Lyle McDonald, an expert on fitness research, mentions impaired sleep as a common cause of overtraining - http://www.bodyrecomposition.com/training/overtraining

Lyle McDonald, an expert on fitness research, mentions impaired sleep as a common cause of overtraining - http://www.bodyrecomposition.com/training/overtraining-overreaching-and-all-the-rest-part-3.html http://www.bodyrecomposition.com/training/overtraining-overr... He's long-winded but his views are definitely founded on scientific research.