Although EMG has been available for
over four decades, relatively recent developments
in instrumentation and sophisticated
electronics have enabled
EMG to become a powerful technique
for studying muscle function and dysfunction.
Because the basis for EMG is
motor unit activity and because techniques
have been developed to record
single fiber,1
motor unit,2
or larger areas
of muscle by surface electrode,3
users
are faced with many practical and technical
considerations in the application
and interpretation of EMG in biomechanics.
In general, EMG can be used in studies
of pure function, such as the evaluation
of results of surgical transfer of
muscle, or in more basic studies, such
as the evaluation of motor unit activity
or the relationship of EMG to muscle
tension. Interpreting EMG data is complicated
because muscle contains elastic
elements both in parallel with and in
series with the contractile component
responsible for producing the recorded
activity. These factors particularly compound
the relationship of EMG to the
tension in the total muscle and must
always be considered. Furthermore, the
multiplicity of data processing techniques
and variables, such as change in
muscle length and type of contraction,
means that information derived by
EMG has to be considered within certain
constraints. We will discuss the use
of EMG as related to muscle function