The potential negative effects of over-exercise include increased risk of injuries, chronic fatigue, and mental burnout. Excessive physical activity without adequate recovery can lead to overuse injuries, such as stress fractures or tendonitis, and may negatively impact immune function. Additionally, over-exercising can result in imbalances in hormones like cortisol and can contribute to anxiety or depression. It’s crucial to listen to the body and incorporate rest days and recovery strategies to maintain a healthy balance in fitness routines and minimize these adverse effects.