Building muscle will make you slower and less flexible. Contrary to what you may think, building a significant amount of lean muscle mass will actually speed you up rather than slow you down.

Muscles are responsible for every movement that your body makes, from running to jumping to throwing. The truth to the matter is that the stronger a muscle is, the more work it can do and the more force it can apply. Having stronger, more muscular legs means increased foot speed, just as having stronger and more muscular shoulders means the ability to throw farther.

Is there an exercise that work all the muscles?

The deadlift will work you from finger to neck to toe. It is a raw, basic power movement and will literally stress every single muscle in your entire body to some degree. The main areas of stimulation are the back (lower and upper) and thighs, but once you start deadlifting on a consistent basis you’ll see gains all over your body

The bad news is that deadlifts are without a doubt one of the most painful and discomforting exercises you will ever come across. When performed properly, they’ll leave you lightheaded, nauseous, gasping for air and will temporarily have you wishing that you hadn’t come to the gym in the first place. But if it’s serious results that you’re after, this is the price you must pay.

Can you actually see your muscle growing in the gym?

Your muscles do not grow in the gym. The work that you accomplish as you train with weights is merely the “spark" that sets the wheels of the muscle growth process into motion. The real magic takes place out of the gym while you are resting and eating, as this is the time when your body will actually be synthesizing new muscle tissue.

Because of this, it is vital that you do not overtrain your muscles. You must always make sure to provide them with sufficient recovery time if you want to see impressive results. Overtraining can actually make your muscles smaller and weaker.

What is then your goal in the gym?

Your goal in the gym should be to train with the minimum amount of volume needed to yield an adaptive response. Once you have pushed your muscles beyond their present capacity and have triggered your thousand-year-old evolutionary alarm system, you have done your job. Any further stress to the body will simply increase your recovery time.