ScienceDaily (Apr. 26, 2012) — Weight training at a lower intensity but with more repetitions may be as effective for building muscle as lifting heavy weights says a new opinion piece in Applied Physiology, Nutrition, and Metabolism.
ScienceDaily (Aug. 11, 2010) — Current gym dogma holds that to build muscle size you need to lift heavy weights. However, a new study conducted at McMaster University has shown that a similar degree of muscle building can be achieved by using lighter weights. The secret is to pump iron until you reach muscle fatigue.
http://www.sciencedaily.com/releases/2010/08/100811125943.htm