Li-shan Chou

Skeletal muscle strength is known to decline with age. Although lower extremity (LE) muscle strength is critical to maintaining dynamic stability, few studies have investigated lower extremity muscle challenge during activities of daily living. The purpose of this study was to investigate the effects of age and obstructed gait on relative lower extremity muscular challenge, with respect to available joint

Lee H-J, Chou L-S. Detection of gait instabil- ity using the center of mass and center of pressure inclination angles. Arch Phys Med Rehabil 2006;87:569-75. Objective: To define a parameter that quantifies balance control during gait and better identifies elderly people who are at a higher risk of falling. Design: Controlled study. Setting: University research laboratory. Participants: Twelve elderly patients

Accidental falls are a leading cause of injury and death in the growing elderly population. Traumatic falls are frequent, costly, and debilitating. Control of balance during locomotion is critical for safe ambulation, but relatively little is known about the natural effect of aging on dynamic balance control. Samples of healthy young ðn ¼ 13Þ and elderly ðn ¼ 13Þ subjects

INTRODUCTION According to Kahnemn's [2] model of information processing, processing capacity in humans is limited. When two tasks are presented to an individual, the desired outcome(s) will occur so long as the capacity of the system has not been exceeded. Once the capacity has been reached, there will be a decline in performance in one or all tasks. It has been estimated that, between the ages of 15-24 years, 133 people out of 100,000 will receive a traumatic brain injury (TBI) each year [3]. This accounts for 31.7% of all concussions. The maintenance of dynamic stability while perturbed by different secondary tasks is crucial day by day. Motor perturbations have been previously described to have significant detrimental effects on a TBI population [1]. To date, there have been no studies measuring a simple reaction time, a cognitive, and a motor dual-task with level walking, specifically in a concussed population. Our study looked to determine how different secondary tasks affe...

Patients with traumatic brain injury (TBI) complain of “imbalance” or “unsteadiness” while walking, despite a normal gait on clinical examination. Thus, the purpose of this study was to determine if it was possible to quantitatively assess dynamic stability that did not have an obvious neuromuscular origin in individuals following TBI. Ten patients with documented TBI and 10 age, gender,

Objective. To determine if medio-lateral motion of the head, trunk, or pelvis demonstrates dynamic stability as well as whole- body center of mass during obstructed walking. Design. Group comparison of two elderly populations using whole-body motion analysis. Background. Detection of imbalance through analysis of center of mass motion is commonly adopted, requiring three-dimen- sional reconstruction of a multi-link biomechanical model.

Stair negotiation is among the most challenging and hazardous types of locomotion for older people. However, the effect of aging on balance control during stair negotiation has not been investigated. Instantaneous inclination angles between the center of mass (CoM) and center of pressure (CoP) have been reported to detect gait instability effectively in the elderly. The purpose of this study

The measurement of gait parameters normally requires motion tracking systems combined with force plates, which limits the measurement to laboratory settings. In some recent studies, the possibility of using the portable, low cost, and marker-less Microsoft Kinect™ sensor to measure gait parameters on over-ground walking has been examined. The current study further examined the accuracy level of the Kinect sensor for assessment of various gait parameters during treadmill walking under different walking speeds. Twenty healthy participants walked on the treadmill and their full body kinematics data were measured by a Kinect sensor and a motion tracking system, concurrently. Spatiotemporal gait parameters and knee and hip joint angles were extracted from the two devices and were compared. The results showed that the accuracy levels when using the Kinect sensor varied across the gait parameters. Average heel strike frame errors were 0.18 and 0.30 frames for the right and left foot, respe...

Mild traumatic brain injury (mTBI) leads to a variety of attentional, cognitive, and sensorimotor deficits. An important aspect of behavior that intersects each of these functions is the ability to cancel a planned action. Thus, the purpose of this study was to determine the effects of mTBI on the ability to perform a countermanding saccade task. In this task, participants were asked to generate a saccade to a target appearing in peripheral vision, but to inhibit saccade execution if an auditory stop signal was presented. The delay between the appearance of the peripheral target and the presentation of the auditory stop signal was varied between 0 and 125ms. We found that the change in the probability of cancelling the saccade as a function of this delay was no different between participants with mTBI tested within 2 days of their injury and matched controls. However, saccadic reaction times and the stop signal reaction time were unexpectedly faster in the participants with mTBI and, furthermore, they inaccurately inhibited saccades during 15% of the trials with no stop signal. Taken together, this data suggests that the ability to cancel planned actions is subtly yet adversely affected by mTBI.

This study evaluated whether Tai Ji Quan: Moving for Better Balance (TJQMBB) could improve global cognitive function in older adults with cognitive impairment. Using a nonrandomized control group pretest-posttest design, participants aged ≥65 years who scored between 20 and 25 on the Mini-Mental State Examination (MMSE) were allocated into either a 14-week TJQMBB program (n=22) or a control group (n=24). The primary outcome was MMSE as a measure of global cognitive function with secondary outcomes of 50-ft speed walk, Timed Up&Go, and Activities-Specific Balance Confidence (ABC) scale. At 14 weeks, Tai Ji Quan participants showed significant improvement on MMSE (mean=2.26, p<0.001) compared to controls (mean=0.63, p=0.08). Similarly, Tai Ji Quan participants performed significantly better compared to the controls in both physical performance and balance efficacy measures (p<0.05). Improvement in cognition as measured by MMSE was related to improved physical performance and bal...

... Parker, Tonya M.; Osternig, Louis R. FACSM; Chou, Li-Shan. ... Whole-body motion data were collected using an eight-camera motion analysis system and two force plates to examine anterior and medial-lateral center of mass (COM) motion (ANTdisp, MLdisp), the peak anterior ...

Patients with mild traumatic brain injury (TBI) often complain of dizziness. However, these problems may be undetected by a clinical exam. Therefore, the purpose of this study was to evaluate the relationships between the subjective and objective measures of balance impairment. Ten patients with TBI (6 men and 4 women) and 10 matched controls participated in this study. Average duration since the TBI was 2.8 years (range 0.4-14.4). Six of the 10 subjects with TBI had abnormal imaging studies. All subjects and controls had a normal neuromuscular exam. Tinetti Balance Assessments were obtained and the TBI group was not significantly different from the control group. The Dizziness Handicap Inventory (DHI) score supported their complaints of "unsteadiness" and "imbalance" from the subjects with TBI. The DHI score was 32 +/- 23 (range 4-68) out of a maximum possible score of 100. Balance was tested using computerized dynamic posturography. The Sensory Organization Test score was significantly lower for subjects who had a TBI (70 +/- 12) compared to the control subjects (80 +/- 8), which indicated that the subjects with TBI had poorer balance than the control subjects. A 13-link biomechanical model of the human body was used to compute the kinematics of the whole body center of mass (COM) while walking on a level surface. The subjects with TBI had significantly less displacement in the anterior/posterior direction, walked significantly slower, had significantly greater medial/lateral sway and velocity than the normal controls, and had significantly greater medial/lateral imbalance. There was a significant relationship between the physical aspects of the DHI and posturography. There was also significant relationship between the physical, functional, and total DHI and the motion of the COM. Overall, the motion of the COM predicted between 42 and 69% of the DHI score. The present study has demonstrated that objective measurements can quantify the patient's functional deficits. Therefore, these objective measurement techniques should be used to assess the clinical complaints of imbalance from patients with TBI.

The purpose of this study was to longitudinally compare the sensitivity of previously documented paradigms for measuring balance control during gait following a concussion. We hypothesized that gait with a concurrent cognitive task would be most sensitive to the effects of concussion on dynamic balance control. Individuals with concussion (n = 30) and matched controls (n = 30) performed a single task of level walking, attention divided walking, and an obstacle-crossing task at two heights. Testing occurred four times post-injury. Balance control during gait was assessed with whole-body center of mass and center of pressure motion. The single-task level walking task did not result in any significant differences in balance control between individuals with concussion and control subjects. Within 48 hours post-injury, individuals with concussion walked slower and allowed less motion of their center of mass in the sagittal plane when attention was divided during walking, but there were no group differences by day 6 for this task. Group differences in balance control during obstacle crossing was unremarkable during the first two testing sessions, but by day 14 individuals with concussion displayed less mediolateral motion of their center of mass. Attention divided gait is able to better distinguish gait adaptations immediately following a concussion, but obstacle crossing can be used further along in the recovery process to detect new gait adaptations.

The purpose of this study was to determine how two diVerent types of concurrent tasks aVect gait stability in patients with concussion and how balance is maintained. Fourteen individuals suVering from a grade II concussion and 14 matched controls per- formed a single task of level walking and two types of concurrent tasks during level walking: a discrete reac- tion time task and a continuous sequential question and answer task. Common gait spatial/temporal mea- surements, whole-body center of mass motion, and the center of pressure trajectory were recorded. Concussed individuals demonstrated diVerences in gait while per- forming single-task level walking and while being chal- lenged with a more diYcult secondary task compared to normal controls. Concussed individuals adopted a slower, more conservative gait strategy to maintain sta- bility, but still exhibited signs of instability with center of mass deviations in the coronal plane increasing by 13% during the question and answer du...

The need to identify functional impairment following a brain injury is critical to prevent reinjury during the period of recovery. However, little is known about the effect of concussion on dynamic motor function. The purpose of this study was to examine the effect of concussion on a dynamic motor task under conditions of divided and undivided attention over the course of 28 d. Fifteen subjects with concussions (CONC) and 15 uninjured controls (NORM) were observed while walking with undivided attention and while concurrently completing simple mental tasks. The CONC were assessed within 48 h of injury and again at 5, 14, and 28 d postinjury. The NORM were evaluated at the same time intervals. Whole-body motion data were collected to examine displacement and velocity of the center of mass (COM) and the maximum separation between the COM and center of pressure (COP). Three-way repeated-measures mixed-design ANOVA and Tukey post hoc tests were completed to determine differences between group, task, and testing day (P<0.05). Several aspects of gait stability were compromised in the CONC group for up to 4 wk after injury. CONC were found to walk significantly slower during dual tasks on all testing days when compared with the uninjured controls. The injured subjects were also found to have greater sway and sway velocity than controls when attention was divided for up to 28 d postinjury. The findings of this study suggest that concussion may have long-term observable and measurable effects on the control of gait stability.

Stair negotiation is among the most challenging and hazardous types of locomotion for older people. However, the effect of aging on balance control during stair negotiation has not been investigated. Instantaneous inclination angles between the center of mass (CoM) and center of pressure (CoP) have been reported to detect gait instability effectively in the elderly. The purpose of this study was to compare the CoM-CoP inclination angles between 12 healthy elderly and 13 healthy young adults when performing stair ascent (SA) and descent (SD) on a three-step staircase. Whole body motion data were collected with an eight-camera motion analysis system. Four force plates were mounted on the floor as well as the first two steps to measure ground reaction forces. No significant group differences were detected in any of the temporal-distance gait measures and CoM-CoP inclination angles during SA and SD. Compared to the floor-to-stair transition phase, both groups demonstrated a significantly greater CoM-CoP medial inclination angle while ascending the stairs. However, a significant reduction in medial inclination was only detected in young adults when transferring from SD to level ground walking. Elderly adults were found to demonstrate a significantly greater medial inclination angle during the stair-to-floor transition phase when compared to young adults. Age-related degenerations in the elderly could compromise their ability to regulate body sway during the stair-to-floor transition, which may subsequently increase the risk of falling.

We studied 7 younger and 5 older patients who had rotating-hinge total knee replacements, 10 patients who had semiconstrained total knee replacements, and 8 younger and 11 older healthy control subjects to determine the effects of the rotating-hinge device on gait and stair stepping. The younger patients with the rotating-hinge device had few significant differences from the younger control subjects during gait or stair stepping. The older patients with the rotating-hinge device had several significant differences from both the older control subjects and subjects with the semiconstrained device during gait and stair stepping. Nevertheless, the proportions of older patients with the 2 devices who were able to perform the step-on activity for the highest step were the same.

During gait the body is in a continuous state of imbalance, with each subsequent step preventing a fall. Gait balance is maintained by regulating the interactions between the center of mass (CoM) and base of support (BoS). The purpose of this study was to investigate the interaction of the CoM position and velocity (CoMv) in relation to the dynamically changing BoS throughout gait. This was quantified using: (1) The shortest distance from the CoM to the boundary of the BoS; (2) The distance from the CoM to the centroid of the BoS; and (3) The distance from the CoM to the BoS along the direction of the CoMv. These interactions were investigated in healthy young adults, healthy older adults, and elderly fallers, who performed level walking at a self-selected speed. Elderly fallers demonstrated a conservative CoM-BoS separation at toe off and reduced balance control ability, specifically a decreased time to contact, when compared to healthy young adults at heel strike. Decreased time available in responding to perturbations might result in a greater number of falls. Understanding foot position and CoM trajectories might allow for appropriate rehabilitation practices.

Foot placement during gait is important in regulating the dynamics of the joints of the supporting limb and in maintaining balance of the whole body. We hypothesized that increasing obstacle height and decreasing toe-obstacle distance (distance between the trailing foot and the obstacle during stance of the trailing foot just prior to stepping over the obstacle) would affect the joint moments of the stance limb differently when stepping over an obstacle. A total of 14 healthy young adults stepped over an obstacle 51, 102, 153, and 204 mm in height in a self-selected manner (i.e. toe-obstacle distance was not controlled) and for toe-obstacle distance targets of 10, 20, 30, and 40% of their step lengths measured during unobstructed gait. The adduction and internal rotation moments at the ankle joint increased as toe-obstacle distance decreased. The adduction and internal rotation moments at the hip joint during early stance, the internal rotation moment at the knee joint during late stance, and the dorsiflexion moment at the ankle joint during late stance increased with obstacle height. Reductions in toe-obstacle distance had greater effects on the moments of the ankle joint, and increases in obstacle height had greater effects on the moments of the hip joint. These greater demands on joint moments may affect the abilities of those elderly having decreased muscle strengths to safely step over obstacles. Copyright 1998 Elsevier Science B.V.

The purpose of this study was to examine the effects of concussion on gait stability when either a cognitive or motor perturbation is imposed. Fourteen individuals suffering from a grade II concussion and 14 matched controls performed a single task of level walking, a continuous sequential question and answer task while walking, and an obstacle-crossing task. Common gait spatial/temporal measurements, whole-body center of mass motion, and center of pressure trajectory were assessed. Concussed individuals adopted a more conservative strategy to maintain gait stability. Some measurements indicating conservative gait were seen during obstacle crossing, but this was most evident during the Q&A task. Concussed individuals also displayed signs of possible instability during the Q&A task. The question and answer task was most sensitive to distinguishing concussed individuals from healthy individuals, supporting the use of a similar dual-task modality in future testing after concussion to determine a proper time for return to activity.

The purpose of this study was to assess the use of a multivariate statistical method to rank clinical and gait variables, thus describing a ranking of patient dysfunction prior to and following total knee replacement (TKR) surgery. Twenty end-stage knee osteoarthritis (KOA) subjects scheduled for TKR and 20 healthy controls performed level walking and stair ascent twice: pre- (P1) and 6 months post-surgery (P2). Clinical and gait measures were entered into a principle component analysis (PCA) to determine orthogonal principle components (PCs). The PCs were entered into a discriminant function analysis to determine the best predictors of group membership. The PCA extracted three PCs for both the P1 and P2 data sets. Three orthogonal dimensions were formed: "knee dysfunction", "gait dysfunction", and "stair ascent dysfunction". For P1 the "knee dysfunction" dimension composed of both subjective and objective measures, best discriminated between end-stage knee osteoarthritis patients and controls. For P2, the "stair ascent dysfunction" dimension best discriminated between 6 months post-TKR patients and controls. The results of this study suggest that a multivariate statistical method provides a clinically relevant ranking of patient dysfunction prior to and following TKR. This ranking of dysfunction could serve to identify rehabilitation priorities.

Patients with traumatic brain injury (TBI) complain of "imbalance" or "unsteadiness" while walking, despite a normal gait on clinical examination. Thus, the purpose of this study was to determine if it was possible to quantitatively assess dynamic stability that did not have an obvious neuromuscular origin in individuals following TBI. Ten patients with documented TBI and 10 age, gender, and stature-matched healthy individuals participated in the study. All subjects were instructed to perform unobstructed level walking and to step over obstacles corresponding to 2.5%, 5%, 10%, and 15% of their height. A 13-link biomechanical model of the human body was used to compute the kinematics of the whole body center of mass (COM). Subjects with TBI walked with a significantly slower gait speed and shorter stride length than their matched controls. Furthermore, subjects with TBI displayed a significantly greater and faster medio-lateral (M-L) COM motion and maintained a significantly greater M-L separation distance between their COM and center of pressure (COP) than their matched control subjects. These measurements indicate that subjects with TBI have difficulty maintaining dynamic stability in the frontal plane and have a reduced ability to successfully arrest their sagittal momentum. These findings provide an objective measurement that reflects the complaints of instability not observable on clinical examination for individuals who have suffered a TBI. This ability to identify any functional impairment after a traumatic brain injury that may affect patient safety is critical for prevention of re-injury during the recovery period.