Potential drawbacks of excessive cardio training include increased risk of injury, muscle loss, and diminished energy levels. Overdoing cardiovascular workouts can lead to chronic fatigue and negatively impact performance in strength training. Additionally, excessive cardio can disrupt hormonal balance, leading to issues like decreased metabolism and increased stress levels. This imbalance can impede recovery and overall health, making it essential to balance cardio with strength training and adequate rest to maintain a well-rounded fitness regimen.