Muscle Fibers Calisthenics Exercises Activate and How to Promote Growth

Hi! I am the author and founder of Old School Calisthenic

February 23, 2020

To clearly understand how and why calisthenics exercises promote muscle and strength growth, you have to know what types of muscle fibers they activate. Then matters the training method, duration, volume, intensity and how you organize these bodyweight exercises in a way that suits your goal and stimulates hypertrophy too.

The muscular system consists of three major muscle types:

  1. Cardiac muscles, which are responsible for the function of your heart;
  2. Smooth muscles that sustain the functionality of all other organs;
  3. And skeletal muscles. They move the bones.

Cardiac and smooth muscles function involuntarily and the skeletal muscles, on the other hand, function voluntarily. Therefore, the skeletal muscles are made of:

  1. Type 1 muscle fibers also known as endurance muscle fibers,
  2. Then, Type 2a muscle fibers
  3. And, Type 2b muscle fibers.

They differentiate through color, size, contractual speed and force, and energy source. Calisthenics exercises activate all these types of muscle fibers individually or at once depending on factors such as time under tension, acceleration, speed, volume, intensity, etc.

The Types of Fibers Calisthenics Engage

Exercises That Activate The Type 1 Muscle Fibers

endurance muscle fibers

Type 1 fibers are known as slow-twitch fibers. They are the smallest fibers with a darkish red color and produce a relatively low force when contracted. They use oxygen to produce energy, and therefore, they are very resistant to fatigue and utilized in any aerobic exercise. For this reason, they have endurance capabilities, and we employ them in our extended running or walking sessions, for instance. But also when you ride the bike, do Jumping Jacks and skip the rope steady and for a long time.

In calisthenics, Wall-Sits, Planks, Short Bridges, Bridges, Sit-Ups and any other exercises that are very easy to do and sustain for a long time will use mostly this type of muscle fibers. But,

Most of the Calisthenics Exercises Activate Type 2a and Type 2b Muscle Fibers

They are known as moderate-fast twitch fibers. Their size is intermediate, larger than type 1 fibers, and still red. Type 2a fibers utilize both aerobic and anaerobic metabolisms by using a combination of oxygen and glucose as a source of energy. Yet, they are typically activated during anaerobic exercise that is moderate in duration and intensity.

The type 2a fibers produce fast and strong muscle contractions. They are more prone to fatigue than type 1. Depending on your strength and muscular endurance level, you may engage these types of fibers with almost all the essential, basic, and compound bodyweight exercises: pull-ups, dips, pushups, leg raises, and squats (variations included).

But certain bodyweight variations like explosive Pull-Ups (Clapping Pull-Ups), Towel Pull-Ups, Lever Pull-Ups, One-Arm Pull-Ups, even Weighted Pull-Ups, plyometrics (High Jumps), and One-Arm Pushups, Handstand Pushups, Weighted Dips, One-Leg Squats contract different types of muscle fibers like Type 2B, which are larger than type 2a and function differently.

In general, beginners in bodyweight training don’t need such challenging variations as I mentioned to engage the largest muscle fibers (Type 2b Muscle Fibers) because even dips and regular chinups can contract the type 2B depending on the acceleration as well. That’s why I said it all comes down to fitness!

For me, chinups most definitely activate the slow-twitch muscle fibers and keep it so for a decent time until I get tired and start to utilize the bigger ones too. That only if I do chinups with regular speed. But if I explosively accelerate on the concentric portion, change the grip in the air and abruptly decelerate to move slow on the eccentric portion, then I might engage the whole muscle fibers at once!

How To Activate The Type 2B Muscle Fibers

The Type 2B fibers are not only the largest but also fast-twitch fibers based on anaerobic metabolism. It’s why their color is white, due to a low oxygen capacity! They fatigue rapidly in just dozens of seconds, depending on the workload and speed.

You can successfully contract them with resistance training, by lifting heavy but also with bursts of power that fatigue quickly like sprints, muscle-ups, explosive pull-ups, jumping powerfully. But they contract strongly also when you do the most difficult bodyweight variations mentioned previously. These exercises generate a lot of tension in the muscles and activate these large muscle fibers even if the speed is slow.

I made this video below on my Instagram where I show you the exact bodyweight exercises best utilized to activate Type 2B muscle fibers. Of course, that depends on individual and fitness a lot, but in general, they should rely on the largest fibers making them excellent for strength and muscle gains:

With training, and through physical adaptation, you can turn these fibers into type 2a. They still remain the same fibers, but you can increase oxygen consumption and enhance resistance to reduce fatigue. It makes a lot of sense! As you continuously train, you become stronger, and you increase the size and capacity of your skeletal muscles. And thus, the exercise that once engaged more of the largest muscle fibers will, at some point, utilize more slow-twitch and type 2a fibers. It’s why I became endurant to muscular fatigue and why I can do hundreds of reps in a workout.

So when you ask whether calisthenics exercises are useful for muscle growth, then just remember they engage the whole muscle fibers exactly as lifting weights. Of course, as I also explained a little, it depends a lot on many factors. Through always challenging your muscles, you force them to grow in all aspects from endurance to size, strength, power, etc. It eventually comes down to the training methods and mechanisms (Which Calisthenics Methods Are Best for Muscle Growth?) utilized best for getting a hypertrophy response.

Remember that these muscle fibers have incredibly high levels of glucose in its stored form of glycogen. Therefore, eat your macros and especially the right types of carbs!

Muscles Follow a Specific Recruiting Order

For any activity and exercise, calisthenics or anything else, your muscles follow a specific recruiting order. The type 1 fibers (the endurance type of fibers) are always activated first, and when drained off, then the type 2 muscle fibers get activated. And after these are maxed out as well, type 2b muscle fibers come in to sustain the exertion furthermore.

So that’s actually excellent news for you because what it says is that, through volume training, you can practically train all the muscle fibers.

As a suggestion, I don’t care if you utilize only the hardest variations out there or train progressive calisthenics, you need volume to fatigue and activate all the muscle fibers. It’s that moment when you get a hypertrophy response from your body! To what degree you utilize a type over another is irrelevant because I recommend you to switch from a calisthenics training method to another. From fast reps to slow reps, and so on.

According to Henneman’s size principle, found on Wikipedia:

“The size principle states that as more force is needed, motor units are recruited in a precise order according to the magnitude of their force output, with small units being recruited first, thus exhibiting task-appropriate recruitment. This has two very important physiological benefits. First, it minimizes the amount of fatigue an organism experiences by using fatigue-resistant muscle fibers first and only using fatigable fibers when high forces are needed. Secondly, the relative change in force produced by additional recruitment remains relatively constant. For counterexample, if all motor units produced similar force, then recruiting an additional unit might increase force by 10% when only 10 motor units are active, but produce only 1% increase when 100 are active.”

The reality is that we all inherited a predominant amount of a particular muscle fiber. That’s why we have a predisposition to specific activities. Some individuals are naturally stronger, while others simply can endure running ultra marathons. Nonetheless, through physical adaption and proper training, we can improve in each area we want.

How Can You Grow Muscles Using Calisthenics?

The resolution is that you absolutely can activate the whole skeletal muscles by using calisthenics exercises and that means you can stimulate muscle growth aka hypertrophy. For that muscular and strength adaptation to occur, you need a high stimulus like resistance training, high intensity, muscular energy drain, lactic acid, etc.

That’s why, for instance, running on flat terrain always will not increase the power and size in your legs except promoting cardiac muscle growth and target the slow-twitch fibers for endurance. It’s the same when you do the lightest bodyweight exercises like Wall-Sits, Planks, Wall Pushups, and maybe even Australian Pull-Ups.

But once you add hill sprints and trail running with a lot of elevation gain into your routine, then you have all the muscle fibers engaged. That can grow your legs whilst still benefit from the aspects mentioned earlier. Regarding squats, you need a broader variety from Pistols, to One-Leg Squats, Jumps, Lunges, Croach Walks and even Weighted Squats (place a training partner on your shoulders if you don’t have a barbell).

Pushups, dips, squats, and pull-ups are calisthenics exercises that can promote muscle growth and especially for beginners or to anyone who struggles with them. It is just that many, at some point, consider that calisthenics isn’t generating enough resistance anymore. Then they switch to weighted calisthenics or do hybrid training (lifting weights too). I also reached this level and still train bodyweight and make gains nonetheless.

However, it is true that once you master basic bodyweight training, the less you utilize the largest muscule fibers linked to hypertrophy. As an example, pushups slowly become easy and start to use more endurance fibers. Even so, there are ways around it!

Modify The Exercises To Activate All The Muscle Fibers!

You can modify the exercises to make them tougher and more challenging (you have plenty of variations to your disposal). Or, start to bring in external resistance and do weighted calisthenics too. It’s more of a preference, like choosing Towel Pull-Ups, Lever Pull-Ups, and Uneven Pull-Ups over different Weighted Pull-Ups variations.

I agree that you need higher and higher stimulus and resistance. It’s why I occasionally do weighted calisthenics as well. But that doesn’t mean it’s the only option. I still consider you don’t necessarily need extra weights.

Add Work Volume, Variety, and Train to Muscle Failure!

It doesn’t matter what exercises you use. I still do regular pushups, dips, squats, and chinups. But I add a lot of work volume, and I do it even if I integrate hard variations too like Handstand Pushups. You need to accrue a higher volume even if you do weighted calisthenics. It’s the key to any training method!

That will bring the extra workload and muscle fatigue. Plus, if I take into consideration the Henneman’s size principle, then eventually, you engage all muscle fibers by training to failure. This is what almost everybody missed.

Hence, use all the calisthenics variations you prefer but bring in volume and make it a real challenge. It’s why I consider it very important to continue changing the training methods and mechanisms, from sets and reps to pyramids, ladders, and circuits. It’s tough to adapt when you constantly challenge. In fact, you can keep destroying them by utilizing almost the same exercises all over again with different strategies.

It’s exactly what I’ve done in my training and became muscular and strong at the same time. Then muscle growth is closely connected to recovery and nutrition, but also to your growth hormone. By doing high-intensity short training, you can stimulate the growth hormone.

To ensure this, then, by all means, include sprint intervals and plyometrics. Not only do you take a break from a strenuous and exhausting routine, but also improve in other aspects and get back fresh to your usual calisthenics sessions.

Several extra things generally dictate muscle growth effectiveness in calisthenics as well:

  • One is the number of sets and reps and total work volume I already discussed. The idea is, of course, bringing the volume close enough to fatigue or failure because it’s when you entirely use all the muscle fibers.
  • Another crucial aspect is speed. You can often see me performing explosively on the concentric part and moving slower on the negative portion. Fast reps simultaneously recruit all the muscle fibers at once, more so if it generates a lot of tension in the muscles, which is essential for muscle growth stimulation. So if you sprint on flat, uphill, or do pull-ups, then accelerate powerfully and decelerate strongly, or move slowly on the negative (eccentric) part.

The higher the force is, the more muscle fibers you recruit. Slower reps eventually use the whole fibers, but they mainly utilize type 1, which isn’t related to muscle growth so much as the others. You get the point! Nonetheless, the most crucial aspect, more important than speed, is definitely muscle fatigue.

Slow negatives are especially useful because you are stronger in that range. That’s why a beginner can utilize slow eccentric moves to strengthen and grow the muscles. It adds to total work volume and fatigues them eventually, making them very sore the next day. An advanced athlete can utilize slow negatives for adding more workload once he can’t go on the concentric move anymore. Or use them for finishing sets, whereas a beginner can do an entire workout upon them. It is associated with making gains. Just think about it. It’s still tension generated in the muscles instead of letting your weight fall down exactly as gravity pulls.

Moreover, controlling the negative part can help improve form and prevent injuries. Your joints will stay protected throughout the whole range of motion and ready you to power up on the concentric if you will and can.

It wasn’t my intention to overcomplicate things for you. I believe I helped oversimplify to understand better how calisthenics exercises work for muscle development. Whatever is that you did wrong until now, I hope that my explanations and experience help you make better decisions over your training. I wish you good luck with your calisthenics journey!

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