Alison C. Novak

Sagittal and frontal lower limb joint moments during stair ascent and descent in young and older adults

Stair negotiation is an essential skill required for independent mobility, and is described by older adults as a challenging task that is associated with high fall risk. Little is known about the age-related changes in joint kinetics and the relative contribution of lower limb joint moments during stair negotiation. This study characterized lower extremity joint kinetics and their variability associated with stair ascent and descent in young and older adults. Twenty three young and 32 older adults (>55 years) participated. Three dimensional, bilateral gait analysis provided ankle, knee, and hip moment profiles, which in the sagittal plane were summed to provide the support moment. In addition, intra- and inter-subject coefficients of variation were calculated for ensemble averaged curves. Age-related differences were found in the magnitudes of the moment contributions during event transitions for stair ascent and descent. Within groups, the moment profiles were generally consistent. Ankle and knee moments predominantly contributed to extensor support in the sagittal plane. In the frontal plane, proximal joint abductor moments maintained lateral stability and were larger at the hip in older adults. Understanding age-related alterations in movement control during functional tasks can help inform the rehabilitation management and assessment of patient populations.

Concurrent validation of Xsens MVN measurement of lower limb joint angular kinematics

This study aims to validate a commercially available inertial sensor based motion capture system, Xsens MVN BIOMECH using its native protocols, against a camera-based motion capture system for the measurement of joint angular kinematics. Performance was evaluated by comparing waveform similarity using range of motion, mean error and a new formulation of the coefficient of multiple correlation (CMC). Three dimensional joint angles of the lower limbs were determined for ten healthy subjects while they performed three daily activities: level walking, stair ascent, and stair descent. Under all three walking conditions, the Xsens system most accurately determined the flexion/extension joint angle (CMC > 0.96) for all joints. The joint angle measurements associated with the other two joint axes had lower correlation including complex CMC values. The poor correlation in the other two joint axes is most likely due to differences in the anatomical frame definition of limb segments used by the Xsens and Optotrak systems. Implementation of a protocol to align these two systems is necessary when comparing joint angle waveforms measured by the Xsens and other motion capture systems.

Gait Changes Following Botulinum Toxin A Treatment in Stroke

Abstract Purpose: To characterize the effects of botulinum toxin A treatment of spastic plantar flexors in stroke on joint mobility and gait kinematics and kinetics. Method: Nine patients with hemiparetic stroke presenting with ankle hypertonicity participated in this exploratory open-label case series study. Comprehensive gait analysis provided bilateral kinematic and kinetic information for the ankle, knee, and hip joints throughout the stance phase. Data were obtained at baseline, 2 weeks, and 10 weeks post botulinum toxin injection of the spastic plantar flexors. Results: Passive ankle range of motion increased post injection (p < .05). The amount of plantarflexion in late stance was significantly reduced (p < .05) while the maximum dorsiflexion increased in midstance at 10 weeks post treatment. The angular displacement profiles for the knee revealed that patients tended to display less hyperextension following treatment (p = .053). No significant changes in kinetic measures were found; however, case-by-case observations suggested that most patients experienced improvements in positive work production. Conclusions: The findings indicate that botulinum toxin treatment results in improved joint mobility and ankle kinematics and, in some patients, increases in positive work, suggesting better gait performance.

Strength and Aerobic Requirements During Stair Ambulation in Persons With Chronic Stroke and Healthy Adults

OBJECTIVE To estimate the cost of stair ascent and descent in relation to a measured standard of strength and metabolic (aerobic) capacities in persons with chronic stroke compared with healthy adults. DESIGN Descriptive cross-sectional study. SETTING Motion analysis laboratory. PARTICIPANTS Persons with stroke (n=10) and sex- and age-matched older adults (n=10). INTERVENTION Not applicable. MAIN OUTCOME MEASURES Lower limb peak joint moments generated during stair walking, expressed as a percentage of the respective isokinetic peak torque, provided an estimate of the relative strength cost. The oxygen consumed during stair walking as a percentage of the maximum oxygen consumption estimated from a submaximal cycle ergometer test reflected the relative aerobic cost of stair ambulation. RESULTS During ascent, plantarflexor strength cost was highest on the affected side (stroke) compared with the less affected side and control subjects. The costs associated with the knee extensors were highest in stroke (both sides) for both ascent and descent, and similarly the costs were highest for the less affected and affected plantarflexors during descent. No differences were detected between the affected and less affected sides. The oxygen consumed when ambulating 1 flight of stairs was comparable between groups, but the relative aerobic cost of stair ascent and descent was higher in stroke survivors because of their lower aerobic capacity. CONCLUSIONS To our knowledge, this is the first study to compare the relative costs of stair ambulation in people with stroke and healthy controls. The higher strength and aerobic costs associated with stair negotiation in stroke resulting primarily from reduced strength and aerobic capacities, respectively, may limit mobility.

Relationship between stair ambulation with and without a handrail and centre of pressure velocities during stair ascent and descent

INTRODUCTION Stair ambulation is one of the most challenging and hazardous types of locomotion for older adults and often requires the adoption of compensatory strategies such as increased handrail use to mitigate disability and increase stability. Centre of pressure velocity (VCOP) describes the neuromuscular response to shifts of the bodys centre of mass and serves as an indicator of stability. Knowledge of VCOP may provide some understanding of strategies to improve measured and perceived stability during stair negotiation. The aim of this study was to compare VCOP during stair ascent and descent with and without a handrail in young, older and older adults with a fear of falling (FOF) populations. METHODS COP velocities of 23 young adults (23.7±3.0 yrs), 26 older adults (66.4±8.3 yrs), and 3 older adults with FOF (80.2±8.0 yrs) were analyzed while they ascended and descended a custom 4-step staircase. VCOP were obtained using a force plate mounted on concrete blocks centered on the second step of the staircase. RESULTS During stair ascent and descent with and without a handrail, the VCOP between young and older adults were comparable. The three adults with FOF demonstrated reduced VCOP during ascent and descent without the handrail and even slower VCOP when ascending and descending stairs with the handrail. These results suggest that handrail use does not increase biomechanical stability for healthy, older adults. However, in the presence of fear of falling the use of the handrail enhances dynamic stability, particularly during stair descent. CONCLUSIONS This study provides the first detailed description of dynamic stability during stair ambulation with and without a handrail. Observations from those with FOF aid in understanding the nature of compensations to improve actual and perceived stability.

Effects of aging on whole body and segmental control while obstacle crossing under impaired sensory conditions.

The ability to safely negotiate obstacles is an important component of independent mobility, requiring adaptive locomotor responses to maintain dynamic balance. This study examined the effects of aging and visual-vestibular interactions on whole-body and segmental control during obstacle crossing. Twelve young and 15 older adults walked along a straight pathway and stepped over one obstacle placed in their path. The task was completed under 4 conditions which included intact or blurred vision, and intact or perturbed vestibular information using galvanic vestibular stimulation (GVS). Global task performance significantly increased under suboptimal vision conditions. Vision also significantly influenced medial-lateral center of mass displacement, irrespective of age and GVS. Older adults demonstrated significantly greater trunk pitch and head roll angles under suboptimal vision conditions. Similar to whole-body control, no GVS effect was found for any measures of segmental control. The results indicate a significant reliance on visual but not vestibular information for locomotor control during obstacle crossing. The lack of differences in GVS effects suggests that vestibular information is not up-regulated for obstacle avoidance. This is not differentially affected by aging. In older adults, insufficient visual input appears to affect ability to minimize anterior-posterior trunk movement despite a slower obstacle crossing time and walking speed. Combined with larger medial-lateral deviation of the body COM with insufficient visual information, the older adults may be at a greater risk for imbalance or inability to recover from a possible trip when stepping over an obstacle.

Gait Analysis in Orthopedic Foot and Ankle Surgery—Topical Review, Part 1 Principles and Uses of Gait Analysis

Gait analysis, the systematic study of human walking, is a field that has been studied for well over 100 years. With the technological and scientific advancements of the last several decades, there has been substantial improvement in our understanding of the mechanics of human walking. Particularly important has been the advancement in understanding of the differences between normal and pathological gait. The purpose of this paper is to review the principles of gait analysis, with a particular focus on the underlying methods and science. This will assist orthopedic foot and ankle surgeons in better understanding the methods and meaning of gait research and the publications that commonly appear in the orthopedic foot and ankle surgery literature. Level of Evidence: Level V, expert opinion.

Mechanical energy transfers across lower limb segments during stair ascent and descent in young and healthy older adults.

Older adults present with altered movement patterns during stair negotiation although the extent to which modifications in pattern and speed influence mechanical efficiency is unknown. This study evaluated mechanical energy transfers attributed to active force production during stair negotiation in young and older adults to provide insight into age-related changes in mechanical efficiency. Secondary analysis on data obtained from 23 young (23.7±3.0 years) and 32 older adults (67.0±8.2 years) during self-paced stair ascent and descent was conducted. Mechanical energy expenditures (MEE) during concentric transfer, eccentric transfer and no-transfer phases were determined for the ankle, knee and hip power profiles in the sagittal plane. Mechanical energy compensations (MEC) were also determined at each joint. During ascent, MEEs were similar for young and older adults although older adults compensated ankle muscles to a lesser extent during concentric muscle action. Controlling for cadence eliminated this difference. During descent, older adults demonstrated lower energy expenditures at the ankle and hip and similar expenditures at the knee compared to young adults. Changes in joint MEE in the older group resulted in reduced energy compensation at the ankle during concentric and eccentric activity and at the knee during eccentric activity. These age-related differences in mechanical energy transfers and related adjustments in MEC were not a function of the slower cadence in older adults and suggest a loss in mechanical efficiency. These results provide a benchmark against which physical impairments in older adults may be explored.

DETERMINING FUNCTIONAL MOBILITY USING THE MODIFIED TIMED UP AND GO TEST: EFFECTS OF SENSORY MANIPULATIONS

To the Editor: It is recommended that mobility assessment tools be made more demanding when targeted to active older adults, to avoid the ceiling effect. Researchers have incorporated this notion during performing the Timed Up and Go (TUG) test by adding secondary tasks or by increasing the walking distance of the TUG from 3 m to 8 m, but these modifications have failed to increase the sensitivity of the TUG to predict future falls and or increase the responsiveness to detect age-related differences in mobility. The purpose of the present study was to investigate whether adding sensory challenges during mobility assessment would provide a more-sensitive indicator of functional mobility in community-dwelling active older adults. Six young (aged 19–31) and six older (aged 65–85) healthy and physically active community-dwelling volunteers participated. They signed an informed consent approved by the institution’s Office of Research Ethics. The participants completed the TUG under two lower-limb proprioceptive conditions: normal input (on hard surface (HS)) and inaccurate input (on compliant surface of medium-density polyurethane foam (CS)). Vision was manipulated on randomly selected trials in both surface conditions by asking them to wear custom-made blurring vision goggles that simulated the consequences of dense cataracts. Thus, there were a total of four sensory conditions: HS plus normal vision (HS1V, control condition), HS plus blurred vision (HS1BV), CS plus normal vision (CS1V), and CS plus blurred vision (CS1BV). Two trials were performed with each condition. The trials were blocked for the surface conditions, and the order of the blocks was balanced between participants. Within the surface condition, the vision condition trials were randomized. Total duration to complete the TUG and the duration required for each mobility component (sit-to-stand, walk up to the 3-m line, turn, and stand-to-sit) was determined for each trial. The time scores were averaged over two trials of similar sensory conditions. The effects of age and sensory challenges were analyzed for each measure using a two-way mixed-factor analysis of variance (ANOVA). The ANOVA revealed a significant age–condition interaction (P 5.04). When data were analyzed for each condition using independent t test, the groups were not different in HS1V (P 5.08) and under HS1BV (P 5.08) conditions. Significant differences between the groups were found only under the CS1BV condition (P 5.03). In addition, under the CS1V condition, the groups were considerably different (P 5.05). The condition effect was significant (Po.001), suggesting that time required to complete the TUG increased as the sensory challenge increased (Figure 1A). The time required for the turn component was significantly longer in older adults than in younger adults (P 5.03) (Figure 1B), independent of the sensory perturbation. Group differences for the sit-to-stand and stand-to-sit components of the TUG task were not significant (P 5.10 and P 5.09, respectively). Surprisingly, sensory manipulations did not influence the sit-to-stand (P 5.94), stand-to-sit (P 5.40), and turn (P 5.27) components. There were no differences between the groups for the walk component (P 5.51). Multiple comparisons of the walk component demonstrated that there were no differences between HS1V and HS1BV (P 5.44) or between CS1V and CS1BV (P 5.64), suggesting no effect of blurring vision on either surface. In contrast, HS1V and HS1BV were significantly different from CS1V (P 5.003 and P 5.009, respectively) and CS1BV (Po.001 and Po.001, respectively), suggesting that the duration of the walk component was significantly longer on the compliant surface, independent of age and vision. The results suggest that, with the sensory challenges provided in this study, the TUG was able to detect even subtle age-related changes in mobility that could not be detected when optimum conditions were available. Thus, modifying the TUG test using deprived sensory conditions may impose adequate challenge and thereby may provide a more-sensitive measure of mobility in community-dwelling active older adults. This modified version can enable clinicians to identify individuals with functional mobility impairments at an earlier stage for implementing preventive measures. The analysis for the TUG components showed that the turn component probably posed more challenge to older adults, independent of the sensory condition, and may necessitate a more-intense rehabilitation process for retraining. No other evidence is available that describes effects 10.9 10.6 10.5 9.9 9.7 11.2 12.7 13.1

Passive restraint reduces visually induced motion sickness in older adults

Virtual environments such as those used in video games and driving/flight simulators are used for entertainment and training, but are often associated with visually induced motion sickness (VIMS). In this study, we asked whether passive restraint of the head and torso could reduce VIMS in younger and older adults. Twenty-one younger (18–35 years) and 16 older (65 + years) healthy adults engaged in a simulated driving task using a console video game while seated. On different days, participants completed 2 conditions: (a) in the unrestrained condition, participants were seated in a chair without a backrest and were free to move and (b) in the restrained condition, participants’ head and torso were passively restrained to the backrest and headrest of the seat using tense elastic strips. Before and after exposure to the driving game, we measured standing postural sway with eyes closed. VIMS severity was quantified using the Fast Motion Sickness Scale and the Simulator Sickness Questionnaire. Results showed that older (but not younger) participants who became sick in the unrestrained condition reported significantly less VIMS when they were passively restrained. The present findings suggest that passive restraint may be useful to reduce, but not fully prevent, VIMS, particularly in older adults.