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P&P #43 Cyclic Motion in Sport May Be a Misleading Rarity.

We often refer to cyclic motion occurring in repetitive activities such as running, cycling, swimming and walking. This generally implies that the athlete produces a particular movement pattern which ocurs in repeated cycles with a characteristic phase angle. We then go on to compare cyclic actions with acyclic actions, which occur in single action sports such as tennis, weighlifting, high jumping, wrestling and golf. These sports do not require the reproduction of the same cycle of action, although the patterns of force production are quite similar in many cases.

However, if true cyclic activity is to occur, then no change in pattern of movement or any of the kinetic descriptors of the action (e.g. velocity or amplitude of the cycle) must occur over a prolonged period. This means that any fatigue or change in cadence to cope with environmental conditions (such as a slope in the road or a wave in the water) must immediately be managed if the cyclical waveform is not to be disrupted.

But is this realistic? Certainly we can expect cyclic motion to occur during cycling on a very regular flat road for a short period, but even then there probably are frequent error corrections occurring at a neuromuscular level. Is it then realistic to talk about cyclic action or should we introduce a variability factor into our computations?

Should we be more attentive to the constant changes in amplitude, velocity and phase during co-called cyclic activities, because these shifts may tell us more about performance than the regularities. After all, from information theory, we know that perfect regularity and cyclicity carry very little or no information. Do we focus too much on cyclicity and periodicity than on variability and 'chaos'? Are we looking for clues to performance and adaptation in the wrong places?

Possibly our focus on regularity and periodicity is most marked in our Western obsession with cardiac 'rhythms' - should our search concentrate more on the more 'chaotic' or stochastic processes involved? After all, some research has shown that cardiac events are associated more with stages of too much regularity rather than disturbances of regular rhythm.

Comment on the concept and role of cyclicity in sport and sports medicine.


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