THE MECHANICS OF THE LOWER EXTREMITIES DURING VERTICAL JUMPING WHEN USING THE "STRENGTH SHOE"

Abstract

According to an advertisement "The Strength Shoe has been proven to increase athletes jumping ability from 5" to 9" and improve speed in the 40 by 2/10 second". The purpose of this study was to investigate the mechanics of the lower extremities during vertical jumping with the strength shoe. Five college-age males (age: 22.5±0.75 yrs; hgt: 185.4±3/5 cm; wgt: 81.8±8.9 kg) performed 10 trials in the Strength Shoe (SS). Reflective markers were placed on the right side of the body at the acromion process, greater trochanter, lateral condyle of the femur, lateral malleolus, and tuberosity of the fifth metatarsal. One Panasonic AG-450 camcorder was positioned perpendicular to the subject for video data collection. The subjects stood with the right foot on an AMTI forceplate interfaced to the Ariel Performance Analysis System (APAS) and surface electrodes were placed on the rectus femoris (RF) and gastrocnemius (GA). The subjects performed maximum vertical jumps under each condition. The kinematic data indicated increased range of motion at the ankle (BS: M=47.8º,SD=1.72 º; M=62.4 º, SD=1.75 º) but no differences at the trunk, hip, knee and total body centre of gravity displacement. The differences at the ankle were expected due to the design of the SS. The ground reaction forces (Fzvertical; Fy-lateral; Fx-horizontal) were greater at both takeoff and landing under the BS condition but jumps of similar magnitude were achieved. Increased amplitude and a decreased activation period was found in the GA during use of the SS. The decreased of force production and dissipation, but increase of GA activation suggests a difference between conditions. The energy usually generated and transferred to the ground with BS is stored in the muscle tendon system of the lower leg with the SS. A difference in mechanics and muscle activation was demonstrated, but additional research must be conducted to investigate the manufacturers' claims of increased vertical jump height and improvements in speed.