When you lift weights, you are creating small tears in the muscle fiber. Your body fixes these, adding a little extra tissue to keep it from happening again. This is what increases strength. The trick is doing enough work and getting enough rest for the muscle to rebuild itself as fast as possible.
The part of the muscle used changes as the motion changes: if you pick up a weight and hold it steady, you will only get strong in that position. Weights should be lifted gradually so the muscles are stressed throughout the movement. Using machines has fallen out of favor in recent years because it holds the weight steady, keeping users from developing stabilization muscles to control the balance of the weight. In other words, just because you can move 200lbs pulling a lever on an exercise machine doesn't mean you can safely lift a 200lb barbell. Strongmen will often train with really awkward objects like sandbags to develop stabilizer muscles.
When lifting, you should concentrate on moving the largest weight you can handle while moving with the correct form. There's some debate on whether or not exercises should be done to failure, literally until you are incapable of performing the motion. While this guarantees that you're doing the most exercise possible, your last rep will probably be bad form, increasing your chance of injury. If you want muscle tone, you need to reduce body fat; doing lots of low weight exercises will have no effect.
How much should you be lifting? 80% or more of your one rep max, the maximum amount of weight you can possibly lift. How many times should you lift? That depends on who you ask. Some programs will have you lift as much as three sets of ten reps, while others using a scaling system where you eventually get close to your 1RM.
Posted 3962 day ago