Throwing Shoulder Range of Motion and Hamstring Flexibility in Adolescent Baseball Players: A Pilot Study.

Overhead throwing athletes with limited hamstring flexibility should be counseled appropriately regarding their risk for shoulder injury. Baseball players should stretch and prepare their bodies to throw to reduce the compensatory mechanisms that may occur from hamstring stiffness. We aim to identify the association between the contralateral hamstring-popliteal angle and throwing shoulder total range of motion (ROM) in high school baseball players. Fifteen high school varsity baseball players (ages 14-18 years old) volunteered for this observational study. All the athletes played five times a week and played different positions. Bilateral hamstring and throwing shoulder total ROMs were measured using a goniometer by the same examiner. Three examiners determined the maximum ROM by joint end feel for each measurement to ensure quality control. Contralateral hamstring flexibility was measured using the popliteal angle test. These measurements were compared to the throwing shoulder total ROM to determine the presence of an association. The relationship between the contralateral hamstring flexibility and throwing shoulder total ROM was determined using a linear regression analysis. The correlation coefficient (r) was +0.3928, indicating a positive linear relationship. We conclude that higher contralateral hamstring-popliteal angles may cause a compensatory increase in throwing shoulder total ROM. We highlight the role hamstring stiffness may play in shoulder injury development in adolescent baseball players.

Stress Injuries of the Knee.

Stress injuries to the bone and physis of the knee are common in the active adolescent patient and can be broken down into bone stress injuries (BSIs) and chronic physeal stress injuries. BSIs result from prolonged, repetitive bone loading, whereas chronic physeal stress injuries develop from repetitive loading to the apophysis or epiphysis. Most stress injuries of the knee resolve with relative rest but will occasionally need surgical intervention in more severe cases. Early and accurate identification is paramount for optimal management and to avoid long-term consequences.

Improved Electrical Signal of Non-Poled 3D Printed Zinc Oxide-Polyvinylidene Fluoride Nanocomposites.

Polyvinylidene fluoride (PVDF) presents highly useful piezo and pyro electric properties but they are predicated upon the processing methods and the ensuing volume fraction of the ß-phase. Production of PVDF with higher ß-phase content for additive manufacturing (AM) is particularly desirable because it can enable the creation of custom parts with enhanced properties. Necessary steps from compounding to the testing of a 3D printed piezo sensitive sensor are presented in this paper. AM process variables and the influence of zinc oxide (ZnO) nanofiller on crystallinity, viscosity, and electromechanical properties of PVDF, have been explored. Fourier-transform infrared spectroscopy (FTIR) measurements confirm that a high cooling rate (HCR) of 30 °C min-1 promotes the conversion of the α-into the ß-phase, reaching a maximum of 80% conversion with 7.5-12.5% ZnO content. These processing conditions increase the elastic modulus up to 40%, while maintaining the ultimate strength, ≈46 MPa. Furthermore, HCR 10% ZnO-PVDF produces four times higher volts per Newton when compared to low cooling rate, 5 °C min-1, pristine PVDF. A piezoelectric biomedical sensor application has been presented using HCR and ZnO nanofiller. This technique also reduces the need for post-poling which can reduce manufacturing time and cost.