Symptoms of muscle fatigue include a feeling of heaviness in the muscles, decreased strength, and an inability to maintain performance levels during exercise. As fatigue sets in, individuals might also experience increased soreness, delayed recovery, and a general sense of exhaustion. In some cases, muscle cramps and spasms may occur. Mental aspects include decreased focus and motivation. Recognizing these signs is crucial for adjusting workout intensity and ensuring adequate recovery time, which allows muscles to heal and grow stronger.