Common signs of overtraining in athletes include persistent fatigue, decreased performance, sleep disturbances, and increased irritability. Other signs can be muscle soreness or stiffness, frequent illnesses, and a lack of enthusiasm for workouts. Overtraining occurs when training intensity and volume exceed the body's ability to recover, leading to hormonal imbalances and increased risk of injuries. Recognizing these signs early is crucial for athletes to adjust their training regimens, incorporate adequate rest, and maintain optimal health and performance.