Why muscles aren’t equal in strength

Muscles can look big in the mirror, but under the bar or in a jump the picture may no longer hold up. This article explains why muscle mass and real strength don’t always grow hand in hand, and how sarcoplasmic and myofibrillar hypertrophy change the outcome of your training.

From the translator: the idea below belongs among those texts that are worth reading whether you are a beginner or a coach. Honestly, this topic is right in front of our eyes in the gym all the time: one guy looks like Tarzan, but the weights he lifts would suit Jane better; another is smaller yet moves impressive weights.

Why do muscles look alike but work differently?

Genetics plays a part in strength and muscle shape. That shouldn’t be glossed over. Still, much of the difference comes from how a person trains in the gym. Two athletes can have a similar body weight, muscularity and build, yet their training methods can be completely different.

A simple truth: muscle growth can be triggered in more than one way. Structurally, the growth of a muscle or muscle fiber can come from two main components. In one case, the fluid, nutrient-rich environment of the muscle cell expands more. In the other, it is mainly the part that actually produces the contraction that grows.

This is exactly what helps explain why some gym-goers look very impressive but are neither explosive nor particularly strong. Others may not look like a stage bodybuilder, yet their squat, row, throw or jump tells a different story. This is where two terms come in: sarcoplasmic hypertrophy and myofibrillar hypertrophy.

Muscles and sarcoplasmic hypertrophy

Sarcoplasmic hypertrophy means that a muscle cell gets bigger mainly because the volume of sarcoplasm increases. Sarcoplasm is the inner environment of the muscle fiber, containing water, nutrients and organelles. The original text states that sarcoplasm makes up approx. 25–30% of muscle fiber size. The exact interpretation may depend on whether you are talking about mass or volume, but the point stays the same: this part is not the direct contractile apparatus.

With this kind of hypertrophy, the cross-section of the muscle grows, but the density of muscle fibers per same area may decrease. Strength numbers may improve, but usually not as sharply as size. In the cited sources it is linked above all to bodybuilding-style training with longer sets (2, 3).

Translator’s note: if you do sets of, say, 8–12 or 8–15 reps, it is often this “watery” part of the muscle fiber that grows. What matters is not only the rep count but also the time under tension. Different texts give 30–70 seconds as a favorable set duration for sarcoplasmic hypertrophy, with 45 seconds on average.

So what actually happens? A long set taxes the muscle metabolically. The muscle uses up glycogen and other substances, plenty of waste products build up, and the blood has to work harder to deliver oxygen and nutrients. During recovery, the muscle starts refilling what was spent. If, figuratively, the quadriceps held 15 g of glycogen and training used it up, then with good nutrition and recovery the muscle may store 17 g of glycogen back. This is an illustrative example, not an exact recipe.

Carbohydrates bind water in the muscle at a ratio of 1:3. So the amount of glycogen rises, along with it the amount of water, and gradually the rest of the cell’s internal reserves too. The capillary network may also improve, because long sets demand more metabolic support. Lysosomes, mitochondria and other organelles are at work in any case, but long sets demand a great deal from them.

How does myofibrillar hypertrophy build strength?

Myofibrillar hypertrophy means that the number and size of myofibrils in the muscle fiber increase. These are tiny protein filaments that run along the length of the muscle and give it the ability to contract. As their density grows, the muscle can become stronger, faster and more explosive (2).

This type of growth is best stimulated by strength training with heavy weights and short sets (3). Think about sport for a moment. The average discus throw lasts 3 seconds. A 1-rep max attempt also lasts about 3 seconds. A swing of a baseball bat takes less than 1 second. A jump to grab a rebound in basketball takes about 1 second as well.

Most such movements don’t call for a big, burning pump, but for strength, speed and good coordination from the nervous system. That is why soccer players, baseball players, basketball players, sprinters, jumpers, wrestlers, powerlifters, throwers and shot putters should also include maximal strength development in their training. Here we are talking about a rep range of 1–5 and weights of 85–100%.

Heavy weights train not only the muscle but also the nervous system. The nerve impulse reaches the muscle better, motor units learn to work more simultaneously, and more muscle fibers are recruited. At the same time, the inhibitory effect of protective mechanisms such as the Golgi tendon organ may decrease (1). This is why heavy strength training adds more to performance in many sports than muscle circumference alone.

The original text also stressed that this kind of training affects especially the fast, high-threshold type II B fibers. Bodybuilding-style work may grow type I and II A fibers and sarcoplasm volume more. Both have their place, but your goal determines which should come first in your program.

The practical choice: muscles, strength and set length

If your goal is mainly appearance and muscle fullness, longer sets have clear value. 10–15 reps can give you good volume, a strong pump and the work needed to maintain muscle mass. For an American football defensive player, for example, extra body weight and mass can be useful, because an opponent can’t push them out of the way as easily.

If your goal is a faster sprint, a better jump, a stronger pull or an explosive throw, the whole program can’t stop at a “pleasant burn”. Long sets of leg presses or leg extensions can leave the thigh pumped full, but they won’t transfer to performance the way heavy squats, deadlifts, cleans or presses do.

That doesn’t mean one method is good and the other bad. Sensible training uses both. The question is one of proportion. Many athletes fall too easily into the trap of the traditional 3 x 10 scheme. It’s simple, familiar and tiring, but not every sport mainly calls for that kind of fatigue.

A coach’s job is to look at what the athlete actually needs. More mass? More maximal strength? Better explosiveness? Or all of it, but in different periods? In that case the program has to be built so that long and short sets serve the goal, rather than simply filling in a table.

FAQ: muscles and hypertrophy

Do big muscles always mean great strength?

Not always. A large muscle may have grown more through sarcoplasmic volume, which adds to its look and size but doesn’t necessarily translate into the same amount of explosive strength.

So is 8–12 reps a bad choice?

No. 8–12 reps works well for building muscle mass and size. If your goal is maximal strength or power, your program also needs shorter sets and heavier weights.

Why is myofibrillar hypertrophy called functional?

Because it builds up more of the muscle’s contractile part. That helps the muscle work more forcefully and quickly, which matters in jumping, sprinting, throwing, lifting and other explosive sports.

References

1. Poliquin, Charles. Modern Trends in Strength Training. Volume 1. QFAC Bodybuilding, 2001.

2. Siff, Mel C. and Yuri V. Verkhoshansky. Supertraining. Colorado: Denver, 1999.

3. Tsatsouline, Pavel. Power to the People. Dragon Door Publications, Inc., 2000.

“Why all muscle was not created equal” Joe DeFranco

Translated and compiled by Janar Rückenberg

Source:Turg.Fitness.ee

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