Walking ability, though important for quality of life and participation in social and economic life, can be adversely affected by neurological disorders such as spinal cord injury, stroke or traumatic brain injury. Rehabilitation of patients with such disorders should include gait training because there is evidence that the desired function or movement has to be trained in a task-specific program [
1,
2]. One contemporary approach is body-weight supported treadmill training in which the patient is suspended over a treadmill and the patient's legs are guided by therapists [
3‐
9]. Several studies have shown beneficial effects of this approach [
10‐
12]. Because other studies [
13,
14] did not find an advantage compared to conventional therapy and systematic reviews [
8,
9] regard the evidence as controversial, further studies are required. There are some indications that an increased training intensity might lead to clearer results [
15‐
18]. However, the manual form of this therapy in which the patient's legs are guided by two therapists holding and moving them along a gait-like trajectory is strenuous for the therapists and labor- and cost-intensive. Depending on the patient's condition, the therapists have to assist the stance leg by extending the knee against the weight of the patient or they have to flex the knee joint, possibly against spasticity, and lift the leg through swing phase. The high physical effort for the therapists often limits the training duration, whereas the patient might benefit from a longer duration. Recently developed rehabilitation robots [
19,
20] allow delivering continuous support for the legs in a physiological gait pattern, high repetition accuracy, and prolonged training duration compared to manual treadmill training. The loss of the physical contact between the therapist and the patient is a disadvantage, yet can partly be overcome by technology. The physical contact was often used by the therapist to "feel" the patient's ability and activity. With this information, the therapist can provide feedback to the patient, give training instructions and help to improve the patient's motivation. Because feedback on the current performance may improve the training effect [
21], a corresponding, computerized feedback is desired for robotic rehabilitation. As
bio logical quantities are transferred to a
bio logical system (human) via artificial
feedback, the term "biofeedback" has been introduced and became widely accepted.
The aim of this study was to develop a biofeedback system for a gait training robot and test its usability in subjects without neurological disorders.