TM-10-1

CHAPTER X – THE MEASUREMENT OF MUSCULAR ENDURANCE

Measuring Muscular Endurance Objectives After reading this chapter you should be able to answer the following questions.

1. What is muscular endurance?

2. How is muscular endurance measured?

3. How can I measure muscular endurance isotonically?

4. What is absolute muscular endurance?

5. What is relative muscular endurance?

6. Is there any relationship between maximum strength and relative or absolute endurance?

7. What is vascularization?

8. How can an increase in vascularization increase muscular endurance?

9. How can I increase vascularization?

10. What are the major differences between muscular strength and endurance?

11. Define muscular endurance and differentiate between isometric and isotonic endurance.

12. Distinguish between absolute and relative endurance measurement.

13. Understand and anticipate some of the administrative problems involved in measuring endurance.

14. Follow the directions for administering practical tests of muscular endurance

Key Terms Isometrics: An isometric exercise is an exercise in which a force is applied against an immovable object.

Isotonic: Isotonics are exercises in which force is applied against a moveable resistance.

Isokinetics: Technically speaking, isokinetic exercise is the same as isotonic exercises. The difference is that the resistance used in isokinetic exercises is such that the speed of movement is constant throughout the entire exercise.

Strength: Strength may be defined as the ability to exert maximum force against either a movable or immovable resistance. Most weightlifters define it as your 1-RM. Absolute Strength: Absolute strength can be defined as the most weight you can lift (1-RM) regardless of your body weight.

Relative Strength: Relative strength can be defined as the most weight you can lift relative to your body weight.

Muscular Endurance It is amazing how many physical education instructors don’t understand the difference between cardiovascular endurance and muscular endurance. Heck, some of them think that strength and muscular endurance is one and the same. They are not. In fact, as mentioned previously cardiovascular endurance, muscular strength, and muscular endurance are all independent components of physical fitness. In truth, there is very little relationship between them. As noted before, a long distance runner would have superb cardiovascular fitness, but may possess very little strength. Conversely, a weightlifter could have extraordinary strength but have relatively little cardiovascular endurance or muscular endurance. Why? Because they are totally independent…they don’t correlate with each other…they are entirely different components of fitness. Now that we got that straighten out for the tenth time, let’s look at muscular endurance.

While muscular endurance is frequently recognized by exercise physiologist as an important factor in the performance of physical skills it is often ignored by physical education instructors. While muscular endurance may be defined generally as the continuous muscular force exerted against movable and immovable objects, it is best measured by tests that require sub-maximum effort for a given movement over a prolonged period of time. The three types of muscular endurance tests are as follows: Isotonic and dynamic Tests: The performer executes identical repetitions of a movement through a designated distance and over either an unlimited amount of time or a specified time interval.

The score is the number of correct repetitions completed. Examples of such tests include barbell exercises with sub-maximal loads, or exercises on a machine with sub-maximal loads. Push-ups, pullups, and sit-ups are also used to measure muscular endurance, but these tests are not valid and should not be used. We will talk about this late on.

Isotonic Repetitive Static Tests: The performer executes repetitions of force against a static measuring device and the score is the number of times the force equals a certain percentage of either the maximum strength of the muscles involved or body weight. An example is the number of times a performer can squeeze 80 pounds on a grip strength dynamometer. The test is usually over when the performer fails to squeeze the prescribed load or falls behind the desired cadence. While some physical educators identify this type of test as a static test, movement over a distance is a factor technically making it an isotonic test.

Timed Static Tests: The performer maintains one continuous muscle contraction rather than executing a series of contractions, and the score is the amount of time the weight is held. An example is the flexed-arm hang test for girls (AAHPERD 1976). The validity of many of these tests is questionable as a measure of muscular endurance. Actually, most of them are not worth a dime…heck; a dime is to much to pay for some of them. We will talk about this later on.

What Is Muscular Endurance?

Muscular endurance is the ability of the muscle to do work over a prolonged period of time. In testing terms, it is an expression of the number of repetitions a muscle or muscle group can repeatedly

perform with a sub-maximal load. Here is something you need to write on your sleeve…yes, it is one of those important things. Muscular endurance is contingent upon vascularization…usually referred to as vasculo-something or other by football coaches from the Southeastern conference. Vascularization is a concept you need to understand in order to know how muscular endurance is developed. If you cut open a muscle (don't do this at home) and look at it under a powerful microscope, you will notice that it's supplied by thousands of capillaries. It is through the walls of the capillaries that there is an essential exchange between vital nutrients and waste products. In short, it is here where the blood feeds the muscle with nutrients and oxygen and absorbs waste products. If you look closely, you will notice that most of the capillaries have blood running through them. However, you will also notice that there are many capillaries that have absolutely no blood running through them. These are called latent blood capillaries. The object of muscular endurance is to open up these latent blood capillaries in the muscle.

Obviously, the better the capillarization or vascularization of the muscle, the better the oxygen supply, and the better the oxygen supply, the better the endurance of the muscle. In other words, the more capillaries you have feeding the muscle, the more oxygen and nutrients it can get, and the more work it can do. Consequently, a muscle that has vascularization will be able to sustain work over a prolonged period of time better than a muscle that has less vascularization. That makes sense…right? Of course, it makes sense! Give me a break here I am just writing this stuff off the top of my head.

Problems Associated with Muscular Endurance Testing Several of the problems and limitations associated with the measurement of muscular endurance are listed and discussed here.

1. Like the muscular strength tests most frequently used test to measure muscular endurance during the past few decades have included test items that, to put it mildly, are ridiculous. For example, the use of the flexed arm hang to measure isometric endurance or the use of pullups, and dips to measure isotonic muscular endurance is…well…ludicrous or ludimus as Mike Tyson would say. The use of sit-ups and push-ups are not much better. These measures are neither relative nor absolute and are unequivocally invalid. The designers of these tests obviously don’t know what the heck they are talking about and that list includes the brilliant people in physical education who came to together and designed the AAHPER fitness. I know I said that before, but it needs to be said a couple hundred times more.

2. A number of tests provide accurate muscular endurance measurement but require expensive equipment; consequently, many schools are unable to include such tests in their physical education program. Isokinetic equipment falls under this category, and for some schools isotonic equipment such as free weights and machines falls under this category.

3. Different grip widths produce different muscular endurance performance results. Thus, it is important to specify which grip width is used when testing muscular endurance.

4. In measuring static or isometric endurance, establishment of precisely the same position or angle for each subject is difficult for certain exercises. Differences in the amount of musculature and fatty tissue and different lengths of body segments pose special problems for accurate testing. It is imperative that such tests start at the same angle and from the

same reference point for each student. For example, specific phrases such as "starting with the elbows at a 90-degree angle" or "starting with the bar between the eyebrows and the hairline" are necessary if comparisons are to be made within a group or with established norms.

5. Most importantly though it should be understood that muscular endurance, like muscular strength, is body specific. There is no single exercise that correlates very highly with total body muscular endurance. This is probably due to the fact that muscular endurance is body specific.

For example, just because your arms have great muscular endurance does not necessarily mean that your legs will have great muscular endurance, or vice versa. Therefore, in order to measure total body muscular endurance, each muscle group would have to be tested independently.

6. Another important factor in evaluating muscular endurance isotonically is skill level and the standardization of the test. A major disadvantage of using free weight exercises to evaluate muscular endurance is the subject’s skill level or the lack of his skill level. By simply changing the biomechanics of the lift you can drastically change the performance on that lift.

Consequently, if the movement is not standardizing for everyone you can get a variation in muscular endurance scores that can be contributed more to skill than to muscular endurance per se. This is a major problem with isotonic strength testing in which free weight is used. As soon as you start testing large groups of subjects, even ones who have experience with free weights, you will find a wide variation in their form and technique. With elite athletes the factor of skill is neutralized to a great extent. With novice athletes skill level can cause variations in scoring that are not attributed to muscular endurance thereby rendering the test invalid.

That is why as a tester you should go to great lengths to try and standardize the procedures for your subjects.

If these problems sound similar to the ones we discussed when we talked about strength training, it is because they are…which tells me you have been paying attention…yes, you get another red star.

Relative and Absolute Muscular Endurance The objective of isotonic muscular endurance tests is to measure muscular endurance through a complete range of movement. There are a number of valid methods for evaluating isotonic muscular endurance; however, all of these methods require some type of equipment. Like muscular strength, muscular endurance can be evaluated in terms of relative and absolute. If you want to measure your relative endurance, you first find your 1-RM for the exercise you want to evaluate. Next, you find 50% of your 1-RM, and using this resistance as your workload, you exercise until exhausted. If you want to measure your absolute endurance with a particular weight or exercise, you simply choose a weight, and then using that resistance, exercise to the point of exhaustion.

With absolute endurance, no consideration is given to strength. Notice, however, that in order to evaluate relative endurance the workload must be proportional to your maximum strength. This is done in order to control for strength as a factor when measuring endurance. Let me explain what I am talking about in greater detail. Let’s do it the fun way. Just the other day Richard Simmons and Oprah

stopped by our office again. Yep! They were arguing. Apparently both of them had been strength training their chest since I last tested them on the bench press. According to Richard, his training had gone so well that he was positive…relatively sure…that his chest was now stronger than Oprah's. Of course, Oprah wasn't studding Richard. She had been training too, and in all candor her chest looked ...well, HUGE. As I told you before though, big is not necessarily better. As you have probably guessed they wanted me to once again determine who was right. So again, I ascertained Richard’s and Oprah's 1RM on the bench press. Obviously, Richard’s training paid off because he did 150 pounds, which was 50 pounds more than he had done when I tested him last. On the other hand, Oprah was incredible. She pumped out a mindboggling 300 pounds for her 1-RM. When Oprah made that lift, Richard let out a scream…the kind of scream that would make Carl Lewis jump. Poor Richard, he was so upset he could have just died. Worse yet, since Richard weighed 125 pounds and Oprah weighed 150 pounds, Oprah was stronger from both a relative and absolute standpoint.

Then all of a sudden Richard got this brainy idea. He said, "Oprah might have a stronger chest than me, but my chest has greater muscular endurance." Was that possible? Of course, it was possible because strength and endurance are independent components of physical fitness. In fact, as I mentioned before, there is very little relationship between them. Actually, Oprah wasn't worried one bit. She loaded the bar to 125 pounds, lay down and then proceeded to pump out 30 hard fought repetitions with the weight. How many repetitions do you think Richard did with the 125 pounds? If you said 5, you guessed right. Think about it. 125 pounds is almost as much as Richard did for his one maximum repetition (1-RM).

But did that mean that Oprah's chest had more muscular endurance than Richard’s chest? The answer is no, because with absolute endurance strength is the determining factor…not endurance. In fact, research indicates that absolute endurance and strength correlate so high that basically they are one and the same. In other words, absolute endurance is really a measure of strength… not endurance. If you are using absolute endurance as a measure of muscular endurance, you are really using a strength test to measure muscular endurance…that’s not good! In short, absolute endurance is an invalid measure of muscular endurance especially if you are going to use these measures to compare students with one another.

Consequently, if you are going to measure muscular endurance you have to factor out strength and the way you do that is to take 50% of your 1-RM and then do that weight as many repetitions as possible. And that's exactly what I did with Richard and Oprah. Hey, I couldn't let Oprah get away with the old absolute muscular endurance trick. Richard used 75 pounds (50% of his 150 pound 1-RM) and Oprah used 150 pounds (50% of her 300 pound 1-RM). Guess what? Oprah kicked Richard’s butt again. She did 17 repetitions and Richard did 16 repetitions. Meaning that Oprah was not only stronger than Richard but she also had greater endurance too…at least in that particular body part. Richard took it like a real man though…he cried.

It might be noted that absolute endurance could be used to monitor improvement in one’s performance from one period of time to the next. Even then though, the resistance would have to be light enough so that the individual could perform at least a 15-RM. Remember what we said about strength and endurance…any time you do more than 5 repetitions you are sacrificing strength for endurance and any time you do less than 15-repetitions you are sacrificing endurance for strength. As a result if you are going to measure muscular endurance a resistance should be used so that the subject can perform at least a 15-RM. If the resistance is too heavy, strength is going to factor in, which will affect the validity of your test. This is one reason why dips, pull-ups or sit-ups are generally poor indicators of muscular endurance. Think about it, most people can’t do 5 pull-ups or dips let alone 15 repetitions.

Not only that but as mentioned these tests are neither absolute nor relative measures. For example, there

is a major difference between the workload required for a guy weighing 300 pounds doing a dip or pullup than for a guy who weighs 150 pounds. Obviously, the guy weighing 300 pounds has to do more work to pull or push himself up than a guy who weighs 150 pounds. Consequently, such tests are neither relative nor absolute and should not be used to measure muscular endurance or strength. The only thing these tests can tell you is how many pull-ups or dips a specific individual can do…they certainly can’t be used to make comparisons, and in general they can’t be used to measure either strength or muscular endurance. They are basically worthless to a researcher or tester.

I know what you are thinking. Many physical education instructors use these test to measure muscular endurance. Well, we already discussed the creditability of some of the most brilliant minds in education in the last chapter. Need I say it again… just because you have a degree does not make you an expert. To put it in other terms, just because you have a Yankee hat does not mean you are Alex Rodriquez.

Okay, now let’s look at some of the test that could be used to evaluate isotonic muscular endurance. As I previously mentioned, the best exercises used for evaluating muscular endurance would be relative measures and the best isotonic test would be the same ones used to measure strength through a full range of motion. Also as mentioned, muscular endurance like muscular strength is body specific, meaning that you will have to measure each body part and muscle independently. There is no single test that correlates with total body muscular endurance. Therefore, in order to measure total body muscular endurance, each muscle group would have to be tested independently. To do this, you first find an exercise in which the muscle you want to test is the prime mover, and then simply determine the maximum number of repetitions you can perform in that exercise. Again though, you must first factor out strength in order to get a true measure of the subjects muscular endurance and the way you do that is to take 50% of your 1-RM in the exercise you are using and then do that weight as many repetitions as possible.