Introduction to Sports Biomechanics: Analysing Human Movement ...

INTRODUCTION TO SPORTS BIOMECHANICS
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6 Explain the main characteristics required of an EMG amplifier. Log on to any
EMG manufacturer’s website (access through a search engine or through one of
the web addresses on this book’s website). Obtain the technical specification of
that manufacturer’s EMG amplifier, and ascertain whether this conforms to the
recommendations of this chapter.
Hint: You may wish to consult the subsection on ‘EMG amplifiers’ (pages 261–3)
before undertaking this task.
7 You are to conduct an experiment in which surface electrodes will be used to record
muscle activity from biceps brachii, triceps brachii, rectus femoris and biceps
femoris. Using a fellow student or friend to identify the muscles, and the recommendations
of Box 6.5 for electrode placement, mark the sites at which you would
place the detecting and ground electrodes for each of those muscles.
Hint: You may wish to consult the section on ‘Experimental procedures in electromyography’
(pages 265–8), as well as Box 6.5, before undertaking this task.
8 If you have access to EMG equipment, and with appropriate supervision if
necessary, perform the preparation, electrode siting and so on from the previous
exercise. Then carry out experiments to record EMGs as follows:
(a) From biceps brachii and the long head of triceps brachii during the raising
and lowering phases of a biceps curl with a dumbbell and from an isometric
contraction with the dumbbell held at an elbow angle of 90°. Check that you
are obtaining good results and repeat the preparation if not. Comment on the
results you obtain.
(b) From the same two muscles as in (a), throwing a dart – or similar object – at
normal speed, much more slowly, and much more quickly. Comment on the
results you obtain.
(c) From the rectus femoris and biceps femoris during rising from and lowering
on to a chair. Again, check that you are obtaining good results, and repeat the
preparation if not. Explain the apparently paradoxical nature of the results (this
is known as Lombard’s paradox).
Hint: You are strongly advised to consult, and follow under supervision, the section
on ‘Experimental procedures in electromyography’ (pages 265–8), as well as Box
6.5, before and while undertaking this task. If you do not have access to EMG
equipment, you can obtain EMGs from these experiments on the book’s website.
You should also answer the multiple choice questions for Chapter 6 on the book’s
website.
GLOSSARY OF IMPORTANT TERMS (compiled by Dr Melanie Bussey)
Central tendency Measures of the location of the middle or the centre of a distribution.
Close-packed position The joint position with maximal contact between the articular
surfaces and in which the ligaments are taut. See also loose-packed position.