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The contact between wheel and rail crucially affects the management of railways, since the vehicle dynamics, safety, and performance, for example, are all dependent on this. Therefore, in this contribution the load-dependence of nominal contact area – a broadly not considered aspect of the wheel-rail contacts within the literature – is addressed. We are applying an ultrasonic technique for the detection of the contact zone and an improved post-processing scheme for the measured ultrasonic reflection data. Accordingly, we found that the nominal contact area shows a power-law dependence on load which only on average is predicted by the elliptical Hertzian contact theory. [ABSTRACT FROM AUTHOR]

Abstract Objectives To assess the effect of competitive level on dynamic postural stability in young elite and sub-elite soccer players. Design Cross-sectional study. Setting Laboratory. Participants Fifty-four male soccer players of Under 16 and Under 17 categories (mean age 15.9 ± 0.6), divided into two groups who regularly compete at national (n = 28) and regional (n = 26) levels. Main outcome measures Dynamic Postural Stability Index (DPSI) and vertical Time to Stabilization (vTTS) for a forward-jump landing. Static postural sway was calculated on the basis of center-of-pressure trajectories for a 20 s one-legged stance. Results Players at national level exhibit better dynamic postural control than those at regional level, as indicated by the significantly lower DPSI (0.327 vs. 0.373, p < 0.001) and vTTS (0.887 vs. 1.158 s, p = 0.003). In contrast, no differences between groups were found in any of the postural sway parameters for the static test. Conclusions Young soccer players at national level are characterized by better balance performance in terms of faster and more efficient stabilization after a forward jump, while one-leg static standing tests appear not challenging enough to reveal differences in balance abilities associated with the combination of superior technical and physical features. Highlights • We analyzed balance in young soccer players of national and regional level. • Dynamic Postural Stability Index and Time to Stabilization were computed. • Players of national level exhibit significantly lower DPSI and TTS. • No differences were found in static postural sway. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to assess the influence of trunk rotation (TR) on postural sway and spatial-temporal parameters of gait in children and early adolescents screened at school for the presence of scoliosis.Methods: Two hundred and fifty-five individuals aged 9-14 (141 boys, 114 girls) underwent trunk rotation (TR) assessment by means of angle of trunk rotation (ATR) measurements performed with Bunnell's scoliometer. Participants with ATR ≥ 5° formed the TR group whose data were compared with those of a control group (CON) composed of individuals with ATR < 5° matched for age and anthropometric features. Postural sway was calculated on the basis of center of pressure (COP) time series acquired using a pressure plate. Spatial-temporal parameters of gait were derived from trunk accelerations collected by a single inertial sensor located in the low-back region.Results: Sway area, sway path, COP velocities in medio-lateral (ML) and antero-posterior (AP) directions and COP displacements in ML direction were found significantly higher in girls with TR, while no differences between the TR and CON groups were detected in boys. Both boys and girls with TR exhibited gait patterns similar to those of their CON schoolmates.Conclusions: These findings suggest that even mild levels of TR may influence balance of female children and early adolescents screened for scoliosis, and thus early interventions including selective and task-oriented exercises appear advisable. In contrast, TR does not appear to influence gait, but further investigations are required to clarify whether different ATR cut-offs may reveal alterations of spatial-temporal parameters. [ABSTRACT FROM AUTHOR]

This study investigated changes in task-induced trunk sway of quay crane operators during a four-hour shift performed in a dedicated simulator as an indicator of postural control system effectiveness. Using a pressure sensitive mat placed on the seat pan, center-of-pressure (COP) time series were acquired and processed to calculate sway area, path length and COP displacements and velocities. The results show a well-defined linear trend for sway path and area, with significant increases starting from 65 to 155 min of work respectively. This indicates non-optimized trunk control most likely originated by the combination of physical and cognitive workload and suggests a possible role of long-term monitoring of trunk sway of crane operators as a useful tool in detecting non-optimized movements potentially associated with deteriorating performance. [ABSTRACT FROM AUTHOR]

Purpose The aim of this study is to assess the effect of actual match effort on dynamic balance abilities in young elite soccer players. Methods Seventeen Under 15 male players who compete at national level participated in the study. Their dynamic balance was assessed by having them jump starting with both feet on the ground in a standing position and land on one foot only. Their vertical time to stabilization (vTTS) and postural sway were calculated before and after 35 min of an unofficial match. Postural sway was assessed on the basis of center-of-pressure (COP) trajectories. Parameters considered were sway area, COP displacements in the antero-posterior (AP) and medio-lateral (ML) directions and COP path length. Results After the match, a significant increase in vTTS (p = 0.007) COP path length (p = 0.001) and COP displacements in ML (p < 0.001) was observed. Such effects involve both non-dominant (vTTS, path length) and dominant limb (COP displacements). Conclusions The physical effort associated with the match induces significant impairments of players' dynamic balance abilities. On the basis of such findings, coaches might consider integrating training sessions with specific balance exercises as well as performing injury-prevention routines even when players are fatigued, to better adapt them to match conditions. [ABSTRACT FROM AUTHOR]

Objectives To assess the existence of correlations between static and dynamic balance abilities in young and professional elite soccer players. Design Cross-sectional. Participants Fifty-one elite players who regularly compete at national level divided into two groups: Professional (age 18-34, n = 20) and Under 15-17 (age 14-16, n = 31). Main outcome measures Dynamic balance was assessed for the case of a single-leg landing task by means of vertical time to stabilization (TTS) and postural sway calculated on the basis of center-of-pressure (COP) trajectories (sway area, COP displacements in antero-posterior and medio-lateral direction, COP path length). The same parameters were also measured for a 20 s one-legged stance to assess static balance abilities. Results No significant correlations were found between static and dynamic balance parameters except for TTS and COP displacements in the antero-posterior direction (r = 0.29, p = 0.003). Professional players are characterized by lower TTS in comparison with youth leagues players (0.767 vs. 1.188 s for the dominant limb, p < 0.001) and exhibit reduced sway area (of 34-40%, p < 0.05) for both conditions tested. Conclusion The assessment of balance in soccer players should be performed with both dynamic and static tests, considering that the postural control performances in the two cases are not related. [ABSTRACT FROM AUTHOR]

This study aims to quantitatively assess the effects of vigorous and light physical activity (VPA, LPA) on static balance, gait and sit-to-stand (STS) tasks in a cohort of healthy older adults. To this end, 34 individuals of age >65 years were divided into two groups ( n = 17 each) who underwent 36 sessions (3 × 12 weeks) of PA characterized by different levels of intensity, assessed through continuous heart rate monitoring during the training session. Their balance and mobility were objectively evaluated on the basis of postural sway and time of STS measurements performed using a force platform. The main spatiotemporal parameters of gait (i.e. speed, stride and gait cycle duration, stance, swing and double support phase duration) were also acquired using a wearable inertial measurement unit. The results show that most gait parameters and STS time significantly improve in the VPA group but not in the LPA one. For the latter group a reduction only of swing phase duration was detected. PA also induced a generalized reduction of postural sway in both groups in the case of absence of visual input. These findings suggest that PA programs characterized by superior levels of intensity might be more suitable in generally improving static and dynamic daily motor tasks, while in terms of static balance acceptable results can be achieved even when only light activity is performed. [ABSTRACT FROM AUTHOR]

• Inter-joint coordination during gait in people with Multiple Sclerosis was assessed. • Cyclograms were built from kinematics of hip, knee and ankle in the sagittal plane. • Coordination was quantified at each joint couple by means of cyclograms geometry. • Cyclograms features were significantly modified in pwMS with respect to controls. • This approach can monitor the disease progression and the rehabilitation efficacy. Walking difficulties, which are widespread among people with MS (pwMS), represent one of the major factors contributing to physical disability and, as such, may greatly affect an individual's independence and quality of life. In this context, the study of lower limb kinematics may provide an important contribution to unveiling the underlying mechanisms of walking dysfunctions in MS. However, limited information about the inter-joint coordination during gait—the functional relationship between joint pairs during the whole gait cycle—is available. We retrospectively analyzed the gait patterns of 104 pwMS (56 women, 48 men, mean age 46.3, average Expanded Disability Status Scale score 3.5) and 84 unaffected individuals age-and-sex-matched, who underwent 3D computerized gait analysis carried out using an optical motion capture system. PwMS were also stratified into two groups according to their level of disability. Those with EDSS ≤ 3.5 (n = 62) formed the "low-mild disability" group, while those with EDSS > 3.5 (n = 42) were assigned to the "moderate-severe disability" group. The raw data were processed to calculate the main spatio-temporal parameters and the kinematics in the sagittal plane at the hip, knee, and ankle joints. At each point of the gait cycle, the angular values were employed to build angle-angle diagrams (cyclograms) for the hip-knee and the knee-ankle joint couples. Inter-joint coordination was quantified using geometric features of the cyclograms (i.e., area, perimeter, and dimensionless ratio) and compared between groups. For pwMS only, we also explored possible relationships between cyclograms parameters, disability level, and spatio-temporal parameters of gait. PwMS exhibit a well-known gait pattern characterized by reduced speed, stride length, increased step width, and double support phase duration. Their inter-joint coordination was found altered at both hip-knee and knee-ankle joint couples, as indicated by the significantly reduced cyclogram area and perimeter with respect to unaffected individuals. However, the detailed analysis of the angle-angle diagram trajectories showed some differences associated with the level of disability. In particular, pwMS with mild-low disability exhibit cyclograms partly superposed with those of unaffected individuals in the first half of the stance phase (hip-knee couple) and the second half of the swing phase (knee-ankle couple), while in those with a moderate-severe disability, the differences are substantially extended to the whole gait cycle. Significant moderate to large correlations were also observed between cyclogram area and perimeter, EDSS score, and spatio-temporal parameters of gait. The study of inter-joint coordination during gait in pwMS represents a useful source of information about the way lower limb joints interact, thus potentially expanding the knowledge of the mechanisms underlying walking dysfunctions associated with the disease. From a clinical perspective, the availability of reference data for the co-variation of hip-knee and knee-ankle joint angles during gait can effectively support both the characterization of the progression of the disease and the assessment of the effectiveness of rehabilitative treatments. [ABSTRACT FROM AUTHOR]

Abstract: The ‘plane vs. plane’ contact involving flat punches has been the subject of many investigations, even in recent years, mainly due to the crucial role that such components play in phenomena, such as fretting fatigue and indentation tests. While the problem has been deeply approached from a theoretical point of view, there is a noteworthy lack of experimental verifications due to the limited number of laboratory techniques capable of supplying detailed information about contact parameters. In order to make a partial contribution towards gaining an understanding of such problems, this study proposes the investigation of flat rounded punch contact with an ultrasound-based technique, which exploits the properties of ultrasonic waves to be differently reflected by a contact interface depending on its stress state. A suitable setup was built in such a way as to ensure a good level of control of contact conditions, and the interface was scanned with a high-frequency ultrasonic transducer so as to acquire the reflection data. While the graphic processing of the ultrasonic coefficient of reflection may easily be displayed as a ‘contact map’, the quantitative accuracy of the method was also investigated by comparing experimental results with those obtained from a Finite Element model of the system. The results show a good level of agreement between the two approaches, thus confirming that the ultrasonic technique can be effectively employed to investigate many contact problems which to date have never (or scarcely) been experimentally validated. [Copyright &y& Elsevier]

• There is scarce data on upper limb use in in people with Multiple Sclerosis (pwMS). • We investigated time and intensity of upper limb activity using accelerometers. • In pwMS overall activity is reduced in comparison with unaffected individuals. • PwMS use mostly their dominant limb with respect to unaffected individuals. Background: Although upper limb (UL) dysfunctions are quite common among people with Multiple Sclerosis (pwMS), there is a scarcity of information about actual UL usage under free-living conditions. The aim of the present study is to quantitatively assess 'real-world' activity time, intensity and possible asymmetry of use among dominant and non-dominant ULs in pwMS. Methods: Twenty-eight pwMS (20 women, 8 men, average EDSS 4.3) and 28 age- and sex-matched unaffected individuals were required to wear a tri-axial accelerometer on each wrist 24h/day for 2 weekdays. Raw accelerations were processed to calculate parameters associated with time and intensity of use of UL both when engaged in uni- or bilateral activities. Results: During the 2-day monitoring period, pwMS were characterized by significantly lower overall activity, they used their dominant limb for a significantly longer time and, while performing bilateral activities, their dominant limb expressed movements of superior intensity in a proportion higher than what was observed in unaffected individuals. Conclusion: The instrumental monitoring of UL activity with two wrist-worn sensors may represent an effective tool for assessing the contribution of each limb to uni- and bilateral movements. Such data can be employed to monitor the progression of UL dysfunctions and the effectiveness of pharmacologic and rehabilitative treatments. [ABSTRACT FROM AUTHOR]

Despite the high prevalence of upper limb (UL) work-related musculoskeletal disorders (WRMSD) among health care workers (HCWs), little is known about their relationship with exposure to biomechanical risk factors. This study aimed to assess UL activity features under actual working conditions using two wrist-worn accelerometers. Accelerometric data were processed to obtain duration, intensity, and asymmetry of UL use in 32 HCWs during the execution of commonly performed tasks (e.g., patient hygiene, transfer, and meal distribution) within a regular shift. The results show that such tasks are characterized by significantly different patterns of UL use, in particular, higher intensities and larger asymmetries were observed respectively for patient hygiene and meal distribution. The proposed approach appears, thus, suitable to discriminate tasks characterized by different UL motion patterns. Future studies could benefit from the integration of such measures with self-reported workers' perception to elucidate the relationship between dynamic UL movements and WRMSD. • Health care workers are characterized by a high prevalence of upper limb disorders. • Wrist-worn accelerometers can provide new insight to assess of upper limb activity. • Accelerometers provide useful information intensity and symmetry of upper limb use. • Accelerometers appears suitable to continuously monitor large cohorts of workers. [ABSTRACT FROM AUTHOR]

Purpose To assess the effects of backpack carriage on plantar pressure distributions and spatio-temporal gait parameters among children. Participants Two hundred-eighteen schoolchildren, aged 6–13, and attending primary and secondary schools in the city of Cagliari (Italy). Methods Participants were tested at school, during regular days. A pressure plate and wearable inertial sensors were used to measure plantar pressures and spatio-temporal parameters of gait. Measures were obtained during both quiet standing and walking, and both with and without a backpack. The latter contained those items a child had on the testing day. Results Participants carried a mean mass in their backpacks of 5.2 kg, and more than half had a backpack/body mass ratio higher than 15%. While spatio-temporal gait parameters were not affected by backpack carriage, significant increases (up to 25%) in plantar pressures were found during both static standing and walking, especially in the forefoot. Conclusion Under realistic conditions, the impact of backpack carriage was more evident on foot-ground interaction than on gait features. However, long-term consequences of altered plantar pressure need to be assessed in future work, considering the actual durations typically spent carrying school items. [ABSTRACT FROM AUTHOR]

Foot deformity is a major component of impaired functioning in cerebral palsy (CP). While gait and balance issues related to CP have been studied extensively, there is little information to date on foot–ground interaction (i.e. contact area and plantar pressure distribution). This study aimed to characterize quantitatively the foot–ground contact parameters during static upright standing in hemiplegia and diplegia. We studied 64 children with hemiplegia (mean age 8.2 years; SD 2.8 years) and 43 with diplegia (mean age 8.8 years; SD 2.3 years) while standing on both legs statically on a pressure sensitive mat. We calculated pressure data for the whole foot and sub-regions (i.e. rearfoot, midfoot and forefoot) and average contact pressure. The Arch Index (AI) served for classifying the feet as flat, normal or cavus feet. The data were compared with those from a sample of age- and gender-matched participants (control group, 68 children). Most of the feet showed very high AI values, thus indicating a flat foot. This deformity was more common in diplegia (74.4%) than in hemiplegia (54.7%). In both diplegic and hemiplegic children, average plantar pressure was significantly increased in the forefoot and midfoot and decreased in the rearfoot ( p < 0.001). The present data indicate an increased load on the front parts of the foot, which may be due to plantarflexor overactivity or knee flexion, combined with an increased incidence of low foot arches. As a low foot arch does not necessarily increase forefoot load, this deformity can be regarded as secondary. [ABSTRACT FROM AUTHOR]