Reducing the energy cost of running using a lightweight, low-profile elastic exosuit

Jaeha Yang,Sungjin Park,Giuk Lee,Junil Park,Jihun Kim

doi:10.1186/s12984-021-00928-x

Jaeha Yang, Sungjin Park + Show 3 more

Open Access

https://doi.org/10.1186/s12984-021-00928-x

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Abstract

BackgroundHuman beings can enhance their distance running performance with the help of assistive devices. Although several such devices are available, they are heavy and bulky, which limits their use in everyday activities. In this study, we developed a lightweight running assistive device with a low-profile design. The device applies a flexion moment to the hip according to the hip extension within a specific range of motion to assist running.MethodsA passive exosuit was fabricated using textile materials and elastic bands. The deformation of the suit was measured and compensated for in the design. The fabricated suit was tested on eight participants (age: 24.4 ± 3.8 y; height: 1.72 ± 0.05 m; weight: 74.5 ± 6.1 kg) who were instructed to run on a treadmill at a speed of 2.5 m/s. Through indirect calorimetry, the metabolic rate was measured for the no-suit condition and three band conditions. Variations in the spatiotemporal parameters were measured using a motion capture system and force-sensing resistors (FSRs).ResultsWhen using the fabricated device, seven out of the eight participants exhibited a reduced metabolic rate in at least one of the three band conditions. An average reduction of − 4.7 ± 1.4% (mean ± standard error of the mean (s.e.m.), two-sided paired t-test, p = 0.017) was achieved when using the best-fitting bands compared to the average of the two no-suit conditions. No statistically significant changes were observed in the spatiotemporal parameters, except for the stance duration in the medium assistance force condition.ConclusionsThe proposed passive exosuit, which has a low weight of 609 g and small extrusion of 2.5 cm from the body in standing posture, can reduce the metabolic rate during running. The proposed device can potentially be used every day owing to its low-profile design and low weight, thereby overcoming the limitations of existing portable devices targeting the hip joints.

Highlights

Human beings can enhance their distance running performance with the help of assistive devices
Kim et al developed an exosuit that used batteries to actively support hip extension [4]; tests on nine participants running at a speed of 2.5 m/s showed that a metabolic cost reduction of 4% could be achieved when running with the proposed device compared to running without it
The statistical analysis showed that the metabolic rates did not significantly vary across conditions

Summary

Introduction

Human beings can enhance their distance running performance with the help of assistive devices. Studies have shown that the metabolic energy cost is linearly related to the time consumed in running a certain distance [1, 2] Based on these studies, many researchers have attempted to develop assistive devices that can reduce the metabolic cost during running, and a few of them have succeeded in achieving this goal [3]. Based on their assistive strategies, devices that can reduce the metabolic cost while running can be classified into active and passive devices, and the former has been studied extensively [4,5,6,7] Devices of this type use external energy sources such as batteries to exert assistive forces on specific parts of the body, thereby reducing the biological moment needed to perform the target motion.

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