Clinical implications of gait analysis in the rehabilitation of adult patients with "Prader-Willi" Syndrome: a cross-sectional comparative study ("Prader-Willi" Syndrome vs matched obese patients and healthy subjects)

Cyclogram-based evaluation of inter-limb gait symmetry in Prader-Willi Syndrome

BACKGROUND

Prader-Willi syndrome (PWS) is characterized by a complex clinical condition, whose typical features lead to impaired motor and functional skills. To date, limited data is available as regards symmetry of gait in PWS.

RESEARCH QUESTION

The aim of this study was to characterize lower-limb asymmetry during gait in a group of Prader-Willi Syndrome (PWS) individuals by using the synchronized cyclograms and to compare it with those of two different control groups, a normal-weight group and an obese group.

METHODS

A total of 18 PWS, 30 normal weight (NW) and 28 obese individuals (OG) matched for age, sex and height were assessed via 3D gait analysis. Gait spatio-temporal parameters were computed together with angle-angle diagrams, characterized in terms of their geometric features (i.e. area, orientation, and trend symmetry index).

RESULTS

Individuals with PWS exhibit reduced speed, stride length and cadence and increased duration of both stance and double support phase than the other groups. OG was characterized by the same pattern when compared to NW. With respect to inter-limb symmetry, individuals with PWS exhibited significantly larger cyclogram areas at hip joint with respect to the other two groups (203.32 degrees2 vs. 130.73 degrees2 vs. 111.59 degrees2) and significantly higher orientation angle (4.17° vs. 2.11° vs. 1.22°) and Trend Symmetry (3.72 vs. 2.02 vs. 1.21) with respect to the other two groups at knee joint; no differences were found at ankle joint. Both individuals with PWS and those of OG exhibited reduced ROM at knee and ankle joints with respect with normal weight, but no statistically significant differences were observed between PWS and OG.

SIGNIFICANCE

The obtained results may provide novel and useful insights to understand better the impairments in motor control associated with this pathological state, supporting clinics in the identification of the best rehabilitation program for this rare pathological state, aimed to improve stability and motor control.

Bone mineral density and its relationship with ground reaction force characteristics during gait in young adults with Prader-Willi Syndrome

Introduction

The incidence of osteopenia and osteoporosis is of concern in adults with Prader-Willi syndrome (PWS). Walking generates reaction forces that could stimulate bone mineralization and is popular in people with PWS. This study compared bone parameters and ground reaction forces (GRF) during gait between young adults with PWS and without PWS and explored associations between bone and GRFs during gait.

Methods

10 adults with PWS, 10 controls with obesity (OB) and 10 with normal weight (NW) matched on sex participated. Segmental and full body dual-energy x-ray absorptiometry scans provided femoral neck, spine, total body minus the head bone mineral density (BMD), bone mineral content (BMC). Vertical GRF, vertical impulse, posterior force and negative impulse were measured during 5 walking trials at a self-selected speed along a 10 m runway.

Results

Multivariate analyses of variance showed that adults with PWS (n = 7-8) had hip and body BMD and BMC comparable (p > .050) to NW and lower (p < .050) than OB. Adults with PWS showed slower speed than NW (p < .050) but similar to OB (p > .050). Adults with PWS presented lower absolute vertical GRF, vertical impulse and negative impulse than OB (p < .050). Pearson r correlations (p < .050) in those with PWS (n = 7-8) indicated that femoral neck BMC was associated with vertical GRF (r = 0.716), vertical impulse (r = 0.780), posterior force (r = -0.805), and negative impulse (r = -0.748). Spine BMC was associated with speed (r = 0.829) and body BMD was associated with speed (r = 0.893), and posterior force (r = -0.780).

Conclusions

Increased BMC in the femoral neck and body were associated with larger breaking forces during walking, a phenomenon normally observed at greater gait speeds. Faster walking speed was associated with greater BMC in the spine and body. Our preliminary results suggest that young adults with PWS could potentially benefit from faster walking for bone health; however, larger prospective studies are needed to confirm this.

Technological Solutions for Human Movement Analysis in Obese Subjects: A Systematic Review

Obesity has a critical impact on musculoskeletal systems, and excessive weight directly affects the ability of subjects to realize movements. It is important to monitor the activities of obese subjects, their functional limitations, and the overall risks related to specific motor tasks. From this perspective, this systematic review identified and summarized the main technologies specifically used to acquire and quantify movements in scientific studies involving obese subjects. The search for articles was carried out on electronic databases, i.e., PubMed, Scopus, and Web of Science. We included observational studies performed on adult obese subjects whenever reporting quantitative information concerning their movement. The articles must have been written in English, published after 2010, and concerned subjects who were primarily diagnosed with obesity, thus excluding confounding diseases. Marker-based optoelectronic stereophotogrammetric systems resulted to be the most adopted solution for movement analysis focused on obesity; indeed, wearable technologies based on magneto-inertial measurement units (MIMUs) were recently adopted for analyzing obese subjects. Further, these systems are usually integrated with force platforms, so as to have information about the ground reaction forces. However, few studies specifically reported the reliability and limitations of these approaches due to soft tissue artifacts and crosstalk, which turned out to be the most relevant problems to deal with in this context. In this perspective, in spite of their inherent limitations, medical imaging techniques-such as Magnetic Resonance Imaging (MRI) and biplane radiography-should be used to improve the accuracy of biomechanical evaluations in obese people, and to systematically validate less-invasive approaches.

Effects of Obesity on Medial Tibiofemoral Cartilage Mechanics in Females-An Exploration Using Musculoskeletal Simulation and Probabilistic Cartilage Failure Modelling

This study examined the effects of obesity on cartilage mechanics and longitudinal failure probability at the medial tibiofemoral compartment, using combined musculoskeletal simulation and probabilistic failure modelling approaches. The current investigation examined twenty obese females (BMI > 30.0 kg/m²) and 20 healthy weight (BMI < 25.0 kg/m²) females. Walking kinematics were obtained via an 8-camera optoelectric system, and a force plate was used to collect ground reaction forces. Musculoskeletal simulation and probabilistic failure modelling were utilized to explore medial tibiofemoral forces and cartilage probability. Comparisons between groups were undertaken using linear mixed-effects models. Net peak cartilage forces, stress and strain were significantly larger in the obese group (force = 2013.92 N, stress = 3.03 MPa & strain = 0.25), compared to health weight (force = 1493.21 N, stress 2.26 MPa & strain = 0.19). In addition, medial tibiofemoral cartilage failure probability was also significantly larger in the obese group (42.98%) compared to healthy weight (11.63%). The findings from the current investigation show that obesity has a profoundly negative influence on longitudinal medial knee cartilage health and strongly advocates for the implementation of effective weight management programs into long-term musculoskeletal management strategies.

Feasibility of wearable technology for 'real-world' gait analysis in children with Prader-Willi and Angelman syndromes

BACKGROUND

Prader-Willi syndrome (PWS) and Angelman syndrome (AS) are neurodevelopmental disorders in need of innovative 'real-world' outcome measures to evaluate treatment effects. Instrumented gait analysis (IGA) using wearable technology offers a potentially feasible solution to measure "real-world' neurological and motor dysfunction in these groups.

METHODS

Children (50% female; 6-16 years) diagnosed with PWS (n = 9) and AS (n = 5) completed 'real-world' IGA assessments using the Physilog®5 wearable. PWS participants completed a laboratory assessment and a 'real-world' long walk. The AS group completed 'real-world' caregiver-assisted assessments. Mean and variability results for stride time, cadence, stance percentage (%) and stride length were extracted and compared across three different data reduction protocols.

RESULTS

The wearables approach was found to be feasible, with all participants able to complete at least one assessment. This study also demonstrated significant agreement, using Lin's concordance correlation coefficient (CCC), between laboratory and 'real-world' assessments in the PWS group for mean stride length, mean stance % and stance % CV (n = 7, CCC: 0.782-0.847, P = 0.011-0.009).

CONCLUSION

'Real-world' gait analysis using the Physilog®5 wearable was feasible to efficiently assess neurological and motor dysfunction in children affected with PWS and AS.

One Year of Recombinant Human Growth Hormone Treatment in Adults with Prader-Willi Syndrome Improves Body Composition, Motor Skills and Brain Functional Activity in the Cerebellum

We compared body composition, biochemical parameters, motor function, and brain neural activation in 27 adults with Prader-Willi syndrome and growth-hormone deficiency versus age-and sex-matched controls and baseline versus posttreatment values of these parameters after one year of recombinant human growth hormone (rhGH) treatment. To study body composition, we analyzed percentage of fat mass, percentage of lean mass, and muscle-mass surrogate variables from dual X-ray absorptiometry. Biochemical parameters analyzed included IGF-I, glucose metabolism, and myokines (myostatin, irisin, and IL6). To explore muscle function, we used dynamometer-measured handgrip strength, the Timed Up and Go (TUG) test, and the Berg Balance Scale (BBS). To study brain activation, we acquired functional magnetic resonance images during three motor tasks of varying complexity. After one year of treatment, we observed an increase in lean mass and its surrogates, a decrease in fat mass, improvements in TUG test and BBS scores, and increased neural activation in certain cerebellar areas. The treatment did not significantly worsen glucose metabolism, and no side-effects were reported. Our findings support the benefits of rhGH treatment in adults with Prader-Willi syndrome and growth-hormone deficiency on body composition and suggest that it may also improve balance and brain neural activation.

Effect of Obesity on Knee and Ankle Biomechanics during Walking

The purpose of this retrospective study was to quantify the three-dimensional knee and ankle joint kinematics and kinetics during walking in young participants with different degrees of obesity and to identify the associated effects by stratifying the obese participants according to their BMI. Thirty-two young obese individuals (mean age 30.32 years) and 16 normal-weight age-matched individuals were tested using 3D gait analysis. Analysis of kinematic and kinetic data revealed significant differences in mechanics at knee and ankle joints in all the evaluated planes of movement. Compared to the healthy-weight participants, obese adults demonstrated less knee flexion, greater knee ab-adduction angle during the entire gait cycle and abnormalities at the knee flex-extension moment. At the ankle joint, reduced range of motion was observed together with a lower peak of ankle plantarflexor moment and power during terminal stance. These results provide insight into a potential pathway by which obesity predisposes a healthy adult for increased risk of osteoarthritis.

Kinematics Adaptation and Inter-Limb Symmetry during Gait in Obese Adults

The main purpose of this study is to characterize lower limb joint kinematics during gait in obese individuals by analyzing inter-limb symmetry and angular trends of lower limb joints during walking. To this purpose, 26 obese individuals (mean age 28.5 years) and 26 normal-weight age- and sex-matched were tested using 3D gait analysis. Raw kinematic data were processed to derive joint-specific angle trends and angle-angle diagrams (synchronized cyclograms) which were characterized in terms of area, orientation and trend symmetry parameters. The results show that obese individuals exhibit a kinematic pattern which significantly differs from those of normal weight especially in the stance phase. In terms of inter-limb symmetry, higher values were found in obese individuals for all the considered parameters, even though the statistical significance was detected only in the case of trend symmetry index at ankle joint. The described alterations of gait kinematics in the obese individuals and especially the results on gait asymmetry are important, because the cyclic uneven movement repeated for hours daily can involve asymmetrical spine loading and cause lumbar pain and could be dangerous for overweight individuals.

Plantar Flexor Function in Adults with and without Prader-Willi Syndrome

PURPOSE

Prader-Willi Syndrome (PWS) is a form of congenital obesity characterized by excessive body fat, hypotonia, muscle weakness, and physical/cognitive disability. However, the sources of muscle dysfunction and their contribution to mobility are unclear. The purposes of this study were to 1) compare plantar flexor function between adults with and without PWS; and 2) to examine the relationship between plantar flexor function and gait speed in adults with PWS.

METHODS

Participants included 10 adults with PWS, 10 adults without PWS and with obesity, and 10 adults without PWS and without obesity (matched on age and sex). Plantar flexor function was assessed using isokinetic dynamometry (peak torque [PT], early/late rate of torque development [RTD]), Hoffman reflex (H/M ratio), ultrasound imaging (cross-sectional area [CSA], echo intensity, pennation angle, and fascicle length), and peak propulsive force and plantar flexor moment during gait. Outcomes were compared between groups using one-way MANOVA. Associations between plantar flexor outcomes and gait speed were assessed using Pearson correlation in the PWS group.

RESULTS

Adults with PWS had lower absolute and normalized early RTD, and lower H/M ratio than controls with and without obesity; lower absolute PT and late RTD than controls with obesity (all P < 0.05). Cross-sectional area, propulsive force, and plantarflexor moment were lower, and echo intensity was higher, in adults with PWS compared with controls without obesity (all P < 0.05). Greater absolute PT (r = 0.64), absolute early RTD (r = 0.62), absolute late RTD (r = 0.64), gastrocnemii CSA (r = 0.55), and propulsive force (r = 0.58) were associated with faster gait speed (all P < 0.05).

CONCLUSIONS

Adults with PWS have impaired plantar flexor function likely attributable to reduced neuromuscular function and altered muscle morphology, which are associated with slower gait speeds.

Gait strategy and body composition in patients with Prader-Willi syndrome

PURPOSE

Individuals with Prader-Willi syndrome (PWS) exhibit reduced lean body mass and increased fat-lean mass ratio when compared with individuals of normal weight and obese ones. Thus, research on the association of functional limitations during gait and body composition may be of great importance from a rehabilitative viewpoint. In particular, the aim of this study was to compare the gait profile of persons with PWS to that of unaffected individuals and to see if a relationship exists between gait profile and body composition in individuals with PWS.

METHODS

Eighteen individuals with PWS and 20 unaffected individuals (Healthy Group: HG) were assessed. Their gait pattern was quantified with 3D-Gait Analysis (3D-GA). Overall body weight, lean and fat masses were measured by dual-energy X-ray absorptiometry.

RESULTS

Individuals with PWS were found to be characterized by a significantly different (p < 0.05) gait pattern with respect to healthy controls in terms of both kinematic and kinetic parameters. No correlations were found between kinematic parameters and overall mass and lean/fat mass, while some parameters associated with ground reaction force were found to be significantly correlated with overall mass, lean mass and fat mass. Significant regression models were obtained, including impact and propulsive force and loading rate.

CONCLUSION

Our data suggest that in individuals with PWS, gait is influenced by the overall and lean body mass. Thus, therapeutic strategies should target both weight reduction and lean mass increase to optimize gait, minimize articular stress, and reduce the risk of repetitive strain on the lower limbs.

LEVEL OF EVIDENCE

Level III: Case-control analytic study.

Changes in symmetry during gait in adults with Prader-Willi syndrome

Most studies on locomotion of individuals with the Prader-Willi Syndrome (PWS) have been performed in a laboratory setting using quantitative motion analysis. Recently, wireless inertial sensors have been successfully employed for gait analysis in different pathological states with the advantages of reproducing a testing condition very close to those encountered in daily living. Using such devices, it is possible not only to characterize the conventional spatio-temporal parameters, but also extract information on further less conventional metrics, such as the harmonic ratio (HR), a measure of step-to-step symmetry based on trunk acceleration processing. In the present study, this technique was used to quantify gait parameters during level walking in 20 adults with PWS who were compared to 20 unaffected individuals. While no differences between the two groups were found in terms of spatio-temporal parameters, individuals with PWS exhibited significantly reduced values of HR in the antero-posterior and vertical directions. Such results, which indicate a poorer gait symmetry in PWS, suggest that upper body accelerations, as well as HR, provide novel information on gait in people with PWS that could not be extracted from spatio-temporal parameters only.

Physical exercise and Prader-Willi syndrome: A systematic review

OBJECTIVE

The aim of this systematic review was to summarize evidence on the acute responses of individuals with Prader-Willi syndrome (PWS) to physical exercise, and on the effectiveness of long-term exercise interventions to improve the clinical manifestations of this syndrome.

DESIGN/METHODS

Relevant articles were identified in the electronic databases PubMed, Medline, CINAHL and SPORTDiscus (from inception to December 2018). Twenty-two studies including a total of 356 patients with PWS met all inclusion criteria and were included in the review.

RESULTS

Patients with PWS present with a decreased physical performance and impaired cardiorespiratory (maximal oxygen consumption, heart rate recovery after exercise) and hormonal (growth hormone release) responses to exercise. Most long-term exercise interventions have proven to decrease body mass while improving physical performance. Some benefits have also been reported in biochemical (glucose homeostasis, lipid profile) and biomechanical (gait pattern) variables, although there is controversy regarding the effects on body composition. No exercise-related adverse events have been reported in patients with PWS.

CONCLUSION

Physical exercise seems to be safe and effective for improving several phenotypes in PWS, notably physical fitness. However, further research is needed to confirm these results and especially to corroborate whether exercise per se or combined with dietary intervention is an effective coadjuvant treatment for reducing body mass in these patients.

Weight loss changed gait kinematics in individuals with obesity and knee pain

BACKGROUND

Obesity is a mechanical risk factor for osteoarthritis. In individuals with obesity, knee joint pain is prevalent. Weight loss reduces joint loads, and therefore potentially delays disease progression; however, how the knee joint responds to weight loss in individuals with obesity and knee pain is not clear.

RESEARCH QUESTION

To assess the effect of weight loss on knee joint kinematics during gait in individuals with obesity and knee pain.

METHODS

We recruited individuals with obesity (BMI ≥ 35) and knee pain who were participating in a weight loss program which included bariatric surgery or medical management. At baseline and 1 year follow-up, participants walked on a treadmill, and their knee joint kinematics were assessed using a dual-fluoroscopic imaging system and subject-specific magnetic resonance imaging knee joint models. Gait changes were represented by change in range of tibiofemoral motion, i.e., excursions in flexion-extension, adduction-abduction, internal-external rotation, anterior-posterior translation, medial-lateral translation, and superior-inferior translation during gait.

RESULTS

Twelve individuals with obesity and knee pain completed the gait analysis at baseline and 1 year follow-up. Participants lost on average 10.4% (standard deviation: 17.2%) of their baseline body weight. Reduction in body weight was associated with increased range of flexion-extension (r = -0.75, p < 0.01) and decreased range of adduction-abduction (r = 0.60, p = 0.04) during gait. The reduction in body weight was also associated with self-reported pain decrease (r = 0.62, p = 0.04); however, the change in pain was not significantly associated with kinematic changes.

SIGNIFICANCE

Weight loss was associated with improved gait kinematics in the sagittal and frontal planes. The change in gait pattern in individuals with obesity and knee pain was not associated with the change in pain given a reduction in body weight.

Hand strength and dexterity in patients with Prader-Willi syndrome: a pilot intervention study

OBJECTIVE

The study aim was to examine the hand function (hand strength and dexterity) and intervention effects of training in adults with Prader-Willi syndrome (PWS).

METHODS

Six adults with PWS (two females; mean age 26.14 years) underwent hand muscle strength and dexterity training for 3 months (2 hours per week). The following hand function tests were performed pre- and post-intervention: (1) hand grip, lateral pinch, and tip pinch hand strength tests, (2) the Box and Block test (BBT) for gross manual dexterity and (3) the Purdue Pegboard test for finger dexterity.

RESULTS

Before treatment, all subjects showed lower hand grip, lateral pinch, tip pinch strength, and poorer manual/finger dexterity relative to healthy adults. After training, hand function scores improved on many test items, but only the left hand tip pinch and the right hand BBT performance showed significant improvements.

CONCLUSIONS

All subjects showed lower hand strength and poorer manual/finger dexterity compared with healthy adults; this should be considered during physical training programs. Owing to limitations in the intervention intensity and possible subject behavioral deficits, further research is needed to clarify the effects of this intervention on hand function in PWS patients.

Waddle and shuffle: gait alterations associated with domestication in turkeys

Domestication has altered turkey morphology by artificially selecting for increased muscle mass and breast meat. Artificial selection has resulted in birds that weigh up to 3 times more than their wild counterparts, with relatively little change in the length of their bones and limbs. Considering these structural changes, it seems probable that domestic turkey locomotor kinematics and kinetics would also be altered. To examine the locomotor dynamics of wild and domestic turkeys, we had both strains walk down a runway with a force plate at the center to measure their ground reaction forces and gait parameters. The location of their center of mass was also quantified using a force plate and bi-planar x-ray and found to be further anterior in the domestic strain. The domestic turkeys locomoted across a lower range of speeds (0.25-1.64 ms^-1) than the wild turkeys (0.26-3.26 ms^-1) and increased their stride frequency at a higher rate. They also displayed large lateral oscillations, i.e. waddling, during walking that translated into relatively high medio-lateral ground reaction forces and lateral kinetic energy (3.5 times higher than that of wild turkeys). The results indicate that domestic turkey locomotion is not simply a slowed down version of wild turkey locomotion. The changes in gait observed are similar to the shuffling gait present in some human populations, such as Parkinson's patients, which serves to increase stability. The domestic turkey's increased body mass and more anterior center of mass position may require these kinematic and kinetic gait differences.

Ventilatory Responses During Submaximal Exercise in Children With Prader-Willi Syndrome

PURPOSE

Prader-Willi syndrome (PWS) is a genetic neurobehavioral disorder presenting hypothalamic dysfunction and adiposity. At rest, PWS exhibits hypoventilation with hypercapnia. We characterized ventilatory responses in children with PWS during exercise.

METHODS

Participants were children aged 7-12 years with PWS (n = 8) and without PWS with normal weight (NW; n = 9, body mass index ≤ 85th percentile) or obesity (n = 9, body mass index ≥ 95th percentile). Participants completed three 5-minute ambulatory bouts at 3.2, 4.0, and 4.8 km/h. Oxygen uptake, carbon dioxide output, ventilation, breathing frequency, and tidal volume were recorded.

RESULTS

PWS had slightly higher oxygen uptake (L/min) at 3.2 km/h [0.65 (0.46-1.01) vs 0.49 (0.34-0.83)] and at 4.8 km/h [0.89 (0.62-1.20) vs 0.63 (0.45-0.97)] than NW. PWS had higher ventilation (L/min) at 3.2 km/h [16.2 (13.0-26.5) vs 11.5 (8.4-17.5)], at 4.0 km/h [16.4 (13.9-27.9) vs 12.7 (10.3-19.5)], and at 4.8 km/h [19.7 (17.4-31.8) vs 15.2 (9.5-21.6)] than NW. PWS had greater breathing frequency (breaths/min) at 3.2 km/h [38 (29-53) vs 29 (22-35)], at 4.0 km/h [39 (29-58) vs 29 (23-39)], and at 4.8 km/h [39 (33-58) vs 32 (23-42)], but similar tidal volume and ventilation/carbon dioxide output to NW.

CONCLUSION

PWS did not show impaired ventilatory responses to exercise. Hyperventilation in PWS may relate to excessive neural stimulation and metabolic cost.

Gait Characteristics of Adults With Intellectual Disability

Gait is a relevant and complex aspect of motor functioning. Disturbances are related to negative health outcomes. Gait characteristics of 31 adults with intellectual disability (ID) without Down syndrome (DS) (42.77±16.70 years) were investigated, and associations with age, sex, body mass index (BMI), and level of ID were assessed. Sex and BMI were significantly associated with some of the gait parameters, while age and level of ID were not. Gait characteristics of adults with ID seem to be comparable to those of the general population of older adults (average 20 years older), except that adults with ID seem to spend less time in stance and double support phase and walk more variable and with a broader base of support.

Estimation of the Effect of Body Weight on the Development of Osteoarthritis Based on Cumulative Stresses in Cartilage: Data from the Osteoarthritis Initiative

Evaluation of the subject-specific biomechanical effects of obesity on the progression of OA is challenging. The aim of this study was to create 3D MRI-based finite element models of the knee joints of seven obese subjects, who had developed OA at 4-year follow-up, and of seven normal weight subjects, who had not developed OA at 4-year follow-up, to test the sensitivity of cumulative maximum principal stresses in cartilage in quantitative risk evaluation of the initiation and progression of knee OA. Volumes of elements with cumulative stresses over 5 MPa in tibial cartilage were significantly (p < 0.05) larger in obese subjects as compared to normal weight subjects. Locations of high peak cumulative stresses at the baseline in most of the obese subjects showed a good agreement with the locations of the cartilage loss and MRI scoring at follow-up. Simulated weight loss (to body mass index 24 kg/m2) in obese subjects led to significant reduction of the highest cumulative stresses in tibial and femoral cartilages. The modeling results suggest that an analysis of cumulative stresses could be used to evaluate subject-specific effects of obesity and weight loss on cartilage responses and potential risks for the progression of knee OA.

Body-scaled action in obesity during locomotion: Insights on the nature and extent of body representation disturbances

OBJECTIVE

Conscious perception of our own body, also known as body image, can influence body-scaled actions. Certain conditions such as obesity are frequently accompanied by a negative body image, leaving open the question if body-scaled actions are distorted in these individuals.

METHODS

To shed light on this issue, we asked individuals affected by obesity to process dimensions of their own body in a real action: they walked in a straight-ahead direction, while avoiding collision with obstacles represented by door-like openings that varied in width.

RESULTS

Participants affected by obesity showed a body rotation behavior similar to that of the healthy weighted, but differences emerged in parameters such as step length and velocity.

CONCLUSION

When participants with obesity walk through door-like openings, their body parts rotation is scaled according to their physical body dimensions; however, they might try to minimize risk of collision. Our study is in line with the hypothesis that unconscious body-scaled actions are related to emotional, cognitive and perceptual components of a negative body image.

Gait initiation and termination strategies in patients with Prader-Willi syndrome

BACKGROUND

Gait Initiation (GI) is a functional task representing one of the first voluntary destabilizing behaviours observed in the development of a locomotor pattern as the whole body centre of mass transitions from a large to a small base of support. Conversely, Gait Termination (GT) consists in the transition from walking to standing which, in everyday life, is a very common movement. Compared to normal walking, it requires higher control of postural stability. For a safe GT, the forward movement of the body has to be slowed down to achieve a stable upright position. Stability requirements have to be fulfilled for safe GT. In individuals with Prader-Willi syndrome (PWS), excessive body weight negatively affects the movement, such as walking and posture, but there are no experimental studies about GI and GT in these individuals. The aim of this study was to quantitatively characterise the strategy of patients with PWS during GI and GT using parameters obtained by the Center of Pressure (CoP) track.

METHODS

Twelve patients with PWS, 20 obese (OG) and 19 healthy individuals (HG) were tested using a force platform during the GI and GT tasks. CoP plots were divided into different phases, and duration, length and velocity of the CoP trace in these phases were calculated and compared for each task.

RESULTS

As for GI, the results showed a significant reduction of the task duration and lower velocity and CoP length parameters in PWS, compared to OG and HG. In PWS, those parameters were reduced to a higher degree with respect to the OG. During GT, longer durations, similar to OG, were observed in PWS than HG. Velocity is reduced when compared to OG and HG, especially in medio-lateral direction and in the terminal part of GT.

CONCLUSIONS

From these data, GI appears to be a demanding task in most of its sub-phases for PWS individuals, while GT seems to require caution only towards the end of the task. Breaking the cycle of gait into the phases of GI and GT and implementing specific exercises focusing on weight transfer and foot clearance during the transition phase from the steady condition to gait will possibly improve the effectiveness of rehabilitation and fall and injury prevention.

Six degree-of-freedom knee joint kinematics in obese individuals with knee pain during gait

Knee joint pain is a common symptom in obese individuals and walking is often prescribed as part of management programs. Past studies in obese individuals have focused on standing alignment and kinematics in the sagittal and coronal planes. Investigation of 6 degree-of-freedom (6DOF) knee joint kinematics during standing and gait is important to thoroughly understand knee function in obese individuals with knee pain. This study aimed to investigate the 6DOF knee joint kinematics in standing and during gait in obese patients using a validated fluoroscopic imaging system. Ten individuals with obesity and knee pain were recruited. While standing, the knee was in 7.4±6.3°of hyperextension, 2.8±3.3° of abduction and 5.6±7.3° of external rotation. The femoral center was located 0.7±3.1mm anterior and 5.1±1.5mm medial to the tibial center. During treadmill gait, the sagittal plane motion, i.e., flexion/extension and anterior-posterior translation, showed a clear pattern. Specifically, obese individuals with knee pain maintained the knee in more flexion and more anterior tibial translation during most of the stance phase of the gait cycle and had a reduced total range of knee flexion when compared to a healthy non-obese group. In conclusion, obese individuals with knee pain used hyperextension knee posture while standing, but maintained the knee in more flexion during gait with reduced overall range of motion in the 6DOF analysis.

Dizziness and Falls in Obese Inpatients Undergoing Metabolic Rehabilitation

Aim

The relationship between dizziness and falls in the obese population is a relatively unexplored issue. The aims of the present study were to define the 1-year prevalence of dizziness in an obese inpatient population undergoing metabolic rehabilitation and to investigate possible correlations with fall events.

Materials and Methods

We recruited 329 obese subjects: 203 female (BMI 43,74 kg/m2 ± 0.5 SE; age 17–83 years, 58.33 ± 0.9 SE) and 126 male (BMI 44,27kg/m2 ± 0.7 DE age 27–79 years, 58.84 ± 1 SE). To assess dizziness we used the validated Italian version (38) of the Dizziness Handicap Inventory (DHI).

Results

Out of the experimental sample, 100 subjects did not complain of dizziness and felt confident about their balance control, while 69.6% reported some degree of dizziness. Their mean DHI score was 22.3, which corresponds to mild dizziness. Twenty-one percent reported more severe dizziness (DHI score > 40). The majority of our sample reported minor dizziness and its perception appears to be independent from BMI: DHI scores were consistent across classes of obesity.

Discussion

The rate of dizziness and falls (30.1%) in an this obese population was higher than that previously reported in a general matched population. However, obese subjects, in our sample, seem to underestimate their risk of fall and DHI score does not appear a reliable predictor of falls. Since complications associated with falls in obese persons generally require longer treatments than in lean individuals, our findings should be taken into account in order to identify other predictors, including cognitive and perceptual, of risk of fall and to implement fall prevention programs.

A Characterization of Movement Skills in Obese Children With and Without Prader-Willi Syndrome

PURPOSE

The aim of this study was twofold: (a) to measure and compare motor proficiency in obese children with Prader-Willi syndrome (OB-PWS) to that in obese children without PWS (OB), and (b) to compare motor proficiency in OB-PWS and OB to normative data.

METHOD

Motor proficiency was measured using the Bruininks-Oseretsky Test of Motor Proficiency-Second Edition-Complete Form, a norm-referenced assessment of motor function. Participants were 18 OB-PWS and 44 OB (8 to 11 years of age). The scores on the 8 subtests and the total motor composite were used to compare OB-PWS and OB. Furthermore, the scores on the 4 motor-area composites were used to compare OB-PWS and OB against normative data.

RESULTS

OB-PWS scored significantly lower than OB across all 8 subtests. OB-PWS also had significantly lower motor proficiency scores on all motor-area composites when compared with the normative sample. OB-PWS most frequently (67%-83%) scored well below average on the gross motor subtests. Although not as high as on the gross motor subtests, this finding also held true for the fine motor subtests with 39% to 45% of OB-PWS scoring well below average.

CONCLUSION

Motor proficiency is very poor in OB-PWS, in particular for gross motor skills. Physical, neurological, and developmental characteristics inherent to the syndrome may explain this low performance.

Growth hormone therapy, muscle thickness, and motor development in Prader-Willi syndrome: an RCT

OBJECTIVE

To investigate the effect of physical training combined with growth hormone (GH) on muscle thickness and its relationship with muscle strength and motor development in infants with Prader-Willi syndrome (PWS).

METHODS

In a randomized controlled trial, 22 infants with PWS (12.9 ± 7.1 months) were followed over 2 years to compare a treatment group (n = 10) with a waiting-list control group (n = 12). Muscle thickness of 4 muscle groups was measured by using ultrasound. Muscle strength was evaluated by using the Infant Muscle Strength meter. Motor performance was measured with the Gross Motor Function Measurement. Analyses of variance were used to evaluate between-group effects of GH on muscle thickness at 6 months and to compare pre- and posttreatment (after 12 months of GH) values. Multilevel analyses were used to evaluate effects of GH on muscle thickness over time, and multilevel bivariate analyses were used to test relationships between muscle thickness, muscle strength, and motor performance.

RESULTS

A significant positive effect of GH on muscle thickness (P < .05) was found. Positive relationships were found between muscle thickness and muscle strength (r = 0.61, P < .001), muscle thickness and motor performance (r = 0.81, P < .001), and muscle strength and motor performance (r = 0.76, P < .001).

CONCLUSIONS

GH increased muscle thickness, which was related to muscle strength and motor development in infants with PWS. Catch-up growth was faster in muscles that are most frequently used in early development. Because this effect was independent of GH, it suggests a training effect.

Gait characteristics in individuals with intellectual disabilities: a literature review

Gait is a functionally highly relevant aspect of motor performance. In the general population poorer gait increases the risk of falls and is a predictor for future disability, cognitive impairment, institutionalization and/or mortality. People with intellectual disabilities (ID) show a delayed motor development, which brings to attention the abnormalities that might accompany gait in this population throughout childhood and adulthood. Therefore, this paper aims (a) to provide a focused review of the available literature on gait characteristics in individuals with ID and (b) to gain insight into available instrumentations measuring gait in this population. We searched the database of PubMed for relevant articles and the reference lists of included articles, resulting in 44 included articles. Forty one studies reported gait characteristics during over-ground walking and six studies during perturbed walking conditions. Most studies investigated syndrome-specific ID populations, only five studies investigated the general ID population. The studies show that gait abnormalities are evident during over-ground walking in the ID population, both in people with genetic syndromes and with ID without genetic syndromes. During perturbed conditions people with ID altered their gait with stability-enhancing adaptations. Abnormalities in gait may be partly explained by physical features, but the interrelatedness between gait and cognition may also be an explanation for the gait abnormalities seen in the ID population. Further research regarding gait characteristics of the ID population, and its relation to cognitive functioning, and adverse health outcomes is needed.

Influences of Obesity on Job Demands and Worker Capacity

Evidence suggests that the growing prevalence of obesity in the workforce has resulted in an increase in the incidence and cost of musculoskeletal injuries. Obesity can modify job demands and affect worker capacity in terms of anthropometry and occupational biomechanics, which may place workers at greater risk of injury. This paper presents a review of studies quantifying the work-relevant impacts of obesity, specifically related to work task demands, capacities, and their potential imbalance. The increased body fat that accompanies obesity leads to larger anthropometric dimensions and inertial parameters, particularly in the trunk and thigh areas. Consequently, individuals who are obese adjust their work postures and motions as an accommodation. These changes may affect the biomechanical demands on the joints and increase the burden on the musculoskeletal system. Independent of job demands, obesity-related differences also occur with respect to strength, fatigue, and task performance. Directions for future research are provided, focusing on the need for workplace redesign to account for changing workforce demographics.

Gait strategy in genetically obese patients: a 7-year follow up

The aim of this study was to quantitatively evaluate the change in gait and body weight in the long term in patients with Prader-Willi Syndrome (PWS). Eight adults with PWS were evaluated at baseline and after 7 years. During this period patient participated an in- and out-patient rehabilitation programs including nutritional and adapted physical activity interventions. Two different control groups were included: the first group included 14 non-genetically obese patients (OCG: obese control group) and the second group included 10 age-matched healthy individuals (HCG: healthy control group). All groups were quantitatively assessed during walking with 3D-GA. The results at the 7-year follow-up revealed significant weight loss in the PWS group and spatial-temporal changes in gait parameters (velocity, step length and cadence). With regard to the hip joint, there were significant changes in terms of hip position, which is less flexed. Knee flexion-extension showed a reduction of flexion in swing phase and of its excursion. No changes of the ankle position were evident. As for ankle kinetics, we observed in the second session higher values for the peak of ankle power in terminal stance in comparison to the first session. No changes were found in terms of ankle kinetics. The findings demonstrated improvements associated to long-term weight loss, especially in terms of spatial-temporal parameters and at hip level. Our results back the call for early weight loss interventions during childhood, which would allow the development of motor patterns under normal body weight conditions.

Center of pressure displacements during gait initiation in individuals with obesity

Background

Obesity is known to affect balance and gait pattern increasing the risk of fall and injury as compared to the lean population. Such risk is particularly high during postural transitions. Gait initiation (GI) is a transient procedure between static upright posture and steady-state locomotion, which includes anticipatory antero-posterior and lateral movements. GI requires propulsion and balance control. The aim of this study was to characterise quantitatively the strategy of obese subjects during GI using parameters obtained by the Center of Pressure (CoP) track.

Methods

20 obese individuals and 15 age-matched healthy subjects were tested using a force platform during the initiation trials. CoP plots were divided in different phases, which identified the anticipatory postural adjustments (APA₁, APA₂) and a movement phase (LOC). Duration, length and velocity of the CoP trace in these phases were calculated and compared.

Results and discussion

The results show that the main characteristic of GI in obese participants is represented by a higher excursion in medio-lateral direction. This condition lead to longer APA length and duration, which are statistical significant during APA2 when compared to control subjects. We also found longer duration of APA1 and LOC phases. In terms of velocity, most of the phases were characterised by a reduced CoP velocity in antero-posterior direction and faster movement in medio-lateral direction as compared to the control group.

Conclusions

Our findings provide novel evidence in GI in obese subjects that may serve for developing exercise programs aimed at specifically improving balance in both the antero-posterior and lateral directions. Such programs together with weight management may be beneficial for improving stability during postural transitions and reducing risk of fall in this population.

Effect of obesity onset on pendular energy transduction at spontaneous walking speed: Prader-Willi versus nonsyndromal obese individuals

OBJECTIVE

To compare the mechanical external work (Wext ) and pendular energy transduction (Rstep ) at spontaneous walking speed (Ss ) in individuals with Prader-Willi syndrome (PWS) versus subjects with nonsyndromal obesity (OB) to investigate whether the early onset of obesity allows PWS subjects to adopt energy conserving gait mechanics.

DESIGN AND METHODS

Wext and Rstep were computed using kinematic data acquired by an optoelectronic system and compared in 15 PWS (BMI = 39.5 ± 1.8 kg m(-2) ; 26.7 ± 1.5 year) and 15 OB (BMI = 39.3 ± 1.0 kg m(-2) ; 28.7 ± 1.9 year) adults matched for gender, age and BMI and walking at Ss .

RESULTS

Ss was significantly lower in PWS (0.98 ± 0.03 m s(-1) ) than in OB (1.20 ± 0.02 m s(-1) ; P < 0.001). There were no significant differences in Wext per kilogram between groups (PWS: 0.37 ± 0.04 J kg(-1) m(-1) ; OB: 0.40 ± 0.05 J kg(-1) m(-1) ; P = 0.66) and in Rstep (PWS: 69.9 ± 2.9%; OB: 67.7 ± 2.4%; P = 0.56). However, Rstep normalized to Froude number (Rstep /Fr) was significantly greater in PWS (6.0 ± 0.6) than in OB (3.8 ± 0.2; P = 0.001). Moreover, Rstep /Fr was inversely correlated with age of obesity onset (r = -0.49; P = 0.006) and positively correlated with obesity duration (r = 0.38; P = 0.036).

CONCLUSION

Individuals with PWS seem to alter their gait to improve pendular energy transduction as a result of precocious and chronic adaptation to loading.

Pathological tremor prediction using surface electromyogram and acceleration: potential use in 'ON-OFF' demand driven deep brain stimulator design

OBJECTIVE

We present a proof of concept for a novel method of predicting the onset of pathological tremor using non-invasively measured surface electromyogram (sEMG) and acceleration from tremor-affected extremities of patients with Parkinson's disease (PD) and essential tremor (ET).

APPROACH

The tremor prediction algorithm uses a set of spectral (Fourier and wavelet) and nonlinear time series (entropy and recurrence rate) parameters extracted from the non-invasively recorded sEMG and acceleration signals.

MAIN RESULTS

The resulting algorithm is shown to successfully predict tremor onset for all 91 trials recorded in 4 PD patients and for all 91 trials recorded in 4 ET patients. The predictor achieves a 100% sensitivity for all trials considered, along with an overall accuracy of 85.7% for all ET trials and 80.2% for all PD trials. By using a Pearson's chi-square test, the prediction results are shown to significantly differ from a random prediction outcome.

SIGNIFICANCE

The tremor prediction algorithm can be potentially used for designing the next generation of non-invasive closed-loop predictive ON-OFF controllers for deep brain stimulation (DBS), used for suppressing pathological tremor in such patients. Such a system is based on alternating ON and OFF DBS periods, an incoming tremor being predicted during the time intervals when DBS is OFF, so as to turn DBS back ON. The prediction should be a few seconds before tremor re-appears so that the patient is tremor-free for the entire DBS ON-OFF cycle and the tremor-free DBS OFF interval should be maximized in order to minimize the current injected in the brain and battery usage.

Blount disease in a case of Prader-Willi syndrome: why is it not as prevalent as in obesity without Prader-Willi syndrome?

BACKGROUND

Prader-Willi syndrome (PWS) is a genetic disorder causing multisystem abnormalities with obesity. Obesity is a well established cause of Blount disease.

METHODS

A 7-year-old girl with PWS presented with genu varum of the left knee with deformity of the proximal medial tibial condyle, which was consistent with Blount disease.

RESULTS

A lateral physeal stapling and subsequent osteotomy for the left proximal tibia and fibula were performed with improved anatomical alignment.

CONCLUSION

Blount disease has not been reported in the literature in association with PWS despite excessive obesity.

The influence of excess body mass on adult gait

BACKGROUND

This study aimed to assess the presentation of gait for adults who are overweight, independent of the confounding influence of velocity.

METHODS

Cross sectional study design. Twenty-five adults of a healthy weight were matched by age, gender, height and velocity to twenty-five adults who were overweight. Participants traversed a 10m walkway embedded with 2 AMTI force platforms (AMTI BP400600 Force Platforms: Advanced Mechanical Technologies, Inc., Watertown, MA, USA) and running between 2 CODA Dual CX1 sensors (CODA CX1: Charnwood Dynamics, Barrow on Soar, Leicestershire, England). Temporal-spatial parameters, maximum ground reaction forces, maximum joint powers, and three dimensional kinematic and kinetic parameters at the 7 events of the gait cycle were assessed.

FINDINGS

With velocity accounted for, relatively few changes in the presentation of gait were seen for adults who were overweight. Alterations included increased stance phase duration, hip flexion, knee flexion, hip abduction, and knee varus for overweight adults. A reduction in hip abductor moment normalised for body mass was noted for overweight adults. Absolute maximum ground reaction forces were increased while maximum hip power absorption was reduced for overweight adults.

INTERPRETATION

Changes were seen at the hip and knee during the swing phase of gait. During swing there is a stronger association with soft tissue injury as compared to joint injury. Overweight individuals were seen to adopt few alterations during the stance phase to accommodate for the increased absolute ground reaction forces. As a result the joint surfaces of overweight adults are exposed to increased loading.

Gait disorder rehabilitation using vision and non-vision based sensors: a systematic review

Even though the amount of rehabilitation guidelines has never been greater, uncertainty continues to arise regarding the efficiency and effectiveness of the rehabilitation of gait disorders. This question has been hindered by the lack of information on accurate measurements of gait disorders. Thus, this article reviews the rehabilitation systems for gait disorder using vision and non-vision sensor technologies, as well as the combination of these. All papers published in the English language between 1990 and June, 2012 that had the phrases "gait disorder", "rehabilitation", "vision sensor", or "non vision sensor" in the title, abstract, or keywords were identified from the SpringerLink, ELSEVIER, PubMed, and IEEE databases. Some synonyms of these phrases and the logical words "and", "or", and "not" were also used in the article searching procedure. Out of the 91 published articles found, this review identified 84 articles that described the rehabilitation of gait disorders using different types of sensor technologies. This literature set presented strong evidence for the development of rehabilitation systems using a markerless vision-based sensor technology. We therefore believe that the information contained in this review paper will assist the progress of the development of rehabilitation systems for human gait disorders.

Lower-limb joint coordination pattern in obese subjects

The coordinative pattern is an important feature of locomotion that has been studied in a number of pathologies. It has been observed that adaptive changes in coordination patterns are due to both external and internal constraints. Obesity is characterized by the presence of excess mass at pelvis and lower-limb areas, causing mechanical constraints that central nervous system could manage modifying the physiological interjoint coupling relationships. Since an altered coordination pattern may induce joint diseases and falls risk, the aim of this study was to analyze whether and how coordination during walking is affected by obesity. We evaluated interjoint coordination during walking in 25 obese subjects as well as in a control group. The time-distance parameters and joint kinematics were also measured. When compared with the control group, obese people displayed a substantial similarity in joint kinematic parameters and some differences in the time-distance and in the coupling parameters. Obese subjects revealed higher values in stride-to-stride intrasubjects variability in interjoint coupling parameters, whereas the coordinative mean pattern was unaltered. The increased variability in the coupling parameters is associated with an increased risk of falls and thus should be taken into account when designing treatments aimed at restoring a normal locomotion pattern.

The effect of growth hormone treatment or physical training on motor performance in Prader-Willi syndrome: a systematic review

Although motor problems in Prader-Willi syndrome (PWS) are prominent in infants, and continue into childhood and adulthood, there is little insight into the factors important for clinical management. The literature was reviewed to: (1) provide an overview of the characteristics and prevalence of motor problems and (2) evaluate the effects of growth hormone (GH) treatment and physical training on motor performance. A systematic search revealed 34 papers: 13 on motor performance; 12 on GH treatment; and nine on physical training. In infants, motor development is 30-57% of the normal reference values, and children and adults also have significant problems in skill acquisition, muscle force, cardiovascular fitness, and activity level. GH treatment positively influenced motor performance in infants, children, and adults, although not all studies demonstrated an effect. All studies on physical training demonstrated beneficial effects in PWS patients. We suggest a combination of GH treatment and physical training to be started as soon as possible, especially in infants, to improve motor development as this will positively influence general development.

Growth hormone treatment in adults with Prader-Willi syndrome: the Scandinavian study

Prader-Willi syndrome (PWS) is characterized by short stature, muscular hypotonia, cognitive dysfunction, and hyperphagia usually leading to severe obesity. Patients with PWS share similarities with growth hormone deficiency (GHD). Few studies have dealt with growth hormone (GH) treatment in PWS adults. The purpose of the Scandinavian study was to evaluate the effects of GH on body composition, lipid and glucose metabolism, physical performance and safety parameters in adults with PWS. Twenty-five women and 21 men with PWS were randomized to treatment with GH or placebo during 1 year followed by 2 years of open labeled GH treatment. At baseline 1/3 had normal BMI, six patients severe GHD, ten impaired glucose tolerance and seven diabetes. At 1 year insulin-like growth factor I (IGF-I) SDS had increased by 1.51 (P < 0.001) and body composition improved in the GH treated group. Visceral fat decreased by 22.9 ml (P = 0.004), abdominal subcutaneous fat by 70.9 ml (P = 0.003) and thigh fat by 21.3 ml (P = 0.013), whereas thigh muscle increased 6.0 ml (P = 0.005). Lean body mass increased 2.25 kg (P = 0.005), and total fat mass decreased 4.20 kg (P < 0.001). The positive effects on body composition were maintained after 2 years of GH treatment. Peak expiratory flow increased by 12% (P < 0.001) at 2 years of GH treatment. Lipid and glucose metabolism were unchanged, however, three patients developed diabetes at 2 years of GH treatment. In conclusion GH treatment had beneficial effects on the abnormal body composition without serious adverse events making it a logic treatment option in adults with PWS.

Muscle-bone characteristics in children with Prader-Willi syndrome

BACKGROUND

A decrease in muscle mass, low motor performance, and normal lumbar spine bone mineral density (BMD) have been reported in children with Prader-Willi syndrome (PWS). However, these data are limited by the fact that PWS children (who have short stature) were compared to age-matched healthy or obese individuals of normal height.

OBJECTIVE

The goal of the present study was to compare bone and muscle characteristics in PWS children to sex- and age- or height-matched healthy subjects.

MATERIALS AND METHODS

The study population included 17 PWS children (ages 6.2 to 17.5 yr; nine girls) who were not treated with GH. The axial skeleton was analyzed at the lumbar spine using dual-energy x-ray absorptiometry, and the appendicular skeleton (radius and tibia) was evaluated using peripheral quantitative computed tomography. Muscle parameters (mass, size, and functional parameters) were measured by dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and jumping mechanography, respectively.

RESULTS

Compared to height-matched controls, PWS patients had normal axial and appendicular BMD, as well as normal muscle size. Compared to age- or height-matched controls of normal weight, PWS patients had lower maximal muscle force and power relative to body mass during jumping. PWS patients had similar absolute maximal muscle force but lower absolute maximal power compared to age- or height-matched controls. Relationships between bone mass and muscle size and force were similar in PWS patients and in healthy subjects.

CONCLUSION

Relative to their height, PWS patients not treated with GH had normal axial and appendicular BMD, muscle size, and muscle-bone relationships.

The effects of DBS patterns on basal ganglia activity and thalamic relay : a computational study

Thalamic neurons receive inputs from cortex and their responses are modulated by the basal ganglia (BG). This modulation is necessary to properly relay cortical inputs back to cortex and downstream to the brain stem when movements are planned. In Parkinson's disease (PD), the BG input to thalamus becomes pathological and relay of motor-related cortical inputs is compromised, thereby impairing movements. However, high frequency (HF) deep brain stimulation (DBS) may be used to restore relay reliability, thereby restoring movements in PD patients. Although therapeutic, HF stimulation consumes significant power forcing surgical battery replacements, and may cause adverse side effects. Here, we used a biophysical-based model of the BG-Thalamus motor loop in both healthy and PD conditions to assess whether low frequency stimulation can suppress pathological activity in PD and enable the thalamus to reliably relay movement-related cortical inputs. We administered periodic pulse train DBS waveforms to the sub-thalamic nucleus (STN) with frequencies ranging from 0-140 Hz, and computed statistics that quantified pathological bursting, oscillations, and synchronization in the BG as well as thalamic relay of cortical inputs. We found that none of the frequencies suppressed all pathological activity in BG, though the HF waveforms recovered thalamic reliability. Our rigorous study, however, led us to a novel DBS strategy involving low frequency multi-input phase-shifted DBS, which successfully suppressed pathological symptoms in all BG nuclei and enabled reliable thalamic relay. The neural restoration remained robust to changes in the model parameters characterizing early to late PD stages.

A systematic review on changed biomechanics of lower extremities in obese individuals: a possible role in development of osteoarthritis

Obesity has been identified as a risk factor for osteoarthritis. For the weight-bearing joints, the combination of increased load and changed joint biomechanics could be regarded as underlying principle for this relation. This systematic review of the literature focused on the differences between obese and normal-weight subjects in biomechanics of the hip, knee and ankle joint during every day movements to summarize differences in joint load due to both higher body weight and differences in movement patterns. A systematic search, up to November 2010, was performed in the Pubmed and Embase databases. This review showed that obese individuals adjust their movement strategy of every day movements. At self-selected speed, obese individuals walked slower, with shorter and wider steps, had longer stance duration and had a greater toe-out angle compared with normal-weight individuals. Obese sit-to-stand movement was characterized by less hip flexion and greater foot displacement. Obese individuals showed altered biomechanics during every day movements. These altered biomechanics could be related to the initiation of osteoarthritis by a change in the load-bearing regions of the articular cartilage in the weight-bearing joints.

Prader-Willi syndrome: A primer for clinicians

The advent of sensitive genetic testing modalities for the diagnosis of Prader-Willi syndrome has helped to define not only the phenotypic features of the syndrome associated with the various genotypes but also to anticipate clinical and psychological problems that occur at each stage during the life span. With advances in hormone replacement therapy, particularly growth hormone children born in circumstances where therapy is available are expected to have an improved quality of life as compared to those born prior to growth hormone.

This manuscript was prepared as a primer for clinicians-to serve as a resource for those of you who care for children and adults with Prader-Willi syndrome on a daily basis in your practices. Appropriate and anticipatory interventions can make a difference.

Effects of obesity and chronic low back pain on gait

Background

Obesity is often associated with low back pain (LBP). Despite empirical evidence that LBP induces gait abnormalities, there is a lack of quantitative analysis of the combined effect of obesity and LBP on gait. The aim of our study was to quantify the gait pattern of obese subjects with and without LBP and normal-mass controls by using Gait Analysis (GA), in order to investigate the cumulative effects of obesity and LBP on gait.

Methods

Eight obese females with chronic LBP (OLG; age: 40.5 ± 10.1 years; BMI: 42.39 ± 5.47 Kg/m²), 10 obese females (OG; age: 33.6 ± 5.2 years; BMI: 39.26 ± 2.39 Kg/m²) and 10 healthy female subjects (CG; age: 33.4 ± 9.6 years; BMI: 22.8 ± 3.2 Kg/m²), were enrolled in this study and assessed with video recording and GA.

Results and Discussion

OLG showed longer stance duration and shorter step length when compared to OG and CG. They also had a low pelvis and hip ROM on the frontal plane, a low knee flexion in the swing phase and knee range of motion, a low dorsiflexion in stance and swing as compared to OG. No statistically significant differences were found in ankle power generation at push-off between OLG and OG, which appeared lower if compared to CG. At hip level, both OLG and OG exhibited high power generation levels during stance, with OLG showing the highest values.

Conclusions

Our results demonstrated that the association of obesity and LBP affects more the gait pattern than obesity alone. OLG were in fact characterised by an altered knee and ankle strategy during gait as compared to OG and CG. These elements may help optimizing rehabilitation planning and treatment in these patients.

The effect of vision on postural strategies in Prader-Willi patients

The aim of this study was to quantify the role of visual contribution in patients with Prader-Willi syndrome (PWS) on balance maintenance using a force platform. We enrolled 14 individuals with PWS free from conditions associated with impaired balance, 44 obese (OG) and 20 healthy controls (CG). Postural sway was measured for 60s while standing on a force platform (Kistler, CH; acquisition frequency: 500 Hz) integrated with a video system. Patients maintained an upright standing position with Open Eyes (OE) and then with Closed Eyes (CE). The ratio between the value of the parameter under OE and CE conditions was measured. Under OE condition PWS and OG were characterized by higher postural instability than CG, with the PWS group showing poorer balance capacity than OG. The Romberg ratio showed that while OG and CG had lower balance without vision, PWS maintained the same performance changing from OE to CE. The integration of different sensory inputs appears similar in OG and CG with higher postural stability under OE than CE. Balance in PWS is not influenced by the elimination of visual input.

Fractal dimension approach in postural control of subjects with Prader-Willi Syndrome

BACKGROUND

Static posturography is user-friendly technique suitable for the study of the centre of pressure (CoP) trajectory. However, the utility of static posturography in clinical practice is somehow limited and there is a need for reliable approaches to extract physiologically meaningful information from stabilograms. The aim of this study was to quantify the postural strategy of Prader-Willi patients with the fractal dimension technique in addition to the CoP trajectory analysis in time and frequency domain.

METHODS

11 adult patients affected by Prader-Willi Syndrome (PWS) and 20 age-matched individuals (

CONTROL GROUP

CG) were included in this study. Postural acquisitions were conducted by means of a force platform and the participants were required to stand barefoot on the platform with eyes open and heels at standardized distance and position for 30 seconds. Platform data were analysed in time and frequency domain. Fractal Dimension (FD) was also computed.

RESULTS

The analysis of CoP vs. time showed that in PWS participants all the parameters were statistically different from CG, with greater displacements along both the antero-posterior and medio-lateral direction and longer CoP tracks. As for frequency analysis, our data showed no significant differences between PWS and CG. FD evidenced that PWS individuals were characterized by greater value in comparison with CG.

CONCLUSIONS

Our data showed that while the analysis in the frequency domain did not seem to explain the postural deficit in PWS, the FD method appears to provide a more informative description of it and to complement and integrate the time domain analysis.

Postural adaptations to long-term training in Prader-Willi patients

Background

Improving balance and reducing risk of falls is a relevant issue in Prader-Willi Syndrome (PWS). The present study aims to quantify the effect of a mixed training program on balance in patients with PWS.

Methods

Eleven adult PWS patients (mean age: 33.8 ± 4.3 years; mean BMI: 43.3 ± 5.9 Kg/m2) attended a 2-week training program including balance exercises during their hospital stay. At discharge, Group 1 (6 patients) continued the same exercises at home for 6 months, while Group 2 (5 patients) quitted the program. In both groups, a low-calorie, well-balanced diet of 1.200 kcal/day was advised. They were assessed at admission (PRE), after 2 weeks (POST1) and at 6-month (POST2). The assessment consisted of a clinical examination, video recording and 60-second postural evaluation on a force platform. Range of center of pressure (CoP) displacement in the antero-posterior direction (RANGE_AP index) and the medio-lateral direction (RANGE_ML index) and its total trajectory length were computed.

Results

At POST1, no significant changes in all of the postural parameters were observed. At completion of the home program (POST2), the postural assessment did not reveal significant modifications. No changes in BMI were observed in PWS at POST2.

Conclusions

Our results showed that a long-term mixed, but predominantly home-based training on PWS individuals was not effective in improving balance capacity. Possible causes of the lack of effectiveness of our intervention include lack of training specificity, an inadequate dose of exercise, an underestimation of the neural and sensory component in planning rehabilitation exercise and failed body weight reduction during the training. Also, the physiology of balance instability in these patients may possibly compose a complex puzzle not affected by our exercise training, mainly targeting muscle weakness.