Srikant Vallabhajosula

The effect of Tai Chi exercise on gait initiation and gait performance in persons with Parkinson's disease

Gait dysfunction and postural instability are two debilitating symptoms in persons with Parkinsons disease (PD). Tai Chi exercise has recently gained attention as an attractive intervention for persons with PD because of its known potential to reduce falls and improve postural control, walking abilities, and safety at a low cost. The purpose of this report is to investigate the effect of Tai Chi exercise on dynamic postural control during gait initiation and gait performance in persons with idiopathic PD, and to determine whether these benefits could be replicated in two different environments, as complementary projects. In these two separate projects, a total of 45 participants with PD were randomly assigned to either a Tai Chi group or a control group. The Tai Chi groups in both projects completed a 16-week Tai Chi exercise session, while the control groups consisted of either a placebo (i.e., Qi-Gong) or non-exercise group. Tai Chi did not significantly improve Unified Parkinsons Disease Rating Scale Part III score, selected gait initiation parameters or gait performance in either project. Combined results from both projects suggest that 16 weeks of class-based Tai Chi were ineffective in improving either gait initiation, gait performance, or reducing parkinsonian disability in this subset of persons with PD. Thus the use of short-term Tai Chi exercise should require further study before being considered a valuable therapeutic intervention for these domains in PD.

Spatiotemporal variability during gait initiation in Parkinson's disease

During gait initiation (GI), consistency of foot placement while stepping is important in making successful transitions from a state of stable static posture to an unstable state of dynamic locomotion. In populations characterized by gait dysfunction and postural instability, such as persons with Parkinsons disease (PD), the ability to generate a consistent stepping pattern during GI may be essential in the prevention of falls. However, little is known about GI variability in persons with PD as compared to their healthy elderly peers. Therefore, this study investigated spatiotemporal variability during the first two steps of GI in 46 persons with idiopathic PD and 49 healthy age-matched adults. Stepping characteristics, including the length, width, and time of the first two steps of GI as well as their coefficients of variation (CV) were compared between groups. Persons with PD initiated gait with significantly shorter steps (swing step length=.463 vs. .537 m, stance step length=.970 vs. 1.10 m) and higher variability in step length (swing step CV=8.82 vs. 5.45, stance step CV=6.76 vs. 3.61). Persons with PD also showed significantly higher variability in the time of the swing step (swing step CV=10.0 vs. 7.4). GI variability did not differ significantly between disease stages in persons with PD. Because greater variability in these measures during gait is related to an increased risk of falls, we propose that higher GI variability may play a considerable role in falls frequently observed during transitions from quiet standing in PD.

Tests of dorsolateral frontal function correlate with objective tests of postural stability in early to moderate stage Parkinson’s disease

A substantial number of individuals with Parkinsons disease who display impaired postural stability experience accelerated cognitive decline and an increased prevalence of dementia. To date, studies suggest that this relationship, believed to be due to involvement of nondopaminergic circuitry, occurs later in the disease process. Research has yet to adequately investigate this cognitive-posturomotor relationship especially when examining earlier disease states. To gain greater understanding of the relationship between postural stability and cognitive function/dysfunction we evaluated a more stringent, objective measure of postural stability (center of pressure displacement), and also more specific measures of cognition in twenty-two patients with early to moderate stage Parkinsons disease. The magnitude of the center of pressure displacement in this cohort was negatively correlated with performance on tests known to activate dorsolateral frontal regions. Additionally, the postural stability item of the UPDRS exhibited poor correlation with the more objective measure of center of pressure displacement and all specific measures of cognition. These results may serve as rationale for a more thorough evaluation of postural stability and cognition especially in individuals with mild Parkinsons disease. Greater understanding of the relationship between motor and cognitive processes in Parkinsons disease will be critical for understanding the disease process and its potential therapeutic possibilities.

Tai Chi Exercise to Improve Non-Motor Symptoms of Parkinson's Disease

BACKGROUND A substantial number of individuals with Parkinsons disease exhibit debilitating non-motor symptoms that decrease quality of life. To date, few treatment options exist for the non-motor symptomatology related to Parkinsons disease. The goal of this pilot investigation was to determine the effects of Tai Chi exercise on the non-motor symptomology in Parkinsons disease. METHODS Twenty-one individuals with Parkinsons disease were enrolled in a Tai Chi intervention (n=15) or a noncontact control group (n=6). Participants assigned to Tai Chi participated in 60-minute Tai Chi sessions three times per week, for 16 weeks. Pre and post measures included indices of cognitive-executive function including visuomotor tracking and attention, selective attention, working memory, inhibition, processing speed and task switching. Additionally, all participants were evaluated on the Parkinsons disease Questionnaire-39 and Tinettis Falls Efficacy Scale. RESULTS Results indicated that the Tai Chi training group had significantly better scores following the intervention than the control group on the Parkinsons disease Questionnaire-39 total score as well as the emotional well-being sub score. Trends for improvement were noted for the Tai Chi group on Digits Backwards, Tinettis Falls Efficacy Scale, and the activities of daily living and communication sub scores of the Parkinsons disease Questionnaire-39. CONCLUSIONS This research provides initial data that supports future studies to definitively establish efficacy of Tai Chi to improve non-motor features of Parkinsons disease.

Age and Parkinson's disease related kinematic alterations during multi-directional gait initiation

Previous literature suggests that older adults and persons with Parkinsons disease (PWP) exhibit impaired performance during gait initiation (GI) and turning while walking. While researchers have identified specific impairments during GI and turning separately in these populations, little is known about when these two tasks occur concurrently. Our objective was to determine how multi-directional GI kinematics are affected by aging and Parkinsons disease. Kinematic data were collected on 12 healthy young adults (HYA), 11 healthy older adults (HOA) and 11 PWP during GI in four conditions: forward, medial 45°, lateral 45°, and lateral 90°. Spatiotemporal characteristics and segmental angles were analyzed using separate 3 (group)×4 (condition) mixed ANOVA. Combined across all the conditions, HOA took a smaller (P=0.009) and slower (P=0.023) first step, and slower second step (P=0.021) compared to HYA. PWP took a slower first step (P=0.009), and longer time to initiate the second step (P=0.017) compared to HOA. Also, PWP had greater head rotation at the start of GI during the medial 45° condition (P=0.043) and reduced overall segmental rotation before toe-off of the second step during the lateral 45° condition (P=0.035), and at heel-strike of first step (P=0.031) and before toe-off of second step during lateral 90° condition (P=0.035). For HOA, their general slowness of movement could be attributed to aging effects. For PWP, rigidity and bradykinesia could impair activities of daily living like multi-directional GI and may be associated with an increased risk of falls.

Frontal joint dynamics when initiating stair ascent from a walk versus a stand

Ascending stairs is a challenging activity of daily living for many populations. Frontal plane joint dynamics are critical to understand the mechanisms involved in stair ascension as they contribute to both propulsion and medio-lateral stability. However, previous research is limited to understanding these dynamics while initiating stair ascent from a stand. We investigated if initiating stair ascent from a walk with a comfortable self-selected speed could affect the frontal plane lower-extremity joint moments and powers as compared to initiating stair ascent from a stand and if this difference would exist at consecutive ipsilateral steps on the stairs. Kinematics data using a 3-D motion capture system and kinetics data using two force platforms on the first and third stair treads were recorded simultaneously as ten healthy young adults ascended a custom-built staircase. Data were collected from two starting conditions of stair ascent, from a walk (speed: 1.42 ± 0.21 m/s) and from a stand. Results showed that subjects generated greater peak knee abductor moment and greater peak hip abductor moment when initiating stair ascent from a walk. Greater peak joint moments and powers at all joints were also seen while ascending the second ipsilateral step. Particularly, greater peak hip abductor moment was needed to avoid contact of the contralateral limb with the intermediate step by counteracting the pelvic drop on the contralateral side. This could be important for therapists using stair climbing as a testing/training tool to evaluate hip strength in individuals with documented frontal plane abnormalities (i.e. knee and hip osteoarthritis, ACL injury).

Selective use of low frequency stimulation in Parkinson's disease based on absence of tremor.

BACKGROUND High frequency stimulation (HFS) of the subthalamic nucleus is one of the most effective treatments for advanced Parkinsons disease (PD). HFS has provided beneficial improvements in the cardinal features of PD, but has not been proven as effective for addressing the axial predominant levodopa resistant symptoms, such as speech disturbances, gait disturbances, and postural instability. Recent studies have suggested that changes in stimulation parameters may influence differing PD symptoms. OBJECTIVE The purpose of this study was to compare the effects of low frequency stimulation (LFS) versus HFS on the Unified Parkinsons Disease Rating Scale (UPDRS), gait, balance, and verbal fluency. METHODS Eight tremor dominant and nine non-tremor dominant participants with bilateral deep brain stimulation of the subthalamic nucleus were tested off stimulation, during LFS, and during HFS. RESULTS Results revealed that HFS significantly reduced UPDRS tremor score in the tremor dominant group; however no differences emerged within the non-tremor dominant group. No differences between groups or stimulation conditions were found for gait, balance, and verbal fluency measures. CONCLUSION These results may suggest that HFS is better than LFS for reducing tremor in tremor dominant patients. However, patients with mild or no tremor show no acute differences in benefit from LFS as compared to HFS.

Do lower-extremity joint dynamics change when stair negotiation is initiated with a self-selected comfortable gait speed?

Previous research on the biomechanics of stair negotiation has ignored the effect of the approaching speed. We examined if initiating stair ascent with a comfortable self-selected speed can affect the lower-extremity joint moments and powers as compared to initiating stair ascent directly in front of the stairs. Healthy young adults ascended a custom-built staircase instrumented with force platforms. Kinematics and kinetics data were collected simultaneously for two conditions: starting from farther away and starting in front of the stairs and analyzed at the first and second ipsilateral steps. Results showed that for the first step, participants produced greater peak knee extensor moment, peak hip extensor and flexor moments and peak hip positive power while starting from farther away. Also, for both the conditions combined, participants generated lesser peak ankle plantiflexor, greater peak knee flexor moment, lesser peak ankle negative power and greater peak hip negative power while encountering the first step. These results identify the importance of the starting position in experiments dealing with biomechanics of stair negotiation. Further, these findings have important implications for studying stair ascent characteristics of other populations such as older adults.

Single-task and dual-task gait among collegiate athletes of different sport classifications: Implications for concussion management.

Gait impairments have been documented following sport-related concussion. Whether preexisting gait pattern differences exist among athletes who participate in different sport classifications, however, remains unclear. Dual-task gait examinations probe the simultaneous performance of everyday tasks (ie, walking and thinking), and can quantify gait performance using inertial sensors. The purpose of this study was to compare the single-task and dual-task gait performance of collision/contact and noncontact athletes. A group of collegiate athletes (n = 265) were tested before their season at 3 institutions (mean age= 19.1 ± 1.1 years). All participants stood still (single-task standing) and walked while simultaneously completing a cognitive test (dual-task gait), and completed walking trials without the cognitive test (single-task gait). Spatial-temporal gait parameters were compared between collision/contact and noncontact athletes using MANCOVAs; cognitive task performance was compared using ANCOVAs. No significant single-task or dual-task gait differences were found between collision/contact and noncontact athletes. Noncontact athletes demonstrated higher cognitive task accuracy during single-task standing (P = .001) and dual-task gait conditions (P = .02) than collision/contact athletes. These data demonstrate the utility of a dual-task gait assessment outside of a laboratory and suggest that preinjury cognitive task performance during dual-tasks may differ between athletes of different sport classifications.

Evidence of a conservative gait strategy in athletes with a history of concussions

Background A history of 3 or more concussions is frequently associated with numerous short- and long-term neuropathologies. Impairments in postural control are a known acute consequence of concussion; however, limited evidence exists on the effects of multiple concussions on gait. The purpose of this study was to assess gait stepping characteristics in collegiate aged student-athletes based on concussion history. Methods There were 63 participants divided into 3 even groups based on concussion history: ≥3 concussions, 1–2 concussions, and 0 concussion. All participants completed 10 trials of gait on a 4.9 m instrumented walkway. The dependent variables of interest included both gait stepping characteristics (step velocity, length, and width, double support time, and the percentage of the gait cycle in stance) and coefficient of variability (CoV) measures (step length, time, and width). The gait stepping characteristics were compared first with a MANOVA with follow-up 1-way ANOVAs and Tukey post hoc tests as appropriate. The CoV measures were compared with 1-way ANOVAs and Tukey post hoc tests. Results There were main effects for group for step velocity, length, width, and double support time. Overall, the 0 concussion group displayed typical healthy young gait parameters and performed significantly better than either concussion group. The 0 concussion group had a significantly greater step length CoV, but there were no differences in the step time or width CoV. Conclusion This finding provides evidence of subtle impairments in postural control during gait among individuals with prior history of concussion which could be an early indicator of future neurological deficiencies. The limited difference in the variability measures is consistent with prior static stance studies and could suggest the individuals constrain their motor systems to reduce variability. Taken together, these findings suggest a conservative gait strategy which is adopted by individuals with a history of concussions.