Chris Pitsikoulis

Progressive resistance training improves gait initiation in individuals with Parkinson\'s disease

An impaired ability to initiate walking is a common feature of postural instability and gait impairment in Parkinsons disease. While progressive resistance training (PRT) has been proposed to be an effective modality to improve balance and gait function in people with Parkinsons disease, there are a limited number of randomized trials and no studies have evaluated gait initiation performance. Thus, the purpose of this study was to examine the potential benefits PRT on GI performance in people with Parkinsons disease. Eighteen individuals with idiopathic PD were randomly assigned to either a twice weekly PRT program or a non-contact control group for 10 weeks. Biomechanical analysis of GI was performed pre- and post-intervention. Dependent variables of interest included the displacement of the center-of-pressure (COP) during the anticipatory postural phase of GI as well as the initial stride length and velocity. The PRT group demonstrated improvements in the posterior displacement of the COP and the initial stride length and velocity. There were no improvements in any variables for the control subjects. These results suggest that PRT may be an effective non-pharmacological and nonsurgical treatment to improve GI performance in PWP.

Dynamic postural stability during sit‐to‐walk transitions in Parkinson disease patients

In an effort to further our understanding of postural control in Parkinsons disease, we biomechanically evaluated the sit to walk task and its component tasks, sit to stand (STS) and gait initiation (GI) in 12 healthy older adults and 12 persons with Parkinsons disease (PWP). Performance was evaluated utilizing motion capture and two force plates. The major finding of this study was the inability of the PWP to appropriately merge the sequential component tasks (STS and GI) during STW. The PWP rose to nearly full height and had a longer delay between seat‐off and gait initiation (P = 0.003 and P < 0.001, respectively) during STW. Additionally, the PWP moved with slower velocities leading to shorter, slower steps and decreased separation of the center of mass and center of pressure. These observed motor sequencing disturbances may be due to a disease related disability or limitations in proprioception, movement speed, muscular strength, and reduced general mobility.

Postural instability and gait impairment during obstacle crossing in Parkinson's disease.

OBJECTIVE To examine whether Parkinsons disease (PD) affects gait behavior and stability while walking over an obstacle. DESIGN Parallel group comparisons were completed in which participants completed 5 trials of normal walking and 5 trials of obstacle crossing while gait kinematics and kinetics were collected. SETTING University biomechanics laboratory. PARTICIPANTS Individuals with PD (n=10) and age- and sex-matched healthy older adults (n=10). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Gait parameters, obstacle clearance parameters, and center of mass motion were calculated during normal walking and obstacle crossing. RESULTS Results revealed that decrements in gait performance in individuals with PD were amplified during obstacle crossing, suggesting that due to disease-related degradation, individuals with PD chose a more conservative strategy for obstacle crossing. Moreover, an increased duration of single limb support (18% increase), a decrease in anteroposterior range of motion (20% decrease), and an increase in mediolateral range of motion (36% increase, though not significant) coupled with the reduction in the distance between the center of pressure and center of mass (mean of 21% decrease across toe-off and heel strike) and increase in margin of stability (31% increase at toe-off and 71% increase at heel strike) may suggest that deficits in muscle strength and balance may contribute to this impairment. CONCLUSIONS Persons with PD alter their behavior to reduce the mechanical demands and increase dynamic stability during obstacle avoidance tasks.

Age impairs sit-to-walk motor performance.

Sit-to-walk (STW) is a common functional and transitional task which challenges an individuals postural control systems. As aging is associated with an increased risk of falls during transitional movements, we biomechanically investigated the STW movement task in 12 healthy young and 12 healthy elderly individuals. Performance was evaluated utilizing motion analysis and two force plates. The principal finding of this study was the impaired performance of the healthy older adults. The older adults generated significantly less momentum prior to rising (p=0.011) and further delayed (p<0.001) the initiation of gait until standing more upright (p=0.036). The young adults successfully merged the component tasks shortly after seat-off and displayed significantly greater step length (p<0.001), step velocity (p<0.001), and tolerated greater separation of the center of pressure and center of mass at the end single support phase of the initial step (p=0.001). While the young adults fluidly merged the standing and walking task components, the older adults displayed a conservative movement performance during the STW task thereby limiting threats to their postural stability.

Sympathetic drive is modulated by central chemoreceptor activation.

To determine the effects of central chemoreceptor stimulation upon sympathetic modulation while minimizing baroreceptor influences, we performed a single-blind, counter-balanced, placebo-controlled trial of a modified hypercapnic/hyperoxic rebreathe protocol stimulus to activate the central chemoreflex. Muscle sympathetic nerve activity (MSNA), heart rate, blood pressure, and ventilation were recorded dynamically as subjects transitioned from a hypocapnia to hypercapnia state. The stages of data recording were defined as hyperventilation (HyV), pre-threshold (PreT) and post-threshold (PostT), with threshold being defined as the point of non-linear deviation in ventilation. The changes in MSNA (-4.2+/-52.4 arbitrary units (AU) vs. 245.0+/-84.0AU) and burst count (-0.1+/-0.7 bursts/segment vs. 2.5+/-1.7 bursts/segment) were significantly different between control and rebreathe for the HyV to PreT step. There was also a significant difference for PreT to PostT for total MSNA (3.9+/-65.4AU vs. 183.7+/-104.2AU). In a hypercapnic/hyperoxic state, the central chemoreceptors modulate sympathetic activity below the chemoreflex threshold independently of the baroreceptors, possibly contributing to basal autonomic/sympathetic tone. Central chemoreceptors also appear to play a significant role in sympathetic modulation after the threshold.