Cyclic Strain Research Articles

Preparation of Gradient Polyurethane and Its Performance for Flexible Sensors.

Flexible sensors are prone to the problems of slow recovery rate and large residual strain in practical use. In this paper, a polyurethane functional composite with a gradient change in elastic modulus is proposed as a flexible sensor to meet the recovery rate and residual strain without affecting the motion. Different hard and soft segment ratios are used to synthesize a gradient polyurethane structure. The conductive percolation threshold was obtained between 45 wt% and 50 wt% of flake silver powder. Both gradient polyurethane and gradient polyurethane composites demonstrated that gradient materials can increase the recovery rate and reduce residual strain. The gradient polyurethane composites had a tensile strength of 3.26 MPa, an elastic modulus of 2.58 MPa, an elongation at break of 245%, a sensitivity coefficient of 1.20 at 0-25% deformation, a sensitivity coefficient of 11.38 at 25-75% deformation, a rate of recovery of 1.95 s at a time, and a resistance to fatigue (over 1000 cycles at a fixed strain of 20% showed a stable electrical response). The sensing performance under different cyclic strain frequencies was also investigated. The process has practical applications in the field of wearable skin motion and health monitoring.

Vitamin D and its effect on the endothelial function of cross-country skiers at various stages of the training cycle

The aim of the study was to assess the level of vitamin D and nitric oxide metabolites, and to search for the relationship between them in cross-country skiers at various stages of the training cycle. During the year, two groups of men (20–26 years old, inhabitants of the Komi Republic) were examined four times: cross-country skiers who are active members of the national teams of the Komi Republic/Russia (n = 11) and office workers (n = 10). It was shown that skiers had higher vitamin D levels duration the year compared to office workers. The fluctuations in the levels of vitamin D, calcium and phosphorus detected in cross-country skiers were seasonal, which could lead to significant changes in the synthesis of nitric oxide and the work of the endothelial system. The greatest number of correlations between the studied metabolites in cross-country skiers was revealed at the beginning and end of the annual training season. A significant imbalance in the levels of vitamin D and nitric oxide metabolites found in them in March may negatively affect the success of performance at important competitions.

Impact of Anaerobic Exercise Integrated Into Regular Training on Experienced Judo Athletes: Running Vs. Repetitive Throws.

Kamandulis, S, Dudėnienė, L, Snieckus, A, Kniubaite, A, Mickevicius, M, Lukonaitiene, I, Venckunas, T, Stasiule, L, and Stasiulis, A. Impact of anaerobic exercise integrated into regular training on experienced judo athletes: running vs. repetitive throws. J Strength Cond Res 38(9): e489-e495, 2024-Anaerobic training in high-level athletes is of considerable interest to practitioners aiming to optimize performance. This study compared the impact of interval anaerobic training (IAT) sessions consisting of either high-intensity running or throwing that were performed twice a week together with regular judo training on the anaerobic and aerobic performance of experienced judo athletes. Employing a repeated-measures, counterbalancing, research design, 12 national team judo athletes (7 women and 5 men; mean age, 20.4 ± 0.95 years; mean judo training experience, 13.4 ± 1.4 years; competitive level, black belt first and second Dan) performed each IAT modality for 6 weeks, for a full training cycle of 12 weeks. Assessments of their anaerobic fitness (Cunningham and Faulkner Anaerobic Treadmill Test), sport-specific anaerobic fitness (Special Judo Fitness Test [SJFT]), and aerobic capacity (maximal incremental treadmill running test) were performed before, after 6 weeks, and after 12 weeks of training. The uphill running performance improved by 13.1% over the 12-week period ( p = 0.047). Simultaneously, there was a 9.0% improvement in the SJFT index and a 6.9% increase in the number of throws ( p = 0.011 and p = 0.017, respectively). Although a trend for throwing drills being more effective than interval sprint running was observed, the interaction effect lacked statistical significance ( p = 0.074). Moreover, no substantial changes were noted in aerobic endurance markers. In conclusion, this study suggests that incorporating specific and nonspecific high-intensity drills into a routine training regimen may enhance anaerobic capacity among well-trained judo athletes, potentially leading to favorable competitive outcomes.

Stiffening of the human proximal pulmonary artery with increasing age.

Adverse effects of large artery stiffening are well established in the systemic circulation; stiffening of the proximal pulmonary artery (PPA) and its sequelae are poorly understood. We combined invivo (n = 6) with exvivo data from cadavers (n = 8) and organ donors (n = 13), ages 18 to 89, to assess whether aging of the PPA associates with changes in distensibility, biaxial wall strain, wall thickness, vessel diameter, and wall composition. Aging exhibited significant negative associations with distensibility and cyclic biaxial strain of the PPA (p ≤ 0.05), with decreasing circumferential and axial strains of 20% and 7%, respectively, for every 10 years after 50. Distensibility associated directly with diffusion capacity of the lung (R2 = 0.71, p = 0.03). Axial strain associated with right ventricular ejection fraction (R2 = 0.76, p = 0.02). Aging positively associated with length of the PPA (p = 0.004) and increased luminal caliber (p = 0.05) but showed no significant association with mean wall thickness (1.19 mm, p = 0.61) and no significant differences in the proportions of mural elastin and collagen (p = 0.19) between younger (<50 years) and older (>50) exvivo samples. We conclude that age-related stiffening of the PPA differs from that of the aorta; microstructural remodeling, rather than changes in overall geometry, may explain age-related stiffening.

Changes in Circulating MicroRNA Levels as Potential Indicators of Training Adaptation in Professional Volleyball Players.

The increasing demand placed on professional athletes to enhance their fitness and performance has prompted the search for new, more sensitive biomarkers of physiological ability. One such potential biomarker includes microRNA (miRNA) small regulatory RNA sequences. The study investigated the levels of the selected circulating miRNAs before and after a 10-week training cycle in 12 professional female volleyball players, as well as their association with cortisol, creatine kinase (CK), and interleukin 6 (IL-6), using the qPCR technique. Significant decreases in the miR-22 (0.40 ± 0.1 vs. 0.28 ± 0.12, p = 0.009), miR-17 (0.35 ± 0.13 vs. 0.23 ± 0.08; p = 0.039), miR-24 (0.09 ± 0.04 vs. 0.05 ± 0.02; p = 0.001), and miR-26a (0.11 ± 0.06 vs. 0.06 ± 0.04; p = 0.003) levels were observed after training, alongside reduced levels of cortisol and IL-6. The correlation analysis revealed associations between the miRNAs' relative quantity and the CK concentrations, highlighting their potential role in the muscle repair processes. The linear regression analysis indicated that miR-24 and miR-26a had the greatest impact on the CK levels. The study provides insights into the dynamic changes in the miRNA levels during training, suggesting their potential as biomarkers for monitoring the adaptive responses to exercise. Overall, the findings contribute to a better understanding of the physiological effects of exercise and the potential use of miRNAs, especially miR-24 and miR-26a, as biomarkers in sports science and medicine.

Gender characteristics of the manifestation of cognitive and sensorimotor functions in young basketball players aged 13-14

It is known that success in sports is associated with the ability to quickly and accurately perform a visual search, store a large number of objects in memory, and respond in a timely manner to changes in the situation. The range of data on cognitive-sensorimotor skills of young basketball players does not sufficiently highlight gender characteristics, the consideration of which in the process of mastery formation is an important factor in achieving success in elite sports. Purpose: to find out the gender characteristics of the cognitive-sensorimotor activity support of basketball players aged 13-14 in the annual training cycle. Material and methods: young basketball players aged 13-14 were studied. Studies of sensorimotor and cognitive development were conducted using automated programs. Slices of cognitive and sensorimotor data were carried out at two stages: at the beginning of the annual training cycle and at its end. Results: data on the manifestation of types of thinking in young basketball players of 13-14 years of age of different genders indicated unequal dominance, in boys the dominant type was logical thinking, regardless of the stage of the study, and in girls - operational thinking. At both stages of the study, basketball players showed a higher level of associative and operational thinking than boys, and basketball players had a higher level of logical thinking than girls. At the end of the study, girls were ahead of boys in terms of abstract thinking, but showed the same performance in spatial thinking. Differences in indicators of sensorimotor functions were obtained. Girls demonstrated higher accuracy of right PPO with the difference maintained throughout the training year. Over the course of the annual training cycle, the advantage of boys in the higher accuracy of PPO from the left-top and the advantage of girls in the speed of RV 1-3 at the exit of the object from the right disappeared. At the same time, the advantage of the boys in the speed of the PZMR for the exit of the object from the left-top and the RV 1-3 for the exit of the object from the left was preserved. Conclusions: different profiles of cognitive and sensorimotor development of 13-14-year-old basketball players of different genders during the annual training cycle were established. The group of basketball players was distinguished by an intensive increase in indicators of operational thinking, accuracy of PPO and РВ1-3 on the movement of the object on the right, speed of PZMR from above. The group of female basketball players was distinguished by an increase in the indicators of abstract and spatial thinking, as well as the accuracy of left, top and bottom PRO. According to the accuracy of response to moving objects, right-sided perceptual dominance was established in boys and left-sided - in girls. It was also established that 13-14-year-old basketball players demonstrated the superiority of the influence of the motor component on sensorimotor development and lower possibilities of influence of the cognitive component than girls, 13-14-year-old female basketball players had the advantage of the influence of the cognitive component on sensorimotor development and lower possibilities of the influence of the motor component than boys.

Enhancement of OCT en face images by unsupervised deep learning

Objective. The quality of optical coherence tomography (OCT) en face images is crucial for clinical visualization of early disease. As a three dimensional and coherent imaging, defocus and speckle noise are inevitable, which seriously affect evaluation of microstructure of bio-samples in OCT images. The deep learning has demonstrated great potential in OCT refocusing and denoising, but it is limited by the difficulty of sufficient paired training data. This work aims to develop an unsupervised method to enhance the quality of OCT en face images. Approach. We proposed an unsupervised deep learning-based pipeline. The unregistered defocused conventional OCT images and focused speckle-free OCT images were collected by a home-made speckle modulating OCT system to construct the dataset. The image enhancement model was trained with the cycle training strategy. Finally, the speckle noise and defocus were both effectively improved. Main results. The experimental results on complex bio-samples indicated that the proposed method is effective and generalized in enhancing the quality of OCT en face images. Significance. The proposed unsupervised deep learning method helps to reduce the complexity of data construction, which is conducive to practical applications in OCT bio-sample imaging.

Sustainability of exercise-induced benefits on circulating MicroRNAs and physical fitness in community-dwelling older adults: a randomized controlled trial with follow up

BackgroundCirculating miRNAs (c-miR) have been shown to be potential biomarkers in sarcopenia, but the miRNAs response to aerobic exercise in older people remains inconclusive. We sought to examine the exercise benefits on physical fitness and miRNAs, and to explore the mediating effect of miRNAs on training-induced fitness changes.MethodsThis controlled trial recruited 58 community-dwelling older adults and randomized them into exercise group (EX) and control group (CON). EX received 8-week supervised moderate intensity cycling training 3x/week. C-miR expression (c-miR-21, c-miR-126, c-miR-146a, c-miR-222), physical fitness (body composition, cardiorespiratory fitness, muscular fitness) and physical activity level (PAL, measured as in daily step counts) were evaluated at baseline, post-training, and post-16-week follow-up. The mediating effect of miRNA expression onto exercise-induced physical fitness change was determined by causal mediation analysis (CMA).ResultsExercise significantly improved body fat and cardiorespiratory fitness in older people while maintaining muscle mass and strength, and augmented expression of c-miR-126, c-miR-146a, and c-miR-222 for up to 16 weeks post-training. Notably, older people in EX had substantially higher daily step counts than CON throughout the study even after the active training period. However, CMA revealed no significant indirect effect but a potential mediating effect of c-miR-21, but not the rest, onto the body composition, cardiorespiratory fitness, and lower limb strength.ConclusionAn eight-week supervised MICT program promoted a higher level of physical activity up to 16 weeks post-training, which induces better cardiorespiratory fitness and resists decline in muscular measures. C-miRNA, especially c-miR-21, potentially mediates the training effect upon fitness.

#192 Intradialytic cognitive and physical training to enhance functional capacity: a randomized controlled trial

Abstract Background and Aims Haemodialysis (HD) patients frequently experience cognitive and physical impairments due to various factors, including age, comorbidities, and the demanding nature of the treatment. This study explores the impact of a 12-week integrated cognitive and physical training program on the functional capacity of HD patients. Method A single-blind, randomized controlled trial was conducted with 44 HD patients. Participants were divided into an experimental (EXP) group (n = 22) and a control (CON) group (n = 22). The EXP group underwent 12 weeks of intradialytic cycling and tablet-based cognitive training three times a week, while the CON group received standard care (Fig. 1). Outcome measures were assessed pre- and post the 12-week intervention. Cognitive performance was evaluated using the Trail Making Tests A and B (TMTA and TMTB), while motor performance was assessed with the Timed Up and Go (TUG) test. Additionally, cognitive-motor interactions were examined using the TUG dual task test (TUG-dual). Results Results showed a significant effect of group*time interaction for TMTA test results (F(1,41) = 16.218, p &amp;lt; 0.001), TMTB test results (F(1,41) = 19.944, p &amp;lt; 0.001) favouring the EXP group. Additionally, a significant interaction was found for TUG test (F(1,40) = 8.854, p = 0.005) and for TUG-dual test (F(1,40) = 8.457, p = 0.006). Within the EXP group we observed significant improvements in cognitive function, as evidenced by decreased TMT completion times (TMTA: −3.6s, p = 0.006; TMTB: −14.0s, p &amp;lt; 0.001; TMTB–TMTA: −10.4s, p = 0.004). In contrast, the CON group experienced a significant decline in TMTA and TMTB (p &amp;lt; 0.009 and p &amp;lt; 0.026). Additionally, the EXP group exhibited enhanced mobility, with reduced TUG completion times (−0.8s, p &amp;lt; 0.001) and improved cognitive-motor performance in the TUG-dual (−1.0s, p &amp;lt; 0.001), while the CON group showed no significant changes (p &amp;gt; 0.05). Conclusion This study demonstrates that a 12-week combined cognitive and physical training program during HD sessions significantly enhances cognitive function and mobility in HD patients. These findings suggest that integrated non-pharmacological interventions can mitigate functional declines in this population and consequently improve their overall quality of life. Further research with larger samples and active control groups is warranted to confirm and expand upon these promising results.

Abdominal Fatigue Impairs Anaerobic, but not Aerobic,Cycling Performance in Untrained Adults

Relevance. Coaches and athletes across a variety of sports commonly perform abdominal exercises to promote core strength and endurance. However, the precise influence of abdominal strength and endurance on cycling performance remains elusive. Purpose. Determine whether abdominal fatigue affects anaerobic sprint and aerobic time- trial (TT) cycling performance. Methods. Twenty-three untrained young adults (age: 19,2 ± 1,0 years, height: 170,4 ± 7,5 cm, and weight: 74,5 ± 14,1 kg) participated in this study. Twelve of the participants completed two Wingate anaerobic power tests on a Monark 834 E ergometer set at 7,5 % of body mass and the remaining 11 participants completed two 3,2 km cycling TTs on an Expresso S3U virtual reality bike; tests were separated by 96 hours. All participants performed abdominal crunches to fatigue prior to the second test. Dependent t-tests were used to assess differences between the cycling trials for the two groups. Results. Abdominal muscle fatigue decreased mean anaerobic power (Pre: 486,75 vs. Post: 408,83 Watts (W, p &lt; 0,001), increased the rate of fatigue (Pre: 42,01 vs. Post: 50,32 %, p = 0,004), and tended to decrease peak anaerobic power (Pre: 643,17 vs. Post: 607,27 W, p = 0,088). However, abdominal muscle fatigue did not affect TT mean power (Pre: 228,18 vs. Post: 220,09 W, p = 0,127) or TT performance (Pre: 382,7 vs. Post: 388,0 seconds, p = 0,222). Conclusion. Abdominal fatigue negatively affects anaerobic cycling performance in untrained young adults. Future studies should evaluate the impact of abdominal fatigue on cycling performance in trained cyclists.

The Clinical Management of Electrical Stimulation Therapies in the Rehabilitation of Individuals with Spinal Cord Injuries.

Background: People with spinal cord injuries (SCIs) often have trouble remaining active because of paralysis. In the past, exercise recommendations focused on the non-paralyzed muscles in the arms, which provides limited benefits. However, recent studies show that electrical stimulation can help engage the paralyzed extremities, expanding the available muscle mass for exercise. Methods: The authors provide an evidence-based approach using expertise from diverse fields, supplemented by evidence from key studies toward the management of electrical stimulation therapies in individuals with SCIs. Literature searches were performed separately using the PubMed, Medline, and Google Scholar search engines. The keywords used for the searches included functional electrical stimulation cycling, hybrid cycling, neuromuscular electrical stimulation exercise, spinal cord injury, cardiovascular health, metabolic health, muscle strength, muscle mass, bone mass, upper limb treatment, diagnostic and prognostic use of functional electrical stimulation, tetraplegic hands, and hand deformities after SCI. The authors recently presented this information in a workshop at a major rehabilitation conference. Additional information beyond what was presented at the workshop was added for the writing of this paper. Results: Functional electrical stimulation (FES) cycling can improve aerobic fitness and reduce the risk of cardiovascular and metabolic diseases. The evidence indicates that while both FES leg cycling and neuromuscular electrical stimulation (NMES) resistance training can increase muscle strength and mass, NMES resistance training has been shown to be more effective for producing muscle hypertrophy in individual muscle groups. The response to the electrical stimulation of muscles can also help in the diagnosis and prognosis of hand dysfunction after tetraplegia. Conclusions: Electrical stimulation activities are safe and effective methods for exercise and testing for motor neuron lesions in individuals with SCIs and other paralytic or paretic conditions. They should be considered part of a comprehensive rehabilitation program in diagnosing, prognosing, and treating individuals with SCIs to improve function, physical activity, and overall health.

Characterization and quantification of in-vitro equine bone resorption in 3D using μCT and deep learning-aided feature segmentation

High cyclic strains induce formation of microcracks in bone, triggering targeted bone remodeling, which entails osteoclastic resorption. Racehorse bone is an ideal model for studying the effects of high-intensity loading, as it is subject to focal formation of microcracks and subsequent bone resorption. The volume of resorption in vitro is considered a direct indicator of osteoclast activity but indirect 2D measurements are used more often. Our objective was to develop an accurate, high-throughput method to quantify equine osteoclast resorption volume in μCT 3D images. Here, equine osteoclasts were cultured on equine bone slices and imaged with μCT pre- and postculture. Individual resorption events were then isolated and analyzed in 3D. Modal volume, maximum depth, and aspect ratio of resorption events were calculated. A convolutional neural network (CNN U-Net-like) was subsequently trained to identify resorption events on post-culture μCT images alone, without the need for pre-culture imaging, using archival bone slices with known resorption areas and paired CTX-I biomarker levels in culture media. 3D resorption volume measurements strongly correlated with both the CTX-I levels (p < 0.001) and area measurements (p < 0.001). Our 3D analysis shows that the shapes of resorption events form a continuous spectrum, rather than previously reported pit and trench categories. With more extensive resorption, shapes of increasing complexity appear, although simpler resorption cavity morphologies (small, rounded) remain most common, in acord with the left-hand limit paradigm. Finally, we show that 2D measurements of in vitro osteoclastic resorption are a robust and reliable proxy.

Training models of highly skilled cyclists in the pre-competitive mesocycle using a pedal power meter

Abstract. The need for systematic improvement of results and demonstration of high sports results, which are sometimes at the limit of human capabilities, substantiates the problem of finding ways to improve the level of special physical fitness of highly qualified cyclists. Studies of the experience of implementing pedaling power control tools in training have shown their effectiveness in various leading cycling countries of the world, which can contribute to improving the level of special physical fitness of athletes in track and highway cycling. The effectiveness of the use of power measuring devices has shown its positive effect in preparing cyclists for highway competitions, which makes it possible to assume the great need to use these devices in the training of track cyclists. The purpose of this work is to develop and test models of pre-competition mesocycles based on pedaling power data. Work results. Experimental development and verification of the effectiveness of training programs with means of controlling pedaling power confirmed their informativeness in the process of conducting mesocycles and the need to use them in the preparation and development of training plans for track cyclists for the main competitions of the year. Conclusions. Based on the data of two macrocycles of 2021 and 2022 training of cyclists, the training and results of highly qualified track cyclists were compared. The intensity of each training session in two mesocycles was established. Structures of microcycles based on power and heart rate data are compared. The training of track cyclists, which includes not only training for power development, but also volume training, has proven to be effective.

Effect of hydrogen on microstructure evolution and properties of high-strain pipeline steel under cyclic strain loading

The microstructure evolution and the fatigue damage mechanism of hydrogen-charged high-strain pipeline steel during the cyclic strain loading is studied. Hydrogen promotes the formation of dislocation walls and cells, and causes the lattice distortion iron atoms to move to the grain boundary, resulting in grain refinement. The fatigue life is reduced to more than 40 % when the strain amplitude reaches 0.5 % after hydrogen-charged. The main reasons for the reduce are the decrease of the number and the change of propagation mode of secondary cracks, and the increase of cleavage fracture and the decrease of deflection angle in the main cracks.

Application of Instrumented Indentation Procedure in Assessing the Low-Cycle Fatigue Properties of Selected Heat-Treated Steels.

The paper presents an analysis of the low-cycle fatigue (LCF) properties of C45, X20Cr13, and 34CrNiMo6 steels subjected to various heat treatment processes. Strain-controlled LCF tests were carried out with a total cyclic strain amplitude equal to 0.5, 1 and 1.5%. Fatigue life, cyclic stress-strain behavior and hardness were analyzed. Qualitative and quantitative relationships between material LCF properties resulting from the heat treatment processes, were related to the indentation force P*, which was derived experimentally by applying an instrumented indentation procedure with the use of the Vickers indenter. The proposed parameter P* and its changes ΔP* seem to be promising for the identification of the structural stress parameter σ* that is necessary for deriving values of the fatigue strength coefficients σf' corresponding to different tempering temperatures. The common feature of all steels analyzed in this paper is that the elastic parts of the strain-life characteristics remain parallel after being subjected to different tempering temperatures.

Intrinsically stretchable phototransistors with polymer-QD-polymer multi-layered hybrid films for visible-NIR perspective electronic skin sensors

Stretchable phototransistors represent a crucial component in the development of skin-inspired optoelectronics. Although there have been significant advancements in the development of skin-like photosensitive semiconductors, technology for stretchable phototransistors that can detect a broad spectrum of wavelengths from near-infrared (NIR) to visible light is still in its early stages. This study introduces an intrinsically stretchable phototransistor employing hybrid semiconductor films consisting of polymer semiconductors (PSC) and quantum dots (QDs). The hybrid multi-layered semiconductor film (PSC/QDs/PSC) possesses wide-ranging color sensitivity from NIR to visible light, along with high photosensitivity and photoresponsivity. Furthermore, our phototransistor exhibits remarkable strain-insensitive, photo-response characteristics, maintaining performance even under 50% strain and enduring 10,000 strain cycles. Notably, the phototransistor array, featuring a distinctive dodecagon shape of source/drain electrodes, effectively responds to NIR and visible light stimuli, even when subjected to substantial areal strains of up to 38%.

Machine learning-based bioimpedance assessment of knee osteoarthritis severity

This study proposes a multiclass model to classify the severity of knee osteoarthritis (KOA) using bioimpedance measurements. The experimental setup considered three types of measurements using eight electrodes: global impedance with adjacent pattern, global impedance with opposite pattern, and direct impedance measurement, which were taken using an electronic device proposed by authors and based on the Analog Devices AD5933 impedance converter. The study comprised 37 participants, 25 with healthy knees and 13 with three different degrees of KOA. All participants performed 20 repetitions of each of the following five tasks: (i) sitting with the knee bent, (ii) sitting with the knee extended, (iii) sitting and performing successive extensions and flexions of the knee, (iv) standing, and (v) walking. Data from the 15 experimental setups (3 types of measurements×5 exercises) were used to train a multiclass random forest. The training and validation cycle was repeated 100 times using random undersampling. At each of the 100 cycles, 80% of the data were used for training and the rest for testing. The results showed that the proposed approach achieved average sensitivities and specificities of 100% for the four KOA severity grades in the extension, cyclic, and gait tasks. This suggests that the proposed method can serve as a screening tool to determine which individuals should undergo x-rays or magnetic resonance imaging for further evaluation of KOA.

The Impact of a 6-Week Nordic Walking Training Cycle and a 14-Hour Intermittent Fasting on Disease Activity Markers and Serum Levels of Wnt Pathway-Associated Proteins in Patients with Multiple Myeloma.

Background: Multiple myeloma (MM) accounts for about 10-15% of all diagnosed hematologic malignancies and about 1-2% of all cancer cases. Approximately 80-90% of MM patients develop bone disease and the changes rarely regress. It is only possible to stop or slow their progression. A major role in bone destruction in MM is attributed to the Wnt signaling pathway, and its action can be modified by various types of interventions including training and diet. Therefore, the aim of this project was to evaluate the effects of a Nordic Walking (NW) training cycle and intermittent fasting (IF) on the levels of selected bone turnover markers associated with the Wnt pathway in patients with MM. Materials and methods: Results from 35 patients divided into training (NW and IF NW) and non-training (IF and control) groups were included in the analysis. A 6-week training cycle involving 60 min workouts 3 times a week was conducted. Body mass and composition as well as the levels of vitamin D, calcium and phosphorus, beta2-microglobulin, and albumin were examined before and after the completion of the training cycle. Markers of bone turnover were also determined: sclerostin (SOST), Dickkopf-related protein 1 (DKK-1), osteoprotegrin (OPG), osteopontin (OPN), and Tartrate-resistant acid phosphatase 5b (TRACP 5b). Results: There was no negative effect of IF or combined training and fasting on the nutritional status of the patients (the level of albumins was unchanged). Both training groups showed an increase in serum concentrations of the active metabolite of vitamin D (IF NW and NW: p = 0.001 and p = 0.022, respectively). The change in the concentration of this vitamin negatively correlated with the concentration of TRACP 5b (r = -0.413, p = 0.014). Evaluating the concentrations of markers related to bone turnover, a reduction in the concentrations of SOST (time: p = 0.026, time vs. group: p = 0.033) and TRACP 5b (time: p < 0.001, time vs. group p < 0.001) was indicated. Conclusions: The obtained results allow one to indicate the training with the poles as a safe and beneficial form of physical activity that should be recommended to patients suffering from MM. However, the results obtained in the present study are not sufficient to show the beneficial effect of IF applied without trainings.

Future teachers’ reflections on mathematical errors made in their teaching practice

This study answers the following research questions: 1) What types of mathematical errors do future teachers identify when they reflect on their practice? and 2) Which levels of development of the didactic suitability assessment competence for the “errors” component can be inferred when they reflect on their practice? To answer these questions, we explain the Didactic Suitability Criteria construct and describe the associated training cycle structure in the theoretical and methodological framework sections. We followed a qualitative research methodology that mainly consists of thematic analysis. The study conducted allows finding inductive categories of types of mathematical errors, such as error in the task instructions, error of proposition, procedural error, error in the representation, error in the definition and error in the argument. It also enables establishing levels of development of the didactic suitability assessment competence of future teachers for the “errors” component. The main conclusion of this research is the importance of the context to decide what a mathematical error is. The need to further examine the notion of mathematical error in the training of future mathematics teachers is also stressed. Another conclusion is the development of a rubric that allows for more accurate and deeper reflections of future teachers on the errors made.

Hybrid Centralized Training and Decentralized Execution Reinforcement Learning in Multi-Agent Path-Finding Simulations

In this paper, we propose a hybrid centralized training and decentralized execution neural network architecture with deep reinforcement learning (DRL) to complete the multi-agent path-finding simulation. In the training of physical robots, collisions and other unintended accidents are very likely to occur in multi-agent cases, so it is required to train the networks within a deep deterministic policy gradient for the virtual environment of the simulator. The simple particle multi-agent simulator designed by OpenAI (Sacramento, CA, USA) for training platforms can easily obtain the state information of the environment. The overall system of the training cycle is designed with a self-designed reward function and is completed through a progressive learning approach from a simple to a complex environment. Finally, we carried out and presented the experiments of multi-agent path-finding simulations. The proposed methodology is better than the multi-agent model-based policy optimization (MAMBPO) and model-free multi-agent soft actor–critic models.