Biomedical Engineering Reference
In-Depth Information
hand is holding the liver fast so that it does not tear and that too much
produce does not come away with the vein. Calculating the rhythm of the
line sets the spacing between the livers, and operators working along the
line do not have enough space to regulate the variability of the product.
Furthermore, task instructions prohibit lagging, i.e. falling behind and
moving down the line. Risks emerge notably in terms of MSDs, along with
phenomena such as self-acceleration, pressures, and contractions to hold
the pace, a reduction in gestural variability, and a feeling of being unable
to do 'quality work':
'We do quantity, not quality'.
'Quickly done is badly done'.
'It is not what I do that I don't like. It's the conditions
which I do it in'.
Operators are not free to choose their gestures in production time.
They cannot cope in real time with the unforeseen events of production.
Some constraints other than an imposed rhythm are liable to explain
the adoption of inefficient or detrimental forms of coordination by the
operator. Newell (1986) pointed out three types of constraints: those
related to the task, to the environment and to the organism. To draw upon
an example given by Bril (2012), multiple constraints are at work that inter-
act with one another and organize movement when bearing a load: the
nature of the ground, the weight of the load and the distance to travel, but
also the aspects related to the potential of the organism (in physiological,
cognitive, affective terms, etc.).
Dynamic models that combine cognitive and biomechanical approaches
are useful when acting on the constraints affecting the voluntary move-
ment of operators. Yet, they remain quite reductive, since they do not
account for the active part that is played by operators when searching for
and producing effective and efficient motor solutions to respond to task
requirements. Hence, these models tend to reduce gesture to movement.
Although a movement is the observable part of the gesture, it can and
should by no means be reduced to it. On the contrary, gestures are com-
plex by nature - that is, they cannot be reduced to any one of their many
dimensions: biomechanical, psychological, social, contextual or cultural.
From this point of view, the biomechanical analysis of gestures is reduc-
tive, since gestures, as complex entities, imply a holistic rather than an
analytical approach. Furthermore, gestures cannot be set apart from a
cultural history, nor from the history of the working environment and
of the transformation of work situations. Thus, the concept of gesture is
close to the concept of bodily technique, as defined by Vigarello (1988),
following from the works of Marcel Mauss: 'the transmissible physical
