Cycling kinematics in healthy adults for musculoskeletal rehabilitation guidance

Background Stationary cycling is commonly used for postoperative rehabilitation of physical disabilities; however, few studies have focused on the three-dimensional (3D) kinematics of rehabilitation. This study aimed to elucidate the three-dimensional lower limb kinematics of people with healthy musculoskeletal function and the effect of sex and age on kinematics using a controlled bicycle configuration. Methods Thirty-one healthy adults participated in the study. The position of the stationary cycle was standardized using the LeMond method by setting the saddle height to 85.5% of the participant's inseam. The participants maintained a pedaling rate of 10-12 km/h, and the average value of three successive cycles of the right leg was used for analysis. The pelvis, hip, knee, and ankle joint motions during cycling were evaluated in the sagittal, coronal, and transverse planes. Kinematic data were normalized to 0-100% of the cycling cycle. The Kolmogorov-Smirnov test, Mann-Whitney U test, Kruskal-Wallis test, and k-fold cross-validation were used to analyze the data. Results In the sagittal plane, the cycling ranges of motion (ROMs) were 1.6 degrees (pelvis), 43.9 degrees (hip), 75.2 degrees (knee), and 26.9 degrees (ankle). The coronal plane movement was observed in all joints, and the specific ROMs were 6.6 degrees (knee) and 5.8 degrees (ankle). There was significant internal and external rotation of the hip (ROM: 11.6 degrees), knee (ROM: 6.6 degrees), and ankle (ROM: 10.3 degrees) during cycling. There was no difference in kinematic data of the pelvis, hip, knee, and ankle between the sexes (p = 0.12 to 0.95) and between different age groups (p = 0.11 to 0.96) in all anatomical planes. Conclusions The kinematic results support the view that cycling is highly beneficial for comprehensive musculoskeletal rehabilitation. These results might help clinicians set a target of recovery ROM based on healthy and non-elite individuals and issue suitable guidelines to patients.Y

Effects of shear-thickening polymer on force attenuation capacities in hip protectors

Many elderly people use hip protectors to prevent hip fractures from sideways falls. These hip protectors absorb or shunt away the energy applied to the greater trochanter. Herein, shear-thickening polymer (STP)-based hip protectors composed of STP and polyurethane foam are studied. The purpose of this study was to identify the main factor that reduces the impact force directly applied to the femoral neck region and to determine the optimal thickness of STP in hip protectors. Seven hip protectors of different thicknesses were prepared, and two sets of free-fall mechanical tests with a low impact energy of 25.1 J and moderate impact energy of 44.1 J were conducted for each hip protector. When the thickness of STP exceeded 8 mm, the resultant peak force tended to plateau under both impact conditions, and the force attenuation capacity decreased even under low impact energy conditions. Thus, a hip protector with a 6 mm or 8 mm STP and 5 mm foam was recommended. The STP was the key factor affecting force attenuation capacity, not the polyurethane foam. However, the foam also played an important role in helping the STP function and improving compliance for users.N