Overtraining or overtesting oneself in workouts can lead to injuries due to excessive strain on muscles, joints, and ligaments. Pushing beyond one's limits increases the risk of musculoskeletal injuries such as sprains, strains, and stress fractures. Additionally, insufficient recovery time exacerbates fatigue and can lead to decreased performance. Signs of overtraining include persistent soreness, diminished strength, and an elevated risk of illness. It's crucial to listen to one's body and balance intense workouts with adequate rest to ensure long-term fitness progression and prevent injuries.