Mediolateral Center Of Pressure Displacement Research Articles

Chronic Ankle Instability Alters Central Organization of Movement

Background Chronic ankle instability alters spinal level sensorimotor function and is hypothesized to alter supraspinal motor control mechanisms. Gait initiation is a functional task modulated by supraspinal pathways, but the effect of chronic ankle instability, a peripheral musculoskeletal impairment, on gait initiation and thus supraspinal motor control mechanisms remains unknown. Purpose This study was conducted to determine if supraspinal aspects of motor control are altered in subjects with chronic ankle instability. Study Design Controlled laboratory study. Methods Subjects with chronic ankle instability (5 males, 15 females; age, 20.5 ± 1.0 years; height, 169.8 ± 9.8 cm; weight, 74.2 ± 20.2 kg) and uninjured controls (4 males, 16 females; age, 20.85 ± 1.6 years; height, 164.3 ± 7.9 cm; weight, 64.2 ± 10.62 kg) completed 5 gait initiation trials for each leg at a self-selected pace. The resulting trajectory of the center of pressure trace was investigated and peak center of pressure excursions in the anteroposterior and mediolateral directions, peak resultant center of pressure excursions, and average direction-specific velocities were calculated. Results Significant group × limb interactions were noted during the first (resultant center of pressure displacement [F1,37 = 4.60, P = .04]) and second (mediolateral center of pressure displacement [F1,37 = 3.82, P = .05]) period of gait initiation. Center of pressure displacement was reduced (impaired) in the involved limb of the chronic ankle instability group (resultant, 0.29 ± 0.02; mediolateral, 0.72 ± 0.02) relative to the uninvolved limb of the chronic ankle instability group (resultant, 0.32 ± 0.02; mediolateral, 0.76 ± 0.02) and both limbs of the control group (resultant, 0.32 ± 0.02; mediolateral, 0.74 ± 0.02) when the involved limb of the chronic ankle instability group served as the initial stance limb. Conclusion These interactions suggest that supraspinal motor control mechanisms are altered in subjects with chronic ankle instability to place a greater emphasis on reducing the postural demands on the involved limb. Clinical Relevance These changes suggest that supraspinal adaptations to motor control may be an important contributor to the underlying neurophysiologic mechanism of chronic ankle instability. The presence of supraspinal adaptations in subjects with chronic ankle instability also indicates that health care providers and rehabilitation specialists treat chronic ankle instability as a global/central and not just a local/peripheral injury.

The immediate effect of physical activity on standing balance in healthy and balance‐impaired older people

To determine if standing balance was affected by moderate levels of physical activity in healthy young, healthy older and balance-impaired older adults. Thirty-one healthy young, 33 healthy older and 22 balance-impaired older adults took part. Centre of pressure (COP) motion was measured before and immediately after participants undertook 14 minutes of self-paced, moderate intensity physical activity. All groups responded in a similar manner. Following the physical activity circuit, mediolateral COP displacement and standard deviation of mediolateral COP position increased by 5% and 17%, respectively. Anteroposterior COP displacement and COP standard deviation, and total COP displacement, did not change. All changes were small compared with the magnitude of the group differences. A small increase in fall risk may exist immediately following physical activity and older people may need to exercise caution following moderate intensity bouts of physical activity to prevent falling.

Applying stabilometry in characterizing floor sitting modes of women

Abstract The study elucidates the applicability of stabiolomety in evaluating floor sitting modes and characterizing the center of pressure (CoP) displacement patterns of women in sitting. The measurement included quantifying the stabilometric dimensions while women (N=10) seated on the piezoelectric force platform in different modes—such as squatting, left leg crossed, right leg vertically bent at knee, and vice versa, both legs bent at knee without pelvic support, legs extended and locked at knee, sideways sitting with legs folded. The principal component analysis of 10 CoP dimensions yielded three-component model, describing (1) the size, radius, and range of the CoP oscillation, (2) the trajectory (trace) length and velocity of CoP displacement, and (3) the directional CoP displacement, such as anterio-posterior (AP) and medio-lateral (ML) displacements. Detailed one-way repeated measures ANOVA showed that the sitting modes had discernable effects on the amplitude deviations as well as velocity parameters derived from CoP co-ordinates. The extending of legs caused the body to move largely in the AP direction, and also markedly influenced the CoP trajectory length as well as the velocity of CoP displacements, indicating greater instability in the postures. Knee bent modes as well as sideways sitting resulted in larger ML excursion of CoP. Squatting with both legs crossed had equilateral AP and ML CoP displacement with least velocity of displacement, and identified as a more stable floor seated posture. Eleven envelopes of CoP trace patterns were characterized in terms of ML, AP, centralized, diffused, and multi-centric CoP movement from its barycenter. The CoP trace patterns did not indicate one pattern—one posture relationship; however, the centralized CoP displacement was most prevalent in squatting as well as sideways sitting postures. The diffused nature of displacement was dominant in knee bent postures. The ML butterfly and AP patterns were evenly present in extended legs, locked at knee postures and in without pelvic support knee bent posture. The first of the kind study reflects a broadened scope of stabilometry in profiling functional measures of postural balance of women in floor sitting modes. Relevance to industry The postural stability/instability is a crucial concern to mitigate risk potentials of spinal and musculo-skeletal injuries at workplaces. The stabilometry is a promising approach to ascertain and characterize women's floor sitting modes, for neurological, orthopedic, and ergonomics applications.

ADAPTATION OF VOLUNTARY STEP INITIATION IN PERSONS WITH PARKINSON'S DISEASE.

Purpose/Hypothesis: Difficulties with gait initiation and other locomotion activities are characteristic and often debilitating problems for people with Parkinson's disease (PD).Anticipatory postural adjustments (APAs) for lateral weight shift and stability normally precede and accompany step initiation. Patients with PD demonstrate prolonged and reduced APAs and delayed step initiation. A lateral postural assist at the pelvis has been shown to acutely decrease APA duration and step onset time in PD. The aim of this study was to determine if patients with PD would adapt to lateral assist training by demonstrating decreases in APA duration and step onset time following removal of lateral assist. Number of Subjects: 6 patients with early-stage PD (Hoehn and Yahr stage 1 & 2) and 6 age-matched controls. Materials/Methods: Ground reaction forces were recorded with two force platforms to determine APA characteristics based on the net medio-lateral center of pressure displacement. Whole body kinematic data were recorded using a 6-camera infrared motion analysis system to determine step characteristics. The lateral assist training session consisted of 3 blocks of trials during rapid forward stepping: 10 baseline trials, 50 trials with lateral assist, and 10 post-assist trials without assist. Ten retention trials without assist were collected one week after the initial session. The lateral assist was provided by a motor driven robotic system with a cable attachment hooked onto a belt around the subject's pelvis. The assist was applied when 55% of the subject's weight was on the swing limb to aid with weight transfer during the APA phase of step initiation. Data was analyzed using ANOVA (p < 0.05). Results: There were no significant group effects between PD and control subjects. However, PD subjects tended to show longer APA duration and slower step onset times compared to controls. Significant condition effects between baseline and lateral assist trials, indicated a decrease in total APA duration (p < 0.01), thrust phase (APA onset to peak amplitude (p < 0.02), unloading phase (peak APA amplitude to end of APA, (p < 0.02), and step onset time (p < 0.01). There was a significant decrease in thrust duration between baseline and retention (p = 0.01).A decrease in APA duration between baseline and retention was marginally significant (p = 0.06) and a shorter step onset time approached significance (p = 0.11). Conclusions: This study supports previous research that a lateral assist can acutely improves step initiation characteristics, in patients with PD. A trend for subjects to retain shorter APA duration and step onset with practice suggested a potential for adaptation. Greater significance may have been achieved with larger sample size. Clinical Relevance: The approach illustrates application of current theories of neural plasticity pertaining to adaptive mechanisms of posture and locomotion interactions and their management in people with PD. To attain greater training effects patients may benefit from increased practice time and additional rest breaks to optimize neural adaptation and minimize fatigue.

Normal and shear strain distributions of the equine third metacarpal during locomotion: Characterizing bone's functional milieu

The study elucidates the applicability of stabiolomety in evaluating floor sitting modes and characterizing the center of pressure (CoP) displacement patterns of women in sitting. The measurement included quantifying the stabilometric dimensions while women (N=10) seated on the piezoelectric force platform in different modes—such as squatting, left leg crossed, right leg vertically bent at knee, and vice versa, both legs bent at knee without pelvic support, legs extended and locked at knee, sideways sitting with legs folded. The principal component analysis of 10 CoP dimensions yielded three-component model, describing (1) the size, radius, and range of the CoP oscillation, (2) the trajectory (trace) length and velocity of CoP displacement, and (3) the directional CoP displacement, such as anterio-posterior (AP) and medio-lateral (ML) displacements. Detailed one-way repeated measures ANOVA showed that the sitting modes had discernable effects on the amplitude deviations as well as velocity parameters derived from CoP co-ordinates. The extending of legs caused the body to move largely in the AP direction, and also markedly influenced the CoP trajectory length as well as the velocity of CoP displacements, indicating greater instability in the postures. Knee bent modes as well as sideways sitting resulted in larger ML excursion of CoP. Squatting with both legs crossed had equilateral AP and ML CoP displacement with least velocity of displacement, and identified as a more stable floor seated posture. Eleven envelopes of CoP trace patterns were characterized in terms of ML, AP, centralized, diffused, and multi-centric CoP movement from its barycenter. The CoP trace patterns did not indicate one pattern—one posture relationship; however, the centralized CoP displacement was most prevalent in squatting as well as sideways sitting postures. The diffused nature of displacement was dominant in knee bent postures. The ML butterfly and AP patterns were evenly present in extended legs, locked at knee postures and in without pelvic support knee bent posture. The first of the kind study reflects a broadened scope of stabilometry in profiling functional measures of postural balance of women in floor sitting modes.The postural stability/instability is a crucial concern to mitigate risk potentials of spinal and musculo-skeletal injuries at workplaces. The stabilometry is a promising approach to ascertain and characterize women's floor sitting modes, for neurological, orthopedic, and ergonomics applications.