This next lesson will cover chapter 5 - using resistance training to improve your muscular strength and muscular endurance
This next lesson will cover Chapter 5, using resistance training to improve your muscular strength and muscular endurance. After this lesson you should be able to identify the benefits of muscular strength and endurance, understand the basic structure of muscles and the mechanics of a contraction or a muscular contraction. You should also know how we measure strength, and be able to apply the FITT formula, just like we did in the last lesson, but this time to develop a resistance training program instead of a cardiovascular endurance program.
Remember that participating in muscle strengthening activities on two or more days of the week is part of the physical activity recommendations for health for the general health of the adults in our country.
Before we talk about the anatomy of muscles and the benefits of having muscular fitness, let's review very quickly the definitions between muscular strength and muscular endurance. You'll remember that each of these is a component of health-related fitness, and muscular strength really deals with the ability of a muscle to exert a single maximum effort, compared to muscular endurance where the muscle or muscle group is asked to exert a repeated force against a resistance or sustain a muscular contraction for a longer period of time. So muscular strength, you can think about lifting something, one time, something as heavy as you can. Muscular endurance would be doing repeated efforts of that muscular endurance. Muscular endurance, again, be careful not to confuse that with cardiorespiratory fitness; that's a different concept altogether. Muscular endurance, for example, would be doing a sit-up test for a minute to see how many sit-ups you could do.
There's so many benefits of having both muscular strength and muscular endurance, and we'll talk about just a few of those here. Imagine your daily life, and think about how many times throughout the course of a day that muscular strength or muscular endurance would be useful for everyday tasks. Some examples here are if you're moving furniture, so say, for example say you're vacuuming your living room and you're doing a really thorough job, you want to move the couch forward to vacuum behind it; that involves some muscular strength and/or endurance. Moving, if you're talking about moving your whole house or apartment, obviously there's some muscular strength or endurance incorporated there. Lots of other examples where muscular fitness is important throughout our everyday life; you could think of many more examples. In addition to being useful for those tasks, helping you do those tasks more efficiently, participation in everyday activities is often easier when you have greater levels of muscular strength or endurance. So moving that couch forwards causes less physical stress on your body if you have greater levels of muscular strength and endurance. Another benefit is that we have improved physical performance in sport or physical activity, so you can think of many examples in sport where being stronger both from muscular strength or having more muscular endurance would be very important and helpful. The muscles are also very important for the integrity of our joints. In particular, you can think about low back pain, often that's caused by some muscle weakness, and so protection from injury is another benefit of having muscular strength and endurance. Increased metabolic rate: your body uses more energy at rest if you have more muscle, so that's a great benefit of having increased muscular strength and endurance. Maintenance of bone mineral density: having that weight-bearing exercise is very important for bone health, and we'll talk about that in a later lesson throughout this course. And finally, muscle tone often makes us look better and feel better about our bodies, so improved body image is the last benefit of muscular strength and endurance that you see on the slide there.
Pictured here are all the major muscle groups of the body. If you think it looks like a lot of muscles, it is. We have more than 600 individual muscles in our body, and although you're not responsible for knowing the muscle anatomy in this class, knowing that anatomy and knowing the different muscle groups and how they work together is very important for developing a resistance training program in the future. So that may be something that you want to get to know in the future, but again, you're not responsible for knowing all of these muscle groups or individual muscles for this class.
Here you can see a very stylized picture of the parts of the muscular system that allow us to move, and what I want you to notice is that the skeletal muscle is receiving a signal from the brain via a motor nerve, and that's because these muscles are voluntary muscles, meaning we are required to send a signal from the brain to activate the muscle. And this is very different from the muscles in your heart that we talked about during the last lesson that contract involuntarily, or without you even thinking about it. So that's a major difference between these muscles that we're talking about here and the cardiac muscles that we talked about in the last lesson. You should also notice in this picture that there's a tendon—in this case we're looking at the biceps tendon—that connects the biceps muscle to the bones of your lower arm. When the muscle contracts, the tendon exerts force on the bone and you get the bicep curl movement.
Now we're taking a look inside the muscle, the skeletal muscle, and here you can see the important parts of the skeletal muscle that are involved in muscular contraction, and you'll notice that the actual skeletal muscle is made up of bundles of muscle fibers, and on the next slide we'll see a close-up of the muscle fiber components that are involved specifically in contraction.
This picture shows the inside of a single muscle fiber. Click on the link below and watch the video about how the actin and myosin, which are parts inside that individual muscle fiber or the skeletal muscle, work together to create a contraction. This video is very detailed, and it gives you an interactive way to see how the actin and myosin actively work together within this one single muscle fiber to produce shortening or contraction of the muscle. (http://www.interactive-biology.com/2012/an-introduction-to-skeletal-muscle-contraction/)
There are two broad categories of muscle fiber types in our bodies. The first is slow twitch and the second is fast twitch. The percentage of each in the muscles is mostly determined by genetics, and the average person has about 50/50, so about half slow twitch and half fast twitch. The slow twitch are fibers that are good for low-intensity aerobic activity, and even moderate-intensity aerobic activity, activity that requires the body to continually contract the muscles, and these slow twitch fibers are slower to contract, but they have a very high resistance to fatigue, meaning they can contract over and over again without fatigue, compared with the fast twitch fibers that are able to contract much more quickly, but also fatigue much more quickly. And so these fast twitch fibers are using glycogen and not oxygen for energy to fuel that contraction, whereas the slow twitch fibers are storing oxygen and using that oxygen to produce the movement. Importantly, slow twitch and fast twitch fibers are not mutually exclusive, so just like we talked about in cardiorespiratory activities or aerobic activities, that sometimes we use anaerobic systems of energy as well, especially at the beginning of aerobic activities. Fast twitch and slow twitch fibers are not mutually exclusive; both types work together to produce muscular movement.
We have two, our muscles have two basic types of muscle actions. The first one is concentric, or shortening of the muscle, and the second is eccentric, or lengthening of the muscle. So if you look at the picture above, the book is providing the resistance here, and you can think about this as a bicep curl movement. In the picture on the top left, the book is being lifted up towards the shoulder. As the person does that, you see that the biceps muscle is getting shorter, so we're going to call that a concentric contraction. In the picture on the bottom right, again the book is the resistance here, and the person is lowering the book down towards their leg or towards the floor, and you can see that the biceps muscle is getting longer and it's doing an eccentric contraction where it's lengthening the muscle. So concentric is shortening, eccentric is lengthening of the muscle. And although it isn't pictured here, you should also know that most of our muscles work together in pairs. In this case, the triceps muscle is not pictured, but the triceps and biceps work together as a pair. In the picture on the left, the biceps muscles are contracting and the triceps muscle is resisting that movement. We call the contracting muscle, in this case the biceps, the prime mover or the agonist. The muscle that resists the movement is called the antagonist; in this case that's the triceps muscle.
Before we move into the last section of this lecture where we talk about how to improve both muscular strength and muscular endurance, there are two terms that it's important to be familiar with. The first is hypertrophy, and here we're talking about the increase in muscle size as a result of training, so your muscles getting bigger, and this is really a result of increased size of the muscle fibers themselves. The second definition, or word, that you should be familiar with is atrophy, and here we're talking about shrinking of the muscles. Usually it comes from a lack of use of the muscle, and one of the most common times you see this is if someone breaks their arm or their leg and it has to be put in a cast; when you take that cast off, the leg is much smaller, or the arm, the casted body part is much smaller because of atrophy, because of the shrinking of those muscles. So this gives us just a good foundation to start talking about developing muscular strength and muscular endurance.
On this slide we'll talk about four factors that contribute to both muscle strength and muscle size. The first two, exercise and diet, are under our control, but the second two, genetics and hormones, are not something that we can control. Exercise, if you remember the principle of overload, if you participate in resistance training activities, or muscular strengthening activities that make the muscles do more work than they're accustomed to, that develops muscle strength and muscle size. And again, that really goes back to the principle of overload from week 1. Diet is another factor that can contribute to muscle strength and muscle size. Just like we need energy to participate in cardiovascular or aerobic activities, we also need energy to build up our muscles, and a common myth is that you need to increase your protein intake above the recommended daily levels in order to build more muscle, and that simply isn't true. It's not necessary to increase your protein levels above the recommended daily levels to build muscle, but you do need to make sure that you have a balanced diet of carbohydrates, proteins and fats, because that all allows the muscles energy to build and work efficiently. And so the last two are genetics and hormones. Our genetics determine our somatotype, or the shape of our body, and you should be familiar with the three different types of shapes, body shapes that are identified in your textbook: mesomorphs, ectomorphs and endomorphs. The mesomorphs are the body types that find it the easiest, or relatively easy, to build muscle. And finally, the levels of testosterone and androgens in your body determine how easy it will be for you to put on muscle, and so that's why some people seem to go to the gym and lift a couple weeks and they start to show signs of improvement, whereas others may lift for months and months and not be able to build the same amount of muscle. So certainly there are multiple different factors included, partially determined by things we can control such as exercise and diet, but partially controlled by things like genetics and hormones that are out of our hands.
When we want to improve our muscular strength or muscular endurance, there are multiple types of resistance training that we can use. The first is static or isometric exercise, and here we're talking about muscular actions when the length of the muscle doesn't change and there's no visible movement. So in the picture on the left you see the gentleman character pressing out against the walls, but the walls are not going to move, his arms are not going to move, he's simply pressing against those walls. On the picture on the right, again you're not seeing movement, the woman is sitting with her back against the wall doing a wall sit, legs at 90 degrees, and she's building strength, but only at that particular joint angle. So although you can build strength in isometric exercise, it only increases strength at that one joint angle, but not throughout the entire joint's range of motion.
The second broad category of resistance training is dynamic resistance, and we'll talk about three different types of dynamic resistance training. First is dynamic constant external resistance, the second is isokinetic exercises, and the third are plyometrics. So the first one we'll talk about in this slide is dynamic constant external resistance, also called isotonic exercises, "Iso" standing for constant and "tonic" for tension, so you have constant tension throughout the range of the motion here. And we're talking about resistance exercises that can occur with free weights and some weight machines also, and here the weight does not change throughout the range of motion, and we'll see a couple examples on the next slide; that's one of the key aspects. The second key aspect of this type of exercise is that there's both a concentric, or lifting phase, or shortening phase of each rep, and also a lowering, or eccentric, and lengthening phase during each repetition. So if you think about a bicep curl with a free weight, you have the concentric as you lift your hands up toward your shoulders, the eccentric phase as you move your hands down, and that weight is not changing as you go through the range of motion. That doesn't mean that it's the same difficulty to move the weight at each joint angle as you go through the range of motion, but the actual weight that you're lifting is not changing, so that is staying constant in these types of exercises.
Here you see an individual doing a chest fly. In this case, again, you see no change in weight throughout the range in motion, so they had the dumbbells in their hands, that weight is remaining the same. You see a concentric, or shortening, phase as they're lifting their arms up above their body. As they lower the weight back down, that's the eccentric phase, that counts as one rep. And so this is a great example of dynamic constant external resistance.
Pictured here you see a gentleman who is participating in dynamic constant external resistance using a weight machine, and here, again, you have a consistent or constant weight across the range of motion, you have a twist to one side being the concentric phase, and then the shift back being the eccentric phase of that same repetition.
The next two types of dynamic resistance exercise are isokinetic resistance training and plyometric resistance training. In isokinetic resistance training, you have a fixed speed of movement throughout the range of motion, and the resistance will vary with the force extended. So, for example, if you're doing a leg extension where you're kicking your leg out, if you push harder on that movement you're going to feel more resistance, and this is very different from the previous example where we were talking about the amount of resistance, or the weight—the barbell or the dumbbell—being fixed. In this case the speed of movement is fixed, and as you push harder through your range of motion you'll feel more resistance. So the final category here are plyometric exercises, and this is defined as a rapid, dynamic, eccentric contraction and stretching, followed by a rapid, dynamic, concentric contraction. So examples of plyometric-type exercises might be jumping onto, doing box jumps, another exercise might be lateral jumps over a stepper or a raised platform, so jumping side to side, and it really is taking advantage of that stretch reflex of your muscle, and then that you follow that with a dynamic contraction of the muscle.
We measure muscular fitness in different ways depending on whether we're interested in someone's muscular strength or their muscular endurance. So for muscular strength, the gold standard test is really a one-rep maximum, finding out what the heaviest weight someone can lift, successfully, one time without sacrificing their form. So using proper form, how much weight can you lift one time? Some alternatives to that one-rep method, if, for safety reasons or for particular populations you don't want to take them to a one-repetition maximum, people might use a three-rep max or a ten-rep max, and here you're looking at how much weight can someone lift for three or ten reps, and then you take a percentage of that to figure out what their one-rep max might be. On the other hand, if you want to test someone's muscular endurance, you would likely use some sort of callisthenic test, so how many push-ups, pull-ups, sit-ups could somebody do in one minute, and that really gets at the ability to repeatedly contract the muscles over a longer period of time.
On the final slide in this lecture we're going to look at how to use the FITT formula to develop a resistance training program, and just like we talked about earlier in this lecture, it's recommended that adults in the US participate in some sort of muscle-strengthening activities on two or more days of the week, and ideally these activities should cover all the major muscle groups, so your legs, your hips, you back, chest, abs, shoulders and arms. All of those major muscle groups should be covered on two or more days of the week. So you can do more than two days, but it's also important to remember that recovery is important, so you want to give yourself a break between lifting the same muscle groups over and over again.
When we talk about the intensity of resistance training, we're really talking about the percentage of your maximum capacity, and so this is where the one-rep, three-rep or ten-rep max comes in handy, because otherwise it's very hard to judge how intense your resistance training program is, and what you'll notice above is that the intensity is connected very much to your strength training goals. So, for example, if you just want to develop muscular endurance, you're going to choose resistance that is between 50 and 65% of your maximum capacity, which is much lower than if your goal is muscular strength, and in that case you're going to look for between 75 and 85% of your maximum capacity. And for general health and fitness you just fall somewhere in between those two. So you'll notice that very much so your intensity and the weight that you choose to lift in your resistance training program is tied to whether you want to build muscular endurance, muscular strength, or whether you just want general health and fitness goals.
The time or duration component of resistance training programs is really determined by the number of repetitions and sets that you complete, which are each defined on the slide here for you, and also the rest that you take between sets. Multi-set training is often the best approach to see advancements in muscular strength, endurance and power. So here we're just talking about doing multiple sets of a particular exercise using the same amount of resistance. So, for example, you could do bicep curls, you could do 2 or 3 sets of bicep curls with 15-pound weights as opposed to just one set of bicep curls.
This chart really shows you some sample weight training programs, and it gives you a sense of if you have a particular goal, what are the number of repetitions, the number of sets, and then also the resistance, the percentage of your one-rep max, and how much rest should you take. So there are many different factors that go into designing an exercise program, and this chart really helps you narrow down, based on your goal, what types of sets, reps, resistance and rest should you be taking. And so you should notice a couple things here; for improving muscular endurance you'll be doing a higher number of repetitions with a lower amount of weight compared to a program if your goal was to improve muscular strength. You should also note that with increasing intensity, so as you increase the weight that you're lifting, the rest between your sets also increases. So there are many different components that you can manipulate here, and you should be pretty familiar with how these components work together.
The final component of the fit formula that's important for your resistance training program are the type of activities that you choose, and you really have lots of different options when it comes to resistance training. You can choose to use your own body weight, so, for example, push-ups, chin-ups, sit-ups, leg lunges that you're not using weights, all those are great examples of using your own body weight to create resistance. You can also use free weights like dumbbells or barbells, often gyms have machines you can use that simulate these movements with free weights and barbells. And it's recommended that you choose multi-joint exercises, or exercises where your body must change the angles of more than one joint. So, for example, in a push-up, that motion affects the muscles of your shoulder, your arms, your chest. That's recommended over single-joint exercises because it incorporates more than one muscle group, so you're training more than one muscle at the same time, and it's a pretty efficient way to do a resistance training program. So lots of different options when it comes to choosing the type of activity and, in particular, the type of resistance that you use.
