Dynamic Analysis and Preliminary Evaluation of a Spring-Loaded Upper Limb Exoskeleton for Resistance Training with Overload Prevention

Abstract

Resistance training has been shown to be effective for developing musculoskeletal strength and is recommended by many major health organizations, such as the American College of Sports Medicine and the American Heart Association. This form of training is available for most populations, including adolescents, healthy adults, the elderly, and the clinical population. Resistance training equipment design relies heavily on the analysis of human movement. Dynamic models of human movement help researchers identify key forces, movements, and movement patterns that should be measured. An at-home resistance training upper limb exoskeleton has been designed with a three-degree-of-freedom shoulder joint and a one-degree-of-freedom elbow joint to allow movement of the upper limb at single and multiple joints in different planes. The exoskeleton can continuously increase the resistance as the spring length changes to train more muscle groups and to reduce the potential risk of muscle injury to the upper limb by free weights and training equipment. The objectives of this research were to develop a dynamic model of the spring-loaded upper limb exoskeleton and to evaluate this model by adopting an appropriate motion analysis system to verify our hypotheses and to determine the optimal configuration of a spring-loaded upper limb exoskeleton for further verification studies.

Biomechanical study of upper-limb exoskeleton for resistance training with three-dimensional motion analysis system

“…This article extends the results of our previous static and dynamic studies [18][19]. The fundamental contributions of this article are as follows: (1) well-established and wellplanned experiments were conducted, analyzed, and interpreted; (2) zero-free-length spring design influenced exoskeleton performance as compared with free-weight exercise; (3) the feasibility of a spring-loaded upper-limb resistance training exoskeleton and its underlying design issues were tested.…”

“…We found that link 2 had a larger mass moment of inertia in the current exoskeleton design relative to the 1 kg dumbbell, which agrees with the experimental results described in Figure 8(a-b). Therefore, the mass of the linkage should further conform to certain additional constraints with respect to the mass moment of inertia of the dumbbell and the linkage, which can be obtained from the dynamic analysis [19].…”

“…This study proposed a rehabilitation exercise training device designed from a strength exercise point of view to reduce the risk of adverse health outcomes, and we developed a general design scheme for the use of spring-loaded upper-limb exoskeletons for resistance training. Compared with our previous studies [18][19], efforts have been made through well-designed experimental investigations to better understand the physical significance of using a spring-loaded exoskeleton for upper-limb resistance training. The collected data, along with the kinematics and dynamics analyses that were performed in our previous studies, may further our understanding of the design requirements of a spring-loaded exoskeleton for upper-limb resistance training.…”

“…The mechanical structure of the new prototype ( Figure 1(a)) consists of four links that create four revolute joints covering the basic DOFs of the human arm, allowing the user to perform a shoulder abduction-adduction (abd-add), a flexion-extension (flx-ext), a horizontal flx-ext, and an elbow flx-ext motion, as well as three sets of zero-freelength springs that provide the required resistance for the designated upper-limb resistance training. Compared with the previous version of this exoskeleton [18][19], several design changes have been made to improve systemic functions. The location of the z 1 * axis was redesigned to shorten the distance between the z 1 axis and the z 1 * axis, which improves shoulder abd-add motion compliance.…”

“…The purpose of this study was to verify our hypothesis that, given zero-free-length springs, a spring-loaded upper-limb exoskeleton is capable of reducing the unfavorable lengthening of the muscles from inertial force during high-intensity free-weight exercises via investigating the joint torques exerted by either the spring-loaded exoskeleton for resistance training (SLERT) [18][19] or a dumbbell through the collection of experimental data, kinematics, and dynamic analysis data. This article extends the results of our previous static and dynamic studies [18][19].…”