Spieractiviteit in de Lokomat.

The Lokomat is a recently developed exo-skeleton that is used to retrain gait skills in persons with reduced locomotor skills due to neurological trauma or disease (Colombo et al 2000). As of yet, it is not known which training protocols for the Lokomat will lead to optimal results. In order to optimize training protocols, it is essential to understand how and to what extent the exoskeleton and the main trainings parameters (gait speeds, BWS, and the amount of guidance) affect the gait pattern. One approach to study these effects is to record patterns of muscle activity by means of EMG, and assess how these patterns are altered as a function of the parameters mentioned above.



Therefore, this study has two objectives. First, to determine the effects of (1) the exoskeleton (2) gait speed (3) level of body weight support (BWS), and (4) level of guidance on the patterns of muscle activity in the lower extremities; Second, to establish differences in the muscular control of walking in the Lokomat and walking overground.



Participants (n=10, between 20 and 30 years of age)) will be assessed both during walking in the exoskeleton of the Lokomat, and during walking overground (i.e. outside the exoskeleton/Lokomat). When walking in the Lokomat, the following parameters will be varied: (1) gait speed (2) the level of BWS, and (3) the level of guidance. The collected EMG data will be assessed by (1) creating a linear model to estimate the relative contributions of body weight support, gait peed, and movement guidance to the observed levels of muscle activity, and (2) statistical comparisons (repeated measures ANOVA) between the integrated levels of muscle activity for 4 subphases of the gait cycle (first double support phase, single support phase, second double support phase, swing phase) to establish the effects of body weight support, gait peed, and movement guidance on the levels of muscle activity.

The Lokomat is a position-controlled exo-skeleton that is used 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 potentially useful approach is to assess how treadmill speed, level of body weight support, and the level of movement guidance affect the neuromuscular control of gait by means of electromyography.



Therefore, the objectives of the study are:
A. To establish the effects of (1) body weight support, (2) treadmill speed, and (3) level of movement guidance provided by the exo-skeleton on neuromuscular control of walking in the Lokomat;

B. To establish the interactions between the above mentioned factors on the neuromuscular control of walking in the Lokomat;

C. To establish whether there are differences in the patterns of muscle activity between overground walking and walking in the Lokomat.

Testing will be conducted in several phases.

1. Measurements and adjustments will be made (e.g. selection of cuffs, adjustments of the length of the exo-skeleton segments) so as to fit the exo-skeleton to the participant (40 minutes);

2. Preparations will be made to apply EMG-electrodes (in particular, localization of the muscles, preparation of the skin) and fit the EMG amplifier (20 minutes);

3. Testing, including 27 trials of 40 seconds each + time in between trails to adapt to the new condition. In between trials, participants will be allowed to rest (45 minutes);

4. Six trails of overground walking will be conducted (15 minutes).



In total, the experiment is expected to last approximately 2 hours.

During testing, participants will be required to walk in the exoskeleton for 27 trials of 40 seconds each. 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). So in total, (3x3x3=) 27 trails of 40 seconds duration will be performed. Because shifts between different conditions may require some time for the participant to adapt, 1 minute acclimation periods will be given between trials. Finally, both prior to testing in the Lokomat and afterwards, participants will produce 3 (i.e. a total of 6) trials of overground walking (10 meters), i.e. without the exoskeleton and treadmill.