Whether you are a guy who wants a V-shape back or a girl who wants her bum to look spectacular, it is importnat to realize that without building some muscle, you will not be able to change the shape of your body. Now building muscle doesn't involve doing tons of cardio and eating like a bird, so the biggest challenge of muscle building is to say goodbye to the notion of looking very lean all year round. It may even involve putting on a little layer of fat. Notice that I say a "little layer" not a insulation layer of a polar bear. Building muscle has many health benefits. Among them are increased strength, higher metabolism, stronger bones, better posture and reduced body fat. Women are especially cautious about building phase as they tend to be afraid of "becoming bulky". In reality, it is much harder to build muscle for a woman than it is for a guy, as women tend to have much lower testosterone levels (unless they use anabolic steroids). So, those women who end up exercising with weights in a mass building program, tend to get slight increases in muscle, burn more fat and look much better and athletic.
Muscle building is based on three principles: Stimulus, Nutrition and Rest. During your workout, the muscle is stimulated for growth, if supplied with a proper nutrition (increased calories) it has the building materials to grow, and during rest (ie, good night sleep) the body switches on the hormones responsible for recovery. During the recovery, your body tries to compensate for the stress it had undergone during the workout by repairing the muscles and making them slightly bigger to make sure that next time you put them through a workout they would be ready to take the abuse. This adaptation will only happen with a presence of excess calories. That means that you will need to eat more quality fats, carbs and proteins.
Any of this will not happen if the stimulus at the gym is not sufficient enough. Your goal at the gym should be to bring your muscle to a maximal tension. Best way to describe maximal tension is when you are trying to move the weight but cannot do so without struggling. During the maximal tension, all the fibers are fired up. Bring the muscle to a mixmal tension a few times during the workout and it gets damaged. The damage I am talking about here is not a torn muscle or any kind of injury. I am talking about micro-tears in your muscle, they are small tears and are beneficial for growth, because when they heal they will overcompensate and become stronger.
There are two ways to increase muscle size a) use lighter weights, higher reps, b) use heavier weights, lower reps. The difference between the two is that higher reps that are brought to maximal tension will give you quicker results, as the muscle's capacity to store water and glycogen will increase. The disadvantage of that is that the size is lost quicker too, if you don't workout for a while. The method of using heavier weights with lower reps will increase the size of the mitochondria within the muscle and muscle loss size will be much slower. The drawback of this method is that the gains come slower as well.
From my experience, I have seen some great gains when I used both approaches in the same program. I would do it either one of these three methods:
- Start Heavy Then Go Light: If I were to do legs that day, I would start with some heavy compounds like squats, and would go for 4-5 sets of 5-6 reps. Then I would go on and do isolation exercises such as leg extensions and leg curls and keep the rep range higher (10-12 reps, 3 sets each).
- One Week Heavy, One Week Light: Keep all the exercises within 6-8 reps per set for one week, then shift the rep range to 12 reps per set the next week. Keep changing it and you will create a greate deal of confusion for you muscle. It will be harder for it to adapt and you will keep making gains.
- Two Weeks High Rep, Two Weeks Moderate Rep, Two Weeks Low Rep, Deload: Another great program is when you go for 3x12 for two weeks, the next two weeks are 4x6-8 reps and last two weeks would be 5x5. Deload means that after the 6 weeks of training you reduce the weight and sets and go light for 2x15. The deload phase is necessary to repair the muscle and prevent overtraining.
Follow these principles to the T and you will make some great gains. Good luck!