Background Elevated energy cost is a hallmark feature of gait in older adults. As such, older adults display a general avoidance of walking which contributes to declining health status and risk of morbidity. Exoskeletons offer a great potential for lowering the energy cost of walking, however their complexity and cost often limit their use. To overcome some of these issues, in the present work we propose a passive wearable assistive device, namely Exoband, that applies a torque to the hip flexors thus reducing the net metabolic power of wearers. Methods Nine participants (age: 62.1 ± 5.6 yr; height: 1.71 ± 0.05 m; weight: 76.3 ± 11.9 kg) walked on a treadmill at a speed of 1.1 m/s with and without the Exoband. Metabolic power was measured by indirect calorimetry and spatio-temporal parameters measured using an optical measurement system. Heart rate and ratings of perceived exertion were recorded during data collection to monitor relative intensity of the walking trials. Results The Exoband was able to provide a consistent torque (~ 0.03–0.05 Nm/kg of peak torque) to the wearers. When walking with the Exoband, participants displayed a lower net metabolic power with respect to free walking (− 3.3 ± 3.0%; p = 0.02). There were no differences in spatio-temporal parameters or relative intensities when walking with or without the Exoband. Conclusions This study demonstrated that it is possible to reduce metabolic power during walking in older adults with the assistance of a passive device that applies a torque to the hip joint. Wearable, lightweight and low-cost devices such as the Exoband have the potential to make walking less metabolically demanding for older individuals.

The size, weight, and power consumption of soft wearable robots rapidly scale with their number of active degrees of freedom. While various underactuation strategies have been proposed, most of them impose hard constrains on the kinetics and kinematics of the device. Here we propose a paradigm to independently control multiple degrees of freedom using a set of modular components, all tapping power from a single motor. Each module consists of three electromagnetic clutches, controlled to convert a constant unidirectional motion in an arbitrary output trajectory. We detail the design and functioning principle of each module and propose an approach to control the velocity and position of its output. The device is characterized in free space and under loading conditions. Finally, we test the performance of the proposed actuation scheme to drive a soft exosuit for the elbow joint, comparing it with the performance obtained using a traditional DC motor and an unpowered-exosuit condition. The exosuit powered by our novel scheme reduces the biological torque required to move by an average of 46.2%, compared to the unpowered condition, but negatively affects movement smoothness. When compared to a DC motor, using the our paradigm slightly deteriorates performance. Despite the technical limitations of the current design, the method proposed in this paper is a promising way to design more portable wearable robots.

Difficulty walking in older adults affects their independence and ability to execute daily tasks in an autonomous way, which can result in a negative effect to their health status and risk of morbidity. Very often, reduced walking speed in older adults is caused by an elevated metabolic energy cost. Passive exoskeletons have been shown to offer a promising solution for lowering the energy cost of walking, and their simplicity could favor their use in real world settings. The goal of this study was to assess if a constant and consistent low torque applied by means of a passive exoskeleton to the hip flexors during walking could provide higher and more consistent metabolic cost reduction than previously achieved. Eight older adults walked on a treadmill at a constant speed of 1.1 m/s with and without the hip assistive device. Metabolic power and spatiotemporal parameters were measured during walking in these two conditions of testing. The hip assistive device was able to apply a low torque which initiates its assistive effect at mid-stance. This reduced the metabolic cost of walking across all the participants with respect to free walking (−4.2 ± 1.9%; p = 0.002). There were no differences in the spatiotemporal parameters reported. This study strengthened the evidence that passive assistive devices can be a valuable tool to reduce metabolic cost of walking in older adults. These findings highlighted the importance of investigating torque profiles to improve the performance provided by a hip assistive device. The simplicity and usability of a system of this kind can make it a suitable candidate for improving older adults’ independence.