Introduction to Sports Biomechanics: Analysing Human Movement ...

INTRODUCTION TO SPORTS BIOMECHANICS
Model entry at one ‘level’ should be completely defined by those associated with it at
the next level down, for example those at the top level 1 – this would be the performance
criterion – by those at level 2. This association should either be a division – as in
the example below (Figure 2.3) for the long jump distance, or a biomechanical relationship.
The latter, of course, will require the analyst to be aware of movement principles
(Appendix 2.1). The difference between this approach and using a list of principles, as
above, is that the principle flows from the model rather than being slavishly adopted
from a list of these things. As well, this modelling approach is easily adapted to alternative
ways of identifying critical features, for example through a constraints-led
approach (pages 71–2). An advantage of hierarchical models over lists of principles is
that they help the movement analyst to spot ‘blind alleys’, as again illustrated in the
following example.
Example: Hierarchical model for qualitative analysis of the long jump
The first step is to define the performance criterion, which is very simple for this task,
being the distance jumped. We will ignore here compliance with the rules of the event –
which are task constraints in their own right, assuming the jumper analysed is able to
conform to the rules. The next step – level two of our model, as in Figure 2.3 – is to ask
if we can divide the distance jumped into other distances, which might relate to the
phases of the movement (see below and Appendix 2.2). Here, it can be subdivided into
the take-off distance, the flight distance and the landing distance (these are explained in
Figure 2.4).
We have now completed level 2 of our long jump model and need to prioritise
further development according to which of the three sub-distances is most important.
Clearly, from Figure 2.4, the flight distance is by far the most important and is the
distance the jumper’s centre of mass (see Chapter 5) travels during the airborne, or
flight, phase. This distance can be specified by a biomechanical relationship as it fits
the model of projectile motion (see Chapter 4). The determining biomechanical
parameters of take-off are the take-off speed, take-off angle and take-off height, as
in Figure 2.5, which is level 3 of our deterministic model for the flight distance.
This distance is also seen to be affected by the aerodynamics of the jumper – the air
Figure 2.3 Levels 1 and 2 of long jump deterministic model – division of distance jumped (level 1) into three components
(level 2).
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