Differences in muscle activity and temporal step parameters between Lokomat guided walking and treadmill walking in post-stroke hemiparetic patients and healthy walkers

Abstract

Background: The Lokomat is a robotic exoskeleton that can be used to train gait function in hemiparetic stroke. To purposefully employ the Lokomat for training, it is important to understand (1) how Lokomat guided walking affects muscle activity following stroke and how these effects differ between patients and healthy walkers, (2) how abnormalities in the muscle activity of patients are modulated through Lokomat guided gait, and (3) how temporal step characteristics of patients were modulated during Lokomat guided walking.

Methods: Ten hemiparetic stroke patients (>3 months post-stroke) and ten healthy age-matched controls walked on the treadmill and in the Lokomat (guidance force 50%, no bodyweight support) at matched speeds (0.56 m/s). Electromyography was used to record the activity of Gluteus Medius, Biceps Femoris, Vastus Lateralis, Medial Gastrocnemius and Tibialis Anterior, bilaterally in patients and of the dominant leg in healthy walkers. Pressure sensors placed in the footwear were used to determine relative durations of the first double support and the single support phases.

Results: Overall, Lokomat guided walking was associated with a general lowering of muscle activity compared to treadmill walking, in patients as well as healthy walkers. The nature of these effects differed between groups for specific muscles, in that reductions in patients were larger if muscles were overly active during treadmill walking (unaffected Biceps Femoris and Gluteus Medius, affected Biceps Femoris and Vastus Lateralis), and smaller if activity was already abnormally low (affected Medial Gastrocnemius). Also, Lokomat guided walking was associated with a decrease in asymmetry in the relative duration of the single support phase.

Conclusions: In stroke patients, Lokomat guided walking results in a general reduction of muscle activity, that affects epochs of overactivity and epochs of reduced activity in a similar fashion. These findings should be taken into account when considering the clinical potential of the Lokomat training environment in stroke, and may inform further developments in the design of robotic gait trainers.

Keywords: Electromyography; Gait; Lokomat; Neurorehabilitation; Robotics; Stroke.

Fig. 1

EMG profiles and average muscle activity per gait phase for (a, b) Gluteus Medius, (c, d) Biceps Femoris and (e, f) Vastus Lateralis. a, c, e : Time normalized EMG profiles (μV) during treadmill walking (left panel) and Lokomat guided walking (right panel), for the affected limb (black lines) and the unaffected limb (grey lines) of stroke patients, and the dominant limb (black dashed line) of healthy walkers. The vertical lines indicate stance-swing transition for the affected limb (black lines) and the unaffected limb (grey lines) of stroke patients, and the dominant limb (black dashed line) of healthy walkers. b,d,f : Average level of muscle activity and standard deviations (μV) during treadmill walking (left panel) and Lokomat guided walking (right panel), for the affected limb (black bars) and the unaffected limb (grey bars) of stroke patients, and the dominant limb (black dashed bars) of healthy walkers, for four subphases of the gait cycle (DS1: first double support phase; SS: single support phase; DS2: second double support phase; SW: swing phase). Statistical results are indicated for affected limb of stroke patients vs. limb of healthy subjects (black signs) and unaffected limb of stroke patients vs limb of healthy subjects (grey signs): * significant main effect of Condition (ANOVA), ^# significant Condition by Group interaction (ANOVA), † significant effect of Group during treadmill walking (independent t-test)

Fig. 2

EMG profiles and average muscle activity per gait phase for (a, b) Gastrocnemius Medialis and (c, d) Tibialis Anterior. a, c : Time normalized EMG profiles (μV) and b, d : Average level of muscle activity and standard deviations (μV). See Fig. 1 for further details

Fig. 3

Mean duration of step phases. The mean relative duration (+ standard deviations) of a : the double support phase and b : the single support phase during treadmill walking and Lokomat guided walking, for the affected limb (black bars) and the unaffected limb (grey bars) of stroke patient, expressed as a percentage of the total gait cycle duration. Statistical results are indicated: ^# significant Condition by Limb interaction (ANOVA)