Mass-spring modelling of vault springboard contact

Vaulting is a discipline in Men's and Women's Artistic Gymnastics. While the springboard contact is not judged, the success of the rest of the vault is underpinned by it. The purpose of this study was to develop an understanding of the mechanics of the springboard contact phase of gymnastic vaulting. An analysis of hopping in place, forward hopping and running jumps on a force platform showed that the force-mass centre displacement relationship during ground contact approximated that of a mass rebounding on a linear spring. Subsequently, two mass-spring models were developed using a symbolic mathematics package. Both models represented the gymnast as a rigid cylinder, with personalized linear and angular inertia characteristics, connected at its mass centre to a linear spring. A one spring model combined the springiness of the gymnast and the springboard in a single linear spring, while a two spring model treated them as separate linear springs. Handspring vaults performed by an elite male gymnast at a range of approach speeds and springboard settings were analysed to provide model inputs. Springboard properties were empirically determined and revealed that the springboard stiffness varied appreciably depending upon feet contact position. Given the touchdown kinematics and takeoff angle of the gymnast, the models estimated spring stiffness and linear and angular takeoff velocities, the spring stiffness and takeoff vertical velocity estimates showing some sensitivity to spring angle at touchdown. Simulations in which the touchdown kinematics and spring stiffnesses were systematically adjusted, identified their influence on takeoff kinematics and provided an insight into the mechanics of springboard. contact. Estimated (leg) spring stiffnesses were consistent with those reported in the literature for other activities and'simulation results showed that simple rebounds accounted for the majority of the takeoff velocities. Spring angle at touchdown was found to be most effective at modifying each of the takeoff variables, however to produce a selective effect on takeoff required a combination of adjustments to the touchdown. In proposing strategies for gymnasts, their ability to control each of the touchdown variables has to be considered

Scaling the pitch for junior cricketers

Although cricket is played around the world by all ages, very little attention has been focused on junior cricket. The research presented here evaluated the effects on junior cricket of reducing the pitch length, developed a method for scaling the pitch to suit the players and applied this method to the under-11 age group. In the first of four studies it was established that shortening the cricket pitch had positive effects for bowlers, batters and fielders at both club and county standards, consequently resulting in matches that were more engaging. The second study found that top under-10 and under-11 seam bowlers released the ball on average 3.4° further below horizontal on a 16 yard pitch compared with a 19 yard pitch. This was closer to elite adult pace bowlers release angles and should enable junior players to achieve greater success and develop more variety in their bowling. The third study calculated where a good length delivery should be pitched to under-10 and under-11 batters in order to provoke uncertainty, and also examined the influence of pitch length on batters decisions to play front or back foot shots according to the length of the delivery. A shorter pitch should strengthen the coupling between the perception of delivery length and appropriate shot selection, and the increased task demand should lead to improved anticipation; both are key features of skilled batting. In the final study a method of calculating the optimal pitch length for an age group was developed which used age-specific bowling and batting inputs. This was applied to scale the pitch for under-11s giving a pitch length of 16.22 yards (14.83 m), 19% shorter than previously recommended for the age group by the England and Wales Cricket Board. Scaled in this way across the junior age groups, pitch lengths would fit the players better as they develop, enabling more consistent ball release by bowlers and temporal demands for batters, as well as greater involvement for fielders

High bar release in triple somersault dismounts

The release from the high bar was analyzed for six performances of triple backward somersaults. All 6 gymnasts released the bar with their mass centers below the level of the bar. The mean horizontal velocity of the mass center away from the bar was 1.2 m . s-I. This horizontal velocity was partitioned into contributions from the tangential and radial motions of the mass center relative to the bar and the movement of the bar relative to its neutral position. It was found that the tangential motion was the major contributor although the radial motion produced substantial positive contributions and the bar movement gave large negative contributions in two cases