The first book I'm reading for the New Year is entitled, "Antifragile," by Nassim Taleb. This was based on several recommendations from friends and colleagues. I'm only two chapters into it, but can already say I've thought about things more and thought about things differently then any other book I've read recently.
Fragile is obviously something you want to avoid as a human. When health is fragile, well, that's no good. Taleb asks the question, "What is the opposite of fragile?" Most people say robust or resilient. He makes the point that robust means things that happen have no impact, they stay the same. If things happen to fragile, they break or are injured. Anti-fragile then has the definition of if things happen to them they actually improve.
FRAGILE ---- ROBUST ----- ANTIFRAGILE
Exercise in the right doses can fall in any of these categories. Extreme stuff, can break you, just as laying in bed for a week can hurt you. This is fragile. In the exact dosage of what you always do, nothing happens. Run the exact same mile loop around your neighborhood and wonder why you don't get faster? Hit the same weights 3x10 2x a week and wonder why you're not stronger a year later? This is Robust. The correct amount stresses your system and requires an adaptation to improve. This is Antifragile.
A helpful analogy in the book that helped me was with medicine. With drugs, you are adding something to your system that you cannot predict the outcomes. Hence, side effects, reactions ect...This would be the opposite of simply eliminating something from your diet, such as gluten or sugar. Drugs would be on the fragile side, eliminating things to see how you react would be antifragile.
A good friend and great strength coach, Stu McMillan, just put up a blog post where he gives the best books he read in 2012. Well worth a look if you are looking on stocking up your library this new year.