The role of rest in bodybuilding cannot be slighted. Those that do so fail in their noble quest to gain mass and muscle out of frustration for not achieving their personal goals. They spend too much time weight training and when that fails to show in terms of bulging biceps and rock solid abs, they increase the time they train. This vicious cycle of self torture continues until one falls down fatigued and dejected.
They fail to realize that without adequate rest and relaxation, the muscles don't get time to recuperate. The muscles use this time to repair worn out tissue and increase in mass and strength. This is because as you work out, the available nutrients are being oxidized to provide your muscles with adequate energy to lift the weights and other equipment in the gym. You could also be doing cardiovascular activities like jogging that also require intensive energy production.
While resting after having a healthy meal of all the required foods, the muscles do not need energy. But the energy is available from the meal just taken. Thus the body utilizes the energy to make more muscles in readiness for future weight training. Thus it is important to rest regularly and preferably in between work out sessions. This allows muscle growth in readiness for added strain.
Most beginners given a weight training schedule of 5 hours a week think they are under utilizing their potential and soon get disoriented from the course. What should be clear to one when beginning is that they first have to get their body accustomed to the rigors of the gym and the rest is to help the body to adjust and replenish itself before trying out a new regimen.
Dangers of overtraining
In athletics, it is called burn out. Just as the name implies, this is overworking your body, giving it more than it can handle. This leads to conditions such as Overtraining Syndrome (OTS). This is characterized by persistent fatigue, depression, low testosterone and blood sugars.
During weight training and cardiovascular activities, the body undergoes much damage when muscle tissue tears due to the challenging weight. This is intentional so as the body repairs that tissue and rebuilds it to be stronger. This is how weight training leads to increase in mass and muscle. Though necessary for bodybuilding, these tears and wear, if not let to be repaired, deteriorates to OTS.
It's a progressive disease whose onset is marked by increased sense of laziness and lethargy. If you can't lift the same weights as you did a day or two ago in the same gym, consider taking a long rest as you might be regressing into OTS.
The solution to OTS is what you haven't been having, rest. Lot's of rest. Supplement rest with glutamine which supposedly speeds up repair and rebuild of tissue. In addition reduce your training sessions to a minimum but do not cut it to zero as you might regress into inactivity.