Abstract
BackgroundBody weight supported locomotor training was shown to improve walking function in neurological patients and is often performed on a treadmill. However, walking on a treadmill does not mimic natural walking for several reasons: absent self-initiation, less active retraction of leg required and altered afferent input. The superiority of overground training has been suggested in humans and was shown in rats demonstrating greater plasticity especially in descending pathways compared to treadmill training. We therefore developed a body weight support system allowing unrestricted overground walking with minimal interfering forces to train neurological patients. The present study investigated the influence of different amounts of body weight support on gait in healthy individuals.MethodsKinematic and electromyographic data of 19 healthy individuals were recorded during overground walking at different levels of body weight support (0, 10, 20, 30, 40, and 50%). Upper body inclination, lower body joint angles and multi-joint coordination as well as time-distance parameters were calculated. Continuous data were analyzed with regard to distinct changes within a gait cycle across all unloading conditions.ResultsTemporal gait parameters were most sensitive to changes in body unloading while spatial variables (step length, joint angles) showed modest responses when unloaded by as much as 50% body weight. The activation of the gastrocnemius muscle showed a gradual decrease with increasing unloading while the biceps femoris muscle showed increased activity levels at 50% unloading. These changes occurred during stance phase while swing phase activity remained unaltered.ConclusionsHealthy individuals were able to keep their walking kinematics strikingly constant even when unloaded by half of their body weight, suggesting that the weight support system permits a physiological gait pattern. However, maintaining a given walking speed using close-to-normal kinematics while being unloaded was achieved by adapting muscle activity patterns. Interestingly, the required propulsion to maintain speed was not achieved by means of increased gastrocnemius activity at push-off, but rather through elevated biceps femoris activity while retracting the leg during stance phase. It remains to be investigated to what extent neurological patients with gait disorders are able to adapt their gait pattern in response to body unloading.
Highlights
Body weight supported locomotor training was shown to improve walking function in neurological patients and is often performed on a treadmill
Step length was significantly increased at 30% body weight support (BWS) compared to baseline and cadence was reduced at 40% and 50% BWS
Stance phase and double support phase were significantly reduced at 20% through 50% BWS single support- and swing phase were prolonged at these respective unloading conditions
Summary
Body weight supported locomotor training was shown to improve walking function in neurological patients and is often performed on a treadmill. Dobkin and colleagues further question the favorable effects of body weight supported treadmill training over overground training [6, 10, 11] These studies investigated changes in ordinal clinical scores or walking speed and distance rather than gait patterns in terms of kinematics and muscle activity. Overground locomotor training enables walking on a natural surface including curved walking, turning or obstacle negotiation (e.g., stairs) while providing adequate sensory feedback and requires gait initiation and termination as well as active propulsion of the body in a desired direction. All these features are essential for ambulation in everyday life and are difficult to train on a treadmill. Overground training is, challenging because neurological disorders often entail muscle weakness and motor control deficits that impede natural walking and create risks of falling
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