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Chapter 6 - During Contact 257
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Time, s ' Load force, N
Figure 6.20 Initial parts of lifts erroneously programmed for a
heavier weight. A. Load force, grip force, vertical position as a
function of time for 5 lifts with 200g programmed for 800 g (solid
line) and for 5 adequately programmed 200g trials (dashed line).
Note the pronounced overshoots in the grip force and position
signals for the erroneously programmed trials. EMG signals refer
to the erroneously programmed 200g lifts (average data). Arrows
indicate points having fairly abrupt changes in the EMG signals.
Trials are synchronized in time at the moment the object started to
move (time=O). B. Grip force, load force rate, and grip force rate
displayed in relation to the load force for erroneously programmed
trials in A (solid line) and for adequately programmed 800g trials
(dashed line). Arrows labelled C and P indicate the load force at
which the object started to move in the current and previous trial,
respectively (from Johansson & Westling, 1990; reprinted by
permission).
by Bronks and Brown (1987), Long (1970), Long, Conrad, Hall and
Furler (1970) and Maier (1992). For analysis of the relationships
among EMG, isometric grip forces, cortical and subcortical structures,
t