Introduction to Sports Biomechanics: Analysing Human Movement ...

QUALITATIVE ANALYSIS OF SPORTS MOVEMENTS
important points. The first of these is that the rapidity of feedback provision may
depend on its role and may be different for a technique change to improve performance
than for feedback of simple notational data. Next, feedback provision needs to address
relevant motor learning research, particularly that of the ecological school. Too few
research studies have addressed these issues in sport.
As an example of how movement analysts and coaches have got feedback wrong, let
us look at how views of the generation of front crawl propulsive force have changed over
the years – the wrong view often led to swimmers being given the wrong feedback.
In the early 1970s, the predominant view was that the hand behaved as a paddle,
pushing the water back – this led to coaches instructing swimmers to pull the hand back
below the body in a straight line. By the mid-1970s to the 1980s, swimmers’ hands had
been shown, through cinematography, to make an S-shaped pattern through the water,
in an outward–inward–outward sculling pattern. The hand was now envisaged as a
hydrofoil, using lift and drag forces (see Chapter 5) to generate propulsion. Coaches
now emphasised to their swimmers the need to develop a ‘feel’ for the water and to use
sideways sculling movements. By the mid-1990s, these observed sideways movements
had been shown to be due to body roll; the pattern of the hand relative to the swimmer’s
frame of reference – his or her body – consisted of an outward–inward scull,
confounding the previous view, which had adopted a frame of reference fixed in the
camera or swimming pool.
If provision of feedback involving knowledge of performance is good, then
movement analysts need ‘models’ against which to realistically assess current performance.
Alas, there is no general agreement about how we establish a model
performance, technique, or movement pattern. Such models clearly need to fulfil
the following functions: comparing and improving techniques, developing technique
training, and aiding communication. As there is no such thing as a general
optimal performance model, we have already noted that any such ‘model’ must be
individual-specific.
Several further issues about feedback revolve around the questions: When is best?
What is best? How is best? Immediate feedback is not necessarily best, as demonstrated
by some of the literature on motor learning. For discrete laboratory tasks, summary
feedback (of results) after several trials has been found to be better than immediate
feedback for the retention stage of skill learning, which is the important stage – we want
our performers to perform better the next day or week, rather than straight after
feedback has been provided. However, it is still not clear if this applies to sport skills,
which are far more complex than discrete laboratory tasks. Some evidence is contradictory;
for example no difference was found for learning modifications to pedalling
technique by inexperienced cyclists when they were provided with feedback from force
pedals. However, do studies that relate to early skill learning also generalise to skilled
performers? The jury still seems to be out on this one.
We might also ask whether the picture changes if we accept the views of ecological
motor control. The constraints-led approach has supported the contention that an
external focus of attention on the movement effects is better than an internal focus on
the movement dynamics. The emphasis on task outcomes allows learners to search for
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