Biomedical subjects

Louis R Osternig

Publications and source records attributed to Louis R Osternig.

9 recordsLinked to original sources

PubMed2006

Cancelling planned actions following mild traumatic brain injury.

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.

Adult↗

PubMed2006

Shoulder joint position sense improves with elevation angle in a novel, unconstrained task.

Proprioception, encompassing the submodalities of kinesthesia and joint position sense, is important in the maintenance of joint stability, especially in the shoulder. The purpose of this study was to examine the effects of plane and elevation angle on unconstrained shoulder joint position sense. Twenty-two subjects (12 male, 10 female) without a history of shoulder pathology were recruited from a university campus. Subjects attempted to replicate, with respect to plane and elevation angles, various target positions. Target positions consisted of five plane angles at 90 degrees of arm elevation and five arm elevation angles in the scapular plane. All target positions were tested twice to assess the reliability of the measurement. Intraclass correlation coefficients were generally low across target positions, possibly owing to the novelty and demanding nature of the task. No differences in repositioning errors were observed between plane angles (p = 0.255). Repositioning errors decreased linearly as the elevation angle increased from 30 degrees to 90 degrees (p = 0.007) and increased again from 90 degrees to 110 degrees of elevation (p = 0.029). Our results suggest that unconstrained joint position sense may be enhanced with increased muscular activation levels. Further, afferent feedback from musculotendinous mechanoreceptors may dominate over that from capsuloligamentous sources in unconstrained movements.

Adult↗

PubMed2006

Gait stability following concussion.

INTRODUCTION: 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. PURPOSE: 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. METHODS: 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). RESULTS: 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. CONCLUSION: The findings of this study suggest that concussion may have long-term observable and measurable effects on the control of gait stability.

Adult↗

PubMed2005

Tracking the recovery of visuospatial attention deficits in mild traumatic brain injury.

The goal of the current investigation was to probe the deficits in the alerting, orienting and executive components of visuospatial attention in individuals who have recently suffered a mild traumatic brain injury (mTBI) and to assess the rate and degree of recovery for each of these components over a month post-injury. A group design was employed to assess and compare the performance of participants (12 males, 8 females; mean age: 21 +/- 1.74 years) identified with mTBI relative to control subjects matched for gender, age, height, weight and activity level. Participants performed the attentional network test, designed to isolate the constituents of attention into alerting, orienting and executive components. Reaction times (RTs) and response accuracy were the main dependent variables. The results showed that the orienting and executive components were significantly affected by mTBI immediately after the injury, whereas the alerting component was not. Furthermore, participants with mTBI recovered from the deficits in the orienting component of attention within a week of their injury, whereas the deficits in the executive component remained throughout the month post-injury. In addition, the RT cost to generate accurate compared with inaccurate responses was significantly larger in participants with mTBI than in controls, and this difference was maintained throughout the 1 month testing period. These findings indicate that the regions of the brain associated with the orienting and executive components of visuospatial attention may be most susceptible to neural damage resulting from mTBI. Moreover, the lack of recovery in the executive component indicates that the degree and time course for recovery may be regionally specific.

Adolescent↗

PubMed2005

The effect of divided attention on gait stability following concussion.

BACKGROUND: The need to identify functional impairment following a brain injury is critical to prevent re-injury during the period of recovery. While many neuropsychological tests have been developed to assess cognitive performance, relatively little information on gait and dynamic stability is available on motor task performance for young adults following concussion. This study was performed to investigate the effect of divided attention following concussion on various gait variables. It was hypothesized that, when compared to uninjured controls, concussed subjects would demonstrate deficits in maintenance of dynamic stability. METHODS: Ten subjects with Grade 2 concussion completed testing within 48 h of injury as well as 10 age-, height-, weight-, and activity-matched controls. The gait protocol consisted of level walking under two conditions: (1) undivided attention (single-task) and (2) while simultaneously completing simple mental tasks (dual-task). Whole-body motion data were collected using a six-camera motion analysis system. A 13-segment biomechanical model was used to compute whole body center of mass motion and velocity. FINDINGS: Walking with a concurrent cognitive task resulted in significant changes in gait and center of mass measurements for both groups. Concussed subjects were found to be able to conservatively adjust their whole body center of mass motion to maintain dynamic stability while walking without divided attention. However, while walking with divided attention, subjects with concussion demonstrated a significantly greater medio-lateral center of mass sway. INTERPRETATION: These data suggest that the ability to control and maintain stability in the frontal plane during walking is diminished under divided attention in individuals following a concussion.

Adult↗

PubMed2004

Bilateral accommodations to anterior cruciate ligament deficiency and surgery.

UNLABELLED: OBJECTIVE To determine bilateral lower extremity joint accommodations during gait in anterior cruciate ligament deficient subjects and uninjured controls. DESIGN: Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and 3 months following reconstructive surgery, and 10 uninjured controls. BACKGROUND: It is possible that bilateral joint accommodations could occur as a result of anterior cruciate ligament injury and in response to surgical repair. Few studies have investigated bilateral joint accommodations to anterior cruciate ligament injury and there is little consistency in the reported results. METHODS: Bilateral lower extremity kinematic and kinetic data were collected from 12 walking trials and inverse dynamics calculations were made to estimate bilateral knee and hip joint angle, moment, and power patterns during the stance phase of gait. RESULTS: Control subjects exhibited asymmetrical hip but symmetrical knee joint moment and power patterns. In contrast, the anterior cruciate ligament deficient subjects exhibited symmetrical hip and asymmetrical knee joint moment and power patterns prior to and following reconstructive surgery. CONCLUSIONS: Gait asymmetry in healthy subjects should not be considered pathological. In addition, chronic anterior cruciate ligament injury results in joint specific, bilateral lower extremity accommodations in gait mechanics. These accommodations persist 3 months following surgical repair.

Adaptation, Physiological↗

PubMed2003

Gait perturbation response in chronic anterior cruciate ligament deficiency and repair.

OBJECTIVE: To determine how chronic anterior cruciate ligament deficient and surgically repaired subjects react to unexpected forward perturbations during gait as compared to healthy controls. DESIGN: Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and three months following reconstructive surgery, and 10 uninjured controls. BACKGROUND: The ability of an anterior cruciate ligament injured individual to react and maintain equilibrium during gait perturbations is critical for the prevention of reinjury. No studies have investigated how these individuals respond to unexpected perturbations during normal gait. METHODS: An unexpected forward perturbation was induced upon heel strike using a force plate capable of translational movement. RESULTS: Prior to surgery, the anterior cruciate ligament subjects exhibited a greater knee extensor moment in response to the perturbation compared to healthy controls. Following surgery, the anterior cruciate ligament injured subjects exhibited a static knee position and a sustained knee extensor moment throughout stance in response to the perturbation as compared to controls. CONCLUSIONS: These data suggest that chronic anterior cruciate ligament deficient subjects rely heavily on knee extensor musculature to prevent collapse in response to an unexpected perturbation. This same reactive response was more pronounced 3 months following surgery. RELEVANCE: The results suggest that, prior to and following surgery, chronic anterior cruciate ligament injured subjects respond differently than healthy controls to an unexpected perturbation during gait. Anterior cruciate ligament injured or repaired subjects do not reduce or avoid vigorous contraction of the quadriceps muscles when responding to gait perturbations.

Adult↗

PubMed2002

Gait mechanics in chronic ACL deficiency and subsequent repair.

OBJECTIVE: To determine how normal gait patterns may change as a result of chronic anterior cruciate ligament deficiency and subsequent reconstructive surgery. DESIGN: Gait testing of 10 chronic anterior cruciate ligament deficient subjects prior to and 3 months following reconstructive surgery, and 10 uninjured controls. BACKGROUND: There is controversy whether persons with chronic anterior cruciate ligament deficiency develop a "quadriceps avoidance" pattern and how anterior cruciate ligament reconstructive surgery influences gait mechanics in these same individuals. METHODS: Gait analysis was employed to determine kinematic, kinetic, and muscle Electromyographic data. RESULTS: Prior to surgery, no anterior cruciate ligament deficient subject exhibited a quadriceps avoidance pattern. Following surgery, the subjects exhibited a significantly greater knee extensor moment during early stance as compared to the control group. Prior to and following surgery, anterior cruciate ligament deficient subjects demonstrated a significantly greater hip extensor moment possibly to reduce anterior tibial translation. CONCLUSIONS; These data suggest that (1) development of a quadriceps avoidance pattern is less common than previously reported, (2) anterior cruciate ligament deficient subjects accommodate through alterations of hip joint mechanics, (3) surgical repair significantly alters lower extremity gait patterns, and (4) re-establishment of pre-injury gait patterns takes longer than 3 months to occur. RELEVANCE: The results suggest that chronic anterior cruciate ligament deficient subjects do not exhibit a quadriceps avoidance gait pattern. Surgical intervention significantly alters lower extremity gait mechanics in a population that has accommodated to anterior cruciate ligament deficiency.

Adult↗

PubMed2002

Reactive balance adjustments to unexpected perturbations during human walking.

The purpose of this investigation was to determine the effect of unexpected forward perturbations (FP) during gait on lower extremity joint mechanics and muscle Electromyographic (EMG) patterns in healthy adults. The muscles surrounding the hip were found to be most important in maintaining control of the trunk and preventing collapse in response to the FP. Distinct lower extremity joint moment and power patterns were observed in response to the FP but an overall positive moment of support (M(s)) was maintained. Therefore, reactive balance control was a synchronized effort of the lower extremity joints to prevent collapse during the FP.

Adult↗