The influence of different Lokomat walking conditions on the energy expenditure of hemiparetic patients and healthy subjects Carmen Krewer * , Friedemann Mu¨ller, Britta Husemann, Silke Heller, Jochen Quintern, Eberhard Koenig Neurologische Klinik Bad Aibling, Kolbermoorer Strasse 72, D-83043 Bad Aibling, Germany Received 13 March 2006; received in revised form 26 September 2006; accepted 5 October 2006 Abstract To determine the strenuousness and efficacy of therapy, the energy expenditure of 10 healthy and 10 hemiparetic subjects were measured while they walked on a treadmill that was combined with a robot-driven gait orthosis, the Lokomat, which physiologically exercises the legs of a patient on a moving treadmill. Subjects performed different Lokomat conditions after measurement of the baseline, i.e., standing in the Lokomat with 30% body weight support (BWS). Robotic strategies with a position control scheme used fixed gait patterns to produce the following conditions: walking with 100% BWS at a speed of 1 km/h versus 2 km/h and walking with 30% BWS at a speed of 1 km/h versus 2 km/h. Another robotic control option with a force control scheme allowed the force to be reduced on only one leg of the orthosis. In this option a reduction to 60% and to 0% assistance was tested. Oxygen consumption and heart rate were measured by a breath-by-breath respiratory gas analyzing system using standard open circuit methodology. The results for O 2 rate [ml/kg/min] indicate that: (1) walking in the Lokomat is not passive; (2) oxygen uptake is significantly increased due to an effect of loading during active stance phase; (3) speed is not a factor leading to increased oxygen consumption; (4) patients do not significantly increase their oxygen uptake due to the advanced force control scheme. # 2006 Elsevier B.V. All rights reserved. Keywords: Stroke; Robotic rehabilitation; Energy expenditure; Gait; Treadmill training 1. Introduction The restoration of walking plays an important role in the rehabilitation of patients with hemiparesis after stroke. Almost two-third of these patients have initially no walking function and cannot walk without assistance [1]. Thus, the ability to walk is a major goal in their rehabilitation. Of the many treatment methods available, treadmill training combined with partial body weight support (BWS) has become an established method for retraining gait in hemiparetic patients [2–4]. Despite the added support, the treadmill training of severely affected non-ambulatory patients is demanding for both patients and therapists. To perform gait training even at very slow speeds patients require the help of two or more therapists. The Lokomat was developed at the Spinal Cord Injury Centre of Balgrist University Hospital, Zurich, Switzerland, to reduce the workload and improve treadmill training for both patients and therapists. It was originally developed for patients with spinal cord injuries (SCI), and its efficacy in these patients has been documented in several studies [5–8]. The Lokomat is an electrically driven gait orthosis consisting of a hip support and two leg orthoses. It is operated in combination with a treadmill and is controlled by a PC. The leg orthoses are each equipped with a hip and a knee joint drive [5,9]. The Lokomat offers a more supportive environment, in which the severely affected patients can practice gait-like movements at near-normal speed, and this training can be performed more regularly over a longer period of time. It can be adjusted to the patient’s needs (for example, the force of the drives of the orthosis can be reduced and the body weight support or the treadmill speed can be changed) to allow severely handicapped patients to www.elsevier.com/locate/gaitpost Gait & Posture 26 (2007) 372–377 * Corresponding author. Tel.: +49 8061 903 0; fax: +49 8061 903 602. E-mail address: CKrewer@schoen-kliniken.de (C. Krewer). 0966-6362/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2006.10.003