I won’t keep you in suspense: It’s range of motion. But the forgotten fact is why it’s important…
If you’ve ever watched a very lean bodybuilder doing leg extensions—lean enough so you can see fibers firing—you’ll notice twitching “explosions” all over the quad muscles as the lower leg extends and retracts.
The muscle fibers fire like a machine gun all the way up and down the stroke. Fibers hand off to other fibers to keep the movement going…
So if you only do a partial range, like say the top half of the leg extension stroke, you may miss activating many fibers that have leverage down near the bottom…
And in fact, down near the bottom of the stroke is where the target muscle is strongest and you get the MOST fiber activation.
So if you were going to emphasize any part of the range, it should be the lower half—but full range is best….
In college I trained at a Nautilus gym, using those machines for almost every muscle. They looked futuristic and were full range. I liked that; however, the creator, Arthur Jones, insisted that the muscle was strongest in the contracted position…
So Jones created a cam shaped like a Nautilus shell, that put more resistance at peak contraction than at near stretch—which we now know is the opposite of correct…
Muscles are strongest near the stretch and weakest at contraction. Researchers Fleck and Kraemer, both Ph.D.s, verify that in their book Designing Resistance Training Programs:
Near a muscle’s stretch position, like the bottom of a standing curl, the actin and myosin filaments within muscle fibers can pull optimally for maximum force—they are best lined up for near-perfect muscular action. But as the muscle shortens, those filaments become more crowded and the ability is significantly reduced. The contracted position, such as a flexed biceps at the top of a curl, is the least advantageous position for the muscle to generate force.
I noticed that on almost all of the Nautilus machines. Like on the biceps curl. Here’s an early version of that machine, with legendary bodybuilder Casey Viator trying to reach peak contraction…
On most of the machines, I would fail when I couldn’t reach the top flexed position, and I’d terminate the set. But there was still a lot of strength left in the bottom half of the stroke.
I was essentially leaving a lot of the muscle under-stimulated and many fibers untapped—and leaving plenty of muscle growth on the table.
So the bottom line is that you should emphasize the ideal exercises with the proper strength curve—hardest near stretch, easiest at contraction—and use a full range of motion to activate as many muscle fibers as possible on every set.
Oh, and stop staring at lean bodybuilder’s quads on the leg extension machine.
For the ideal exercise for each muscle, my complete workouts, exercise start/finish photos, and details on building muscle fast and efficiently, see Old Man, Young Muscle.
Till next time, train hard—and smart—for BIG results.
Steve Holman
Former Editor in Chief, Iron Man Magazine
www.X-Rep.com
3 Workouts a Week, 35 Minutes Each for Jacked Mass
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