Although gait disorders represent a highly prevalent condition in older adults, the alterations a... more Although gait disorders represent a highly prevalent condition in older adults, the alterations associated with physiologic aging are often not easily differentiable from those originated by concurrent neurologic or orthopedic conditions. Thus, the detailed quantitative assessment of gait patterns represents a crucial issue. In this context, the study of trunk accelerations may represent an effective proxy of locomotion skills in terms of symmetry. This can be carried out by calculating the Harmonic Ratio (HR), a parameter obtained through the processing of trunk accelerations in the frequency domain. In this study, trunk accelerations during level walking of 449 healthy older adults (of age > 65) who were stratified into three groups (Group 1: 65–74 years, n = 175; Group 2: 75–85 years, n = 227; Group 3: >85 years, n = 47) were acquired by means of a miniaturized Inertial Measurement Unit located in the low back and processed to obtain spatio-temporal parameters of gait and H...
The aim of this study was to assess the inter-limb symmetry during gait in post-stroke patients u... more The aim of this study was to assess the inter-limb symmetry during gait in post-stroke patients using the synchronized cyclograms technique. In total, 41 individuals with stroke (21 left and 20 right hemiplegic patients; age: 57.9 ± 12.8 years; time stroke event 4.6 ± 1.8 years) and 48 age-, sex-, and height-matched individuals (control group: CG; age: 54.4 ± 12.5 years) were assessed via 3D gait analysis. Raw kinematic data were processed to compute spatio-temporal parameters (speed, stride length, cadence, stance, swing, and double support phases duration) and angle–angle diagrams (synchronized cyclograms), which were characterized in terms of area, orientation, and trend symmetry indices. The results reveal that all spatio-temporal parameters are characterized by abnormal values, with reduced speed, stride length, cadence, and swing phase duration and increased stance and double support phases duration. With respect to inter-limb symmetry, higher values were found in post-stroke ...
Subtle alterations of gait patterns in people with Multiple Sclerosis (pwMS) with minimal or no d... more Subtle alterations of gait patterns in people with Multiple Sclerosis (pwMS) with minimal or no disability often coexist with normal spatio-temporal parameters. Here, we retrospectively investigate the existence of possible anomalies in lower limb inter-joint coordination (i.e., the functional relationship between joint pairs) in pwMS with apparently physiologic gait features. Twenty-seven pwMS with Expanded Disability Status Scale scores ≤ 2, and 27 unaffected age-and-sex-matched individuals, were tested using 3D computerized gait analysis. Raw data were processed to extract the main spatio-temporal parameters and the kinematics in the sagittal plane at the hip, knee, and ankle joints. Angle-angle diagrams (cyclograms) were obtained by coupling the flexion-extension values for the hip-knee and knee-ankle joint pairs at each point of the gait cycle. Cyclogram area, perimeter, and dimensionless ratio were employed to quantify inter-joint coordination. The results demonstrate that cyc...
Hypoxia can impair cognitive performance, whereas exercise can enhance it. The effects of hypoxia... more Hypoxia can impair cognitive performance, whereas exercise can enhance it. The effects of hypoxia on cognitive performance during exercise appear to be moderated by exercise duration and intensity and by severity and duration of hypoxia and cognitive task. In normal individuals, exercise under hypoxia can evoke adverse post-exercise mood states, such as tension and fatigue. However, little is known about the effects of hypoxia during exercise in trained athletes. The purpose of this study was to investigate how hypoxia affected executive functions and mood states, assessed, respectively, during and post-exercise and to explore the role of motivation moderators, such as inhibition and activation systems (BIS-BAS). Two different sessions of exercise in normoxia and hypoxia (FiO2 13%), each lasting 18 min, were randomly assigned in a counterbalanced order and administered to seventeen male athletes. During exercise bouts, participants performed a mental task (BST) aimed to produce cogn...
The use of wrist-worn accelerometers to perform assessment of physical activity features and post... more The use of wrist-worn accelerometers to perform assessment of physical activity features and posture recognition, has significantly increased in the last decades, but remains limited in ergonomic contexts. In particular, to our knowledge, no studies employed them to investigate symmetry of use of upper limb (UL) during actual work shifts, even though such information would be useful to identify potentially unbalanced use of dominant and non-dominant limb. In the present study we aimed to estimate intensity and symmetry of use of UL while, at the same time, analyzing the amount of time spent in sedentary behavior in workers engaged in physically demanding and sedentary tasks.2.MethodsTwenty-two full-time workers employed in a metalworking company were recruited for the study and divided into two groups (n=11 each) according to the task they usually performed as follows:1)Machine tools operators, who are required to perform several kinds of machining processes such as cutting, turning...
Objective: Whole body electrical garment – Mollii suit delivers sensory input to improve sensorim... more Objective: Whole body electrical garment – Mollii suit delivers sensory input to improve sensorimotor organisation, balance muscle tone, facilitate muscle contraction and reduce pain experience. The aim of this study was to evaluate 4 weeks of Mollii intervention on lower limb strength, gait speed, lower back pain, quality of life and fatigue in a female person with Multiple Sclerosis (pwMS). Methods: Mollii was programmed by physiotherapist and subsequently worn at home for 60 minutes for 4 weeks every second day, by a female participant with primary progressive MS. Participant was walking with 2 elbow crutches. Stimulation parameters: pulse width 25-175 microseconds, constant current at 20 Hertz. Usability and perceived effects were monitored by a weekly phone call. Five time sit to stand (5xSTS) was used for functional lower limb strength, Timed Up and Go test (TUG) to evaluate gait speed, Visual analogue scale 0-10 (VAS) for the perceived back pain, Multiple Sclerosis Impact sca...
Computer Methods in Biomechanics and Biomedical Engineering, 2020
Most studies on locomotion of individuals with the Prader-Willi Syndrome (PWS) have been performe... more 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.
Considering the relevant amount of time spent by children at school, it is essential to ensure th... more Considering the relevant amount of time spent by children at school, it is essential to ensure that suitable levels of physical activity (PA) are guaranteed. This study aimed to assess possible changes induced in the amount and type of PA performed following the 2 schedules in Italian primary schools, namely regular and full time (30-40 h/week respectively). A sample of 169 children wore a triaxial accelerometer 24h/day for 7 consecutive days. Raw data were processed to calculate the number of steps, amount and intensity of the PA performed in morning, afternoon and evening time slots. During weekday afternoon times (1:30 to 4:30 PM), children attending the full-time schedule spent significantly less time in sedentary behavior with respect to those who attend the regular time (54.7% vs. 60.0%, P < .001) and more time in moderate-to-vigorous activity (18.0% vs. 15.0%, P = .004). No differences between morning and evening times were found. The structure of the full time schedule, w...
BACKGROUND Although upper limb (UL) dysfunctions are quite common among people with Multiple Scle... more 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.
International Journal of Occupational Safety and Ergonomics
Accurate assessment of biomechanical risk associated with pushing/pulling tasks represents a chal... more Accurate assessment of biomechanical risk associated with pushing/pulling tasks represents a challenging issue, especially in the health system where personnel are often required to maneuver beds and carts. Most studies in this field have been carried out in laboratory, while few data have been collected under actual working conditions. This study aims to characterize the forces exerted during non-powered hospital bed maneuvering. Twenty participants were required to move a bed (equipped with a customized handlebar to measure exerted forces) along an actual hospital path which included straight, turn and maneuver phases. The results show that the higher forces are associated with the initial phase (peak and mean values 222 and 68 N) while straight, turn and maneuvering phases required similar (lower) efforts. The combined effect of left, right and transversal forces suggests that the trunk of the operator might experience axial rotation, thus calling for further investigations on this aspect.
The main purpose of the present study was to assess the effects of foot drop stimulators (FDS) in... more The main purpose of the present study was to assess the effects of foot drop stimulators (FDS) in individuals with stroke by means of spatio-temporal and step-to-step symmetry, harmonic ratio (HR), parameters obtained from trunk accelerations acquired using a wearable inertial sensor. Thirty-two patients (age: 56.84 ± 9.10 years; 68.8% male) underwent an instrumental gait analysis, performed using a wearable inertial sensor before and a day after the 10-session treatment (PRE and POST sessions). The treatment consisted of 10 sessions of 20 min of walking on a treadmill while using the FDS device. The spatio-temporal parameters and the HR in the anteroposterior (AP), vertical (V), and mediolateral (ML) directions were computed from trunk acceleration data. The results showed that time had a significant effect on the spatio-temporal parameters; in particular, a significant increase in gait speed was detected. Regarding the HRs, the HR in the ML direction was found to have significantl...
OBJECTIVES To assess the effect of competitive level on dynamic postural stability in young elite... more 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.
The Proceedings of International Symposium on Seed-up and Service Technology for Railway and Maglev Systems : STECH, 2009
The ability to predict the criticality of internal cracks in railway wheels requires accurate kno... more The ability to predict the criticality of internal cracks in railway wheels requires accurate knowledge of stress intensity factors K I , K II , K III under contact loads. These factors depend both on the total load acting on the wheel and on how the load is transmitted through the wheel/rail interface, that is to say, they depends on the pressure distribution between wheel and rail. However, till today the solutions commonly used consider a theoretical (Hertzian) pressure distribution, even though the real contact patch may be far different for most of the lifespan of the wheel due to wear or to the dynamic conditions. In this paper an approach is developed with the aim of solving the case of an internally cracked wheel subjected to an arbitrary contact patch and pressure distribution. In particular, attention is focused on the case of hollow wear, which makes it possible to obtain very conformal contacts. The results are discussed and compared with the analytical solutions that consider Hertzian pressure distributions with the same total load.
This study investigated changes in task-induced trunk sway of quay crane operators during a four-... more 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.
Although gait disorders represent a highly prevalent condition in older adults, the alterations a... more Although gait disorders represent a highly prevalent condition in older adults, the alterations associated with physiologic aging are often not easily differentiable from those originated by concurrent neurologic or orthopedic conditions. Thus, the detailed quantitative assessment of gait patterns represents a crucial issue. In this context, the study of trunk accelerations may represent an effective proxy of locomotion skills in terms of symmetry. This can be carried out by calculating the Harmonic Ratio (HR), a parameter obtained through the processing of trunk accelerations in the frequency domain. In this study, trunk accelerations during level walking of 449 healthy older adults (of age > 65) who were stratified into three groups (Group 1: 65–74 years, n = 175; Group 2: 75–85 years, n = 227; Group 3: >85 years, n = 47) were acquired by means of a miniaturized Inertial Measurement Unit located in the low back and processed to obtain spatio-temporal parameters of gait and H...
The aim of this study was to assess the inter-limb symmetry during gait in post-stroke patients u... more The aim of this study was to assess the inter-limb symmetry during gait in post-stroke patients using the synchronized cyclograms technique. In total, 41 individuals with stroke (21 left and 20 right hemiplegic patients; age: 57.9 ± 12.8 years; time stroke event 4.6 ± 1.8 years) and 48 age-, sex-, and height-matched individuals (control group: CG; age: 54.4 ± 12.5 years) were assessed via 3D gait analysis. Raw kinematic data were processed to compute spatio-temporal parameters (speed, stride length, cadence, stance, swing, and double support phases duration) and angle–angle diagrams (synchronized cyclograms), which were characterized in terms of area, orientation, and trend symmetry indices. The results reveal that all spatio-temporal parameters are characterized by abnormal values, with reduced speed, stride length, cadence, and swing phase duration and increased stance and double support phases duration. With respect to inter-limb symmetry, higher values were found in post-stroke ...
Subtle alterations of gait patterns in people with Multiple Sclerosis (pwMS) with minimal or no d... more Subtle alterations of gait patterns in people with Multiple Sclerosis (pwMS) with minimal or no disability often coexist with normal spatio-temporal parameters. Here, we retrospectively investigate the existence of possible anomalies in lower limb inter-joint coordination (i.e., the functional relationship between joint pairs) in pwMS with apparently physiologic gait features. Twenty-seven pwMS with Expanded Disability Status Scale scores ≤ 2, and 27 unaffected age-and-sex-matched individuals, were tested using 3D computerized gait analysis. Raw data were processed to extract the main spatio-temporal parameters and the kinematics in the sagittal plane at the hip, knee, and ankle joints. Angle-angle diagrams (cyclograms) were obtained by coupling the flexion-extension values for the hip-knee and knee-ankle joint pairs at each point of the gait cycle. Cyclogram area, perimeter, and dimensionless ratio were employed to quantify inter-joint coordination. The results demonstrate that cyc...
Hypoxia can impair cognitive performance, whereas exercise can enhance it. The effects of hypoxia... more Hypoxia can impair cognitive performance, whereas exercise can enhance it. The effects of hypoxia on cognitive performance during exercise appear to be moderated by exercise duration and intensity and by severity and duration of hypoxia and cognitive task. In normal individuals, exercise under hypoxia can evoke adverse post-exercise mood states, such as tension and fatigue. However, little is known about the effects of hypoxia during exercise in trained athletes. The purpose of this study was to investigate how hypoxia affected executive functions and mood states, assessed, respectively, during and post-exercise and to explore the role of motivation moderators, such as inhibition and activation systems (BIS-BAS). Two different sessions of exercise in normoxia and hypoxia (FiO2 13%), each lasting 18 min, were randomly assigned in a counterbalanced order and administered to seventeen male athletes. During exercise bouts, participants performed a mental task (BST) aimed to produce cogn...
The use of wrist-worn accelerometers to perform assessment of physical activity features and post... more The use of wrist-worn accelerometers to perform assessment of physical activity features and posture recognition, has significantly increased in the last decades, but remains limited in ergonomic contexts. In particular, to our knowledge, no studies employed them to investigate symmetry of use of upper limb (UL) during actual work shifts, even though such information would be useful to identify potentially unbalanced use of dominant and non-dominant limb. In the present study we aimed to estimate intensity and symmetry of use of UL while, at the same time, analyzing the amount of time spent in sedentary behavior in workers engaged in physically demanding and sedentary tasks.2.MethodsTwenty-two full-time workers employed in a metalworking company were recruited for the study and divided into two groups (n=11 each) according to the task they usually performed as follows:1)Machine tools operators, who are required to perform several kinds of machining processes such as cutting, turning...
Objective: Whole body electrical garment – Mollii suit delivers sensory input to improve sensorim... more Objective: Whole body electrical garment – Mollii suit delivers sensory input to improve sensorimotor organisation, balance muscle tone, facilitate muscle contraction and reduce pain experience. The aim of this study was to evaluate 4 weeks of Mollii intervention on lower limb strength, gait speed, lower back pain, quality of life and fatigue in a female person with Multiple Sclerosis (pwMS). Methods: Mollii was programmed by physiotherapist and subsequently worn at home for 60 minutes for 4 weeks every second day, by a female participant with primary progressive MS. Participant was walking with 2 elbow crutches. Stimulation parameters: pulse width 25-175 microseconds, constant current at 20 Hertz. Usability and perceived effects were monitored by a weekly phone call. Five time sit to stand (5xSTS) was used for functional lower limb strength, Timed Up and Go test (TUG) to evaluate gait speed, Visual analogue scale 0-10 (VAS) for the perceived back pain, Multiple Sclerosis Impact sca...
Computer Methods in Biomechanics and Biomedical Engineering, 2020
Most studies on locomotion of individuals with the Prader-Willi Syndrome (PWS) have been performe... more 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.
Considering the relevant amount of time spent by children at school, it is essential to ensure th... more Considering the relevant amount of time spent by children at school, it is essential to ensure that suitable levels of physical activity (PA) are guaranteed. This study aimed to assess possible changes induced in the amount and type of PA performed following the 2 schedules in Italian primary schools, namely regular and full time (30-40 h/week respectively). A sample of 169 children wore a triaxial accelerometer 24h/day for 7 consecutive days. Raw data were processed to calculate the number of steps, amount and intensity of the PA performed in morning, afternoon and evening time slots. During weekday afternoon times (1:30 to 4:30 PM), children attending the full-time schedule spent significantly less time in sedentary behavior with respect to those who attend the regular time (54.7% vs. 60.0%, P < .001) and more time in moderate-to-vigorous activity (18.0% vs. 15.0%, P = .004). No differences between morning and evening times were found. The structure of the full time schedule, w...
BACKGROUND Although upper limb (UL) dysfunctions are quite common among people with Multiple Scle... more 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.
International Journal of Occupational Safety and Ergonomics
Accurate assessment of biomechanical risk associated with pushing/pulling tasks represents a chal... more Accurate assessment of biomechanical risk associated with pushing/pulling tasks represents a challenging issue, especially in the health system where personnel are often required to maneuver beds and carts. Most studies in this field have been carried out in laboratory, while few data have been collected under actual working conditions. This study aims to characterize the forces exerted during non-powered hospital bed maneuvering. Twenty participants were required to move a bed (equipped with a customized handlebar to measure exerted forces) along an actual hospital path which included straight, turn and maneuver phases. The results show that the higher forces are associated with the initial phase (peak and mean values 222 and 68 N) while straight, turn and maneuvering phases required similar (lower) efforts. The combined effect of left, right and transversal forces suggests that the trunk of the operator might experience axial rotation, thus calling for further investigations on this aspect.
The main purpose of the present study was to assess the effects of foot drop stimulators (FDS) in... more The main purpose of the present study was to assess the effects of foot drop stimulators (FDS) in individuals with stroke by means of spatio-temporal and step-to-step symmetry, harmonic ratio (HR), parameters obtained from trunk accelerations acquired using a wearable inertial sensor. Thirty-two patients (age: 56.84 ± 9.10 years; 68.8% male) underwent an instrumental gait analysis, performed using a wearable inertial sensor before and a day after the 10-session treatment (PRE and POST sessions). The treatment consisted of 10 sessions of 20 min of walking on a treadmill while using the FDS device. The spatio-temporal parameters and the HR in the anteroposterior (AP), vertical (V), and mediolateral (ML) directions were computed from trunk acceleration data. The results showed that time had a significant effect on the spatio-temporal parameters; in particular, a significant increase in gait speed was detected. Regarding the HRs, the HR in the ML direction was found to have significantl...
OBJECTIVES To assess the effect of competitive level on dynamic postural stability in young elite... more 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.
The Proceedings of International Symposium on Seed-up and Service Technology for Railway and Maglev Systems : STECH, 2009
The ability to predict the criticality of internal cracks in railway wheels requires accurate kno... more The ability to predict the criticality of internal cracks in railway wheels requires accurate knowledge of stress intensity factors K I , K II , K III under contact loads. These factors depend both on the total load acting on the wheel and on how the load is transmitted through the wheel/rail interface, that is to say, they depends on the pressure distribution between wheel and rail. However, till today the solutions commonly used consider a theoretical (Hertzian) pressure distribution, even though the real contact patch may be far different for most of the lifespan of the wheel due to wear or to the dynamic conditions. In this paper an approach is developed with the aim of solving the case of an internally cracked wheel subjected to an arbitrary contact patch and pressure distribution. In particular, attention is focused on the case of hollow wear, which makes it possible to obtain very conformal contacts. The results are discussed and compared with the analytical solutions that consider Hertzian pressure distributions with the same total load.
This study investigated changes in task-induced trunk sway of quay crane operators during a four-... more 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.
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