The more weight you lift, the more overload you put on the muscles. As a result of this increased overload, the more muscle you build
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And that's a good thing because gaining muscle is not a difficult thing to do, as long as you do 2 things right.

1. Lift heavier weights over time.
2. Eat supportively to grow muscle

Let's tackle each of those here.

The key to muscle growth is overload. Not just lifting a weight, but a weight that gets heavier, over time.

Want to know how to gain muscle? One week, lift 20 pounds. Next week, try 22 pounds. Next week, 25 pounds.

Progressively heavier weight, over time, stresses and forces the muscle to respond to that additional stress by getting bigger.

Providing you eat enough calories to be used to grow the muscle. Lift heavy. Eat enough quality calories.

That's muscle growth, in it's most simple form.

To show you an example, here are some of the lifts I was doing In January of 2001.

Flat bench press--285 pounds
Incline bench press 215 pounds
Squats 385 pounds
Alternate dumbbell curls--50 pounds each arm
Straight bar bicep curls--100 pounds
Seated dumbbell shoulder presses--50 pound dumbbells
1 arm dumbbell rows--60 pounds

About 12 weeks after, my lifts were:

Flat bench press--365 pounds
Incline bench press 265 pounds
Squats 525 pounds
Alternate dumbbell curls--80 pounds each arm
Straight bar bicep curls--145 pounds
Seated dumbbell shoulder presses--90 pound dumbbells
1 arm dumbbell rows--120 pounds

And guess what happened as a result? Yes, I gained about 20 pounds of muscle in this time period, because I forced my body to do it.

It was this increase in overload that made my muscles respond and get bigger. I also ate enough protein and calories to give the raw materials needed.

The whole point of this is to show you how muscle gains are going to occur. By lifting more weight, over time.

Nothing else will stimulate muscle growth. So if you've been lifting the same weights for the past year or more, chances are, you haven't gained very much muscle.

So, to change this, start trying to increase all of your lifts, the next time you step in the gym.

Muscle growth occurs from lifting heavy and eating supportively. If you continued to lift the same old weight over time and time again, your body has no need to create new muscle growth and strength.

It can already handle what it's doing with what you have.

And finally, always keep a written journal or log for your workouts. If you are at all serious about building muscle and increasing strength--this is a must.

It's the only way you can keep track of your lifts and know when its time to go up in weight.

Just use a small pocket notebook and write all your lifts and weights used in it.

Please do this--it's that important.

Let's say you didn't use a notebook and decided to go by memory. Say that you had a great bench day and ended up going up 5 pounds in weight.

But you fail to write it down and think, "I'll remember that I went up."

Now, a week goes by and you've totally forgotten the weight you used last bench day, so bench time comes around again and you're scratching your head, wondering what it is you last did for weight.

Chances are you're going to put on your old weight, not the new weight (that you added 5 pounds to). When that happens, you went backwards and have lost the progress you made.

Believe me, forgetting your weights happen.

You have 30 or so exercises to keep track of, it's easy to forget one or two of your weights.

And if you forget a weight and do the same weight again when you should have went up, you just wasted your time and energy.

You just did something you were already capable of doing and have missed the chance to increase the overload you were using (and in turn, the muscle and strength that would have come with the new overload).

Please use a journal for your workouts. It's just one of the simple basics of building muscle.