Muscle shape: can training change it?

Muscle shape is an old debate in bodybuilding: can you really change it with training, or is everything predetermined by your genes? The short answer is a cautious yes, but not as simplistically as it used to be put. Exercises, load and the style of your repetitions can influence which muscle fibers do more of the work.

Why does muscle shape cause so much debate?

Bodybuilding has few absolute truths. There was a time when people seriously claimed that the squat is bad for your knees and that you’re better off choosing the leg press or leg extension. In the same way, people feared dietary fat and believed that a high-protein diet would wreck your kidneys right away. Many such firm claims have since become far more nuanced.

The question of whether training can change how a muscle looks is much the same. One camp says a muscle contracts as a whole, so it also grows as a whole. The other camp believes that different exercises and angles can load different regions of the same muscle slightly differently. Dr. Jose Antonio and Mike Meija have pointed out several reasons why the old bodybuilders’ idea may not be entirely a myth.

It pays to keep a cool head here. Nobody can use training to change where a muscle attaches or the shape of their skeleton. That is genetics. What training can influence, though, is which part of the muscle develops more and how clearly the muscle stands out.

Muscle shape and regional hypertrophy

In plain language, regional hypertrophy means that a muscle doesn’t always grow completely evenly. Some regions may receive more stimulus if the exercise, the movement angle or the load favors them. Coaches and researchers have been arguing about exactly this for years.

Dr. Jose Antonio published a review on the topic in the Journal of Strength and Conditioning Research. His central question was a simple one: why should we look at a muscle as a single uniform piece when it consists of different fibers and regions? If different exercises can activate different segments, growth may also differ from region to region.

• Why couldn’t we treat a muscle as a collection of muscle fibers lying side by side, running from the origin to the insertion?
• Various studies suggest that the exercise and the load used may influence which segments of the muscle are recruited more.
• There is no single best exercise that guarantees maximal growth in every part of a muscle.

Honestly, this sounds quite familiar in the gym. A bodybuilder doesn’t train the chest with just one press or the back with just one row. They change the angle, the grip, the tempo and the repetition range, because the body doesn’t respond to every load in exactly the same way.

How are muscle fibers recruited?

There are different types of muscle fibers inside a muscle. In simplified terms, people talk about slow and fast fibers. Slow muscle fibers, or type I, are endurance fibers. They work well when the effort lasts longer and the force doesn’t need to be maximal.

Fast fibers are divided further. Type IIA is something in between: it has both endurance and speed characteristics. Type IIB is more explosive. These fibers produce a lot of strength and power, for example when lifting a heavy weight or during a very fast, short effort, but they fatigue quickly.

So what actually happens? At low loads, slow fibers do most of the work. When the weight increases or the effort becomes sharp at the end of a set, the nervous system recruits more and more fast fibers. During heavy negatives, fast glycolytic muscle fibers may be preferentially brought into play (7).

This matters because different fibers aren’t neatly lined up in one row in the muscle. They are distributed throughout it. If a particular method loads one fiber type more, the end result may not be completely even growth across the whole muscle. Fast fibers often respond to heavy loads with stronger growth than slow fibers do (1,5).

Muscle shape and training: what should you do?

The practical conclusion is not that every exercise sculpts a muscle like clay. The simple truth: genes set the frame. Training fills that frame as well as it can.

If you want to develop a muscle as completely as possible, don’t get stuck on one favorite exercise. Periodically change your exercises, repetition ranges and loads. In one period heavier work suits you; in another, slightly more volume. In some phases it’s worth emphasizing the controlled negative portion, and in others a cleaner mind-muscle connection and a longer range of motion.

That doesn’t mean flailing around at random. If you change everything every week, it’s hard to tell what is working. It’s better to keep your training stable for a while, track your progress and then make a deliberate change. That way you can load the muscle from several angles while still keeping measurable progress.

An important point from Dr. Antonio’s analysis is this: no strength training method or single intensity guarantees proportional, lasting development in all muscle fibers. That’s why varying repetitions, sets and exercises over time makes sense, rather than being just a passing fad.

FAQ: muscle shape and training

Can muscle shape be completely remodeled?

No. Training doesn’t change attachment points, your skeleton or the basic structure of a muscle. What it can do is build muscle mass, improve proportions and bring out different areas more clearly.

Can a single exercise develop one part of a muscle more than another?

Yes, it can. The angle, weight, range of motion and type of effort in an exercise can influence which fibers and regions receive more training load.

Should I change my exercises every workout?

No. Switching too often makes it hard to track your progress. It makes more sense to change your program in phases, when progress slows or when you want to load the muscle from a different angle.

Translator’s note: the second part confirms even more clearly that different parts of different muscles can be influenced!!!

To be continued…

Translated by Janar Rückenberg

Source:Turg.Fitness.ee

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