Common signs of muscle fatigue include increased discomfort, a feeling of heaviness, and decreased strength during physical activity. Individuals may also notice a reduced ability to maintain optimal performance, leading to slower movements or difficulty completing repetitions. Additionally, symptoms such as muscle soreness and an overall sense of tiredness are indicative of fatigue. These signs can occur after intense workouts or prolonged activity, which signifies the necessity of adequate recovery time. Listening to the body's signals is crucial for preventing injury and promoting efficient recovery.