The Deformation Characteristics and Lateral Stress of Roadside Crushed Rocks with Different Particles in Non-Pillar Coal Mining

Gob-side entry retaining formed by roof fracturing (GERRF) is a popular non-pillar mining method. The method uses crushed rocks in gob side to support and control the movements of the gob roof. These crushed rocks will deform under roof pressure and generate desirable lateral stress on support structures of gangue rib. In this study, the deformation behavior of crushed mudstones with different particle sizes under incremental loading was investigated with an innovative experimental device that simulated boundary conditions of the GERRF method. Influence of particle size of the crushed mudstones to the generation of lateral stress applied on support structures were concurrently observed and analyzed. Research outputs from the tests showed that: (1) The particle size exerted a significant influence on the accumulated axial deformation, period axial deformation, and lateral stress applied on support structure of crushed rocks. (2) Under the same axial stress, the larger the particle size, the smaller the accumulated axial deformation of the crushed rock; A skeletal loading-bearing effect was apparent in the rock samples with larger particles (S-2, S-3). The compressive deformation process of samples S-2, S-3 divided into structural adjustment, skeletal load-bearing and crushing cum filling phases. At skeletal loading-bearing phase, the crushed rocks showed better deformation resistance and stability than other phases; (3) Two types of periodic stress-strain curves were observed for crushed mudstones in the tests. The “down-concave” type implied the deformation for the crushed mudstones was primarily a consequence of the compression in the void spaces. While the “upper-convex” type curve was resulted in particle crushing cum filling again; (4) The lateral pressure generated by large-size samples was smaller than that of small-size samples. Additionally, a poor regularity of lateral stress was observed in compression test of large-size sample (S-3). The relationship between the axial stress and lateral stress generated on the support structure was found to be approximately linear relationship under the condition that lateral pressure shows good regularity.

ПОБУДОВА ТРЕНУВАЛЬНОГО ПРОЦЕСУ У СПОРТСМЕНІВ З МІЖНАРОДНОГО ВІЙСЬКОВО-АВІАЦІЙНОГО П’ЯТИБОРСТВА ДЛЯ УЧАСТІ У СПОРТИВНОМУ КОНКУРСІ (ПОДОЛАННЯ СМУГИ ПЕРЕШКОД І СПОРТИВНЕ ОРІЄНТУВАННЯ)

Objective: to increase the efficiency of the training process of athletes in military aviation pentathlon through the additional introduction of crossfit exercises and cognitive training. Material and methods of research: analysis of literature sources, questionnaires, testing, statistical analysis. The study involved 48 first-year cadets of the Ivan Kozhedub Kharkiv National University of the Air Force (men), aged 17-18, including 38 candidates for masters of sports and 10 masters of sports. The obtained results: a combination in a single algorithm of training first-year cadets - candidates for the national team with VAP exercises for the development of motor coordination skills, develop the maximum number of competencies (motor abilities). Using crossfit exercises with maximum agility, accuracy, balance, flexibility, mobility in the joints, jumping, accuracy, rhythm and plasticity allow cadets to develop maximum physical performance and endurance. Conclusions: Exercises for the development of cognitive abilities allow you to understand in more detail and then perform new exercises, to concentrate as much as possible on the ultimate goal of the exercises. Pilates largely avoids high impact, high power output, and heavy muscular and skeletal loading. Pilates largely avoids high impact, high power output, and heavy muscular and skeletal loading.

Serum Sclerostin, Body Composition, and Sarcopenia in Hemodialysis Patients with Diabetes

Sclerostin (Scl) is an osteoblast-inhibiting glycoprotein that is secreted mainly by osteocytes and is regulated by hormonal changes and skeletal loading. Decreased physical function and high serum Scl concentrations have been reported in chronic renal failure patients but little is known to date about the differences between diabetic and non-diabetic patients on hemodialysis who are susceptible to both sarcopenia and bone fragility. Objective.To determine the prevalence of sarcopenia and its association with serum Scl concentrations and metabolic parameters in 92 patients on hemodialysis. Anthropometric data and physical performance were evaluated in this study. Blood samples were collected for Scl, glucose, cholesterol, triglycerides, calcium, phosphate, PTH, and 25 OH-vitamin D measurements. Lean mass was evaluated using multifrequency electro-bioimpedance after dialysis session. Results. Mean age was 63.3 ± 13.6 years, 63% of patients were male, and 44.6% had diabetes. Mean body mass index (BMI) was higher in diabetics (26.6 ± 5.2 vs. 24.1 ± 3.7; p=0.01) and there were no differences in gait speed and handgrip strength between diabetic and non-diabetic subjects. A low skeletal muscle mass index (SMI) was identified in 65.2% of the participants, and among them 76.7% were men and 36.7% were diabetics. Mean serum Scl was 86.9 ± 39.0 pmol/L, which was higher in men (94.6 ± 41.7; p=0.017), in those individuals with low SMI (94.9 ± 40.7; p<0.001), and in diabetics (97.2 ± 46.6; p<0.003). After multivariate analysis and adjustments for potential confounders, high serum Scl was independently associated with low SMI and with the presence of diabetes. The following variables correlated positively with diabetes: blood pressure; BMI; waist circumference; waist/hip ratio; plasma glucose; serum Scl; and fat mass. Conclusions. We found higher serum Scl concentrations in hemodialysis patients with diabetes and these were inversely related to muscle mass.

Clinical evaluation of education relating to nutrition and skeletal loading in competitive male road cyclists at risk of relative energy deficiency in sports (RED-S): 6-month randomised controlled trial

ObjectiveTo clinically evaluate education to improve eating behaviour and skeletal loading exercise in male cyclists at risk of poor bone health and impaired performance due to relative energy deficiency in sports.MethodsEarly race season, 50 competitive male road cyclists were matched, in pairs, based on Z-scores for lumbar spine bone mineral density (BMD). One member of each pair was randomly allocated to receive educational interventions. After the season, 45 cyclists returned for dual-energy X-ray absorptiometry scans and blood tests. Least significant change was applied to identify clinically meaningful BMD changes. Cyclists completed a follow-up sport-specific questionnaire and clinical interview to ascertain adherence to the interventions.ResultsThe questionnaire and clinical interview categorised behaviour changes as positive, negative or unchanged. Positive changes in nutrition and skeletal loading were associated with a statistically significant increase of 2.0% in lumbar spine BMD; 7 of 11 cyclists’ increases were clinically meaningful. Negative changes in both behaviours were associated with a significant decrease of 2.7% in lumbar BMD; all nine cyclists’ BMD decreases were clinically meaningful. Regarding performance, taking account of functional threshold power, changes in nutritional behaviour accounted for gains or losses of 95 British Cycling racing points. Cyclists reported psychological barriers to change in behaviours, specifically fear of negatively impacting performance.ConclusionsEducational nutritional and skeletal loading interventions can improve bone health, well-being and race performance in male cyclists over a 6-month race season. Psychological support may be required to help some athletes change behaviour.