It will be the healing for these micro-tears (in the presence of excess protein within your body) that result in muscle demand. The more intensely you train, and therefore the more micro tears you cause, superior for muscle development. Intensity is usually attained by lifting heavier and resting less between sets.
For people who currently wake up in the morning feeling tired - even after sleeping eight hours - training at night after work may very well be disrupting your sleep and recovery process.
