Pressure distribution under the foot at the take off in volleyball jumps and fosbury flop high jumps

Abstract

s-International Society of Biomechanics XIV Congress 1993 677 PRESSURE DISTRIBUTION UNDER THE FOOT AT THE TAKE OFF IN VOLLEYBALL JUMPS AND FOSBURY FLOP HIGH JUMPS Thomas L. Milani and Ewald M. Hennig Biomechanik Labor, Universitat GHS Essen, Germany For injury prevention and to optimize the perfomlance of athletes, the knowledge of local pressures under the foot may reveal important informations for medical doctors, therapists, and coaches.Using in-shoe pressure dishibution measurements, the present study was performed to investigate the loads beneath the foot in high jumps and during the take off phase to volleyball jumps. Founy healthy track and field athletes volunteered to participate in this study. They performed 5 repetitive trials of fosbury flop and volleyball jumps in one experimental session, using the same shoe. Ten piezoceramic sensors were taped onto the plantar surface of the foot at defined anatomical landmarks. All measurements were performed with a portable, battery operated unit at a rate of 750 Hz per channel. Data collection was triggered by remote control using a radio-controlled signal. Based on five jumping trials the mean peak pressures, impulses, relative loads and contact times under the foot were determined. The general pattern shows a high lateral loading of the foot during fosbury flop high jumps and a strong medial load for the volleyball take off. The highest peak pressure values were found for the fosbury flop under the medial and lateral heel. In the rearfoot, increased peak pressures and relative loads are apparent for the medial heel region in both conditions. This is probably due to a strong pronation at the initial contact of the foot in both movements. The extreme eversion of the foot during the fosbury flop results in an excessive pronation, thus producing high mediolateral pressure differences in the heel. Accentuated peak pressures were found under the heel and the first ray of the foot during the take off in VOlleyball jumps. This is also visible in the relative load pattern. The first ray of the foot has to bear 45.9 % of the total Ioad.This large contribution demonstrates the importance of the fust ray in lifting the body for predominantly vertical jumps. PLAYER CONTRIBUTIONS IN A RUGBY UNION SCRUM Peter D. Milbum Department of Biomedical Science University of Wollongong, Wollongong NSW 2500, Australia Despite its importance to the game and the fact the strum is the collective effort of eight players each having a distinctive role, very little information is available on the contributions of individual players. Each unit of the scmm (front-row only, front-row plus second-row, full strum minus flankers, and full strum minus lock) were measured for force generated by pushing against an instrumented strum machine. A subtractive model was used to determine the contribution of each sub-unit. The large forces exerted at engagement sometimes exceeded the reported structural limits of the cervical spine and represented a potential for serious injury. The contribution of strum units were front-row (37%), second-row (42%), flankers (9%) and number eight (12%). Vertical and lateral shear forces changed little with the addition of more players. The combined maximum forward force for each player was 17725 N which represented three times that recorded for the full strum (5760 N). This reflects the extent to which player’s efforts were attenuated by the elastic and compressive tissues in the body as well as some of the forward force being “lost” to less efficient lateral and vertically directed components of force. WEIGHT TRANSFER IN BASKETBALL SHOOTING S.A. Miller and R.M. Bartlett Sport and Exercise Science Research and Development Unit, Crewe+Alsager Faculty, Manchester Metropolitan University, Alsager ST7 2HL, UK. Three-dimensional cinematographic techniques were used to determine the pattern of weight transfer for right-handed subjects at three shooting distances (2.74 m, 4.57 m, 6.40 m). Both antero-posterior and medio-lateral support base dimensions were similar at all distances. A posterior-anterior transfer was found for all shooting distances, an increasing amount of which occurred between take-off and ball release as shooting distance increased. Weight transfer from right to left was also in evidence, with the final position being increasingly closer to the leftmost edge of the base of support. Thus, short range shots were character&d by weight transfer from right posterior to mid support base, and medium and long range shots by transfer from mid-Iear to left-anterior support base. As at&o-posterior movement is required as an aid to ball release speed, it is recommended that medio-lateral movement at release is eliminated by moving the ball to the mid-sagittal plane of the body as early as possible during the shooting process.