BodyBuilding.com and LiveStrong claim that over-training (training excessively/while being sore) reduces muscle mass.
LiveStrong says:
Over-training describes a state where your muscles are not given sufficient time between workouts to recover and grow. If you train too hard and too often, the anabolic process of hypertrophy cannot occur. Include a couple of days off from exercise per week and include periodic phases of lighter or less frequent workouts to avoid becoming over-trained.
BodyBuilding.com says:
If you overtrain your muscles will not grow in size or strength and can actually get weaker or smaller.
It seems counter-intuitive that the body reduces the volume/power of the muscle that is clearly in frequent and excessive use.
Is there any validity to this claim?