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

THE EFFECT OF MUSCLE SETTING ON KINETICS OF UPPER EXTREMITY IN A BASEBALL PITCHING MODELING: A CASE STUDY

The purpose of the current research was to calculate the joint torques and joint reaction forces of the upper extremity with and without muscles in the AnyBody Modeling System in baseball pitching in order to investigate the importance of including muscles on the joint torques and joint reaction forces. We also compare our results to previous studies obtained by inverse dynamics without muscles. One elite college baseball pitcher volunteered to be the participant. A motion analysis system was used to collect kinematic data for the AnyBody Modeling System in order to derive the joint torques and joint reaction forces. The results showed that joint torques of our study with muscles included were similar between previous and current researches. However, the joint reaction forces obtained with muscles included were significantly higher in the current model than the previously reported models and the current model without muscles. This suggests that the disregarding muscles underestimate the joint reaction forces and the risk of injury in joint contact areas

IMAGE-BASED MODELING AND SIMULATION OF THE SHOULDER DURING BASEBALL PITCHING

The imaged-based modeling and simulation such as the virtual, interactive, musculoskeletal system (VIMS) software provides accurate muscle orientations and their relative moment arms. An imaged-based biomechanical model of upper extremity can be used for understanding of neuromuscular control and simulation of sports activities and surgery reconstruction after injuries. The relative movement of the skeletal segments cause a change of muscle orientation and its moment arm, and then affect the role of the muscle loading during the motion. This paper reviews studies in applying three-dimensional shoulder model for investigation of the multi-joint muscle function. An image based and graphic-enhanced, quantitative model of the musculoskeletal system would be utilized for dynamic shoulder analysis with accurate muscle line of action incorporating bone movement and muscle wrapping around the joint

ASSESSING KINEMATICS AND KINETICS OF HIGH-SPEED RUNNING USING INERTIAL MOTION CAPTURE: A PRELIMINARY ANALYSIS

The purpose of this study was to determine whether inertial motion capture (IMC) in combination with musculoskeletal modeling is a suitable method to assess lower limb kinematics and kinetics during high-speed running. Optical motion capture (OMC), IMC and ground reaction forces (GRF) were used as input for musculoskeletal models. Kinematics showed excellent correlations (knee: ρ=0.98, rRMSE=21.0%, hip: ρ=0.95, rRMSE=18.5 %, ankle: ρ=0.93, rRMSE=46.6%). The ground reaction force predictions showed varying results (anteroposterior: ρ=0.77, rRMSE=33.4%, mediolateral: ρ=0.04, rRMSE=69.1%, vertical: ρ=0.78, rRMSE=25.7%). The examined IMC and musculoskeletal modeling approach was proven a useful alternative to OMC and force plates for outdoor measurements in high-speed running

Personalized hip joint kinetics during deep squatting in young, athletic adults

The goal of this study was to report deep squat hip kinetics in young, athletic adults using a personalized numerical model solution based on inverse dynamics. Thirty-five healthy subjects underwent deep squat motion capture acquisitions and MRI scans of the lower extremities. Musculoskeletal models were personalized using each subject's lower limb anatomy. The average peak hip joint reaction force was 274 percent bodyweight. Average peak hip and knee flexion angles were 107 degrees and 112 degrees respectively. These new findings show that deep squatting kinetics in the younger population differ substantially from the previously reported in vivo data in older subjects

EFFECT OF MENTAL DEMAND ON KNEE FORCES IN PROFESSIONAL YOUTH SOCCER PLAYERS

Soccer is one of the most popular sports all around the world. It is an injurious type of sport with a focus on lower extremities and high psychological pressure during matches. The stressor is linked with injuries and an increased musculoskeletal loading. This study investigates the influence of cognitive stress on the load profile of the knee joint. Twelve professional youth soccer players performed highly dynamic runs with and without additional cognitive stress. The runs were analysed with a musculoskeletal simulation software. The data analysis shows no difference in knee joint reaction loading under additional mental stress compared to the baseline. Yet running times are significantly lower in the baseline. While there is no increase in the joint loads, the running times indicate an altered movement behaviour when the subjects are exposed to additional mental demand

Fatigue evaluation in maintenance and assembly operations by digital human simulation

Virtual human techniques have been used a lot in industrial design in order to consider human factors and ergonomics as early as possible. The physical status (the physical capacity of virtual human) has been mostly treated as invariable in the current available human simulation tools, while indeed the physical capacity varies along time in an operation and the change of the physical capacity depends on the history of the work as well. Virtual Human Status is proposed in this paper in order to assess the difficulty of manual handling operations, especially from the physical perspective. The decrease of the physical capacity before and after an operation is used as an index to indicate the work difficulty. The reduction of physical strength is simulated in a theoretical approach on the basis of a fatigue model in which fatigue resistances of different muscle groups were regressed from 24 existing maximum endurance time (MET) models. A framework based on digital human modeling technique is established to realize the comparison of physical status. An assembly case in airplane assembly is simulated and analyzed under the framework. The endurance time and the decrease of the joint moment strengths are simulated. The experimental result in simulated operations under laboratory conditions confirms the feasibility of the theoretical approach