Studies show the high potential of shoes to impact human movement and reduce the risk of injuries during normal and high-demanding activities. This review will delve into the existing literature on mechanical and biomechanical tests of shoes and their effects on the human body. Mechanical tests mainly include compression, bending, torsional flexibility, and impact tests. Biomechanical tests, on the other hand, study the kinematics and kinetics of the human body while performing different tasks. The primary goal of this review is to highlight the importance of isolating parameters in shoe design and testing to achieve optimal results in providing comfort, support, and injury prevention. Key conclusions include the influence of lattice structures on shoe stiffness and stress distribution, the effectiveness of composite loofah sponge for vibration damping, the benefits of Poron insoles for impact attenuation, the potential injury risk reduction with auxetic shoes, and the need for future research on mechanical tests, parameter investigation, and optimization of shoe sole structures.

The present study examined the effects of auxetic shoes on the biomechanics of the spine, as compared to barefoot and conventional shoe conditions, during gait and drop vertical jump (DVJ) activities using a combined in vivo and musculoskeletal modeling approach. Motion and force-plate data as well as electromyographic (EMG) activities of select trunk muscles of 11 individuals were collected during foregoing activities. In DVJ activity, two main phases of first landing (FL) and second landing (SL) were studied. In the FL phase of DVJ noticeable alternations were observed when auxetic shoes were used. That is, compared to the conventional footwear condition, smaller EMG activities in extensor muscles (by ~ 16–29%, p < 0.001), smaller anterior–posterior (AP) distance between the center of pressure of ground reaction force and heel (by ~ 19%, p = 0.002), generally larger maximal hip, knee, and ankle flexion angles (p < 0.005) and finally smaller maximal L5-S1 compression force and maximal external moment (by ~ 12 and 8%, respectively, p < 0.001) were obtained by wearing auxetic shoes. Our results, therefore, indicate that using auxetic shoes can reduce load on the lumbar spine during high-demanding activities such as vertical jump and thus may decrease the musculoskeletal risk of injuries during these activities.

The present study examines the mechanical properties of auxetic stents with the tetra-star-chiral structure. The tetra-star-chiral geometry is parametrically modeled. Then, the design of experiments (DOE) is developed by defining the elastic properties of the stents and using the response surface method (RSM). Finite element (FE) analysis is performed in order to find a polynomial relationship between the geometric parameters as inputs and the elastic parameters as the outputs. Then, the optimal stent is found in terms of elasticity parameters by using RSM and NSGA-II methods and the two-dimensional Pareto front is plotted. The optimal parameters of the stent including flexural stiffness, axial elasticity modulus, radial elasticity modulus and Poisson’s ratio are obtained as 10.66 mPa m⁴, 5.37 MPa, 33.2 MPa and − 0.41, respectively. Moreover, a method is proposed to find an analytical solution for metal elastic stents in order to verify the FE model results, and also the blood vessel compliance of the optimal stent is examined.

Bone and Site Hold Tendon Inside (BASHTI) technique is an organic implant-less technique for anterior cruciate ligament (ACL) reconstruction with some clinical advantages, such as speeding up the healing process, over implantable techniques. The study aims to compare the mechanical properties of BASHTI technique with the conventional interference screw technique. To investigate the mechanical properties, 20 in-vitro experimental tests were conducted. Synthetic dummy bone, along with fresh digital bovine tendons, as a graft, were used for experiments. Three loading steps were applied to all specimens, including a preconditioning, a main cyclic, and a pull-out loading. The mechanical characters of an interference screw technique using an 8 mm tendon diameter, including fixation strength, average cyclic stiffness (ACS), and average pull-out stiffness (APS) were found to be 439 ± 132 N, 10.3 ± 5.3 kN/mm, and 109 ± 40 N/mm, respectively. In the case of an interference screw using a 9 mm tendon, the fixation strength, ACS, and APS were obtained 549 ± 87 N, 10.3 ± 4.7 kN/mm, and 91 ± 13 N/mm, respectively. In parallel, the fixation strength, APS, and ACS of BASHTI technique using an 8 mm tendon were 360 ± 123 N, 3.3 ± 0.6 kN/mm, and 79 ± 27 N/mm, respectively, while, for 9 mm tendon 278 ± 103 N, 2.4 ± 1.2 kN/mm, and 111 ± 40 N/mm, were reported for fixation strength, APS, and ACS respectively when BASHTI technique was used. About 50% of interference screw samples showed superior mechanical properties compared to BASHTI technique, but in another half of the samples, the differences were not significant (N.S.). However, due to organic advantages of BASHTI technique and lower cost, it could be used as a substitute for interference screw technique, especially where fast recovery is expected.

The goal of this study is to investigate the effects of tendon and cannulated drill bit diameter on the strength of the bone and site hold tendon inside (BASHTI) fixation technique for an anterior cruciate ligament (ACL) reconstruction. Bovine digital tendons and Sawbones blocks were used to mimic the ACL reconstruction. Mechanical strength of the specimens was measured using a cyclic loading continued by a single cycle pullout load until failure to simulate the real postsurgical loading conditions. Finally, failure modes of specimens and ultimate failure load were recorded. The maximum possible tendon surface strain (i.e., tendon compression [TC]) for tendon diameters of 6, 7, 8, and 9 mm were 0.73, 0.8, 0.7, and 0.65, respectively. Eighty per cent of the specimens with tendon diameter of 6 mm and 20% of specimens with tendon diameter of 7 mm failed on the torn tendon. All samples with larger tendon diameters (i.e., 8 and 9 mm) failed on the fixation slippage. The maximum fixation strength according to the most suitable core bones for 6, 7, 8, and 9 mm tendons were 148 ± 47 N (core 9.5 mm), 258 ± 66 N (core 9.5 mm), 386 ± 128 N (core 8.5 mm), and 348 ± 146 N (core 8.5 mm), respectively. The mode of tendon failure was significantly influenced by the tendon diameter. Also, an increase in TC raised the fixation strength for all tendon diameters; however, tendon over compression decreased the fixation strength for the 8 mm tendon group. Finally, an empirical equation was proposed to predict BASHTI fixation strength. This research was performed at Biomechanics Laboratory, Sharif University of Technology. All procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted. These tests were approved by Sharif Ethics Committee with 45784 permit number. Each author certifies that his or her institution approved the animal protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research. Informed consent was obtained from all individual participants included in the study. All authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Hadi Moeinnia, Amirhossein Borjali, Mahdi Mohseni, Narges Ghias, and Hossei Korani. The first draft of the manuscript was written by Hadi Moeinnia and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Received: 23 January 2020 Accepted: 21 July 2020 Publication Date: 08 September 2020 (online) Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.