Most of us at some point have probably wondered what it would be like to have bigger muscles. And some have worked to turn that wonder into a reality as there are people that have developed incredible increases in the size of their muscles. But what is actually going on when you increase the size of a muscle? And what are some important training principles to stimulate muscle growth? Well, today we're going to discuss these training principles and for even more fun, we're going to dive into the physiology of muscle and talk about some of the characteristics of muscle tissue.
that allows for these amazing size and strength increases. Plus, we'll discuss if there's an actual difference between increasing strength versus increasing the size of a muscle. It's going to be a hypertrophic one.
So, let's do this. As we get into this discussion about increasing muscular size, did you know there are actually three different types of muscle tissue in the human body? And I'm not talking about fiber types here like fast twitch or slow twitch, I'm talking about actual different types of muscle tissue.
And I think going over these different types of muscle tissue will give us an even greater understanding on not only how we increase muscular size, but also what's going on at the cellular level. Plus, it's just really cool to know the differences in muscle tissue. Now, as we talk about the muscles, I do want to say that often you hear the phrase muscle fibers.
And these are actually the muscle cells that make up the whole muscle. Like the biceps is made up of thousands and thousands of muscle cells. But just know that if I ever say muscle cells or muscle fibers, I'm talking about the same thing. But on to the different types of muscle tissue.
And these are non-striated or smooth muscle, striated cardiac muscle, and striated skeletal muscle. Striated refers to this stripe-like pattern, these dark and light alternating bands that can be seen under the microscope. But from here on out, we'll just simply refer to them as smooth, cardiac, and skeletal muscle tissue. Now all three of these different types of muscle tissue have this amazing ability to contract, but they also have some major differences like where you find it in the body, how it's hooked up to the nervous system, differences in architecture and structure, and of course differences in how muscle tissue grows and gets bigger and stronger. With smooth muscle tissue, the muscle cells are smaller and have this spindle-like appearance and you find smooth muscle lining the walls of your organs.
I often will tell students if it's a tube or a hollow structure, It's likely going to have smooth muscle built into the wall. Now, that may sound a little bit funny at first, but we have a lot of tubes inside of us. Our digestive tract is a tube. We have respiratory tubes, blood vessels, urinary tubes, and many genital structures are tubes. And all these have smooth muscle built into the wall that will contract to move along and or influence the flow of what's ever inside the tube.
Now, smooth muscle is under involuntary control. It can work reflexively and is controlled by your autonomic nervous system. So luckily... You don't have to think about it, but could you imagine if you did have to think about contracting all the smooth muscle in your body?
Like if you ate a cookie, you might have to pause, stop what you're doing, and think about contracting the muscles of the digestive tract and maybe even include some shimmy shake maneuver to move that nutritious cookie around one of the bends of your jejunum. And your intestines are over 20 feet long, so that would be quite the distraction during your already busy day. But luckily, you don't have to do that because your autonomic nervous system does this for you automatically. But I do think that we should be grateful or at least have a moment of silence or a moment of gratitude that the very, very beginning and the very, very end of your digestive tract is skeletal muscle, which is under voluntary control. I mean, could you imagine if your external anal sphincter was smooth muscle and it just opened and closed whenever it wanted to?
That would be a disaster, literally. And here's a little quiz question for you. Do you know what the largest smooth muscle mass is in the human body? Here's a little hint. I don't have it.
It's actually the uterus. Now, I grew up with three sisters, and they definitely had some very interesting ways to describe how the smooth muscle making up the uterus was not under voluntary control during menstrual cramping. This thing just contracts however and whenever it wants to, right? And I shouldn't laugh because I can't really experience that, but...
Even during labor, it's involuntary contracting. So as another FYI, when everybody in the delivery room is saying, okay, give me a push, it's not like mom has the ability to contract the uterus during labor more forcefully. Mom is actually contracting the abdominal muscles, which will increase the intra-abdominal pressure, which will assist the uterus in pushing a baby out.
But one last point I wanna make about smooth muscle, and we can also relate this to skeletal muscle growth. And this is that smooth muscle, can also grow and get larger and it does this through a process called hyperplasia which is an increase in the number of cells and keep that in mind when we talk about cardiac and skeletal muscle. There's going to be an important difference there. And so, think about the uterus again.
When pregnancy occurs, the uterus goes through dramatic changes and gets huge. And part of the reason for this is that the smooth muscle cells will divide and therefore increase the overall number of smooth muscle cells making the uterus bigger. Plus, those smooth muscle cells can also just get larger, which when a cell gets larger, we call that hypertrophy. So, two processes can contribute to the overall increase in size of the smooth muscle, hyperplasia, and hypertrophy. But let's see how this works with the heart and skeletal muscle tissue.
Cardiac muscle tissue, as the name implies, is only going to be found in the heart. And under the microscope, these cells are longer and larger than smooth muscle cells. And the cardiac muscle cells branch, which we'll see is different than the skeletal muscle cells.
Now obviously, these cardiac muscle cells will contract and make the heartbeat pumping the blood throughout the body. And as you may have guessed, cardiac muscle tissue is under involuntary control. It has its own built-in pacemaker.
and it is also hooked up to the autonomic nervous system. Now, I have had some students occasionally argue the point that their cardiac muscle tissue is voluntary for some reason. And then I usually look them in the eye and I say something like, make your heart beat at 52 beats per minute now. Go.
We don't have that kind of direct control over our heart. We obviously know that our heart rate will increase if we go running down the street, or if we relax and do deep breathing, generally our heart rate will go down. But again, this is not a direct...
precise control over our heart rate. Now something that I hinted to earlier that is important for us to consider with cardiac muscle is that cardiac muscle cells cannot divide and that's different than what we learned with smooth muscle. And let's think about this from two different perspectives, from a clinical perspective and an exercise perspective. From a clinical perspective, if you kill any of those cardiac muscle cells, you can't really replace them and that's why something like a heart attack, also known as a myocardial infarction, can be so detrimental.
If you have a heart attack that kills a lot of these cardiac muscle cells, they get replaced with scar tissue and then the heart will not be able to contract as efficiently as it did before. But from an exercise perspective, if the cardiac muscle cells can't divide, how does the heart get stronger? Well, let's answer that question and keep it in the back of our minds after we get into a little bit more detail with skeletal muscle tissue.
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Skeletal muscle tissue, as its name implies, attaches to and moves the skeleton. There are a few exceptions to this, like the muscles of facial expression actually attach to and move your facial skin so you can show emotions and make all sorts of funny faces and expressions of people. The skeletal muscle is what we typically think about when we are working out and increasing the size of our muscles, mostly through resistance training.
Skeletal muscles are under voluntary control, and for the most part, we can contract them whenever we want to. But again, here's something that's very important. Similar to cardiac muscle cells, skeletal muscle cells cannot divide.
Now, for all the physiology nerds out there, I do need to mention satellite cells. Satellite cells are these small stem cells embedded between the larger, mature... non-dividing skeletal muscle cells.
But these satellite cells retain the capacity to fuse with one another or with damaged skeletal muscle cells that can help regenerate. these damaged muscle cells. However, the number of new skeletal muscle cells that can be formed by satellite cells is not enough to compensate for significant skeletal muscle damage or degeneration. And so, skeletal muscle tissue that has been damaged significantly will still be replaced by scar tissue. And therefore, any regeneration of skeletal muscle tissue is greatly limited.
So again, with mature skeletal muscle cells not being able to divide and the limitations we just discussed with these satellite cells, How do our skeletal muscles get bigger and stronger? Well, you've probably seen this coming and hopefully you learned some cool stuff along the way, but the skeletal muscle cells that you already have just get bigger. And when cells get bigger, as we've already mentioned, we call this hypertrophy. And even though we're going to focus the remainder of our discussion on skeletal muscles and talk about what's actually going on during hypertrophy, I do want to just mention that this is also how cardiac muscle gets bigger and stronger.
The cardiac muscle cells that you do have just get bigger and they undergo hypertrophy as well. But what exactly happens when our skeletal muscle fibers or skeletal muscle cells undergo hypertrophy? Hypertrophy is due to an increased production of the contractile protein units within a skeletal muscle cell.
Maybe you've heard of these contractile units before, like myofibrils and sarcomeres. And we have a video coming soon going into the amazing details of the myofibrils and sarcomeres. But for today, know that these myofibrils and the sarcomeres within them generate the force inside the skeletal muscle cell.
And the increased production of these units is one of the major contributors to the muscle cell getting bigger. But other changes also contribute to hypertrophy, such as the development of more mitochondria and other organelles within the muscle cell. For example, the sarcoplasmic reticulum, which is a modified smooth endoplasmic reticulum that stores calcium within the muscle cell.
And as an FYI, calcium is extremely important for muscle cell contractions. Increased fluid content within the muscle cell can also contribute to hypertrophy and we're going to discuss that in a little bit more detail in just a minute. But hypertrophy results or is stimulated I should say from forceful repetitive muscular activity which is often done through resistance training and because hypertrophied muscles often contain more myofibrils and therefore sarcomeres, in general a larger muscle with a greater cross-sectional area is capable of producing more force or in other words is stronger. But obviously an important part of this video is what exactly is meant by forceful repetitive muscular contractions?
What does this mean for the specifics of an exercise routine? Well, this does depend a little bit on the person because for example almost anyone that is just starting with resistance training and lifts relatively heavy weights will increase strength and muscular size with a variety of different rep and set schemes. But as people get more advanced you start to diverge more into is your main goal strength or is your main goal.
hypertrophy because as you get more advanced you will start to train a bit differently for those two goals and you start to get more into power lifting routines versus bodybuilding routine. In general, those that have strength as the main goal follow more of a power lifting routine and the lifts tend to be higher in intensity so a higher percentage of a person's one rep max. These would be loads or weights that someone may only be able to lift one to five times and because of the higher intensity The rest period is typically longer with people resting about three minutes, sometimes even up to five minutes in between sets.
They also tend to make compound exercises, the staple of their routines, and often don't include a lot of isolation exercises. And just to be clear, a compound exercise would involve multiple joints and multiple muscle groups like a squat or a bench press, whereas an isolation exercise would typically involve one muscle group and one joint like a biceps curl. Now for those that are more concerned with hypertrophy, you start to follow more of a bodybuilding routine.
Compound exercises are often a part of this routine but they tend to do a greater amount of isolation movements than those that are more concerned purely with strength. And if hypertrophy is the main goal, then there obviously is some interest in how the muscles look aesthetically. And so these isolation movements can allow for more specific targeting of certain muscles to really get that balanced look in physique.
And in general, the loads are a lower percentage of a one rep max compared to that which power lifters use. This doesn't mean the routines are easy. The weights are still somewhat heavy, but with higher reps. Common rep numbers would be something they could lift 8 to 15 times. There are routines that work for hypertrophy and bodybuilding that can have higher reps and even sometimes lower, but in general that 8 to 15 is a good place to start. And due to the weight of each lift generally being lower than in power lifting.
The rest periods are often shorter from about 60 to 90 seconds and the overall lifting volume per session and even throughout the week is typically higher and this training strategy tends to be a greater stimulus for hypertrophy more so than strength. You might be thinking, wait a minute Jonathan, you told us earlier that a big part of what causes hypertrophy is an increase in the production of the contractile protein subunits within a skeletal muscle. So isn't a bigger muscle a stronger muscle?
Well, in general, yes. But again, as you get more and more advanced, you start to see more of a divergence between strength-based routines versus hypertrophy-based routines. And therefore, this results in differences in the main physiological adaptations that occur. Now clearly, these two adaptations, strength versus hypertrophy, don't exist completely in their own little bubbles because if you look at powerlifters whose main goal is strength, they obviously have large muscles and if you look at bodybuilders whose main goal is muscular size and hypertrophy, they obviously are still quite strong.
So in a way, all we are seeing is a greater manifestation of one of these two adaptations. If you're mostly concerned with strength and you are following more of a powerlifting routine, you're going to get a greater manifestation. or development of more of those contractile protein units, the myofibrils and the sarcomeres, which as we already learned are what produces the force within the muscle cell.
Plus, there's a major contribution from the nervous system. The nervous system will get better at coordination and recruitment of more motor units with strength-based training, and therefore this nervous system adaptation is going to be something else that contributes to the greater strength that you can see in power lifters. If you're more concerned with hypertrophy, and following more of a bodybuilding routine, yes, you are going to get increases in the contractile protein units.
But part of that increase in size is theorized to come from an increase in the fluid content within the muscle cells. And this is referred to as sarcoplasmic hypertrophy, which is kind of this disproportionate increase of the sarcoplasmic fluid compared to the increase in the number of myofibrils, giving us a theory as to why people may not see a proportional increase in strength. with their increases in muscular size as they get more advanced in their bodybuilding routines.
Now just to be clear, the sarcoplasm is just the cytoplasm or the inside fluid containing area of a muscle cell and again increasing the fluid within the sarcoplasm will give an overall increase in the size of the muscle cell. Now as I've hinted, we don't exactly know all the reasons why this sarcoplasmic adaptation occurs but we do see the differences between bodybuilders and the power lifters. So hopefully more answers to come with further research in the future. But hopefully this did give you some useful information about the basics of different training methodologies of strength versus hypertrophy and hopefully you enjoyed learning more about the different types of muscle tissue found in your body.
And if you're interested in learning more about muscles as we age, we'll link some videos on screen here. And thanks for supporting the channel. Let me know what muscle tissue you think is the coolest in the comments and we'll see you soon.