for some outdoor activities. Horseback riding (HR) is an alternative treatment that has been reported to be beneficial for children with cerebral palsy (CP). However, understanding the mechanism of improving postural control is unknown. The aim of this study was to investigate the feasible of IMU to determine pelvic and trunk kinematics during HR in children with CP and with typical development (TD). Twenty children (10 CP, 10 TD; age: 4-12 years) were recruited. The movement of the pelvis and trunk in children with CP and TD including angular displacement and velocity were measured by inertial measurement sensors during horseback riding. The result found that no differences were found for pelvis and trunk angular displacement or velocity. For children with CP, pelvis and trunk correlations were strong in angular displacement in the sagittal plane (r=0.65, p=0.04 for pelvis and trunk flexion-extension and r=0.75, p=0.01 for pelvis flexion-extension and trunk inclination) and in angular velocity in the frontal and horizontal plane (r=0.82, p=0.02 for lateral flexion and r=0.73, p=0.02 for rotation). For children with TD, pelvis and trunk correlations were strong only for angular velocity in the sagittal plane (r=67, p=0.03). In conclusion, it is possible to use the IMU technology to capture movement of children during HR. The motion parameters including pelvis and trunk angular displacement and velocity that can be used to detect a degree of functional impairments and monitor the progress of treatment.

Age-Related Differences in Arm and Trunk Responses to First and Repeated Exposure to Laterally Induced Imbalances.

The objective of this study was to examine age-related differences in arm and trunk responses during first and repeated step induced balance perturbations. Young and older adults received 10 trials of unpredictable lateral platform translations. Outcomes included maximum arm and trunk displacement within 1 s of perturbation and at first foot lift off (FFLO), arm and neck muscle activity as recorded using electromyography (EMG), initial step type, balance confidence, and percentage of harness-assisted trials. Compared to young adults, older adults demonstrated greater arm and trunk angular displacements during the first trial, which were present at FFLO and negatively associated with balance confidence. Unlike young adults, recovery steps in older adults were directed towards the fall with a narrowed base of support. Over repeated trials, rapid habituation of first-trial responses of bilateral arm and trunk displacement and EMG amplitude was demonstrated in young adults, but was absent or limited in older adults. Older adults also relied more on harness assistance during balance recovery. Exaggerated arm and trunk responses to sudden lateral balance perturbations in older adults appear to influence step type and balance recovery. Associations of these persistently amplified movements with an increased reliance on harness assistance suggest that training to reduce these deficits could have positive effects in older adults with and without neurological disorders.

Impact of visual signals on axial segmental control during walking in patients with vestibular disorder and healthy persons

Head and trunk control during standing in patients with vestibular disorder may depend on intact visual signal to override vestibular disturbance. It is unknown if such process during walking would change. Therefore, the aims of this study were to quantify (1) head and trunk control in healthy participants (HPs) and patients with unilateral vestibular hypofunction (UVH) during walking with and without visual manipulation; and (2) the correlation/association between vestibular function and head/trunk control during walking with visual manipulation in patients. Seventeen UVH patients and 15 HPs completed all the tests. They participated in the caloric test, which was used to examine vestibular function, and walked on a treadmill with and without visual manipulation. Head and trunk angular displacement and velocity were primary outcome measures, deviation of center of mass and step variability were secondary. Head roll angular displacement (7.38° ± 1.38 [mean ± SE] v.s. 12.95° ± 1.48, p = 0.004) and head-trunk correlation (in the pitch/sagittal plane: 0.22 ± 0.05 v.s. 0.38 ± 0.05, roll/frontal plane: 0.35 ± 0.06 v.s. 0.55 ± 0.06, p < 0.05) were significantly lower in patients compared to HPs. Head pitch angular velocity (8.58°/s ± 2.17 v.s. 14.23°/s ± 1.22, p = 0.026) and step width variability (0.075 ± 0.010 v.s. 0.083 ± 0.009, p = 0.04) increased with visual manipulation only in patients. No significant correlation/association was found between vestibular function and head/trunk control. Lower head-trunk correlation in patients suggests an independent head-trunk control strategy in response to vestibular impairment. Visual input could be used by patients to compensate for vestibular disturbance for head control and foot placement. Severe UVH may not lead to worse postural control compared to mild disorder.

The relation between abdominal muscle asymmetry and trunk postural stability: An ultrasound imaging study.

The core stability theory has emphasized symmetric co-contraction of both anterolateral abdominal muscles (AAM), but there is a lack of research on whether the symmetric co-contraction of AAM is related to the postural stability of the trunk. This study aimed to investigate the correlation between the symmetric co-contraction of bilateral AAM and trunk angular displacement during sudden trunk perturbation. Eighteen subjects were asked to maintain half-seated posture against backward trunk perturbation. Muscle thicknesses of external oblique (EO), internal oblique (IO), and transversus abdominis (TrA) were measured using ultrasound imaging. 3D motion analysis system was utilized to calculate the amount of trunk angular displacement during perturbation. There were significant differences of side-to-side muscle thickness in TrA (P= 0.02) and EO (P= 0.02), but the difference disappeared during sudden external loading. No significant correlation was identified between the asymmetry of abdominal muscle thickness and the amount of trunk angular displacement. These findings indicate that the side-to-side asymmetry of AAM measured in a static position is rarely related to the core stability because the asymmetry can disappear during trunk stabilization.

Influence of handrail height and fall direction on center of mass control and the physical demands of reach-to-grasp balance recovery reactions

The ability to maintain and recover center of mass (COM) and trunk control after a destabilization is critical for avoiding falls and fall-related injuries. Handrails can significantly enhance a person’s ability to recover from large destabilizations, by enabling the person to grasp and apply high forces to the rail to stabilize their COM. However, the influence of handrail height and falling direction on COM control and the demands of grasping are unknown. We investigated the effect of handrail height (34, 38, 42 in.) and fall direction (forward, backward) on COM and trunk control, and the corresponding physical demands of reach-to-grasp balance reactions. Thirteen young adults were destabilized with platform perturbations, and reached to grasp a nearby handrail to recover balance without stepping. COM kinematics and applied handrail forces were collected. COM control was evaluated in terms of: (1) COM range and peak displacement, velocity and momentum in all Cartesian axes; and (2) trunk angular displacement, velocity and momentum in the roll and pitch axes. The physical demands of grasping were estimated via resultant handrail impulse. Compared to forward-directed falling, backward-directed falling was generally associated with greater peak COM and trunk angular displacement, velocity and momentum, along with greater handrail impulse. Higher handrails generally resulted in reduced peak COM and trunk angular displacement, velocity and momentum, as well as reduced handrail impulse. These results suggest that higher handrails may provide a stability advantage within the range of handrail heights tested, with better COM control achieved with lower physical demands of grasping.

Estimating Neural Control from Concentric vs. Eccentric Surface Electromyographic Representations during Fatiguing, Cyclic Submaximal Back Extension Exercises.

Purpose: To investigate the differences in neural control of back muscles activated during the eccentric vs. the concentric portions of a cyclic, submaximal, fatiguing trunk extension exercise via the analysis of amplitude and time-frequency parameters derived from surface electromyographic (SEMG) data.Methods: Using back dynamometers, 87 healthy volunteers performed three maximum voluntary isometric trunk extensions (MVC's), an isometric trunk extension at 80% MVC, and 25 cyclic, dynamic trunk extensions at 50% MVC. Dynamic testing was performed with the trunk angular displacement ranging from 0° to 40° and the trunk angular velocity set at 20°/s. SEMG data was recorded bilaterally from the iliocostalis lumborum at L1, the longissimus dorsi at L2, and the multifidus muscles at L5. The initial value and slope of the root mean square (RMS-SEMG) and the instantaneous median frequency (IMDF-SEMG) estimates derived from the SEMG recorded during each exercise cycle were used to investigate the differences in MU control marking the eccentric vs. the concentric portions of the exercise.Results: During the concentric portions of the exercise, the initial RMS-SEMG values were almost twice those observed during the eccentric portions of the exercise. The RMS-SEMG values generally increased during the concentric portions of the exercise while they mostly remained unchanged during the eccentric portions of the exercise with significant differences between contraction types. Neither the initial IMDF-SEMG values nor the time-course of the IMDF-SEMG values significantly differed between the eccentric and the concentric portions of the exercise.Conclusions: The comparison of the investigated SEMG parameters revealed distinct neural control strategies during the eccentric vs. the concentric portions of the cyclic exercise. We explain these differences by relying upon the principles of orderly recruitment and common drive governing motor unit behavior.

Trunk Stability, Trunk Strength and Sport Performance Level in Judo.

Although trunk muscle function has been suggested to be a determinant of judo performance, its contribution to high-level performance in this sport has been poorly studied. Therefore, several tests were used to assess the differences in trunk muscle function between 11 international and 14 national level judo practitioners (judokas). Trunk strength and endurance were assessed using isokinetic tests and core stability was assessed using two protocols: 1) sudden loading, to assess trunk responses to unexpected external perturbations; 2) stable and unstable sitting, to assess the participants’ ability to control trunk balance. No differences between groups were found for trunk flexor isokinetic strength, trunk responses against lateral and posterior loading and trunk control while sitting. However, international level judokas showed significantly higher trunk extensor isokinetic strength (p <0.05) and lower trunk angular displacement after anterior trunk loading (p <0.05) than national level judokas. Few and low (r < 0.512) significant correlations were found between strength, endurance and stability parameters, which suggests that trunk strength and endurance are not limiting factors for trunk stability in competitive judokas. These results support the importance of trunk extensor strength and trunk stability against forward perturbations in elite judo performance.

Effects of different biofeedback training techniques on the static balance of hemiplegic patients

Objective To compare the static standing balance of stroke patients after different biofeedback protocols. Methods Thirty-two stroke patients were randomly divided into a knowledge of performance (KP) group, a knowledge of results (KR) group and a control group. All 3 groups received 4 weeks of conventional rehabilitation training plus another 30min of static standing balance training per day. The KP group received audio-visual feedback in real time during the training. The KR group received section result feedback. The control group received no feedback during the extra balance training. Before and after the training, the performance of the 3 groups was evaluated using Berg's Balance Scale (BBS) and a portable biofeedback device. Results Average BBS performance improved significantly more in the KP group (3.08±1.08) than in KR group (1.30±0.67) and control group (1.20±0.79) (P 0.05). The average improvements of the KP group in terms of Standing with Eyes Closed and Tandem Standing (0.92±0.79 and 0.83±0.39) were significantly higher than those in the KR (0.30±0.48 and 0.20±0.42) and control groups (0.01±0.01 and 0.40±0.52) (P<0.05). Average trunk angular displacements in all four directions[Anterior (2.83±0.93; 6.15±1.85), Posterior (2.56±0.88; 5.97±1.74); Left (2.86±1.16; 6.49±2.42), Right (2.68±1.43; 5.98±2.05)]in the KP group was significantly higher than in the others (P<0.05). No significant differences were detected between the KR and control groups in BBS results or in posture. Conclusions Static standing training should incorporate real time biofeedback. It is then more effective than conventional standing training or training with section results feedback. It is worth spreading in clinical applications. Key words: Biofeedback; Training; Static balance; Stroke

Accuracy and repeatability of an inertial measurement unit system for field-based occupational studies

The accuracy and repeatability of an inertial measurement unit (IMU) system for directly measuring trunk angular displacement and upper arm elevation were evaluated over eight hours (i) in comparison to a gold standard, optical motion capture (OMC) system in a laboratory setting, and (ii) during a field-based assessment of dairy parlour work. Sample-to-sample root mean square differences between the IMU and OMC system ranged from 4.1° to 6.6° for the trunk and 7.2°–12.1° for the upper arm depending on the processing method. Estimates of mean angular displacement and angular displacement variation (difference between the 90th and 10th percentiles of angular displacement) were observed to change <4.5° on average in the laboratory and <1.5° on average in the field per eight hours of data collection. Results suggest the IMU system may serve as an acceptable instrument for directly measuring trunk and upper arm postures in field-based occupational exposure assessment studies with long sampling durations.Practitioner Summary: Few studies have evaluated inertial measurement unit (IMU) systems in the field or over long sampling durations. Results of this study indicate that the IMU system evaluated has reasonably good accuracy and repeatability for use in a field setting over a long sampling duration.

The effects of initial movement dynamics on human responses to postural perturbations

Falls are a major cause of injury, and often occur while turning, reaching, or bending. Yet, we have little understanding of how an ongoing feet-in place activity at the onset of imbalance, and its associated cognitive and biomechanical demands, influence our ability to recover balance. In the current study, we used an ankle-rocking paradigm to determine how the nature of the baseline task influences the balance recovery response to a backward support surface translation. Fourteen participants were instructed to “recover balance without stepping” and were perturbed at vertical while standing quietly (“S”), while ankle rocking and moving forward (“A_f”), or while ankle rocking and moving backward (“A_b”). The results showed that changes in rocking velocity at the time of the perturbation elicited changes in the incidence of stepping, magnitude of trunk angular displacements (p<.01), and the onset latencies of distal muscles (gastrocnemius and soleus, both p<.01) used to recover balance. In addition, plots of onset latencies across all muscles showed that onset latencies appeared to occur earlier in many muscles when participants held a static position compared to when they performed a dynamic task at the onset of the perturbation. The results suggest that muscle activities used to recover balance are tailored to the nature of the perturbation and the ongoing task, and that onset latencies are later when participants are performing a dynamic as opposed to static task at the time of a perturbation. These findings support previous research suggesting that automatic postural responses are highly adaptable to environmental, situational, and task demands.

Intensive unilateral neuromuscular training on non-dominant side of low back improves balanced muscle response and spinal stability

Effective stabilization is important to increase sports performance. Imbalanced spinal muscle responses between the left and right sides increase the risk of spinal buckling and microtrauma at the intervertebral joints. The purpose of this study was to confirm whether intensive unilateral neuromuscular training (IUNT) focusing on the non-dominant side of the low back improves balanced muscle responses and spinal stability. The IUNT group (n = 8) performed side bridge and quadruped exercises using their non-dominant trunk muscles for 8 weeks, while the control group (n = 8) performed their regular training. Before and after the training, motion-capture cameras measured trunk angular displacement, and electromyography recorded the activities of both multifidus muscles (L4-5) during unexpected sudden forward perturbation. After the training in the IUNT group, the difference in onset time between both sides decreased to approximately 120 % compared with that before the training. The asymmetry of muscle activities also decreased from 56 to 23 %. Moreover, the angular displacement on the sagittal plane decreased to approximately 35 % after the training. We expect that IUNT focused on the non-dominant side of the low back will be useful to improve balanced back muscle responses and spinal stability during sudden trunk perturbation.

Direction-dependent neck and trunk postural reactions during sitting

Postural reactions in healthy individuals in the seated position have previously been described and have been shown to depend on the direction of the perturbation; however the neck response following forward and backward translations has not been compared. The overall objective of the present study was to compare neck and trunk kinematic, kinetic and electromyographic (EMG) stabilization patterns of seated healthy individuals to forward and backward translations. Ten healthy individuals, seated on a chair fixed onto a movable platform, were exposed to forward and backward translations (distance = 0.15 m, peak acceleration = 1.2 m/s 2). The head and trunk kinematics as well as the EMG activity of 16 neck and trunk muscles were recorded. Neck and trunk angular displacements were computed in the sagittal plane. The centers of mass (COMs) of the head (HEAD), upper thorax (UPTX), lower thorax (LOWTX) and abdomen (ABDO) segments were also computed. Moments of force at the C7-T1 and L5-S1 levels were calculated using a top-down, inverse dynamics approach. Forward translations provoked greater overall COM peak displacements. The first peak of moment of force was also reached earlier following forward translations which may have played a role in preventing the trunk from leaning backwards. These responses can be explained by the higher postural threat imposed by a forward translation.

Postural stability effects of random vibration at the feet of construction workers in simulated elevation

The risk of falls from height on a construction site increases under conditions which degrade workers’ postural control. At elevation, workers depend heavily on sensory information from their feet to maintain balance. The study tested two hypotheses: “sensory enhancement” – sub-sensory (undetectable) random mechanical vibrations at the plantar surface of the feet can improve worker’s balance at elevation; and “sensory suppression” – supra-sensory (detectable) random mechanical vibrations can have a degrading effect on balance in the same experimental settings. Six young (age 20–35) and six aging (age 45–60) construction workers were tested while standing in standard and semi-tandem postures on instrumented gel insoles. The insoles applied sub- or supra-sensory levels of random mechanical vibrations to the feet. The tests were conducted in a surround-screen virtual reality system, which simulated a narrow plank at elevation on a construction site. Upper body kinematics was assessed with a motion-measurement system. Postural stability effects were evaluated by conventional and statistical mechanics sway measures, as well as trunk angular displacement parameters. Analysis of variance did not confirm the “sensory enhancement” hypothesis, but provided evidence for the “sensory suppression” hypothesis. The supra-sensory vibration had a destabilizing effect, which was considerably stronger in the semi-tandem posture and affected most of the sway variables. Sensory suppression associated with elevated vibration levels on a construction site may increase the danger of losing balance. Construction workers at elevation, e.g., on a beam or narrow plank might be at increased risk of fall if they can detect vibrations under their feet. To reduce the possibility of losing balance, mechanical vibration to supporting structures used as walking/working surfaces should be minimized when performing construction tasks at elevation.

Strategies for Posture Transfer Adopted by Elders during Sit-To-Stand and Stand-To-Sit

This study investigated whether three posture-transfer strategies, No support, Chair-arm, and Cane, were associated with the smallest hip-compressed angle and the smallest ankle-compressed angle during sit-to-stand and stand-to-sit for 12 elders (M age = 81.3 yr., SD = 5.9) who volunteered to participate. Using an optoelectronic movement analyzer, the smallest compressed angles of the hip and ankle were measured during standing up and sitting down. The adopted strategies had significant effects on the smallest hip-compressed angle, but not the smallest ankle-compressed angle. Although cane use led to a larger trunk angular displacement than did chair-arm use, a cane can provide help during the whole transfer process. These two strategies may be seen as adaptive mechanisms to decrease risk of anterior disequilibrium.

Dynamic trunk stability is improved in paraplegics following kayak ergometer training

The purpose of the study was to assess whether postural stability in persons with spinal cord injury (SCI) could be affected by training. Ten post-rehabilitated persons with thoracic SCI performed 30 sessions of kayak ergometer training during a 10-week period. The ergometer was modified with a balance module adjustable in the medio-lateral direction. Before and after the training period, horizontal support-surface translations were presented randomly, either in the forward or backward direction, or to the side, while subjects sat in their own wheelchairs. The platform perturbation consisted of an unpredictable initial acceleration, followed by a constant-velocity phase and a predictable deceleration. Markers were applied on the trunk and movement data were recorded in 3D. Four kinematic responses of trunk angular and linear displacement were investigated. In general, postural stability was improved after training with smaller rotational and linear displacements of the trunk observed during both predictable and unpredictable translations in all directions. Thus, the training was able to improve the ability of persons with long-standing SCI to maintain an upright sitting posture in response to externally generated balance perturbations, which should imply an increased capacity to master similar challenges to balance in everyday life.

Is fall prevention by vitamin D mediated by a change in postural or dynamic balance?

The objectives were:(1) to validate a quantitative balance assessment method for fall risk prediction; (2) to investigate whether the effect of vitamin D and calcium on the risk of falling is mediated through postural or dynamic balance, as assessed by this method. A secondary analysis of a double blind randomized controlled trial was employed, which included 64 institutionalized elderly women with complete balance assessment (age range: 65-97; mean 25-hydroxyvitamin D levels: 16.4 ng/ml (SD +/-9.9). Participants received 1,200 mg calcium plus 800 IU cholecalciferol (n=33) or 1,200 mg calcium (n=31) per day over a 3-month treatment period. Using an electronic device attached to the lower back of the participant, balance was assessed as the degree of trunk angular displacement and angular velocity during a postural task (standing on two legs, eyes open, for 20 s) and a dynamic task (get up from a standard height chair with arm rests, sit down and then stand up again and remain standing). It was found that both postural and dynamic balance independently and significantly predicted the rate of falling within the 3-month follow-up. Vitamin D plus calcium reduced the rate of falls by 60% [relative risk (RR)=0.40; 95% CI: 0.17, 0.94] if compared with calcium alone. Once postural and dynamic balance were added to the regression analysis, they both attenuated the effect of vitamin D plus calcium on the rate of falls. For postural balance, the RR changed by 22% from 0.40 to 0.62 if angular displacement was added to the model, and by 9% from 0.40 to 0.49 if angular velocity was added. For dynamic balance, it changed by 1% from 0.40 to 0.41 if angular displacement was added, and by 14% from 0.40 to 0.54 if angular velocity was added. Thus, balance assessment using trunk angular displacement is a valid method for the prediction of falls in older women. Of the observed 60% reduction in the rate of falls by vitamin D plus calcium supplementation compared with calcium alone, up to 22% of the treatment effect was explained by a change in postural balance and up to 14% by dynamic balance.