Take one concept. Overtraining. What the hell is that? Show me any studies defining that concept or demonstrating what it is. In the absence of any such definition we find all manner of explanations and theories that show nothing at all. It has yet to be established there is any such thing.
I agree with you that many myths are propogated and spread in the muscle mags. I disagree that overtraining is such a concept. Overtraining is well-documented in the literature and is generally defined as "Untreated overreaching that results in chronic decreases in performance and impaired ability to train. Other problems may result and may require medical attention."
The sources are too numerous to mention here but include:
Costill, D.L., Flynn, M.G., Kirwan, J.P., Houmard, J.A., Mitchell, J.B., Thomas, R. & Park, S.H. (1988). Effect of repeated days of intensified training on muscle glycogen and swimming performance. Medicine and Science in Sports and Exercise, 20, 249-254.
Davis, J.M. & Hertler-Colbert, L. (1997). The athlete's immune system, intense exercise, and overtraining. In: Lamb, D.R. & Murray, R. (Eds.). Optimizing Sport Performance: Perspectives in Exercise Science and Sports Medicine. Vol. 10, (pp.269-311).
Fry, R.W., Morton, A.R. & Keast, D. (1991). Overtraining in athletes: an update. Sports Medicine, 12, 32-65.
Krieder, R.B., Fry, A.C. & O'Toole, M.L. (1998). Overtraining in Sport. Human Kinetics: Champaign, IL.
Kuipers, H. (1998). Training and overtraining: an introduction. Medicine and Science in Sports and Exercise. 30, 1137-1139.
Kuipers, H. & Keizer, H.A. (1988). Overtraining in elite athletes: review and future directions. Sports Medicine, 6, 79-920.
Morgan, W.P., Brown, D.R., Raglin, J.S., O'Connor, P.J. & Ellickson, K. A. (1987). Psychological monitoring of overtraining and staleness. British Journal of Sports Medicine, 21, 107-113.
O'Connor, P.J. (1997). Overtraining and staleness. In: W.P. Morgan (Ed.). Physical Activity & Mental Health. (pp. 145-160). Taylor & Francis, Washington, D.C.
Raglin, J.S. Overtraining and staleness: Psychometric monitoring of endurance athletes. (1993). In R.N. Singer, M. Murphey & L.K. Tennet (Eds), Handbook of Research in Sport Psychology. (pp. 840-850), Macmillan: New York.
Raglin, J.S., & Wilson, G.S. (In press). Overtraining in athletes: In Emotion in Sports. Y.L.Hanin, (Ed.). Human Kinetics.
Urhausen, A., Gabriel, H.H.W., Weiler, B. & Kindermann, W. (1998). Ergometric and psychological findings during overtraining: a long-term follow-up study in endurance athletes. International Journal of Sports Medicine.19, 114-120.