Acta of bioengineering and biomechanics最新文献

Purpose: The objective of the study was to describe and compare the acute response of muscle oxygen saturation (SmO2) and hemoglobin concentration (Hgb) in the vastus lateralis (VL) during resistance exercise protocols until failure.

Methods: Sixteen males were considered (mean ± SD, age = 36.12 ± 6.40 years). Two familiarization sessions and one evaluation session were carried out where three force protocols were executed in the VL, one of them was isometric load (P1) and two of dynamic load (P2 and P3). SmO2 [%] and Hgb [g/dL] were measured before and after each of these protocols. For P1, three series of 8 s of maximum isometric strength with the rest of 60 s between each set, the average isometric strength (AIS), and the isometric peak strength (IPS) were also recorded. After five minutes, P2 was performed, with an initial load of 40% of AIS. Then, at 30 minutes, P3 was performed considering an initial load of 40% of IPS.

Results: The results suggest (I) minimum levels of SmO2 (66.31 ± 9.38%) and Hgb (12.22 ± 0.55 g/dL) during P2, (II) no significant differences were observed between the average loads of the respective protocols for SmO2 and (III) muscle Hgb differed significantly between rest with P1 and P3.

Conclusions: Exercises of increasing intensity and of short duration do not significantly modify SmO2. However, Hgb increases substantially compared baseline values.

Purpose: The aim of this study was to determine the affinity to crystal, calculi and biofilm deposition on ureteral double-J stents (DJ stents) after ureterorenoscopic-lithotripsy procedure (URS-L). The analysis was performed in two aspects: to determine which material used for fabricating ureteral stents promotes encrustation and which part of the DJ stents is the most vulnerable for blockage.

Methods: One hundred and twenty patients with an indwelling DJ stent duration between 7 and 78 days were included in this study. The encrustation of DJ stents was characterized by scanning electron microscopy (SEM), and the mechanical properties of DJ stents were examined using the standard MTS Micro Bionix tensile test.

Results: This study showed that polyurethane catheters have a much higher affinity for encrustation than styrene/ethylene/butylene block copolymer. Obtained results indicated the proximal (renal pelvis) and distal (urinary bladder) part is the most susceptible to post-URS-L fragments and urea salt deposition. Both the DJ ureteral stents' outer and inner surfaces were completely covered even after 7 days of implantation.

Conclusions: Performed analysis pointed out that polyurethane DJ stents have a much higher affinity for encrustation of calculi and NaCl crystals compared to the silicone-based copolymer. The surface of the ureteral stents needs improvement to minimize salt and kidney stone deposition, causing pre-biofilm formation and the occurrence of defects and cracks.

Purpose: The aim of the study was to analyse the contrary body movement in Viennese waltz performed by dancesport athletes and to determine its relationship on scores awarded by the adjudicators.

Methods: Six high-level and six intermediate dance couples took part in the study. Each couple performed three identical series of three natural turns figure in the Viennese waltz. All of them were recorded on camera while performing to music. All the trials of each couple were evaluated by 6 international adjudicators as to the technical quality component from the Absolute Judging System. A device for measuring triaxial rotational angular velocities was mounted on the dorsal part of the pelvic girdle and on the back of the chest of each athlete.

Results: An analysis of covariance revealed that the mean squares of the difference in angular rotation velocity of the pelvic girdle and thoracic spine of the tested dancers were strongly associated with scores given by the adjudicators (F1.9 = 11.5, p = 0.0240, ηp2= 0.449) independently of the assignment to the given group.

Conclusions: The analysis and comparison of top level and intermediate athletes showed that the suggested method of measurement, presentation and analysis of the profile motion of pelvic girdle and chest motion may become a good tool for a general evaluation of the movement technique as well as a quick and effective qualitative and quantitative biomechanical assessment of selected components of movement technique in dancesport.

Purpose: The aim of this study was to determine the influence of factors such as temperature and glutaraldehyde (GA) concentration on the mechanical properties of porcine pericardia, in order to propose the recommended optimal conditions of a cross-linking process. It was also to verify whether tannic acid (TA), a natural cross-linking agent that stabilizes collagenous tissues by a different mechanism than GA, may positively influence the strength of pericardium.

Methods: The samples were incubated at various temperatures (4, 22, and 37°C) and GA concentration solutions (0.6, 1.5 and 3%) for 7 days. Three series were selected and additionally cross-linked with 0.3% TA for another 7 days. Mechanical properties of cross-linked pericardium samples, i.e., ultimate tensile strength (UTS) and elastic modulus (E) were measured in uniaxial tensile testing. The hyperelastic model for incompressible materials - isotropic by Ogden [24] and anisotropic by Fung [7] were utilized to describe the mechanical behaviour of treated pericardium.

Results: The temperature has an influence on cross-linking effects; the lowest values of UTS were reported for specimens cross-linked at 22 °C, while the mechanical properties of series treated at 4°C or 37°C were comparable. At a particular temperature of incubation, the GA concentrations have not affected the mechanical properties of tissues. The dependence between mechanical parameters and agent concentration was only observed for specimens treated with GA at 37 °C.

Conclusions: The conditions of the cross-linking process affect the mechanical properties of the porcine pericardium. Room temperature (22 °C) and the concentration of 1.5% GA occurred to be ineffective. The mechanical properties of GA-treated pericardium were improved by an additional TA cross-linking.

Purpose: The aim of the current study was to examine the variation on the kinematic parameters in the basketball shot associated with the shooting distance.

Methods: Twenty-seven female adolescent basketball players aged 12.1 ± 0.9 years completed 10 BS trials from a frontal position of 4.75 m and 5.75 m from the basket. Nine anatomical markers were placed on the participants' dominant side to assess the kinematic variables. The following variables were analyzed: angle, velocity, and height at ball release; centre of mass horizontal displacement and maximum height attained; maximum hip height and hip height at release; shoulder, elbow, and knee angular position and velocity at ball release; deepest knee flexion during the preparatory phase; the peak of the angular velocity of the shoulder, elbow, and knee joints.

Results: At release, the angle decreased while velocity increased significantly at 5.75 m. During the release, greater shoulder flexion and increased joint (shoulder and knee) angular velocity were observed. The deepest knee flexion and the centre of mass horizontal dis- placement were accentuated at 5.75 m. The ball release occurred before the peak of the jump phase.

Conclusions: To compensate for the long ball trajectory to the basket, participants perform a set of adjustments in the body segmental organization to increase the ball veloc- ity at release. The coaches' feedback should focus on the shooting arm's positioning and in the jump phase (to jump as close to vertical as possible). Also, a consistent shooting technique should be acquired close to the basket before expanding the shooting range.

Purpose: The aim of this study was to determine the impact of isometric and isokinetic hip abductor muscle strength on the quality of maintaining static balance in healthy subjects.

Methods: The study enrolled 51 healthy women aged 18-25. Balance assessment was carried out according to the M-CTSIB protocol and Single Leg Stance Test (with eyes open and closed) using the Biodex Balance System. An isokinetic evaluation conducted at 30 °/s and an isometric evaluation of the hip abductors were performed with the Humac Norm system.

Results: Regression analysis for Sway Index (SW) and Stability Index (ST) in bipedal standing showed a significant importance of the presence of visual feedback (RSW EO = -0.922; p < 0.0001; RST EO = -0.613; p = 0.0493), and unstable surface (RSW US = 1.253; p < 0.0001; RSW US = 2.547; p < 0.0001). Regression analysis for single-leg stance showed correlations between the following indices: overall sway index (OR) in single-leg stance, the antero-posterior (AP) sway index and the medio-lateral (ML) sway index on the one hand and isometric abduction time to peak torque (ROR TPT = 0.769; p = 0.0005; RAP TPT = 0.565; p = 0.008; RML TPT = -1.74; p < 0.05, respectively) as well as the test conditions on the other.

Conclusions: Physiological activation of the hip abductors may be important for physiological maintenance of postural balance in young people, in both leg standing as well as in single-leg stance. The present results warrant prospective, randomized studies of larger groups that are diversified with regard to age and gender of the participants.

Purpose: The purpose of the current study is to understand pedestrian kinematics, biomechanical response and injury risk in high speed vehicle crashes.

Methods: Vehicle-to-pedestrian crashes at the impact speeds of 40 km/h (reference set) and 70 km/h (analysis set) were simulated employing FE models of a sedan front and an SUV front together with a pedestrian FE model developed using hollow structures. The predictions from crash simulations of different vehicle types and impact speeds were compared and analyzed.

Results: In crashes at 70 km/h, pedestrian head-vehicle contact velocity is by about 20-30% higher than the vehicle impact speed, the peak head angular velocity exceeds 100 rad/s and is close to the instant of head-vehicle contact, brain strain appears two peaks and the second peak (after head contact) is obviously higher than the first (before head contact), and AIS4+ head injury risk is above 50%, excessive thorax compression induces rib fractures and lung compression, both sedan and SUV cases show a high risk (>70%) of AIS3 + thorax injury, and the risk of AIS4 + thorax injury is lower than 40% in the sedan case and higher than 50% for the SUV case.

Conclusions: Pedestrians in vehicle crashes at 70 km/h have a higher AIS3 + /AIS4 + head and thorax injury risk, high vehicle impact speed is more easily to induce a high head angular velocity at the instant of head-vehicle contact, brain strain is strongly associated with the combined effect of head rotational velocity and acceleration, and pedestrian thorax injury risk is more sensitive to vehicle impact speed than the head.

Purpose: Gait changes are more prominently observed in older adults than in young adults, especially in kinematics of lower extremities and trunk. These changes can result in incidental falls during gait, possibly leading to inability to perform activities of daily living independently. This study aimed to investigate the effect of gender and age on gait changes, such as spatiotemporal parameters and peak joint angles in lower extremities and trunk during gait.

Methods: A total of 387 participants (223 women) were included. The Microsoft Kinect V2 sensor was used to obtain the coordinate data of lower extremities and trunk during gait. The coordinate data obtained were processed using the software. Walking speed, stride length, stride time and cadence were calculated as spatiotemporal variables of walking. Forward trunk tilt angle (FTT), hip flexion and extension, and knee flexion and extension were measured as peak angles during one-gait cycle. Participants were categorized into five groups according to age by five years. Multivariate analysis of variance was performed to compare the spatiotemporal and kinematical data among groups.

Results: Significant differences among age groups were noted in terms of the walking speed and stride length. Significant differences were also observed in the FTT and hip extension angle.

Conclusions: Increased gait changes, increased peak FTT and decreased peak hip extension angle were observed with an increase of age. These altered symptoms may contribute to the screening of older adults at risk of declined physical function at an early stage.

Purpose: A three-dimensional finite element model of the lower cervical spine was established to evaluate the biomechanical stability and stress distribution of the new lower cervical interzygapophyseal fusion device (IZFD) developed by ourselves under different construct. The aim of this study was to provide theoretical basis for further clinical application.

Methods: A normal fresh cadaveric specimen (male, 35 years old) was used to establish an intact three-dimensional finite element model of C3-C6. On this basis, the comparative finite element models of the lateral mass screw rod (LMSR) system and LMSR+IZFD were established. Only C4-C5 is fixed in the lateral mass. The range of motion (ROM) and stress distribution in the flexion,extension, lateral bending and rotation of the C4-C5 segment under the three constructs were analyzed.

Results: The ROM and stress distribution of the three-dimensional finite element model under load construct were within a reasonable range, which proved the validity and reliability of the model. The ROM and stress distribution of C4-C5 segment was significantly decreased in both LMSR and LMSR+IZFD constructs than those in the intact construct. The ROM and stresss distribution were even smaller in LMSR+IZFD construct than in LMSR construct.

Conclusions: The IZFD combined with LMSR system can provide satisfactory stability for the lower cervical spine, and the IZFD can further improve the fixation effect of the LMSR system.