Supplement Doctor's Blog

When it comes to bodybuilding SIZE DOES MATTER. You're goal is to make Godzilla proud. So how do you achieve the massive thighs of Godzilla and the trunk-like arms of King Kong? Needless to say there are several aspects to producing large muscles that you should know. Skeletal muscle has the unique ability to adapt in a highly specific manner to different forms of exercise. Think of the marathon runner with skinny legs, torso, and arms. His muscles are chockfull of mitochondria (the aerobic powerhouse of the cell). On the other hand, bodybuilders are the opposite. They have very large muscles. This is due primarily to an increase in muscle fiber SIZE. But we can't rule out that at the highest levels (e.g., Dorian Yates, Ronnie Coleman, Popeye the Sailor Man), it may be possible to increase muscle fiber number. But for most of us, getting larger muscle FIBERS rather than a greater number of fibers is the way to go.

 

MUSCLE FIBER TYPES
Skeletal muscle is made up of two basic fiber types: fast-twitch and slow-twitch. Slow fibers have a slow contraction velocity, produce less tension, but have a high endurance capacity. Fast-twitch fibers generate the most tension (i.e., great for power/strength development) and have the fastest contractile velocity;on the other hand, they fatigue quickly. It actually is a little bit more complicated than that; you could get into the different subtypes of fast fibers etc. But for the purposes of bodybuilding, keep in mind that your goal is to make ALL fibers types bigger. And the primary key to that is lifting heavy (or for us science geeks, subjecting your muscle fibers to very high tension).

NEURAL ADAPTATION
According to the size principle of motor unit recruitment, the smallest motor units (i.e. slow-twitch or Type I) are recruited before the larger motor units (i.e., fast-twitch - Type IIa , Type IIx). But we know that it is possible to recruit our fast fibers, even at relatively low weights (30-60% of max). But in order to MAXIMALLY target all fibers, it's a good idea to occasionally lift very heavy weights (1-3 repetitions maximum). Another thing to keep in mind is that strength and size are NOT necessarily related. Why? Because enhanced motor unit recruitment and/or a greater firing frequency of your nerves can by itself increase strength.

 

HORMONAL RESPONSE

Although levels of blood testosterone and growth hormone have been found to be enhanced during an acute bout of bodybuilding exercises, it isn't known if this has any long-term significance. With regards to a chronic adaptation, serum hormones in elite endurance athletes (swimmers) and elite weightlifters increased slightly (+1.2% swimmers, +2.1% weightlifters) over a one year period. In well-trained distance runners, however, serum testosterone is much lower than untrained men. So what do you make of this? Don't do lots of aerobic exercise! It'll drop your testosterone faster than a bullet train.

SHAPING YOUR MUSCLES
Although many scientists have scoffed at the idea that you can shape your muscles via specific exercises, there is evidence which shows otherwise. For example, in college age women who performed isotonic knee extension exercise three times a week for eight weeks, they had a preferential hypertrophy (growth) of the rectus femoris and vastus lateralis muscles in comparison to the vastus medialis and intermedius muscles. In another study, sixteen weeks of unilateral triceps exercises (consisting of the French press exercise) resulted in significant growth in the middle region of the triceps muscle; however, there was no change in the proximal or distal end of the muscle. So it's clear that you can cause specific regions of a muscle to grow. The science in this area is still in its infancy; however, you can often figure out what works best for YOU by trial and error. So don't hesitate to mix up your exercises to get a maximal growth effect.

SIDE BAR
Increase muscle fiber size or number?
There are two ways by which new skeletal muscle fibers can be formed. First, large fibers can split into two or more smaller fibers (i.e., fiber splitting) and second, satellite cells can undergo mitosis and fuse with each other resulting in de novo fiber formation. So we know conclusively that a mechanism exists for skeletal muscle fibers to increase in number. But what is the experimental evidence?
We do know that birds, cats, and rats can increase fiber number. So why not Homo sapiens? Well, we CAN increase fiber number. But it'll probably take more of an effort than your average bodybuilder is willing to put out. Also, the role of anabolic steroids in augmenting fiber number is an area that needs further exploration. For now, go for bigger muscle fibers...and if you're lucky, maybe fiber number will go up a little bit.

Bottom Line: Size Matters...both in the gym and between the sheets.

Reference
Antonio J. Nonuniform response of skeletal muscle to heavy resistance training: can bodybuilders induce regional muscle hypertrophy? Journal of Strength and Conditioning Research. 2000, 14(1):102-113.