The right angle: the geometry behind building muscle

Men's Fitness, April, 1999 by Christopher M. Lockwood

Remember the Pythagorean theorem? The one stating that the square of the hypotenuse of a right triangle is equal to the sum of squares of the other two sides? Doesn't ring a bell? Well, don't worry about it.

Even if high school geometry wasn't your best subject, you can still take advantage of the relations of lines and angles when it comes to building and sculpting muscle. With our Cliffs Notes version of basic body geometry (plus a little anatomy and kinesiology), it'll be like you never missed geometry class at all.

Body basics

Your body has more than 430 skeletal muscles to move its 206 bones. Each muscle begins on one bone (point of origin) and ends on another (point of insertion). The direction in which the individual muscle fibers run between these two points is known as your muscles' angle of pennation; this is what determines the direction of a muscle contraction.

Because the point of origin can sometimes differ greatly in size from the point of insertion, hitting muscles from various angles can have a profound effect on their growth. Also, certain muscles act upon, or cross over, more than one joint (for example, the biceps brachii and triceps brachii), while other complex muscle groups, such as the back, are actually made up of a large number of individual muscles whose fibers run m different directions.

Knowing and understanding all of your muscles' points of origin and insertion, muscle-to-joint anatomy and angles of pennation would undoubtedly go a long way toward optimizing your weight training. Unfortunately, learning all that would take years of schooling in kinesiology and biomechanics.

And even if you did have such an education, scientifically sound workouts that look good on paper don't always work for everyone in the weight room. Anatomy is an exact science; training is not. Bottom line: You need to change your regimen on a regular basis and bombard your muscles with different exercises and different angles to intensify your muscle-building efforts.

Angles of attack

THE CHEST

Origins and insertions are the keys to understanding how angle variations can help induce muscle growth.

For example, your chest - the pectoralis major-sternal (lower and mid-pec region) and pectoralis major-clavicular (upper-pec region) - is a prime example of a muscle whose point of origin covers a much larger surface area than its point of insertion.

Imagine a triangle lying on its side that's one side of your chest muscle. The crease that runs down the center of your chest is the pec's point of origin; its point of insertion is a point on your humerus (upper arm). Draw some straight lines from the larger side to the smaller point on the humerus and you can see the direction and angle in which your pectoral muscle fibers run. Moving your arms over and across your chest at varying angles stimulates these muscle fibers in a different fashion.

Knowing this, is the bench press still king of the chest exercises? Not really. To build a large chest, you have to hit it from different angles. Executing a combination of flat, incline and decline presses, along with various flyes, cable crossovers and dips, is the most effective overall approach.

THE BACK

While the in your and triceps basically run in the same direction, other muscle complexes in your body aren't quite so simple.

Your back is actually made up of all sorts of smaller muscles that originate and insert in different places. In order to develop your back fully, you must perform different exercises that vary in directional pull. Even small variations can create big effects with multi-muscle muscles such as the back and shoulders.

For example, by altering your grip on a pull-down from wide to reverse, you work not only the latissimus dorsi, teres major and rhomboids as you would during a standard wide-grip pull-down, but also the middle trapezius.

Changing the directional pull (angle) from the vertical plane (pulldowns) to the horizontal plane (seated rows) de-emphasizes the stress on your latissimus dorsi and teres major while placing the emphasis onto your rhomboids.

The point is, the bigger and more complex the muscle or muscle group, the more angles you need to use in your attack. And the more angles you use, the more muscle you'll build. Now, that's the kind of geometry worth knowing.

THE ARMS

Although most of your muscles have larger points of origin than of insertion, muscles such as the biceps brachii and triceps brachii do not. This doesn't mean that hitting them at different angles is useless, though. Because these two muscles cross over, or act upon, more than just one joint, they, too, are affected by different angles of attack.

The biceps brachii and the triceps brachii both originate on your shoulder complex and insert on one of your forearm bones (biceps on the radius, triceps on the ulna). When you perform a standing barbell curl or a triceps pressdown, you are effectively working your biceps or triceps as it relates to your elbow joint, but not as it relates to your shoulder joint.