In this book, I explain my work in the estimation of muscle force and muscle fatigue. In this work we create artificial intelligence models, which can estimate muscle activities without the necessity of using the long and complex mathematical procedures. This work improves the muscle activity estimation by using artificial intelligence methods. Our method of improving can be divided into three steps. First step, is simplifying the analyzing of the raw EMG signal by utilizing genetic algorithm and fuzzy logic. Second step, is simplifying the estimation of human muscle force by demonstrate artificial models based on the recorded EMG signal. Third step, is improving the estimation and localizing of muscle fatigue by employing of fuzzy logic method to create the estimation model.