Acta of bioengineering and biomechanics最新文献

Purpose: This study aimed to examine the effects of age on vertical jump height and handgrip strength measurements in women. A secondary aim was to investigate the correlations between vertical jump height and handgrip strength.

Methods: Twenty young (21.5 ± 2.8 years) and twenty older (67.0 ± 5.5 years) healthy women participated in this study. Handgrip contractions were used to assess strength measurements of peak force and rate of force development at different time intervals. Vertical jumps were performed on a jump mat. The jump mat measured vertical jump height based on flight time.

Results: The older women had lower vertical jump height (P < 0.001) and handgrip peak force (P = 0.028) and rate of force development values (P = 0.003-0.016) than the younger women. A larger difference was observed between the groups for vertical jump height (41%) than handgrip peak force and rate of force development (12-17%). Of all the strength measurements, handgrip rate of force development at 200 ms in the young (r = 0.502, P = 0.024) and older (r = 0.446, P = 0.049) women exhibited the strongest correlation with vertical jump height.

Conclusions: This investigation showed significantly lower vertical jump height and handgrip peak force and rate of force development values in older compared to younger women. Interestingly, the difference between age groups was larger for jump height than handgrip peak force and rate of force development. This suggests that vertical jump performance may be more severely affected by age than handgrip strength characteristics.

Purpose: The aim of this paper was the application of a new dynamic-passive method of treatment in correction of hallux valgus and coexisting static deformities of the foot (transverse-plane and plano-valgus foot).

Methods: The study involved 50 patients; 26 with full big toe correction after the passive correction grip (group I) and 24 with big toe correction requiring additional passive abduction (group II). The patients regularly performed exercises using the designed device according to the planned schedule. The progress of the correction was assessed by a medical examination and additional tests.

Results: The cross-sectional area [cm2 ] of the abductor hallucis muscle in three-time points among I and II groups of patients with the hallux valgus was measured based on MRI images. The STIR examination showed, among others, the abductor hallucis muscle edema after exercises with the DPc device were carried out. It evidences that exercises with the new device activate the muscle. Alignment of the big toes of both feet in groups I and II were obtained with a statistically significant result ( p < 0.05). The percentage progression of correction for HV and I/II IM was calculated.

Conclusions: Based on the new correction approach the alignment of the big toe phalanges and the remaining toes was obtained. The passive setup of the tendons with their distal inserts at the level of the big toe phalanges to the correct path of their course with the withdrawal of articular subluxations was obtained. Simultaneously, the big toe's passive correction was dynamically consolidated through a specially selected set of exercises.

Purpose: The aim of this study was to investigate the force characteristics of novice athletes and professional athletes in completing a cross spike at position four from the perspective of electromyographic characteristics.

Methods: Ten novice and ten professional athletes were selected as subjects. The electromyographic characteristics of the athletes were obtained by the Noraxon Ultium electromyography (EMG) and compared.

Results: In the first stage, i.e., the takeoff stage, the activation level of the rectus abdominis and external abdominal obliques was significantly higher in the professional group (p<0.05). During the second stage, i.e., the stage of flying to hit the ball, the professional group had a higher integrated electromyography (iEMG) value in the trapezius. Moreover, it showed significantly higher muscle contribution from the rectus abdominis (5.59 ± 1.58%), external abdominal obliques (3.67 ± 1.21%), and trapezius (10.12 ± 2.61%) compared to the novice group (p<0.05). In the third stage, i.e., the stage of landing and buffering, p<0.05 in the comparison of the iEMG values of trapezius and gluteus maximus between the two groups. Moreover, the professional group exhibited higher muscle activation levels in all muscles except for the gastrocnemius, compared to the novice group (p<0.05).

Conclusions: Professional athletes display superior muscle coordination and more effective muscle force generation in the trunk and lower limbs during the execution of the jump spike action.

Purpose: Titanium and its alloys are widely used as biomaterials for long-term implants, but they are usually surface-modified due to their weak bioactivity and wear resistance. Laser processing was used to modify the surface layer, and elemental carbon was a component of the deposited coatings. This research aims to use a combination of both methods based on preliminary electrophoretic deposition of multi-wall carbon nanotubes (MWNCTs) followed by pulse laser treatment. Carbon nanotubes were chosen due to their mechanical and chemical stability as well as their tubular shape, resulting in enhanced mechanical properties of laser-modified layers.

Methods: The pulse laser power and laser scanning speed were defined as variable process parameters. The microstructure, roughness Ra, nanohardness H, Young's modulus E, and indent depth values were measured, and the H/E, H 3/E2, and relative changes of all these values in comparison to MWCNTs-coated and non-coated surfaces, were calculated.

Results: The obtained results show that the best mechanical properties of MWCNTs-coated and laser-treated specimens are obtained at a laser power of 900 W and laser feed of 6 mm/s. The observed relations can be explained considering processes occurring on the surface such as deposition of carbon nanotubes, melting and re-crystallization of the surface layer, formation and possible partial decomposition of titanium carbides, and associated changes in local chemical composition, phase composition, and a level of residual stresses beneath the surface.

Conclusions: The developed process can substitute the time and money-consuming carbonization of titanium and its alloys.

Purpose: The authors of the current study aimed to propose a calibration method for accurate augmented reality visualisation using an optical see-through head-mounted display, and to qualitatively evaluate visualisation accuracy for the application in computer assisted surgery.

Methods: An adaptation of stereo single-point active alignment method was proposed as the calibration procedure together with verification. Three tests were performed: display of points in 3D space, on the plane and on the surface of a skull phantom on inexperience users (5 participants) and experienced users (17 participants).

Results: The highest accuracy of visualization was obtained for skull phantom visualisation for an inexperienced user (3.00 mm, std 0.75 mm), while the lowest accuracy was obtained in a 3D visualisation test for an inexperienced user (22.95 mm, std 18.04 mm). The largest error was related to the depth component and amounted to 18.49 mm, std 18.10 mm for an inexperienced user.

Conclusions: It is possible to achieve relatively high visualisation accuracy (less than 5 mm for visualisation in space) for selected users but providing it for the group of inexperienced users seems to remain a major challenge. The accuracy of point indication can be substantially and statistically significantly increased by visualising objects on surfaces. The proposed methods and obtained results can serve as a basis for further implementation of augmented reality visualisation on an optical see-through head-mounted display in applications requiring high-quality augmented reality guidance of manual tasks.

Purpose: Physical activity (PA) is a well-known, simple and effective preventive and therapeutic intervention for low back pain (LBP). In spite of the growing interest in active lifestyles and its benefits, more needs to be known about the relationship between energy expenditure, body mass and lumbar-pelvic kinematics during the forward bending movement in a group of young asymptomatic people who met PA guidelines. Young people can be identified as a future risk group of civilisation diseases and lumbar-hip kinematics can be considered as a predictor of LBP occurrence. The aim of this study was to identify the association of gender, self-reported energy expenditure, body mass index, and lumbar-hip kinematics in young people.

Methods: Sixty-four students at pre-employment stage participated in the study. They declared moderate-to-high PA and activity-induced energy expenditure (AEE) was self-reported. Kinematic data of the lumbar spine, pelvis and hip were collected during forward bending using a 3D motion capture system.

Results: Sex was found to be associated with pelvis (β = -0.38 p = 0.002) and lumbar mobility (β = 0.49, p < 0.001) during forward bending and BMI was related only to lumbar mobility (β = -0.41, p = 0.001). Recreation AEE significantly predicted hip flexion mobility (β = 0.38, p = 0.002).

Conclusions: This study showed that among a sample of physically active young people, BMI, self-reported AEE and sex can partially predict lumbar-hip kinematics during trunk flexion. Recreational PA can be regarded as improving hip mobility and thus making forward bending more effective and less prone to injury.

Purpose: The research was focused on determining basic mechanical properties, surface, and phase structure taking into consideration basic cytotoxicity analysis towards human cells.

Methods: Biological tests were performed on human C-12302 fibroblasts cells using 3D-printed Ti6Al4V alloy (Ti64), produced by laser-based powder bed fusion (LB-PBF) and Alumina Toughened Zirconia 20 (ATZ20), produced by lithography-based ceramic manufacturing (LCM). Surface modifications included electropolishing and hydroxyapatite or hydroxyapatite/zinc coating. Structure analysis was carried out using a variety of techniques such as X-Ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM), followed by mechanical properties evaluation using nanoindentation testing.

Results: Samples subjected to surface modifications showed diversity among surface and phase structure and mechanical properties. However, the cytotoxicity towards tested cells was not significantly higher than the control. Though, a trend was noted among the materials analysed, indicating that HAp/Zn coating on Ti64 and ATZ20 resulted in the best biological performance increasing cell survivability by more than 10%.

Conclusions: Hydroxyapatite coating on Ti64 and ATZ20 resulted in the best biological properties. Tested materials are suitable for in vivo toxicity testin.

Purpose: Patellofemoral pain syndrome is a common orthopedic trauma among runners. It is unclear whether patellofemoral joint stress (PFJS) is the highest (or lowest) when the knee joint flexion angle and extension moment are in combination under the condition that vastus medialis (VM) activation decreases. This study aimed to investigate the effects of changes in the PFJ contact area by decreasing the activation of the VM muscle on PFJS.

Methods: A PFJ sagittal model was used to quantify PFJ reaction force and PFJS. The PFJ model and mathematical modelling procedure were used to quantify PFJS based on previous studies. The simulation ranges were set to knee joint flexion angles of 10-45° and extension moments of 0-240 Nm. PFJS was calculated for the normal condition (NC) and decrease condition (DC) in VM activation.

Results: When the knee joint angle and knee joint moment were at the maximum, the PFJS showed the maximum value under both conditions (NC; 14.9 N/cm2, DC; 16.4 N/cm2). PFJS was found to be higher in DC than that in NC for all simulation ranges.

Conclusion: Decreased VM activation may be involved in the mechanism of patellofemoral pain syndrome. In addition, the results of this study provide evidence that clinicians can enhance VM to relieve pain in patients with patellofemoral pain syndrome.

A high in-stent restenosis rate and thrombosis have compromised clinical benefits after vascular stent placement. Exercise rehabilitation after stenting emerges as a promising and practical therapeutic strategy to improve the clinical performance of this therapy, although it remains controversial. The present study aimed to explore the impact of exercise training on hemodynamic performance after vascular stent implantation. Different 3-dimensional computational models based on the patient-specific carotids were constructed to calculate hemodynamic parameters, including flow velocity, time-averaged wall shear (TAWSS), oscillatory shear index (OSI) and relative residence time (RRT). The results demonstrated that exercise training increased TAWSS but decreased OSI and RRT in some cases after the intervention, and high-intensity exercise further suppressed the adverse blood flow. However, exercise training remarkably reduced TAWSS and elevated OSI and RRT in patients with mild stenosis at upstream of stented segment. Additionally, we discovered that the hemodynamic environment change induced by exercise training was not significant compared to the stent position in some cases. Exercise had a less beneficial impact on the disturbed blood flow after the distal common carotid artery (CCA) stenting. These findings highlighted that exercise-induced hemodynamic changes differ under different conditions. The exercise training for the intervention patients should only be performed after a comprehensive vascular function assessment.