Introduction to Sports Biomechanics: Analysing Human Movement ...

INTRODUCTION TO SPORTS BIOMECHANICS
Figure 3.14 Angle–angle diagrams for three strides in treadmill running: (a) hip–knee coupling; (b) ankle–knee coupling.
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until ‘f’ both joints flex in-phase during the next part of the swing phase, after which
the knee extends while the hip continues to flex until ‘g’; both joints then extend inphase
until around touchdown. Note that this pattern involves seven changes in the coordination
of the two joints. Six of these changes are from in-phase to anti-phase or vice
versa, similar to the changes in the simplified pattern known as decoupled coordination
(Figure 3.12(e)). Only one change, at point ‘a’ in Figure 3.13(a) close to touchdown,
is from in-phase (extension) to in-phase (flexion). You should now try to repeat this
description of joint movements for the same running stride but looking at the ankle–
knee and ankle–hip joint couplings, in Figures 3.13(b) and (c) (see Study task 3).
The study of movement coordination is crucial for the movement analyst; one
method uses angle–angle diagrams, which have both advantages and disadvantages.
Their advantages include that we don’t have to flip between angle–time graphs (such