Before you close out of this article because it sounds like a "meathead" topic, you should know a few important things about muscle. Growing muscle doesn't mean getting "bulky!" Instead, it simply means that you are laying down lean and dense fibers that can replace fat and boost your metabolism. Muscle is also what lifts your chest, fills out your butt and gives you shapely legs and toned arms.
Now that we've established that the goal is not to develop arms that scare away small children, let's talk about how to make your muscles bigger.
How do Muscles Grow?
Take your biceps on the front your arms as an example. Like all other muscles in your body, the biceps are comprised of tightly woven bundles of muscle fibers, which are in turn made of muscle cells.
When you produce a force, such as lifting a couch, most of those muscle fibers in your biceps are exposed to tension (especially if your couch has a fold-out bed hidden inside).
The tension from the weight of that couch stretches the fibers and can cause tiny tears in them -- and when the cells in your muscle fibers sense this trauma, they rally the muscle-building troops from your body to repair the tears.
These muscle-building troops include hormones, growth factors and white blood cells, which not only repair the muscle fibers in your biceps, but also increase the size of the fibers and the strength of nerves that activate them, so that next time you lift a couch, you strain a bit less. But there are better ways to make your muscles grow than by lifting the occasional couch.
The Best Exercises for Muscle Growth
The best exercises for muscle growth are ones that require you to use multiple joints. For example, squats, cleans, deadlifts and bench presses are all very effective at helping your muscles get bigger, and for toning your entire body.
So how much weight should you lift? Your muscles must be subjected to enough weight for actual muscle fiber tearing to occur, and for most people, that means lifting about 65-85 percent of what you could normally lift only one time (this is called your "one rep max" or "1RM"). For example, if you can bench press 100 pounds, then your weight for increasing the size of your chest muscles would be 65-85 pounds. Most people can lift 65-85 percent for 8-12 repetitions.
Because your muscles need a significant amount of time under tension (about 60 seconds) for actual muscle tearing to occur, you need to do multiple sets of these 8-12 reps. Though you certainly could perform just one very long set for each muscle group, that is mentally challenging, extremely uncomfortable and very risky. So instead, perform at least 3 and at most 6 six sets for each exercise. Each set should include one to two minutes of recovery for the muscle group you are working.
Before you rush off to do biceps curls every day until your arms are popping out of your coat, you must understand that there can certainly be too much of a good thing. If you stress, traumatize, or tear a muscle every day, your body will not have enough time to repair the muscle fibers, resulting in uncomfortable levels of soreness, low muscle growth and joint injury. So give your muscles 2-3 days of recovery before re-stimulating those fibers again, and don't starve yourself -- muscle needs calories to grow and repair!
Ultimately, the trick to growing muscle is to stress it, allow it to recover while eating enough healthy food to feed the new muscle, and then repeat! With this strategy, you can safely build one to two pounds of muscle each week -- and since muscle takes up much less room than fat, those pounds will look tight and lean. Once you've built your new muscle, let me know. I have some heavy couches that need moving.
Ben Greenfield is a fitness and triathlon expert and host of the Get-Fit Guy podcast on the Quick and Dirty Tips network. His book, "Get-Fit Guy's Guide to Achieving Your Ideal Body -- A Workout Plan for Your Unique Shape," will be published by St. Martin's Press in May 2012.