Title: Contribution to the evaluation of muscle fatigue and recovery model.

Abstract:

Automation has changed the working conditions in industries and manufacturing process, but still many industries needs manual operations and handling for various tasks. These manual operations lead to work-related Musculoskeletal Disorders (MSD) which is one of the major problems for industrial workers. Muscle fatigue is one of the reason leads to Musculo-Skeletal Disorder. The society/companies have to pay attention on this issue due to the new laws on penibility or repetitive tasks. In this thesis we are focusing on the development of an adequate and realistic dynamic muscle fatigue and recovery model for dynamic work posture, its applications and validation through experiments. Firstly, we have introduced a new dynamic muscle fatigue model with a newly introduced co-contraction factor to predict the physical strength in dynamic conditions. A recovery model is used to predict the recovery after fatigue. Both the models are first validated theoretically and compared with previous models and then validated experimentally. In theoretical analysis models are compared using regression method. Secondly, experiments were conducted on 10 subjects for push pull motion of the arm to study the muscle strength and rate of recovery. Electromyography (EMG) technique is used to analyze the muscle activity. At last the experimental data are used to validate muscle fatigue and recovery model. It has been found that with the increase in muscle fatigue co-contraction index decreases and most of the subjects followed the exponential function predicted by fatigue model. With the use of co-contraction factor dynamic maximum endurance time (DMET) decreases by 25.9 % as compare to R. Ma's Model. Al last, the normalized values of fatigue rate and co-contraction factor are used to predict the DMET for various work load. The fatigue and recovery model proposed in this thesis can be useful in analyzing the muscle fatigue and recovery parameters, to analyze human posture and in improving working ergonomics conditions.