Exposure to unaccustomed eccentric exercise causes muscle damage. Popping sarcomere theory [1] has been proposed and assumed that eccentric contractioninduced muscle damage predominantly occurs at muscle length on the descending limb of the force-length relationship. This study investigated changes in the mechanical properties following maximum effort eccentric exercise at systematically different muscle lengths for the human ankle dorsiflexors. The results of this study showed that the eccentric exercise of the ankle dorsiflexors decreased the peak torque, shifted the optimal joint angle towards longer muscle length without changes in the level of muscle activation. However, no difference in the shift of the optimal ankle joint angle was observed between the groups that performed eccentric exercise at long muscle length (ECC_L) and at short muscle length (ECC_S). In conclusion, the muscle length at which the eccentric exercise was performed did not produce differential effects on the neuromechanical properties of in-vivo human ankle dorsiflexors, and thus the popping sarcomere theory might not be the sole mechanism to account for the eccentric contractioninduced optimal muscle length change.
Fracture phenomena of plate and dome shaped specimens using a shock tube for glass‐filled ceramics were investigated. Glass‐filled ceramics have been considered a promising candidate material for the dome port cover of an air breathing engine. This part of the air breathing engine has an important role in separating solid and liquid fuel, and needs a frangible characteristic that the fracture of a part should not affect the internal components of combustion. The objective of this study is to evaluate the fracture pressures for various thicknesses and diameters of the shock impact area. Also, fracture phenomena of separated membrane using a shock tube are compared with a numerical method. The experimental apparatus consists of a driver, a driven section and a dump tank. The used material is a glass‐filled ceramic made from Corning Company. Specimens are used with 3, 4.5 and 6 mm thicknesses, respectively. It is expected that the results obtained from this study can be used in the basic data for the dome port cover design of an air breathing engine.
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