Journal of Rehabilitation Medicine 51-4inkOmslag | Page 66

A. van Ommeren et al.
Maximal handgrip strength
Maximal handgrip strength of the most-affected hand was
measured with a Jamar hydraulic hand dynamometer (Patterson
Medical Ltd, Warrenville, IL, USA) with the handle position
set at 4 for all subjects. The positioning of each subject was
standardized, as described by the American Society of Hand
Therapists (22). The participant had to squeeze the handgrip
of the dynamometer maximally for 5 s. Handgrip strength
was expressed in kg. The subject had 3 attempts, which were
separated by at least 60 s rest. The mean of the 3 attempts was
used for analysis.
Standardized reach-and-grasp task
Before participants started with the reach-and-grasp task, they
were instructed about how to use the ironHand system properly
and they tried it for a few minutes until they felt comfortable
with its use.
Next, participants performed the standardized reach-and-
grasp task (see Fig. 2 for the experimental set up) to assess
movement execution with and without the ironHand glove.
In the starting position, each participant was seated with the
upper arm aligned with the trunk, the elbow flexed 90° and
the palm of the hand positioned on the middle of the table at
a predefined start position. The cylindrical object was placed
in front of the hand and a platform was positioned within the
maximal reaching range of motion of the participant. The task
involved: (i) grasping a cylindrical object; and (ii) moving the
cylindrical object to the predefined position on the platform;
(iii) releasing the object at the platform; and (iv) returning the
hand to the predefined start position. The task was performed
with 2 differently weighted cylindrical objects (diameter 5 cm)
of, respectively, 100 g (light condition) and either 1,000 g or
2,500 g (heavy condition), both with and without the glove. The
light condition was included to assess the effect on movement
execution without the weight of the object interfering with the
Fig. 2. Schematic measurement set up with marker placement.
execution of movement. The heavy condition was included to
simulate an ADL task, in which weight is usually involved. In
each condition, the task was repeated 3 times. Prior to the start
of the measurements, participants had to lift an object of 2,500
g once to the platform/off the table. If they succeeded, the task
was performed with the 2,500 g weight; otherwise, the task
was performed with 1,000 g. The order of cylindrical weight
was randomized.
3D motion analysis
During all trials, movements of the trunk and upper extremity
segments were captured with 6 infrared cameras of the motion
capture system VICON MX13+ (Oxford Metrics, Oxford, UK)
by recording the position of reflective markers. In total, 15 re-
flective markers were placed on the hand, arm, thorax and neck
(Fig. 2), according to the guidelines of the International Society
of Biomechanics (23). In addition, 3 markers were placed on the
cylindrical objects to record their movements during the task.
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Fig. 3. Division of tangential velocity profile of the hand marker in 5 phases. The horizontal line represents the threshold used for the detection of
the 5 phases of the reach-and-grasp task (schematic representation).
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