Acta of bioengineering and biomechanics最新文献

Purpose: The acute effects of static stretching (SS) on dynamic balance, a key fitness component that contributes to injury prevention, has been a subject of significant debate. This study aimed to investigate the acute effect of short-duration SS exercises on dynamic balance following different recovery durations in youth female volleyball players. Methods: Thirteen volunteers U-14 female players were included. Eight random assessments were carried-out on separate days. They consisted of 2D-kinematic analysis of frontal and/or sagittal balance of the center of mass (COM) displacement, velocity, and acceleration on wobble board conducted without SS, immediately after and following 2 and 10 minutes of SS. Results: Repeated-measures ANOVA showed a significant difference between conditions in the velocity (p = 0.002 to 0.049; d = 0.844 to 2.200) and the acceleration (p = 0.014 to 0.021; d = 1.532 to 1.657) of the COM in both frontal and sagittal planes sway. Post-hoc analysis revealed decreased COM velocity (p = 0.001 to 0.030; d = 2.501 to 6.750) and acceleration (p = 0.001 to 0.030; d = 2.501 to 6.750) in the frontal plane, regardless of the recovery time. The most prominent decrease in both parameters was observed immediately after SS (p = 0.001 to 0.013; d = 2.907 to 6.750). However, in the sagittal balance, we observed an immediate increase in COM acceleration following SS (p < 0.001; d = 4.223). Conclusion: Short-duration SS leads to improved dynamic balance, particularly on the frontal plane, with the most favorable effect observed immediately after stretching. Practically speaking, short-duration SS appears to be an effective exercise modality for inducing acute enhancements in dynamic balance among youth female volleyball players.

Bacterial infections pose a serious threat to human health. For many years, there has been a search for materials that would inhibit their development. It was decided to take a closer look at various elastomeric materials with the addition of chitosan. Mixtures based on silicone, silicone with a platinum catalyst, acrylonitrile-butadiene rubber, natural rubber, and ethylene-propylene-diene rubber were developed and tested for antibacterial and physico-mechanical properties. The dispersion of chitosan in the elastomer was also investigated using a scanning electron microscope. Of the tested mixtures, three were selected, characterised by the best antibacterial and physico-mechanical properties and a very good dispersion of chitosan in the matrix. The mixtures were based on silicone, silicone with a platinum catalyst and natural rubber. Tests were performed to measure the release of compounds into water for these mixtures. Furthermore, cytotoxicity with L929 cells and cytocompatibility in direct contact with MG63 cells were investigated for silicone samples. The results showed that these materials were not toxic to mammalian cells and supported their growth. The best bactericidal properties against E. coli and S. aureus strains compared to the other tested materials (>99.0-99.9% of killed bacteria) were shown by samples made of silicone and silicone with a platinum catalyst and added chitosan. At the same time, the best physico-mechanical properties were found for the samples with chitosan based on silicone with added platinum and natural rubber. Developed materials appeared to be good candidates for manufacturing medical equipment on which the adhesion and growth of bacteria should be prevented.

Purpose: This study explores how thoracic orientation affects lung pressure and injury outcomes from shock waves, building on earlier research that suggested human posture impacts injury severity. Methods: A layered finite element model of the chest was constructed based on the Chinese Visual Human Dataset (CVH), including the rib and intercostal muscle layers. The dynamic response of the chest under 12 different angle-oriented shock waves under incident pressures of 200 kPa and 500 kPa was calculated. The correspondence between lung pressure at various angles, chest wall motion velocity and lung stress, and differences in pressure/stress of lung tissue behind ribs and intercostal muscle were analyzed. Results: The dynamic response of the chest can be roughly divided into four processes. High local intrapulmonary pressure areas were primarily in the anterior lobe margin and the lung's central region. A 500 kPa incident wave at 0° could cause slight lung injury, whereas at 240°, the pressure was non-harmful. Lung tissue pressure and stress induced by chest wall movement were significantly higher behind the intercostal muscles than behind the ribs, with a difference of about 2-3 times. Conclusions: This layered model provides a cost-effective tool for large-scale shock wave impact simulations on the chest. Chest wall movement velocity strongly correlates with lung stress distribution. The significant density and sound velocity differences among ribs, intercostal muscles and lungs cause an acoustic impedance mismatch, leading to "striped bleeding" marks in post-impact lungs. This research enhances understanding of chest and lung injury mechanisms and informs the development of protective measures.

Purpose: The utilization of intra-aortic balloon pump (IABP) and Impella has been suggested as means of left ventricular unloading in veno-arterial extracorporeal membrane oxygenation (VA-ECMO) patients. This study aimed to assess the local hemodynamic alterations in VA-ECMO patients through simulation analyses. Methods: In this study, a 0D-3D multiscale model was developed, wherein resistance conditions were employed to define the flow-pressure relationship. An idealized model was employed for the aorta, and simulations were conducted to contrast the hemodynamics supported by two configurations: VA-ECMO combined with IABP, and VA-ECMO combined with Impella. Results: In relation to VA-ECMO alone, the combination treatment had the following differences: (1) overall mean mass flow rate increased significantly when combined with Impella and did not change significantly when combined with IABP. Blood flow pulsatility was the strongest in ECMO + IABP, and blood flow pulsatility was significantly suppressed in ECMO + Impella; (2) for all arterial inlets, HI was decreased with ECMO + Impella and increased with ECMO + IABP; (3) the flow field did not change much with ECMO + IABP, with better blood flow compliance, whereas the flow field was relatively more chaotic and disorganized with ECMO + Impella; (4) the difference between shear stress values in ECMO + IABP and ECMO alone was small, and ECMO + Impella (P6) had the largest shear stress values. Conclusions: Variances in hemodynamic efficacy between VA-ECMO combined with IABP and VA-ECMO combined with Impella may underlie divergent prognoses and complications. The approach to ventricular unloading during ECMO and the degree of support should be meticulously tailored to individual patient conditions, as they represent pivotal factors influencing vascular complications.

Purpose: The purpose of this study was to quantify the impact of smartphone use while sitting on the toilet on the spinal flexion angles and the time effect. Methods: Measurements of the spinal flexion angles in the sagittal plane were made by thirty participants while they sat on the toilet for 10 min, using a smartphone in either one, both, or neither hand. The individual's forehead, cervical, thoracic and lumbar spinal areas were each fitted with five different inertial motion sensors. SPSS 26.0 software was used to statistically evaluate all of the data. Results: People who used smartphones with both hands had considerably larger (P < 0.05) cervical and spinal flexion angles than those who did not. A statistically significant (P < 0.001) association was observed by regression analysis between time and spinal flexion angle (r = 0.747 for no smartphone, r = 0.793 for a smartphone used in one hand and r = 0.855 for a smartphone used in both hands). Consequently, when using the smartphone with both hands, the flexion angle of the spine entered a more stable state of angles. Conclusions: The results showed that the cervical region's flexion angles change when using a smartphone while sitting on the toilet. Even when not using a smartphone, the flexion angle of the spine when sitting on the toilet will progressively increase.

Purpose: This study aimed to quantify multi-segmental coordination using Uncontrolled Manifold (UCM) analysis to examine the effect of speed reduction on the control of stair descent. Methods: Twenty healthy participants performed stair descent at a self-comfortable pace for normal speed conditions and at a slow speed set to a metronome rhythm of 60 beats/min. UCM analysis was separately conducted for the center of mass (COM) and swing foot, with anteroposterior and vertical movements designated as task variables, and segment angles defined as elemental variables. ΔV, the normalized difference between the variance in segment angle that does not affect task performance (VUCM) and the variance that does affect task performance (VORT) was calculated separately for the COM and swing foot and compared between normal and slow speeds. Results: The VORT for the COM and the swing foot in the anteroposterior direction were significantly lower at slow speeds than at normal speeds. The VORT of task-relevant segment angles affecting COM control in the vertical direction was significantly higher at slow speed compared to normal speed. Additionally, the ΔV in segment angle variance impacting swing foot control in the anteroposterior direction was significantly greater at slow speed than at normal speed. Conclusions: The findings suggest that descending stairs at reduced speed promotes enhanced coordination of lower limb segments for controlling the swing foot in the anteroposterior direction, while concurrently increasing segmental variability that destabilizes the vertical COM.

Purpose: This study aimed to explore how the microarchitectural features of lacunae and perilacunar zones impact the biomechanics of microdamage accumulation in cortical bone, crucial for understanding bone disorders' pathogenesis and developing preventive measures. Methods: Utilizing the phase field finite element method, the study analyzed three bone unit models with varying microarchitecture: one without lacunae, one with lacunae and one including perilacunar zones, to assess their effects on cortical bone's biomechanical properties. Results: The presence of lacunae was found to increase microcrack initiation risk, acting as nucleation points and accelerating microcrack propagation. Proximity to Haversian canals exacerbated stress concentration, speeding microdamage progression. Conversely, perilacunar zones mitigated both initiation and propagation. An elevated critical energy release rate correlated with slower crack growth and reduced damage severity. Conclusions: The research sheds light on the intricate mechanisms governing microcrack behavior in compact bone, highlighting the significant role of bone's microarchitectural features in its biomechanical response to microdamage. These insights are valuable for the development of strategies to prevent and treat bone-related disorders.

Purpose: External factors can disrupt postural control, but the intricate workings of the postural control system enable an appropriate response. This study seeks to assess how external perturbations affect postural control. Methods: Twenty women participated in study, which consisted four trials involved quiet standing and experiencing induced perturbations by being struck with a boxing bag from the back, right, and left sides, respectively. The center of pressure (CoP) path length was recorded for each of the mentioned trials. Sample Entropy (SampEn), Lyapunov Exponent (LyE), and Fractal Dimension (FD) were computed for the CoP time series, separately for the anterior-posterior (AP) and mediolateral (ML) directions. The nonparametric Friedman ANOVA with Dunn-Bonferroni post-hoc analysis was employed to investigate the influence of external perturbations on both linear and nonlinear parameters on postural control. Results: The post-hoc analysis showed for LyE_AP_quiet (1.02 ± 0.18) significantly higher values than for LyE_AP_right (0.92 ± 0.22) and significantly higher for LyE_AP_left. Lyapunov Exponent was the parameter that differentiated the most between samples. Conclusions: The greatest number of significant differences between samples were demonstrated by the Lyapunov Exponent. This nonlinear parameter should be used to evaluate various perturbations during upright position in healthy subjects.

Purpose: The aim of this work was to assess the effect of a conservative therapeutic intervention on the changes in the foot load distribution in people with femoroacetabular impingement (FAI) syndrome practising long-distance running. Methods: The study involved 44 men, aged 30 to 50 years, practising long-distance running. Two rounds of tests were conducted in the Laboratory of Biokinetics of the AWF in Kraków. The first measurements were carried out in January 2020, and the second ones - after a 6-month therapeutic intervention in July 2020. The measurements of the distribution of foot pressure on the ground in static conditions and during barefoot running were performed with the use of the FOOTSCAN 7.111 podobarographic platform. Parameters showing the distribution of pressure in the individual foot areas and the trajectory of force distribution during the contact of feet with the ground were measured. Results: After the completion of the physiotherapy protocol, the FAI group differed significantly from the n-FAI group in relation to the Max F range in the areas of the first, fourth and fifth metatarsal bones, and as far as the impulse in the areas of the first, fourth, and fifth metatarsal bones and in the big toe area. Conclusions: A comparison of the results of the first and second run of tests showed more positive changes in the FAI group than in the n-FAI group. This demonstrates a favourable effect of the conservative physiotherapy protocol in people with FAI - it can be an effective alternative to the surgical treatment.

Purpose: This study aimed to investigate the differences in spatiotemporal gait parameters in patients who underwent surgery for hip fractures when using walking poles and T-canes. Methods: This cross-sectional study enrolled eight patients who underwent surgery for a unilateral hip fracture (mean age of 79.0 ± 7.9 years) and 34 healthy individuals who had no symptoms (mean age of 32.1 ± 6.2 years). The outcome measures were the walking speed, trunk acceleration, and lateral lean angles of the trunk, shoulder and pelvis during walking. The results were compared among the three types of walking aids, namely, a T-cane, double T-canes and walking poles. Results: Acceleration indices step symmetry in the vertical and anteroposterior directions in walking with walking poles were significantly larger than that in walking with a T-cane. These results were common in patients with fractures and healthy individuals. Conclusions: Walking with walking poles might be a more symmetrical gait style than walking with a T-cane in patients who underwent surgery for hip fractures.