Vertical Impact Load Research Articles

Biomechanical considerations of impact forces and foot stability in running

The interaction between "man-shoe and surface" is presented as a model to discuss the complexity of human locomotion. Only if the physiological system "man" interacts positively with the physical requirements of shoe and surface quality running will become effective and economical. Especially during the early ground contact phase the hardness of the shoe construction determines the height of the vertical impact load. These adaptations have consequences in the emg amplitudes during the stretch activation phase of the contact. Comparing various jogging shoes with altered construction properties it can be shown that the "hardness" of the shoe material is well adapted by the variation in the emg amplitude. The influence of the amount of pronation on the impact forces has been confirmed in a separate study. Increased pronation resulted in an increased emg amplitude in the extensor muscles whereas activation in the flexor muscles was decreased. By means of different shoe and insole constructions it is possible to adjust the "man-shoe-surface" interaction to an optimum to carry loads by muscles, joints and ligaments and to avoid overuse and injuries.

An experimental study on the characteristics of the impact load of falling rock

Abstract An experimental study on rock falling was carried out to clarify the characteristics of impact load. For this study, a two dimensional dynamometer was constructed and validated to detect and record vertical and horizontal impact loads. Experimental results show that the ratio of horizontal impact load against vertical impact load is larger than expected. There are cases that the ratio is greater than 40%. Moreover, it has been revealed that the direction of horizontal impact loads are both in valley and mountain sides. These results are considered to be very important in evaluating the dynamic response of concrete structures, such as rock sheds, built at the foot of steep slopes.

Prevention of Overuse Injuries of the Foot by Improved Shoe Shock Attenuation

In a randomized prospective study among 390 recruits, the hypothesis that improved shoe shock attenuation could lessen the incidence of overuse injuries was tested. During the 14 weeks of training, 90% of the recruits sustained overuse injuries. Recruits training in a modified basketball shoe had a statistically significant lower incidence of metatarsal stress fractures and foot overuse injuries, compared with standard infantry boots, but their overall incidence of overuse injuries was not reduced. The effect of improved shoe shock attenuation was limited to those overuse injuries resulting from vertical impact loads.

ジャッキアップリグの着底時の脚部衝撃力に関する研究

In the installation operation of a jack-up rig, the legs will be subjected to impact loads when colliding with the sea bottom due to the rig's motion in waves. To avoid the damages of legs and jacking mechanisms, several operational manuals restrict an operation up to 1.5m in wave height. This standard, however, is not reasonable because it is determined with no relation to an wave period and a bottom rigidity. Excessively conservative standards may lead to much down-time in operation. Then, both from structural and operational viewpoints, it is important to clarify the characteristics of impact loads on legs.In this study, experiments on a model rig subjected to both vertical impact load and horizontal frictional loads from bottom are carried out in regular waves. Theoretical analyses in time domain are also performed using newly developed analytical model where legs are treated as elastic bodies. Based on these results, the occurrence mechanisms and response characteristics of vertical impact loads and impact bending moment at platform bottom are investigated. The accuracy and the reasonableness of conventional simplified formula to estimate impact loads based on the energy concept are also discussed, and finally, an allowable wave height on a proto-type rig is investigated.