The effects of body weight support, guidance, and gait speed on the patterning of muscle activity in the Lokomat

The Lokomat is a position controlled exo-skeleton that is utilize for the
training of gait skills in (neurological) patients. During training in the
Lokomat, a number of relevant parameters can be precisely adjusted by the
trainer: (1) treadmill speed (2) the amount of body weight support, and (3) the
level of movement guidance delivered by the Lokomat. For the development of
effective training programs it is important to understand how settings of these
parameters affect the control of gait in the Lokomat. A logical approach is to
assess how treadmill speed, level of body weight support, and the level of
movement guidance affect the neuromusculair patterns of gait, and how these
differ from normal, overground walking.

a. To establish the effects of (1) body weight support (2) treadmill speed, and
(3) level of movement guidance provided by the exoskeleton on the neuromuscular
control of the lower extremities.
b. To establish the interactions between the above mentioned factors on the
neuromuscular control of the lower extremities.
c. To establish whether there are differences in the patterns of muscle
activity between those obtained during walking in the Lokomat and those
obtained during walking overground.

Participants will be required to walk in the exoskeleton for trials of 40
seconds, while the activity of the following muscles will be measured by means
of electromyography (EMG): (1) Gastrocnemius medialis (2) peroneaus longus (3)
soleus (4) tibilais anterior (5) rectus femoris (6) vastus medialis (7)
Semitendinosus (8) biceps femoris. During each individual trial, a unique
combination of gait speed, body weight support, and guidance will be presented
to the participant. All independent variables will be varied at 3 levels (gait
speed: 1,3, and 5 km/h; body weight support: 0, 15, an 30% of the participants*
body weight; guidance: no guidance, moderate guidance, strong guidance). In
total, (3x3x3=) 27 trails of 40 seconds duration will be performed. In
addition, participants will walk an overground trajectory (10 meters), i.e.
without the exoskeleton, a total of six times.

Sixteen self-adhesive electrodes will be attached to the skin of each
participant.

Walking in the exoskeleton may be somewhat fatiguing to some people, when
extremely low treadmill speeds (< 2km/h) and high levels of body weight support
(> 30% of body weight) are used. Because participants wear a harness, and the
treadmill Is equipped with hand rests, participants will not be able to fall.
In case of unexpected calamities, the experimenter as well as the participant
can press a *emergency-stop*, which will halt the treadmill and the
exo-skeleton immediately. If walking in the Lokomat becomes uncomfortable for
some reason (e.g. skin irritation, pain in muscles/tendons), the participant
can indicate this and the experiment will be paused or aborted.

The required gait activity of participants is similar to everyday walking. The
participant is not likely to experience any burden from the elektrodes of the
EMG system.

In the light of the relatively low burden and the small risks associated with
this study, it seems justified to conduct this study because it may yield
important information that can be used to develop training protocols for
neurological patients.