Because calisthenics skills often put your body in complex positions it sometimes might be confusing to tell which muscles are used in particular ones. I’ve noticed that there’s a lot of misconceptions around this topic. Does back lever uses your back or your abs? What about front lever? In this video I’m gonna answer those questions, but also explain the principles that say why it’s that way. So let’s dive into the mechanics of calisthenics. First, we need to cover the basics of kinetics of human body. Why does my arm move? We can look at it as a set of joints and muscles. Joints allow movement in certain directions and muscles are what makes the arm move by contracting. When you contract your muscle, it gets shorter and pulls the part that is behind the joint. This is the most important information here: the muscle can only pull, it cannot push. So when I want to bend my arm this way, it is my biceps that gets shorter and it pulls the forearm up. When I rotate the arm and extend it this way, now the triceps is doing the work of pulling and the forearm goes up. The same rules apply when you move your whole body, but instead of one particular muscle, the whole chain of them contracts to perform a specific action. If you want to do a hollow body hold, your abs, quads and hip muscles work in unison by getting shorter and thus lifting your shoulders and legs above the ground. Sometimes it may be difficult to see which muscles are contracted, especially when we’re talking about static holds. In these situations muscles are not getting shorter or longer, because there is no movement. However, by representing the body using simple schematics of segments connected by joints and applying some simplified forces, we can easily conclude which part of the body is being stretched. And this is what we’re interested in, because it means that this part of the body is counteracting the stretching by contracting the muscles and thus training them. Just like in that dragon flag example – the weight of the body forces it to bend, granted that you hold tightly with your arms and shoulders, so it provides sufficient support. So, to keep it straight you need to contract your abs and quads. Let’s now move to real life examples and I’m gonna start with front lever. I am using a resistance band here, but let’s pretend that it’s not there for a moment. The schematics of this position look like that. The joint that gets the most stress in this case is your shoulders, so you need to push down with your hands to stop the body from going down. This is accomplished by your triceps, rear deltoid, lats and other minor back muscles in this area. But if you were to use only those, your front lever would look like this. To keep the rest of your body horizontal you need to contract your abs and quads. Those muscles are used to counteract the gravitation and they do most of the work, but it doesn’t mean that the rest of the muscles in your body is limp. When holding positions like front lever, we usually flex most of the muscles in our body, because it helps with stabilization and generally the more muscles we flex, the more power can our body generate. But this is more like passive flexing when the muscle is not loaded in any way. Just like when you flex your abs for the picture. I’ve heard some people saying that they feel their chest after training front lever. This can happen when you passively contract it hard. It may also happen when instead of pushing precisely down with your hands, you also try to bring them toghether. This make you use chest muscles, but is not necessary to hold the position. Now, let’s adress the resistance band and use this position to show what I think is the best way of using bands to learn skills and why is that. When you want to lift up a horizontally placed stick on one finger without it changing it’s orientation, where would you place it? Naturally in the middle of the stick, because that’s where its center of mass is. The same thinking should be applied when using resistance bands. If you want it to help you without forcing you to change position in any way it needs to lift you upwards in the center of your mass. Center of mass of your body in that position is somewhere between your belly button and your crotch, so this is the optimal placement of the resistance band. An alternative method, that I saw people use, would be putting your feet in the loop. Here, you can see that the force from the band that is supposed to help you hold the position isn’t facing upwards and isn’t applied at the center of your mass. When I decompose that force into components you can see that one is lifting you upwards, but the other one is pushing backwards changing the position slighly. Plus when that upward force is applied at your feet it takes away some of the load from your abs. To see that clearly, I can show you another example. I placed my shoulders on a support, but this is the same thing that you’re trying to do with your arms in a front lever provide a support for the rest of the body. When my feet is in the air, just like in front lever, the top of my body is under stress. But when I put my feet on a support it all changes. Now what keeps my hips from going down is my lower back. Here, you can see how stress function changes. Of course the resistance band doesn’t provide the same support, it just applies a force there, but if that force is big enough, the effect is essentially the same – transfering the stress from the abs to lower back. So if you want to get the most genuine feel of holding the position, then use the band on your lower back. Of course I’m not saying you cannot learn front lever using the resistance band on your feet, I’m just saying that it changes the mechanics of the position slightly and may not be the an optimal way of doing that. Planche hold is pretty much the exact mirror reflection of front lever, so it uses the opposite muscle groups. Again I have to use a band to show you anything, but let’s pretend that it’s not there. The most loaded joint here is the shoulder joint and the muscles used to hold the position are mainly your front deltoids, but also trapezius and chest muscles. What keeps the rest of your body horizontal is your lower back and butt muscles. Squeezing your abs will definitely help you to hold the position, but those muscles only play supporting and stabilizing role, as they’re not directly loaded. One additional joint that is stressted here is the wrist, so the muscles in your forearms are also being used heavily. Next, let’s look at the human flag starting with your arms. Ideally, both your arms should be straight and that means that there’s not a lot of movement involved. The range of motion of a straight arm is rather limited and comes from the scapula. When holding the flag, the upper arm is pulled out of the shoulder joint whereas the bottom one is pushed in. So to counteract those forces you need to pull with your upper scapula and push with the bottom one. Figuring out how to do that might be difficult, especially in the beginning, so it’s worth it to practice the moves separately. First – pulling. You need to grab the bar with one hand and pull yourself up without bending the elbow. This is called scapular pull up. You can use your other hand to help yourself, but eventually you need to be able to do it with one arm. ou can see how my scapula is going up and down in relation to my head or the other scapula. The second exercise, that helps you practice pushing straight arm is an exact opposite of scapular pull up. You need to get to a handstand, get on one hand and push away from the ground as much as you can and then go down by relaxing the muscles. Those two actions are necessary to hold the flag properly – pulling with the upper arm and pushing with the bottom one. If you see someone bending an elbow of their upper arm, it’s because their scapula isn’t strong enough and they cheat the move by pulling with the biceps. As for the rest of the body, you need to contract the muscles on the side of your waist, that is facing up. The side of your abs is doing most of the work to keep here. So to conclude, your shoulders, back muscles that hold your scapulas and obliques are doing the hardest work in human flag. And lastly, back lever which is very similar to planche as far as used muscle groups go. The schematics of this position are the same as for the front lever, so the shoulder joint does the most work here. This time, however, you pull down with your chest facing the ground, so you use front parts of the deltoid muscles, your chest and biceps. As for the rest of the body, now instead of the abs you need to contract your lower back, butt muscles and glutes. And again, squeezing your abs does help with stabilizing the body, but those muscles do not take part in supporting your body weight in that position. All the previous exercises that included grabbing a bar require you to use the forearm muscles as well. I didn’t want to repeat myself everytime, so I just mention it here. When you want to clench your fist, the muscles in your forearm contract to pull the tendons in your fingers. When you require those fingers to hold your entire bodyweight, those muscles need to work very hard to keep the fingers from straightening. I hope I didn’t complicate the topic too much, but my main goal here was to explain why this or that muscle is used. I can’t cover every single position here, but when you understand those simple rules, hopefully, you will be able to answer your own questions for other calisthenics skills. Hope you liked this video, leave a thumb up if you did and I will see you in the next one.