Acute changes in kinematic and muscle activity patterns in habitually shod rearfoot strikers while running barefoot

The aim of this study was to observe changes in the kinematics and muscle activities when barefoot running was initially adopted by six habitually shod, recreational rearfoot striking runners. Participants ran on a treadmill shod for 5 min, completed 3 × 10-min intervals of barefoot running and then completed a final minute of shod running at a self-selected pace. Dependent variables (speed, joint angles at foot-contact, joint range of motion (ROM), mean and peak electromyography (EMG) activity) were compared across conditions using repeated measures ANOVAs. Anterior pelvic tilt and hip flexion significantly decreased during barefoot conditions at foot contact. The ROM for the trunk, pelvis, knee and ankle angles decreased during the barefoot conditions. Mean EMG activity was reduced for biceps femoris, gastrocnemius lateralis and tibialis anterior during barefoot running. The peak activity across the running cycle decreased in biceps femoris, vastus medialis, gastrocnemius medialis and tibialis anterior during barefoot running. During barefoot running, tibialis anterior activity significantly decreased during the pre-activation and initial contact phases; gastrocnemius lateralis and medialis activity significantly decreased during the push-off phase. Barefoot running caused immediate biomechanical and neuromuscular adaptations at the hip and pelvis, which persisted when the runners donned their shoes, indicating that some learning had occurred during an initial short bout of barefoot running

Systematic nonlinear relations between displacement amplitude and joint mechanics at the human wrist

This study quantified the systematic effects on wrist joint mechanics of changes in amplitude of displacement ranging from within the region of short range stiffness (0.2% of resting muscle length) up to 3% of resting muscle length. The joint mechanics were modelled using a second order system from which estimates of joint stiffness, viscosity, inertia, natural resonant frequency and damping ratio were obtained. With increasing amplitude of displacement, the stiffness decreased by 31%, the viscosity decreased by 73%, the damping ratio decreased by 71% and the resonant frequency decreased from 10.5 Hz to 7.3 Hz. The patterns of change in joint mechanics with displacement amplitude were nonlinear but systematic and were well described by power relationships with high R2 values. These relationships provide normative data for the adult population and may be used in the modelling of human movement, in the study of neurological disorders and in robotics where human movement is simulated. The observed patterns of high initial stiffness and viscosity, decreasing progressively as displacement amplitude increases, may provide a good compromise between postural stability and liveliness of voluntary movement

Phenotypic Variability of Childhood Charcot-Marie-Tooth Disease

IMPORTANCE: Disease severity of childhood Charcot-Marie-Tooth disease (CMT) has not been extensively characterized, either within or between types of CMT to date. OBJECTIVE: To assess the variability of disease severity in a large cohort of children and adolescents with CMT. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional study was conducted among 520 children and adolescents aged 3 to 20 years at 8 universities and hospitals involved in the Inherited Neuropathies Consortium between August 6, 2009, and July 31, 2014, in Australia, Italy, the United Kingdom, and the United States. Data analysis was conducted from August 1, 2014, to December 1, 2015. MAIN OUTCOMES AND MEASURES: Scores on the Charcot-Marie-Tooth Disease Pediatric Scale (CMTPedS), a well-validated unidimensional clinical outcome measure to assess disease severity. This instrument includes 11 items assessing fine and gross motor function, sensation, and balance to produce a total score ranging from 0 (unaffected) to 44 (severely affected). RESULTS: Among the 520 participants (274 males) aged 3 to 20 years, CMT type 1A (CMT1A) was the most prevalent type (252 [48.5%]), followed by CMT2A (31 [6.0%]), CMT1B (15 [2.9%]), CMT4C (13 [2.5%]), and CMTX1 (10 [1.9%]). Disease severity ranged from 1 to 44 points on the CMTPedS (mean [SD], 21.5 [8.9]), with ankle dorsiflexion strength and functional hand dexterity test being most affected. Participants with CMT1B (mean [SD] CMTPedS score, 24.0 [7.4]), CMT2A (29.7 [7.1]), and CMT4C (29.8 [8.6]) were more severely affected than those with CMT1A (18.9 [7.7]) and CMTX1 (males: 15.3 [7.7]; females: 13.0 [3.6]) (P < .05). Scores on the CMTPedS tended to worsen principally during childhood (ages, 3-10 years) for participants with CMT4C and CMTX1 and predominantly during adolescence for those with CMT1B and CMT2A (ages, 11-20 years), while CMT1A worsened consistently throughout childhood and adolescence. For individual items, participants with CMT4C recorded more affected functional dexterity test scores than did those with all other types of CMT (P < .05). Participants with CMT1A and CMTX1 performed significantly better on the 9-hole peg test and balance test than did those with all other types of CMT (P < .05). Participants with CMT2A had the weakest grip strength (P < .05), while those with CMT2A and CMT4C exhibited the weakest ankle plantarflexion and dorsiflexion strength, as well as the lowest long jump and 6-minute walk test distances (P < .05). Multiple regression modeling identified increasing age (r = 0.356, β = 0.617, P < .001) height (r = 0.251, β = 0.309, P = .002), self-reported foot pain (r = 0.162, β = .114, P = .009), and self-reported hand weakness (r = 0.243, β = 0.203, P < .001) as independent predictors of disease severity. CONCLUSIONS AND RELEVANCE: These results highlight the phenotypic variability within CMT genotypes and mutation-specific manifestations between types. This study has identified distinct functional limitations and self-reported impairments to target in future therapeutic trials

Evidence of viscerally-mediated cold-defence thermoeffector responses in man

Sudomotor activity is modified by both warm and cold fluid ingestion during heat stress, independently of differences in core and skin temperatures, suggesting independent viscerally-mediated modification of thermoeffectors. The purpose of the present study was to determine whether visceral thermoreceptors modify shivering responses to cold stress. Ten males (27 ± 5y, 1.73 ± 0.06 m, 78.4 ± 10.7 kg) underwent whole-body cooling via 5 °C water perfusion-suit, on four occasions, to induce a steady-state shivering response, at which point two aliquots of 1.5 ml/kg (SML) and 3.0 ml/kg (LRG), separated by 20- min, of either 7°C, 22°C, 37°C or 52°C water were ingested. Rectal, mean skin and mean body temperature (Tb), electromyographic activity (EMG), metabolic rate (M) and whole-body thermal sensation on a visual analogue scale (WBTS) ranging from 0 mm [very cold] to 200 mm [very hot] were all measured throughout. Tb was not different between all fluid temperatures following SML (7°C:35.7 ± 0.5°C, 22°C:35.6 ± 0.5°C, 37°C:35.5 ± 0.4°C, 52°C:35.5 ± 0.4°C; P = 0.27) or LRG (7°C:35.3 ± 0.6°C, 22°C:35.3 ± 0.5°C, 37°C:35.2 ± 0.5°C, 52°C:35.3 ± 0.5°C; P = 0.99) fluid ingestion. With SML ingestion, greater metabolic rate and cooler thermal sensations were observed with 7°C (M:179 ± 55 W, WBTS:29 ± 21 mm) compared to 52°C (M:164 ± 34 W, WBTS:51 ± 28 mm; all P < 0.05) ingestion. With LRG ingestion, compared to shivering and thermal sensations with 37 °C ingestion (M:215 ± 47 W, EMG:3.9 ± 2.5%MVC, WBTS:33 ± 2 mm) values were different (all P < 0.05) following 7°C (M:269 ± 77 W, EMG:5.5 ± 0.9%MVC, WBTS:14 ± 12 mm), 22°C (M:270 ± 86 W, EMG:5.6 ± 1.0%MVC, WBTS:18 ± 19 mm) and 52°C (M:179 ± 34 W, EMG:3.3 ± 2.1%MVC, WBTS:53 ± 28 mm) ingestion. In conclusion, ingesting 52°C fluids decreased shivering and the sensation of coolness, whereas 22°C and 7°C fluids increased shivering and sensations of coolness to similar levels, independently of core and skin temperature

The facilitators and barriers to exercise in the Noongar Aboriginal population in Perth, Australia

Indigenous Standpoint Theory forms the epistemological foundation for this study and methodological choices were made within this theoretical framework to ensure culturally responsive research processes that engaged the Indigenous agenda of self-determination and rights. The objectives of this research were to determine: (i) Indigenous perceptions of the facilitators and barriers to exercise; (ii) The potential feasibility and sustainability of an exercise intervention. In this context, Participatory Action Research methods were used to design the data-gathering instrument for the study - a questionnaire, co-designed with the Noongar Aboriginal community of Perth, Western Australia. This self-administered questionnaire, distributed to participants by email, post and manual delivery, sought to elicit the factors that impact uptake and retention of regular exercise activities. Questionnaire data included individual demographic detail and specific question responses on labelled 5 point Likert Scales. Specific question responses were tabulated by Likert Scale label category and the response distribution for each question was enumerated. Simple descriptive statistics (measures of central tendency and variance) were used to characterize the data set and the Chi squared test was used to evaluate frequency differences between males and females. A total of 133 participants (71 females) completed the questionnaire. The results indicated that people valued exercise. The most common barriers indicated by participants were exercising with an injury (63%), changing diet (58%), finding time to exercise every day (55%) and exercising the next day with pain from exercising the day before (54%). A larger proportion of males (34%) than females (24%) reported greater ease in finding time to exercise every day (p < 0.05). Facilitators mainly related to the potential social and community benefits of exercising with other people, preferably in small groups, and the importance of a culturally secure venue. These findings shed light on what a culturally secure exercise programme might involve for the Noongar community. As this may have implications for other Aboriginal and Torres Strait Islander and international First Nations' Peoples, more focused research is needed on the place of traditional physical activities and the nature of culturally secure exercise programmes and spaces to enable wider application

The facilitators and barriers to exercise in the Noongar Aboriginal population in Perth, Australia

Indigenous Standpoint Theory forms the epistemological foundation for this study and methodological choices were made within this theoretical framework to ensure culturally responsive research processes that engaged the Indigenous agenda of self-determination and rights. The objectives of this research were to determine: (i) Indigenous perceptions of the facilitators and barriers to exercise; (ii) The potential feasibility and sustainability of an exercise intervention. In this context, Participatory Action Research methods were used to design the data-gathering instrument for the study—a questionnaire, co-designed with the Noongar Aboriginal community of Perth, Western Australia. This self-administered questionnaire, distributed to participants by email, post and manual delivery, sought to elicit the factors that impact uptake and retention of regular exercise activities. Questionnaire data included individual demographic detail and specific question responses on labelled 5 point Likert Scales. Specific question responses were tabulated by Likert Scale label category and the response distribution for each question was enumerated. Simple descriptive statistics (measures of central tendency and variance) were used to characterize the data set and the Chi squared test was used to evaluate frequency differences between males and females. A total of 133 participants (71 females) completed the questionnaire. The results indicated that people valued exercise. The most common barriers indicated by participants were exercising with an injury (63%), changing diet (58%), finding time to exercise every day (55%) and exercising the next day with pain from exercising the day before (54%). A larger proportion of males (34%) than females (24%) reported greater ease in finding time to exercise every day (p \u3c 0.05). Facilitators mainly related to the potential social and community benefits of exercising with other people, preferably in small groups, and the importance of a culturally secure venue. These findings shed light on what a culturally secure exercise programme might involve for the Noongar community. As this may have implications for other Aboriginal and Torres Strait Islander and international First Nations’ Peoples, more focused research is needed on the place of traditional physical activities and the nature of culturally secure exercise programmes and spaces to enable wider application

Maturation-based Corrective Adjustment Procedures (Mat-CAPs) in youth swimming: Evidence for restricted age-group application in females.

Inter-individual differences in maturation-associated development can lead to variations in physical performance, resulting in performance (dis)advantages and maturation selection bias within youth sport systems. To address such bias and account for maturational differences, Maturation-based Corrective Adjustment Procedures (Mat-CAPs) could be beneficial. The present study aimed to: (1) determine maturity timing distributions in youth female swimming; (2) quantify the relationship between maturation status and 100-m front-crawl (FC) performance; (3) implement Mat-CAPs to remove maturational influences upon swimming performance. For Aim 1 and 2, participants were 663 female (10–15 years) swimmers who participated in 100-m FC events at Australian regional, state, and national-level competitions between 2016–2020 and underwent anthropometric assessment (mass, height and sitting height) to estimate maturity timing and offset. For Aim 3, participants aged 10–13 years were categorised into maturity timing categories. Maturity timing distributions for Raw (‘All’, ‘Top 50%’ and ‘Top 25%’) and Correctively Adjusted swim times were examined. Chi-square, Cramer’s V and Odds Ratios determined the presence of maturation biases, while Mat-CAPs identified whether such biases were removed in targeted age and selection-groups. Results identified that between 10–13 years, a significantly higher frequency of ‘early’ maturers was apparent, although tapered toward higher frequencies of ‘Late-normative’ maturers by 14–15 years. A curvilinear relationship between maturity-offset and swim performance was identified (R2 = 0.51, p<0.001) and utilised for Mat-CAPs. Following Mat-CAPs application, maturity timing biases evident in affected age-groups (10–13 years), and which were magnified at higher selection levels (‘Top 50%’ & ‘25%’ of swim performances) were predominantly removed. Findings highlight how maturation advantages in females occurred until approximately 13 years old, warranting restricted Mat-CAPs application. Mat-CAPS has the potential to improve female swimmer participation experiences and evaluation

Turbo Expander Technology Contribution in Development of Ethylene Plant Process

LectureLecture 8: Ethylene plant process and turbo expander technology developments have been interrelated and dependent on each other’s. Design improvements and technology innovations associated with inflow radial turbine, turbo expander, have been the main motivation for the improved and more productive ethylene plant processes. The early process design that was based on Jule Thompson expansion valve was replaced by the process designs that utilize several stages of expander -compressor or expander- generators. The latest technology innovation that was embraced by the ethylene plant engineering companies and the owners was expander-compressor with active magnetic bearings. The early applications of expander-compressor with magnetic bearings began in the 1980’s.The present product improvement activities by turbo expander suppliers are to reduced number of expansion stages. High head and low flow coefficient expander wheel as well as high peripheral speed wheels are being developed to achieve the latter objective. The next innovative technology that is knocking at the door of ethylene plants is expander - high speed permanent magnet generator with magnetic bearings. In this paper the authors present a brief history of ethylene plant process, expander technology developments and show their reliance. The authors will also present their suggestions about the next innovation of the expander with high speed generator