2.5.3. Tactile sensitivity
The method used for measurement of tactile sensitivity was the
monofilament test. This method has been reported to have good
reliability and validity (Jerosch-Herald, 2005). A SemmeseWeinstein
monofilament test set (Roylan, USA) was used. This consisted of 20
nylon testing filaments all with the same calibrated length of 38 mm
but of varying diameters. The force produced by a touch of the filament
is a function of the length and diameter of the filament, and is
repeatable and remains constant over the duration of the test (BellKrotoski
and Tomancik, 1987). After familiarising each participant
with the test procedure, measurements followed the recommended
protocol given by Bell-Krotoski (1990). All tests were conducted by
the same investigator in a quiet room and the participants were asked
to turn their head so that they could not see their hand during the
measurements. They were instructed to say “touch”, when they
recognized that they were being touched by a filament. Each filament
Fig. 2. Sequence of performing the simulated task using the pliers.
416 I. Dianat et al. / Applied Ergonomics 43 (2012) 413e423
in turn was applied vertically over the selected hand area and slowly
moved down until the filament was bent and applying force (as the
filament bowed over). This was maintained for 1.5 s before removing
the filament. Filaments were presented in both ascending and
descending orders of diameter to minimise influence on the participant
through anticipation of the order of presentation (Bell-Krotoski,
1990). The touch sensitivity threshold was therefore defined by the
smallest filament that could be sensed by the participant.