The kinematics and kinetics of jumping for distance with particular reference to the long and triple jumps
The common aim of the long and triple jumps is to attain maximum horizontal distance from the front of the take-off board. This is achieved by converting some of the horizontal velocity developed in the approach run into vertical velocity at take-off. The aim of this thesis was to examine a theoretical model and to identify kinematic and kinetic factors that facilitate the generation of vertical velocity in the long and triple jump take-offs. A pivot mechanism was defined to act between touch-down and the instant the centre of mass was directly above the toe of the support foot. This mechanism was found to be the largest contributor to the gain in vertical velocity in all take-offs, accounting for 83.0% in the long jump and 63.7%, 69.8% and 70.7% in the hop, step and jump take-offs. The contribution of the pivot to the gain in vertical velocity at take-off in the long jump was significantly greater than in each of the triple jump take-offs, (all P<0.002). A relative momentum approach was used to determine the contribution of the free limbs to the generation of vertical velocity. In the long jump, the free limbs made a 10.8% contribution to the gain in vertical velocity, compared to 12.2%, 19.0% and 19.0% in the triple jump take-offs. Multiple regressiona nalysesw ere used to identify factors relating to the generationo f vertical velocity in the long jump (n=14). The greatestg ains in vertical velocity were associatedw ith techniquest hat emphasiseda low centre of mass and extended knee joint at touch-down and the ability to resist knee flexion in the compression phase, R2=72.7%. The greatest losses in horizontal velocity were associated with excessiveh ip adduction, less hip extensiona nd greater increasesin height from touchdown to take-ofll R2=84.5%. Ground reaction forces and net joint moments were measured during short approach running jump tests. Peak vertical impact forces were greater in simulated 'drop' take-offs, 5080 N, compared to those experienced in 'flat' approach take-offs, 3250 N, (P=O. 002). Peak horizontal braking forces were 1800 N in both types of take-off. However, the peak net joint moments about the ankle, (403 N. m and 387 N. m), knee (233 N. m and 296 N. m) and hip (292 N. m and 249 N. m) were similar between the 'flat' and 'drop' take-offs. This suggests that athletes adapt their technique in the 'drop' take-off to distribute the larger forces effectively and to keep the net joint moments within controllable limits. Results indicated that strength about the ankle joint was particularly important in both types of take-off, but depending on the athlete's technique strength about the knee and hip are also vital. Greater flexion of the knee joint at touch-down and maximum knee flexion were found to be associated with greater average knee moments, R2=30.8% and 75.5% respectively, and greater angles of leg placement were moderately associated with greater average hip moments, R2=23.5%. In conclusion, this thesis has provided a greater insight into the kinetics and kinematics of jumping for distance. It has quantified the contribution made by the pivot mechanism and the free limbs to the generation of vertical velocity, and has assessetdh e demandso n the musculoskeletal system in terms of ground reaction forces and net joint moments. The results indicate that elite performers cannot rely on speed alone, and that strength and technique are major factors of successful performance.