Secret #1: Muscle fibers, like children, have different
Your skeletal muscles—the ones you check out in the mirror—have
two main types of fibers.
Type I fibers, also called slow-twitch, are used mainly for
endurance activities. Type II, or fast-twitch, begin to work
when a task utilizes more than 25 percent of your maximum
strength. A movement doesn't have to be "slow" for the
slow-twitch fibers to take over; it just has to be an action
that doesn't require much of your fast-twitch strength. And an
effort doesn't have to be "fast" to call your fast-twitch fibers
A personal-record bench press is going to use every possible
fast-twitch fiber (plus all the slow-twitchers, as we'll explain
below), even though the bar probably isn't moving very fast.
Most people are thought to have a more or less equal mix of
slow- and fast-twitch fibers. (Elite athletes are obvious
exceptions—a gifted marathoner was probably born with more slow-
than fast-twitch fibers, just as an Olympic-champion sprinter or
NFL running back probably started life with more fast-twitch
fibers.) However, the fast-twitch fibers are twice as big as the
slow ones, with the potential to get even bigger. Slow-twitch
fibers can get bigger, too, although not to the same extent.
So one strategy comes immediately to mind. . . .
To grow large, you must lift large.
When you begin a task, no matter if it's as simple as getting
out of bed or as complex as swinging a golf club, your muscles
operate on two basic principles of physiology:
1. The all-or-nothing principle states that either a muscle
fiber gets into the action or it doesn't. (As Yoda said, long
ago in a galaxy far away, "There is no try.") If it's in, it's
all the way in. So when you get up to walk to the bathroom,
incredibly enough, a small percentage of your muscle fibers are
working as hard as they can to get you there. And, more
important, all the other fibers are inactive.
2. The size principle requires that the smallest muscle fibers
get into a task first. If the task—a biceps curl, for
example—requires less than 25 percent of your biceps' strength,
then the slow-twitch fibers will handle it by themselves. When
the weight exceeds 25 percent of their strength, the type II,
fast-twitch fibers jump in. The closer you get to the limits of
your strength, the more fast-twitch fibers get involved.
Here's why this is important: One of the most pervasive myths in
the muscle world is that merely exhausting a muscle will bring
all its fibers into play. So, in theory, if you did a lot of
repetitions with a light weight, eventually your biggest type II
fibers would help out because the smaller fibers would be too
tired to lift the weight.
But the size principle tells you that the biggest fibers are the
Mafia hit men of your body. They don't help the underlings
collect money from deadbeats. They suit up only when the work
calls for their special talents, and when no one else can be
trusted to do the job right.
In other words, a guy who's trying to build as much muscle as
possible must eventually work with weights that require
something close to an all-out effort. Otherwise, the
highest-threshold fibers would never spring into action.
Moreover, the smaller fibers don't need any special
high-repetition program of their own, since the size principle
also says that if the big fibers are pushed to the max, the
small ones are getting blasted, too.
You can save your bones by building your muscles.
Many have tried to disparage the squat, framing it as an
exercise that's brutal to back and knees. The charges never
stick. Sure, the exercise can be tough on the knees, but no
tougher than full-court basketball or other full-bore sports.
And for guys with healthy backs and knees, the squat is among
the best exercises for strength, mass, sports performance, and
even long-term health. The heavy loads build muscle size and
strength, along with bone density, and thicker bones will serve
you well when you finally break into that 401(k). So you won't
be the guy who fractures his hip and ends up in a nursing home,
although you'll probably pay some visits to your nonsquatting
Setup: Set a bar in supports that are just below shoulder
height and load the weight plates. (Be conservative with these
weights if you've never squatted before. There's a learning
curve.) Grab the bar with your hands just outside your
shoulders, then step under the bar and rest it on your back.
When you pull your shoulder blades together in back, the bar
will have a nice shelf to rest on. Lift the bar off the supports
and take a step back. Set your feet shoulder-width apart, bend
your knees slightly, pull in your lower abs, squeeze your glutes,
and set your head in line with your spine, keeping your eyes
Descent: To begin the squat, bend your knees and hips
simultaneously to lower your body. Squat as deeply as you can
without allowing your trunk to move forward more than 45 degrees
from vertical. Make sure your heels stay flat on the floor.
Ascent: Squeeze your glutes together and push them
forward to start the ascent, which should mirror the descent.
Keep your knees the same distance apart (don't let them move in
or out). Your hips and shoulders need to move at the same
angle—if your hips come up faster, you increase your trunk angle
and risk straining your lower back. At the top, keep a slight
bend in your knees.