CHAPTER IX â&#x20AC;&#x201C; THE MEASUREMENT OF MUSCULAR STRENGTH

Measuring Muscular Strength Objectives After reading this chapter the student should be able to answer the following questions: 1. What is muscular strength? 2. What is the difference between isotonic, isometric and isokinetic exercises? 3. How do you measure muscular strength? 4. What is relative and absolute muscular strength 5. What are some of the administrative problems involved in measuring strength? 6. What are the directions for administering tests of strength?

KeyTerms 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. Concentric contraction: Concentric contraction is the shortening of a muscle fiber. Eccentric contraction: Eccentric contraction is the lengthening of a muscle fiber.

Strength Strength is frequently recognized by physical educators as the most important factor in the performance of physical skills. While strength may be defined generally as the muscular force exerted against movable and immovable objects, it is best measured by tests that require one maximum effort for a given movement or position. The two types of muscular contraction most frequently measured in physical education classes are static (isometric) and dynamic (isotonic and isokinetics). An isometric exercise is an exercise in which a force is applied against an immovable object. The muscles attempt to contract but are unable to overcome the resistance being used. An example would be if you stood in a doorway and pushed against the sides of the door with your handsâ&#x20AC;Śprovided of course, you donâ&#x20AC;&#x2122;t move the walls! During such an exercise, the muscles involved are statically contracted (isosame; metric-measure). It might be noted that in isometric contraction, muscular force is exerted over a brief period (usually 6 to 10 sec) without movement of the object of resistance or the body joints involved. Isotonics are exercises in which force is applied against a moveable resistance. During this type of exercise, the muscle is either concentrically contracted (shortened) such as when you curl a weight with your arm, or eccentrically contracted (lengthened) as when you slowly lower the weight. The use of the term isotonic (iso = same; tonos = tension) is somewhat misleading because as a weight is moved, the tension is not really constant but varies with the joint angle or position of the weight. With isotonics muscular force moves an object of resistance through a range of movement. Probably the greatest advantage is that isotonic exercises develop the muscle through a full range of motion, thus eliminating the problem of specificity associated with isometric exercises. We will talk about the importance of strength specificity in a moment. Another exercise that is of significance when talking about strength development and measurement is isokinetics. Technically speaking, isokinetic exercises (iso=same; kinetic=movement) are simply a variation of 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. This enables the individual to place maximum resistance on the muscle at every point throughout the range of motion. In isokinetic exercises, no matter how much (or how little) force is generated, the resistance continues to move at a constant speed. Thus, a muscle that is loaded isokinetically can be exercised throughout the full range of motion with maximum resistance, provided that the individual exerts maximum force. Practically the same advantages that were mentioned for isotonics are inherent to isokinetics. However, as previously stated, unlike isotonics, isokinetics have the advantage of putting the muscle under maximum tension at every point in the range of motion. Since isokinetic exercises are always performed with the use of machines, isokinetics can be somewhat safer than isotonics. Unfortunately, most of these machines are expensive and therefore are cost prohibitive for most average school settings. Conversely, isometrics and isotonics can be measured easily and inexpensively in most average school situations. While a certain degree of strength is necessary in performing daily activities, strength in most sports activities is regard as essential for success. It is also considered one of the major aspects of physical fitness. Consequently, it is extremely important to physical education instructors and sports coaches

What Is Strength?

Before you evaluate something, you undoubtedly have to know what you are evaluating…that, as they say, is a blinding flash of the obvious…right? With that being said, strength may be defined as the ability to exert maximum force against either a movable or immovable resistance. I know I already said that but something need to said more than once. Most weightlifters define it as your 1-RM (one-repetition maximum). Now here is something you may have noticed if you watch Popeye a lot. Big isn’t always better. Just because an individual has larger muscles than another person does not mean that he is stronger. How many times did Popeye kick Brutus’ butt? Trust me on this one, it wasn’t the spinach. Is it possible that Popeye was stronger even though he was a lot smaller? The answer is yes. Two muscles that have the same circumference may differ in strength because of the amount of fat tissue they contain. Although fat adds to the circumference of the muscle, it lacks contractile power, and in fact limits the contractibility of the muscle. Most likely, Brutus was carrying a lot of body fat. Also, the arrangement of muscle fibers determines the force with which a muscle can contract. Research has revealed that when muscle fibers run at oblique angles, they can exert greater force than when they run parallel to the long axis of the muscle. Thus, two muscles could be the same size, but have different contractile power because of the arrangement of the muscle fibers. Perhaps, Popeye’s muscles, although smaller, were more contractually efficient than Brutus’ muscles. However, all factors being equal, the larger the muscle the greater the strength. In fact, the absolute strength of a muscle is directly proportional to its circumference. In other words, there is a relationship between strength and muscle size and/or mass. In general, the stronger you get, the bigger your muscles will get.

Problems Associated with Strength Testing Several of the problems and limitations associated with the measurement of strength are listed and discussed here. 1. The muscular strength tests most frequently used during the past few decades have included test items of …well…dubious validity. For example, the use of sit-ups in the isotonic strength test designed by Johnson or the inclusion of the lung capacity measure in the Rogers strength test, and the use of push-ups in the AAHPER fitness test have raised many eyebrows among fitness experts over the years. Also, inclusion of muscular endurance items, such as pull-ups and dips for maximum repetition, has added to the confusion concerning strength test results and their interpretation. For one good reason too… the aforementioned items do NOT measure strength. And 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. It is garbage, but I will save that little tidbit for later on in the book. 2. A number of tests provide accurate strength 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. 3. At the present time, measurement of abdominal strength has been quite limited. Many of the better known strength tests have avoided this area entirely, although abdominal strength is important in various activities. The sit-up test with maximum (or near maximum) resistance behind the neck presented in many strength test batteries is rather dangerous. Just as significant is the fact that they are NOT a