Search Results (269)

Objectives: The aim of this study was to compare the effects of eight-week hamstring stretching programs, implemented at different times during physical education classes (i.e., warm-up, cool-down, and both periods), on primary schoolchildren’s back-saver sit-and-reach scores. Methods: A total of 275 schoolchildren (141 females and 134 males; age 8.82 ± 1.63 years) were divided into four groups: the WUG performed stretching during warm-up, the CDG during cool-down, and the MXG during both. The NSG followed the standard classes of physical education without any stretching. During physical education classes WUG, CDG, and MXG performed a 4 min stretching program twice a week. Hamstring extensibility was assessed before and after the program using the back-saver sit-and-reach test. Results: The CDG is the one that achieved statistically significant improvements compared with the WUG, MXG, and NSG (p ≤ 0.01; d = 0.50–0.71). Moreover, the CDG statistically increased the percentage of schoolchildren achieving healthy hamstring extensibility from pre-intervention (49%) to post-intervention (66%). Conclusions: This knowledge could guide teachers to design programs that guarantee feasible and effective development of hamstring extensibility in the physical education setting. Full article

This study presents a methodology for extracting precise insights on sediment transport in the minor bed of a watercourse using MIKE 21 hydrodynamic modelling software. By integrating geotechnical, geomorphological, and hydrological datasets with a good-resolution Digital Terrain Model (DTM), sediment quantities along a 4.9 km stretch of the Șolea stream—spanning from its source to its confluence with the Vâlsan River (Argeș hydrographic basin)—were determined. A three-month simulation using MIKE 21’s “Mud Transport Module” enabled the comparison of pre- and post-simulation terrain models, yielding detailed information on sediment distribution across the riverbed. These results offer predictive capabilities regarding erosional dynamics and inform mitigation measures to address sedimentary erosion within the study area. The study also presents proposals for land reclamation necessary to prevent the degradation of the riverbed and slopes, such as gabion retaining walls and check dams in the riverbed. Full article

Background: High-intensity interval training (HIIT) is a time-efficient approach that has been recognized to enhance cardiometabolic health and aerobic capacity in adolescents. The purpose of this study was to investigate the effects of various HIIT durations on cardiometabolic health and aerobic ability in adolescent women aged 17 to 19 years. Methods: Participants were separated into two intervention groups: HIIT 1 (6 weeks) and HIIT 2 (8 weeks), along with a control group. Both HIIT regimens included two weekly sessions: warm-up (jogging, accelerated running, and dynamic stretching), major sets (2 × 6–9 bouts of 30 s training at 90–95% HR_max with active recovery), and cooldown. Pre- and post-intervention measurements included body mass, BMI, body fat percentage, lipid profile, blood pressure, fasting glucose, and VO_2max. Results: Both HIIT programs resulted in significant reductions in body weight, BMI, and body fat percentage (all p < 0.001), as well as improvements in total cholesterol, triglycerides, LDL cholesterol, and systolic and diastolic blood pressure (all p < 0.001), compared to the control group. The changes in glycemia (p = 0.078) and HDL cholesterol (p = 0.825) were not statistically significant. Both HIIT groups showed significantly higher VO_2max (p < 0.001). Conclusions: Adolescent women’s cardiometabolic health and aerobic capacity increased considerably following 6- and 8-week HIIT training. These findings emphasize HIIT as a practical and time-saving strategy for this population, highlighting its effectiveness in improving key health parameters within a relatively short period. Full article

Background: Arthroereisis is a well-accepted and relatively easy procedure to treat the flexible flatfeet in children and adolescents. A mild calf-muscle shortening is not seldom an accompanying feature. The need for a gastrocnemius recession in addition to arthroereisis is controversial. Therefore, the objective of this study is to investigate the need for a gastrocnemius recession in mild cases of gastrocnemius shortening to improve ankle dorsiflexion in addition to arthroereisis. Methods: Twenty-seven patients (ages 9–15 years) who underwent arthroereisis for painful idiopathic flatfeet were included in this non-randomised retrospective study, approved by Friedrich-Alexander University, Erlangen-Nürnberg (22-86-Br). The gait data of 18 typically developed children in same age group was used as reference. Based on the intraoperative Silfverskjöld test, two groups could be identified in the collective, one with shortened of gastrocnemius who underwent gastrocnemius recession (FFGR) and one without (FF). A control group included 18 feet of 18 typically developing children. Outcomes were evaluated by comparing pre- and postoperative clinical assessments including pain scores, gait analysis using a multi-segmental foot model, and radiological imaging. The mean follow-up was 22.1 months, and statistical analysis included a two-factor ANOVA. Results: No statistically significant differences in anthropometric, clinical, and gait parameters were observed between the groups preoperatively. Improvements in ankle dorsiflexion and pain were seen in both groups without statistical significance. There was no loss of calf-muscle strength or ankle power. Conclusions: Arthroereisis effectively corrects an idiopathic flexible flatfoot and reduces pain in children and adolescents. The gastrocnemius muscle stretches following arthroereisis and therefore, no lengthening is necessary when mildly shortened. The major limitations of this study are its retrospective nature, non-randomisation, and small size of the study collective. Full article

Conventional strengthening measures for existing structures are usually not effective for the self-weight, which accounts for around 70% of the total load in reinforced concrete structures. Therefore, their effect on the overall load-bearing capacity is low. A self-weight-effective alternative for flexural strengthening is the thermal prestressing of additional reinforcement installed on the structure. In this method, reinforcing bars are slotted into the tensile zone, embedded in filler material, and tempered from the outside. They are thermally stretched, and once cooling starts, the bond with the hardened filler prevents re-deformation. The induced prestressing force counteracts dead loads and relieves the tensile zone, making the additional bars effective for the self-weight. In this paper, the effectiveness of the strengthening method is experimentally investigated in the serviceability and the ultimate limit states. Experiments involve strengthening a reinforced concrete beam under load by a thermally prestressed additional bar. Moreover, two reference tests are made to evaluate the method. An unstrengthened beam characterizes the lower capacity limit. Another beam with the same reinforcement amount as the strengthened one, but completely installed at casting, serves as the upper benchmark. All beams are loaded until bending failure. The strengthening method is assessed by means of the load-bearing behavior, deflection, crack development, and the strains in the initial as well as the added reinforcement. The results demonstrate the effectiveness of the strengthening method. The thermally prestressed bar achieves an effective pre-strain of approximately. 0.4‰ by heating at about 70 °C. The induced prestressing force and associated compression reduce tensile cracks by approx. 45% and increase stiffness. The strengthened beam reaches the maximum load of the upper benchmark, but with about 33% less deflection. The filler, which also expands thermally, generates an additional prestressing force that is effective up to about 20% of the load capacity. Beyond this, the filler begins to crack and its effect decreases, but the pre-strain in the reinforcing bar remains until maximum load. Full article

Soft robot motion performance has long been a core focus in scientific research. This study investigates the motion capabilities of soft robots constructed using poly(N-isopropylacrylamide) (PNIPAM) hydrogels, with key innovations in material design and functional enhancement. By optimizing the hydrogel formulation and incorporating molybdenum disulfide (MoS₂) to endow it with photothermal response properties, the material achieves muscle-like controllable contraction and expansion deformation—a critical breakthrough in mimicking biological motion mechanics. Building on this material advancement, the research team developed a series of soft robotic prototypes to systematically explore the hydrogel’s motion characteristics. A flytrap-inspired soft robot demonstrates rapid opening–closing movements, replicating the swift responsiveness of natural carnivorous plants. For terrestrial locomotion, a hexapod crawling robot utilizes the photo-induced stretch-recovery mechanism of both horizontally configured and pre-bent feet to achieve stable directional propulsion. Most notably, a magnetically driven rolling robot integrates magnetic units to realize versatile multimodal movement: it achieves a stable rolling speed of 1.8 cm/s across flat surfaces and can surmount obstacles up to 1.5 times its own body size. This work not only validates the strong potential of PNIPAM hydrogel-based soft robots in executing complex motion tasks but also provides valuable new insights for the development of multimodal soft robotic systems, paving the way for future innovations in adaptive and bio-inspired robotics. Full article

Background/Objectives: Cancer represents a significant health challenge, with high mortality and morbidity rates. Its diagnosis often triggers chronic stress, adversely affecting patient outcomes. Exercise has emerged as complementary therapy, enhancing treatment adherence and mitigating the side effects of chemotherapy. This study examines the effects of mild exercise during chemotherapy on patient anxiety. Methods: This prospective paired cohort study was conducted in the General Oncology Hospital of Kifisia “Agioi Anargyroi” in Athens, Greece. Adult cancer patients undergoing chemotherapy participated, excluding those with cognitive, hearing, or motor impairments, those who experienced side effects, or those who declined consent. Anxiety was measured before and after a 20-minute exercise routine performed during chemotherapy, using the Greek-translated State–Trait Anxiety Inventory (STAI). The exercise regimen included warm-up, full-body stretching, and cool-down exercises. Pre- and post-exercise scores were analyzed using the Wilcoxon signed-rank test. Results: Forty-five patients (20 women, 25 men; mean age 69.02 ± 10.62 years) with various cancer backgrounds participated. Pre-intervention anxiety levels were in the borderline “moderate” range, dropping post-exercise to the “low” range. Mean STAI scores decreased from 37.73 ± 13.33 to 32.00 ± 14.22 (p < 0.0001), with a medium-large effect size (Cohen’s d for paired samples = −0.646). No significant correlation was found between age and anxiety scores. Discussion: This study found a significant short-term reduction in anxiety, suggesting that incorporating mild exercise during chemotherapy may help in alleviating patient stress. The medium-to-large effect size supports the potential for meaningful short-term benefits. Conclusions: Incorporating mild exercise during chemotherapy may help reduce anxiety and psychological burden. These findings underscore the need for more comprehensive research in larger, more diverse populations to better understand the benefits of incorporating mild exercise during chemotherapy. Full article

In order to obtain the optimal heat treatment process of Er-containing 7075 aluminum alloy, the effects of pre-stretching and the interval time between pre-stretching and aging on the microstructure and mechanical properties of Er-containing 7075 aluminum alloy during solution treatment followed by pre-stretching and two-stage aging processes were investigated by mechanical property tests, metallographic tests, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that the mechanical properties of Er-containing 7075 aluminum alloy can be significantly improved by increasing the extrusion ratio. Pre-stretching provides nucleation sites for the precipitation of reinforcing phases, accelerates the aging strengthening process, and shortens the peak aging time. The crack source of fracture in Er-containing 7075 aluminum alloy is attributed to the segregated second phases containing Cu and Er in the alloy. The research results have significant engineering significance for the optimization of the heat treatment process of Er-containing 7075 aluminum alloy. Full article

The structural units with different characteristic scales in gradient nanostructured (GS) 316L stainless steel act synergistically to achieve the matching of strength and plasticity, and the intrinsic plasticity of nanoscale and ultrafine grains is fully demonstrated. The macroscopic stress–strain responses of each material unit in the GS surface layer can be measured directly by tension or compression tests on microspecimens. However, the experimental results based on microspecimens do not reflect either the extraordinary strengthening effect caused by non-uniform deformation or the intrinsic plasticity of nanoscale and ultrafine grains. In this paper, a method for constructing depth-dependent constitutive relationships of GS materials was proposed, which combines strain hardening parameter (hardness) with physics-informed neural networks (PINNs). First, the microhardness distribution on the specimen cross-sections was measured after stretching to different strains, and the hardness–strain–force test data were used to construct the depth-dependent PINNs model for the true strain–hardness relationship (PINNs_εH). Hardness–strain–force test data from specimens with uniform coarse grains were used to pre-train the PINNs model for hardness and true stress (PINNs_Hσ), on the basis of which the depth-dependent PINNs_Hσ model for GS materials was constructed by transfer learning. The PINNs_εσ model, which characterizes the depth-dependent constitutive relationships of GS materials, was then constructed using hardness as an intermediate variable. Finally, the accuracy and validation of the PINNs_εσ model were verified by a three-point flexure test and finite element simulation. The modeling method proposed in this study can be used to determine the position-dependent constitutive relationships of heterogeneous materials. Full article

Muscle–joint flexibility is defined as the ability of a muscle to stretch in a controlled manner, allowing a wide range of movement at the joints. While numerous methodologies exist for improving flexibility, few studies have investigated the role of athletes’ perceptual processes and awareness related to their own body and movement control during such training. In this pilot study, we explored how two different training protocols—static and dynamic stretching (control group, CON) and multi-joint resistance training (experimental group, EXP)—influence both flexibility and psychophysical awareness, understood as a multidimensional construct involving perceived flexibility improvements, self-assessed control over exercise execution, and cognitive-emotional responses such as engagement, motivation, and satisfaction during physical effort. The study involved 24 male amateur track-and-field athletes (mean age 23 ± 2.5 years), randomized into two equal groups. Over 12 weeks, both groups trained three times per week. Flexibility was assessed using the Sit and Reach Test at three time points (pre-, mid-, and post-intervention). A 2 × 3 mixed ANOVA revealed a significant group × time interaction (F = 20.17, p < 0.001), with the EXP group showing greater improvements than the CON group. In the EXP group, Sit and Reach scores increased from pre = 28.55 cm (SD = 4.91) to mid = 29.39 cm (SD = 4.67) and post = 29.48 cm (SD = 4.91), with a significant difference between pre and post (p = 0.01; d = 0.35). The CON group showed minimal changes, with scores of pre = 28.66 cm (SD = 4.92), mid = 28.76 cm (SD = 5.03), and post = 28.84 cm (SD = 5.10), and no significant difference between pre and post (p = 0.20; d = 0.04). Psychophysical awareness was assessed using a custom questionnaire structured on a 5-point Likert scale, with items addressing perception of flexibility, motor control, and exercise-related bodily sensations. The questionnaire showed excellent internal consistency (Cronbach’s α = 0.92). Within the EXP group, psychophysical awareness increased significantly (from 3.50 to 4.17; p = 0.01; d = 0.38), while no significant change occurred in the CON group (p = 0.16). Post-hoc power analysis confirmed small to moderate effect sizes within the EXP group, although between-group differences lacked sufficient statistical power. These results suggest that resistance training may improve flexibility and concurrently enhance athletes’ psychophysical self-awareness more effectively than traditional stretching. Such findings offer practical implications for coaches seeking to optimize flexibility training by integrating alternative methods that promote both physical and perceptual adaptations. Full article

The Southern Lhasa Terrane, as the southernmost tectonic unit of the Eurasian continent, has long been a focal area in global geoscientific research due to its complex evolutionary history. The Yeba Formation exposed in this terrane comprises an Early–Middle Jurassic volcanic–sedimentary sequence that records multiphase tectonic deformation. This study applies structural analysis to identify three distinct phases of tectonic deformation in the Yeba Formation of the Southern Lhasa Terrane. The D₁ deformation is characterized by brittle–ductile shearing, as evidenced by the development of E-W-trending regional shear foliation (S₁). S₁ planes dip northward at angles of 27–87°, accompanied by steeply plunging stretching lineations (85–105°). Both south- and north-directed shear-rotated porphyroclasts are observed in the hanging wall. ⁴⁰Ar-³⁹Ar dating results suggest that the D₁ deformation occurred at ~79 Ma and may represent an extrusion-related structure formed under a back-arc compressional regime induced by the low-angle subduction of the Neo-Tethys Ocean plate. The D₂ deformation is marked by the folding of the pre-existing shear foliation (S₁), generating an axial planar cleavage (S₂). S₂ planes dip north or south with angles of 40–70° and fold hinges plunge westward or NWW. Based on regional tectonic evolution, it is inferred that the deformation may have resulted from sustained north–south compressional stress during the Late Cretaceous (79–70 Ma), which caused the overall upward extrusion of the southern Gangdese back-arc basin, leading to upper crustal shortening and thickening and subsequently initiating folding. The D₃ deformation is dominated by E-W-striking ductile shear zones. The regional shear foliation (S₃) exhibits a preferred orientation of 347°∠75°. Outcrop-scale ductile deformation indicators reveal a top-to-the-NW shear sense. Combined with regional tectonic evolution, the third-phase (D3) deformation is interpreted as a combined product of the transition from compression to lateral extension within the Lhasa terrane, associated with the activation of the Gangdese Central Thrust (GCT) and the uplift of the Gangdese batholith since ~25 Ma. Full article

This study investigates the mechanical properties of ABS parts fabricated via used deposition modeling (FDM) through integrated experimental and numerical approaches. ABS resin was used as the experimental material, and tensile tests were conducted using a universal testing machine. Finite element analysis (FEA) was performed via ANSYS 2021 to simulate stress deformation behavior, with key parameters including a gauge length of 10 mm (pre-stretching) and printing temperature gradients. The results show that the specimen exhibited a maximum tensile force of 7.3 kN, upper yield force of 3.7 kN, and lower yield force of 3.2 kN, demonstrating high strength and toughness. The non-proportional elongation reached 0.06 (6%), and the quantified enhancement multiple of AM relative to traditional manufacturing was 1.1, falling within the reasonable range for glass fiber-reinforced or specially formulated ABS. FEA results validated the experimental data, showing that the material underwent 15 mm of plastic deformation before fracture, consistent with ABS’s ductile characteristics. Full article

In this work, a finite element modelling methodology is presented for the prediction of the bending behaviour of a glass fibre-reinforced elastomer composite with embedded shape memory alloy (SMA) wire actuators. Three configurations of a multi-layered composite with differences in structural stiffness and thickness are experimentally and numerically analysed. The bending experiments are realised by Joule heating of the SMA, resulting in deflection angles of up to 58 deg. It is shown that a local degradation in the structural stiffness in the form of a hinge significantly increases the amount of deflection. Modelling is fully elaborated in the finite element software ANSYS, based on material characterisation experiments of the composite and SMA materials. The thermomechanical material behaviour of the SMA is modelled via the Souza–Auricchio model, based on differential scanning calorimetry (DSC) and isothermal tensile experiments. The methodology allows for the consideration of an initial pre-stretch for straight-line positioned SMA wires and an evaluation of their phase transformation state during activation. The results show a good agreement of the bending angle for all configurations at the activation temperature of 120 °C reached in the experiments. The presented methodology enables an efficient design and evaluation process for soft robot structures with embedded SMA actuator wires. Full article

Efficient and accurate recognition of highway pavement cracks is crucial for the timely maintenance and long-term use of expressways. Among the existing crack acquisition methods, human-based approaches are inefficient, whereas carrier-based automated methods are expensive. Additionally, both methods present challenges related to traffic obstruction and safety risks. To address these challenges, we propose a fixed pan-tilt-zoom (PTZ) vision-based highway pavement crack recognition workflow. Pavement cracks often exhibit complex textures with blurred boundaries, low contrast, and discontinuous pixels, leading to missed and false detection. To mitigate these issues, we introduce an algorithm named contrast-enhanced feature reconstruction (CEFR), which consists of three parts: comparison-based pixel transformation, nonlinear stretching, and generating a saliency map. CEFR is an image pre-processing algorithm that enhances crack edges and establishes uniform inner-crack characteristics, thereby increasing the contrast between cracks and the background. Extensive experiments demonstrate that CEFR improves recognition performance, yielding increases of 3.1% in F1-score, 2.6% in mAP@0.5, and 4.6% in mAP@0.5:0.95, compared with the dataset without CEFR. The effectiveness and generalisability of CEFR are validated across multiple models, datasets, and tasks, confirming its applicability for highway maintenance engineering. Full article

Accurate image registration is essential for synthetic aperture radar (SAR) applications such as change detection, image fusion, and deformation monitoring. However, SAR image registration faces challenges including speckle noise, low-texture regions, and the geometric transformation caused by topographic relief due to side-looking radar imaging. To address these issues, this paper proposes a novel two-stage registration method, consisting of pre-registration and fine registration. In the pre-registration stage, the scale-invariant feature transform for the synthetic aperture radar (SAR-SIFT) algorithm is integrated into an iterative optimization framework to eliminate large-scale geometric discrepancies, ensuring a coarse but reliable initial alignment. In the fine registration stage, a novel similarity measure is introduced by combining frequency-domain phase congruency and spatial-domain gradient features, which enhances the robustness and accuracy of template matching, especially in edge-rich regions. For the topographic relief in the SAR images, an adaptive local stretching transformation strategy is proposed to correct the undulating areas. Experiments on five pairs of SAR images containing flat and undulating regions show that the proposed method achieves initial alignment errors below 10 pixels and final registration errors below 1 pixel. Compared with other methods, our approach obtains more correct matching pairs (up to 100+ per image pair), higher registration precision, and improved robustness under complex terrains. These results validate the accuracy and effectiveness of the proposed registration framework. Full article