Muscle Fatigue Analysis Using OpenSim

In this research, attempts are made to conduct concrete muscle fatigue analysis of arbitrary motions on OpenSim, a digital human modeling platform. A plug-in is written on the base of a muscle fatigue model, which makes it possible to calculate the decline of force-output capability of each muscle along time. The plug-in is tested on a three-dimensional, 29 degree-of-freedom human model. Motion data is obtained by motion capturing during an arbitrary running at a speed of 3.96 m/s. Ten muscles are selected for concrete analysis. As a result, the force-output capability of these muscles reduced to 60%-70% after 10 minutes' running, on a general basis. Erector spinae, which loses 39.2% of its maximal capability, is found to be more fatigue-exposed than the others. The influence of subject attributes (fatigability) is evaluated and discussed

Investigating the Effects of Blood Flow on Muscle Fatigue and Recovery in the First Dorsal Interosseous Muscle

The purpose of this study was to gain insight into the physiological principles driving blood flow and fatigue both during and following different levels of intermittent exertion. Utilizing diffuse correlation spectroscopy (DCS) allowed microvascular blood flow (BF) to be observed continuously, providing new insight into the behaviors of BF within the exerting muscle. This experiment was conducted with 11 healthy, adult participants, (5 male, 6 female), fatiguing the First Dorsal Interosseous (FDI) muscle through the abduction of the index finger. The study monitored BF and fatigue in response to 3 levels of intermittent exertion (20%, 30%, and 40% MVC) under constant duty cycle (DC=50%) and cycle time (CT=90s). MANOVA on BF and MVC showed that time, exertion level (EL), and their interaction were significant during both exertion and rest (

Evaluation of control strategies for overhead work using electromyography of rotator cuff muscles

Work-related musculoskeletal disorders (MSDs) of shoulder have a significant impact on overall health and economics in the industrialized nations. Rotator cuff is the most frequently injured region in the shoulder complex. Overhead work is considered as one of the most predominant causes of rotator cuff injuries. The workers in construction, automotive, and aerospace industries are routinely exposed to overhead exertions. Elimination of overhead work is nearly impossible due to various task and technology constraints. Therefore, appropriate intervention strategies based on the engineering and administrative controls opt to be used to prevent the hazardous impact of overhead exertions. The objective of this study was to design administrative controls based on the principles of ergonomics and biomechanics and test their influence on the fatigue response of the rotator cuff muscles. As a first step towards developing such controls, a preliminary study was completed to understand baseline behavior of the rotator cuff muscles in terms of their strength, endurance, and fatigue response and subsequently two specific aims on control strategies were completed. The first specific aim evaluated the effect of four different task rotation sequences on the activation and fatigue response of rotator cuff muscles. In the sequences, three different exertions (Hard (H), Medium (M), and Low (L)) were performed in the following orders: increasing (LLMMHH), decreasing (HHMMLL), upward parabolic (HMLLMH), and downward parabolic (LMHHML). Trends in the median frequency of surface electromyography (EMG) data, maximum strength, and ratings of perceived exertion were used as the fatigue indicators. Despite the similar levels of muscle activation, the effect of task rotation sequence on muscle fatigue development was significant. The median frequency-based fatigue indicator reduced by 54% for supraspinatus, 53% for infraspinatus, and 39% for teres minor when high fatigue sequence (decreasing) was compared with low fatigue sequence (upward parabolic). In the second specific aim, a moderate gripping exertion was added to the task rotation sequences to evaluate the effectiveness of a refresher exertion on the active recovery and the fatigue response of the rotator cuff muscles. On average, presence of the griping task reduced the percent drop in the median frequency by 36% for supraspinatus, 56% for infraspinatus, and 58% for teres minor when compared with the task rotation without gripping exertions (aim 1 study). In conclusion, the results of this study indicate that performing tasks with a constant workload in different orders can alter rotator cuff muscles’ fatigue development. A shorter duty cycle for the intense tasks, warm up exertions prior to the intense tasks, and low intensity/refresher exertions between the work cycles seem to be the key factors in designing control strategies based on task rotations