Introduction to Sports Biomechanics: Analysing Human Movement ...

INTRODUCTION TO SPORTS BIOMECHANICS
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Finally, we need to ensure that, in this stage, we attend to issues that affect our ability
to assess, and improve, intra- and inter-analyst reliability. Reliability is consistency in
ratings by one analyst, so we need to be able to check this over several days. Objectivity
is consistency in ratings across several analysts, so we need enough analysts to be able to
check this; clearly, this will be affected by how well trained the analysts are. Our
assessments of objectivity and reliability can be improved by identifying critical features
and how, and in which order, they will be evaluated; developing specific rating scales;
analyst training and practice; and increasing the number of analysts or trials.
EVALUATION AND DIAGNOSIS STAGE – ANALYSING WHAT’S RIGHT AND
WRONG IN A MOVEMENT
The hard work for this stage should already have been completed during the preparation
stage – the identification of the critical features of the movement. The observation
stage should then have allowed you to collect the video footage you need to evaluate
these critical features in the performances that you have recorded. This stage also
prepares us for the intervention stage. Often, in the evaluation and diagnosis stage –
probably the most difficult of the four-stage process – you will start by describing the
movement and progress to analysing it; trying to analyse a movement before you have
thoroughly and scientifically described it can be fraught with difficulties. In this context,
it should be noted that the work we do in this stage can do more harm than good;
that is, we could reduce performance or increase injury risk, particularly if we have not
identified and prioritised the correct critical features. This overall stage could be called
the analysis stage; however there are two separate aspects to this stage (although they
often overlap):
To evaluate strengths and weaknesses of performance (what the symptoms are).
To diagnose what weaknesses to tackle and how (diagnose symptoms and prepare to
treat the condition).
Evaluation of performance
To evaluate performance we effectively need to compare the observed performances
with some model of good form. However, as there is no general optimal performance
model, we need a model that is appropriate for the performers being evaluated – the
model needs ‘individual specificity’. This clearly requires prior identification of critical
features in the preparation stage. Furthermore, a ranking of the ‘correctness’ of the
identified critical features on some scale or within some band of correctness can be very
helpful; for example, ‘joint range of motion: inadequate; within good range; excessive’;
or ‘excellent 5 . ...... OK 3 ....... poor 1’. As well as needing a ‘model’ that is
individual-specific, other difficulties arise in the evaluation of performance. The first of