Let us start at the left branch of the model in Figure 2.12 and work to the right. We have already identified fast run-up speed as a critical feature (CF1) for this event.
We have already noted that maximising the mean force and the acceleration path are desirable to maximise take-off speed (but see below), so we now need only to translate these terms into things we can observe. The mean forces are maximised by the jumper maximising force generation (Figure 2.13). This can be done in three ways: directly, by a fast and full extension of the take-off leg (CF2) increasing the force on the take-off Moving on to maximising the vertical acceleration path, we first note that this is expressed as the difference between the heights of the athlete’s centre of mass at take-offand touchdown.
The jumper can achieve a high centre of mass at take-off by a com-bination of critical features 2 to 4 (CF2–4). A lowish centre of mass at touchdown might suggest a pronounced flexing of the knee at touchdown. Although knee flexion will occur to some extent and this will reduce impact forces and thereby injury risk, it would be a mistake for the jumper to try to increase this flexion – it would lower the centre of mass height at touchdown but have far more important and deleterious effects on the take-off speed.
A mechanism that good long jumpers tend to use to lower the centre of mass at touchdown is a lateral pelvic tilt towards the take-off leg. This is clearly evident from a front-on view and illustrates two important points for a successful qualitative movement analysis: know your sport or event inside out and never view a sporting activity just from the side, even when it seems two-dimensional board and, indirectly, by a fast, high and coordinated swing of the free leg (CF3) and the two arms (CF4). If the indirect contributions are not clear, refer to Figures 1.21 and 1.22 (pages 24–5), in which the normal and model swings of the arms in the standing vertical jump both increased jump height