Alternatives to Manual Muscle Testing



Alternatives to Manual Muscle Testing



Introduction


Manual muscle testing is a foundational measure of strength that is widely used across the health professions for both diagnosis and rehabilitation. Yet manual muscle testing has specific limitations, as discussed in Chapter 2. Consequently, alternative strength measures are needed in certain cases such as when strength exceeds a functional threshold, when strength of the patient is greater than that of the therapist, when subtle differences exist between sides or between the agonist and antagonist, or when power or endurance need to be measured. The most commonly used alternatives to manual muscle testing are equipment-based tests.


There are many options for equipment-based testing, and each has its advantages and disadvantages. Choosing the best option depends on clinic space constraints, available budget, the type of patient, the goals of treatment, and how comprehensive the evaluation needs to be. For example, in a small outpatient clinic where most of the patients have low back or neck pain, the approach to equipment-based testing will differ substantially from that required in most acute care settings. Strength-testing instruments that can be used effectively for children and older adults will differ from those used for a sports team. The equipment-based tests presented in this chapter represent the more popular approaches, are appropriate for older adults, and also have demonstrated reliability and validity.



General Testing Considerations


It is presumed that any therapist conducting a strength testing session, particularly one requiring maximal effort from a large muscle group, will perform a prescreening exam for red-flag conditions. Maximal strength testing for the back extensors in a patient with severe osteoporosis, for example, may not be appropriate. Likewise, a patient with unstable blood pressure may have an adverse reaction while exerting maximum effort on a leg press, particularly if the patient—incorrectly—holds his or her breath. It is also presumed that muscular strength will be assessed after the patient has warmed up the muscle before testing. The typical warm-up includes completing three to five sub-maximal contractions at 40% to 50% of maximum using the muscle or muscle group that is being tested.1 Active range of motion should be assessed to determine if adequate joint range and muscle length will allow maximum effort in the correct test position.



One-repetition Maximum Test


The one-repetition maximum (1-RM) test is regarded as the “gold standard” of standardized muscle strength testing. The 1-RM refers to the amount of load the patient can move one time (and one time only) through full range in a controlled manner with good form.1 It is a safe technique, perhaps safer than a sub-maximum strength test, even though muscle soreness may occur and blood pressure may spike during a maximum exertion test.2 1-RM tests are highly reliable when specific procedures are followed, more so than any other type of strength assessment.3 Additionally, the fundamental method for establishing 1-RM is the same for each muscle group and thus the 1-RM test is more precise than most.


Several factors are important in optimizing 1-RM performance. Obtaining a patient’s maximum strength may serve to establish the amount of resistance needed for an exercise prescription; it may help determine the progress of a progressive, resistive exercise program; or it may be used to compare the patient to established norms. Many normative values for men and women of all ages exist for movements such as bench press, latissimus dorsi pull-down, leg press, and knee extension and are listed throughout this chapter.



Technique


The basic steps for performing a 1-RM are as follows:



The final weight that the patient can move successfully is recorded as the definitive 1-RM.



Selecting the Starting Weight


Selecting the amount of the starting weight is crucial because no more than four repetitions to reach 1-RM should be performed to avoid muscular fatigue and to prevent an underestimation of the true 1-RM. It is helpful for the tester to have knowledge of norms. For example, standing from a chair requires quadriceps strength of nearly half a person’s body weight, no matter what the age. Therefore, when performing a 1-RM using a leg press to test the quadriceps of a person having difficulty standing from a chair, a starting weight might be 75% of the patient’s body weight. Alternatively, norms exist for the leg press based on age. These norms might present a starting point for establishing a 1-RM. Other variables that can be factored into the clinical decision of the initial load are body size (muscular versus thin), fitness level, and the patient’s self-perception of ability.


Other considerations that should also be attended to during 1-RM testing include breathing, form, and pain. First and foremost, patients should not hold their breath during the test. Thus, breath control should be practiced during the warm-ups. Second, the patient should maintain correct form throughout the test. For example, the patient should not be permitted to pitch the trunk forward during the knee extension test so as to avoid muscle substitution or the use of momentum. Joint movements during the test should be executed smoothly and consistently throughout the entire concentric and eccentric phase, in a controlled manner without jerking the bar or weight. If the test causes pain, an alternative to the 1-RM test should be selected, such as a multiple repetition maximum test.



Multiple-repetition Maximum Test


A multiple-RM test is based on the principles of a 1-RM test. The multiple-RM test is the number of repetitions performed using good form and proper breath technique at the point of muscle failure. Although not as exact as a 1-RM, a multiple-RM test may be desirable for certain situations. For example, some older adults are not comfortable exerting the kind of effort necessary for a true 1-RM. When joint or soft tissues are compromised (e.g., connective tissue disease, rotator cuff tear, ligamentous injury, post-surgery) a safer approach than a 1-RM may be preferred. The multiple-RM test, such as an 8- or 10-RM test is safer than the 1-RM test particularly for those with no exercise history and for patients who cannot tolerate high joint compression forces, such as those with osteo- and rheumatoid arthritis, or with systemic weakness.


A 1-RM test can be estimated from a multiple-RM test (Table 8-1), although this estimation has been shown to be quite variable (Table 8-2).4 As the percent of 1-RM increases, the number of repetitions decreases (Table 8-3). Large muscle group exercises allow the completion of more repetitions than small muscle groups at the same relative intensity.5 Because the volume of work is greater with a 10-RM than a 1-RM, fatigue will be a factor. The 1-RM and multiple-RM tests can be performed using the same equipment.




Table 8-2


NUMBER OF REPETITIONS PERFORMED AT 80% OF THE 1-RM4
























































Exercise Trained Untrained
Men Women Men Women
Leg press 19 22 15 12
Lat pull down 12 10 10 10
Bench press 12 14 10 10
Leg extension 12 10 9 8
Sit up 12 12 8 7
Arm curl 11 7 8 6
Leg curl 7 5 6 6


image



The number of repetitions performed at a given percent of 1-RM is influenced by the amount of muscle mass used because more repetitions can be performed during the back squat than either the bench press or arm curl.5 The 4- to 6-RM is more accurate than the 10-RM. Variability increases with decreased loads.6



Equipment-Based TESTING


Because practice patterns have changed so extensively since the advent of manual muscle testing, methods to identify muscle weakness have also evolved. The days of polio are behind us and the need to identify deficiencies from sports-related injuries, trauma, aging, and a host of other clinical conditions has resulted in the development of new and better testing techniques for the characterization of muscle weakness. This chapter segment will present an overview of some of the more popular approaches.


Equipment-based tests offer many advantages. The main advantage of using equipment (such as a strength-testing device) for repetition maximum testing is that the stability afforded by the device allows for highly controlled single plane movements, thus increasing the patient’s safety. In addition, normative data for many movements are available with equipment-based testing. The disadvantages of using devices for testing are that 1) they take up space, 2) they can test only one plane of movement, and 3) they can test only a finite number of muscle groups.



Unilateral Knee Extension Test






Position of Patient:

Seated comfortably on a knee extension machine that has been adjusted for leg length. A seat belt may be placed around patient’s pelvis, if needed, to provide stability (Figure 8-1; seat belt not shown in figure). If necessary, padding may be placed beneath the thigh being tested for patient’s comfort.


image
FIGURE 8-1




Scoring


Record the highest weight the patient could lift to reach full knee extension. The multiple-RM is recorded as the pounds at last repetition and the number of repetitions it took to achieve muscle failure. (Note: Extension through full range of motion, particularly the last 15° to 0°, must be achieved for a successful test.)



Helpful Hints





Leg Press Test


The leg press machine is one of the most useful devices in a clinic. The force output generated by a patient will tell the therapist whether the patient has enough strength to be functional in activities of daily living or with sport activities requiring a huge amount of strength such as soccer.





Testing Procedure:

After the patient is comfortably seated on the machine, have him or her place both feet on the footplate, approximately 12 inches apart, directly under the hips. Adjust the seat distance so that the knees are bent to approximately 110°. Have the patient put his or her hands on the grab bars (Figure 8-2). Select the desired weight on the weight stack, put in the pin to keep weights in place and have the patient fully extend the footplate against the chosen resistance. The knees should be fully extended at the end of the push. Note: some leg press machines require the therapist to place weights on either side of the footplate bar (e.g., two 25-pound weights) and lock the weights in place.


image
FIGURE 8-2





Scoring


Record the highest weight the patient can push while fully extending the knees.



Helpful Hints




• The leg press is the only machine that uses the closed chain approach (distal end of the kinetic chain is fixed).


• Foot position low on the plate (see Figure 8-3) elicits greater muscle activity from the quadriceps and gastrocnemius than high foot position (see Figure 8-2), suggesting that the feet should routinely be positioned low on the plate.7 Not all patients, however, can comfortably assume a low-foot position; in terms of importance, comfort should outweigh muscle activation. But be aware that if a patient cannot assume the low foot position, then maximal muscle activation is not likely to occur.


• There are established norms for leg press for men and women ages 20 through early 60s, which is hardly comprehensive of all age groups. Nonetheless, it is important to have an understanding of what should be expected in terms of “normal” strength. Norms are expressed as a ratio of force output to body weight. Thus, a typical ratio for a young woman in her 20s is 2.05, meaning that she should be able to generate force equivalent to twice her body weight. Normative data for the leg press and bench press on hundreds of men and women that have been tested by the Cooper Institute are presented in Table 8-4.




Latissimus Dorsi Pull-down Test


The latissimus dorsi pull-down test (lat pull-down test) is a general measure of bilateral shoulder adduction and scapular downward rotation. The lat pull-down is available in most clinics and in all wellness centers and workout facilities. The test is one of the safest and easiest to perform of all upper extremity exercises.





Testing Procedure:

Place the pull-down seat in a position so that the patient’s feet are on the floor during the test. The patient is then seated astride a bench, typically facing the weight stack, with the back unsupported (Figure 8-4). Based on the initial physical therapy screening (e.g., can the patient pull against manual resistance easily?), select a weight stack that is relatively easy, such as 20 pounds for a woman and 40 pounds for a man. Have the patient reach overhead and grab a horizontal bar to which the weight stack is attached. The bar is grasped so that the arms are wide apart and the forearms are in pronation (more difficult) or supination (easier). Hands on the bar should be slightly further apart than the shoulders. After the patient has pulled the bar down to shoulder height in front of the body, the test is considered successful. The position of pulling down in front of the head provides the greatest activation of the latissimus dorsi.8


image
FIGURE 8-4

After a 30- to 60-second rest, the patient is asked to pull the bar down once again, this time with another 5 to 10 pounds added, depending on how easy or difficult the first repetition was. Additional weights are added in 5- to 10-pound increments until the patient reaches failure. Norms for the latissimus pull-down activity are typically 66% of body weight for young men and 50% of body weight for young women.9 Norms for men and women who are middle-aged and older have not been established. This test is feasible for patients of nearly all ages.







Free Weights Testing


Free weights are the “gold standard” for reliability and validity of the 1-RM method because of their ease of application. They offer a number of important advantages for muscle testing: 1) they permit the therapist to assess strength in both the concentric and eccentric modes, 2) they are readily available in any clinical setting and are readily accessible in the home where household items can easily be substituted for weights, and 3) they can be used through full range and through multiple planes.


Moreover, free-weight exercises require greater motor coordination and better balance, resulting in greater muscle recruitment. They employ important stabilizing muscles to complete a lift, compared with machines, which do not emphasize the stabilizing musculature because movements occur in only one plane of motion. And they allow the therapist the freedom to test different exercise variations compared to resistance machines.


Some disadvantages of using free weights are that: 1) greater control is required through all planes of movement; 2) testing can be unwieldy and proper positioning is critical for safety and test reliability; 3) free weights can be dropped, potentially causing injury; and 4) free weights can challenge the entire kinetic chain, thus stressing the “weakest link” rather than the targeted muscle, unless proper stabilization is provided. Probably the biggest disadvantage of using free weights is that maximum muscle loading only occurs at the weakest point in the range of motion.



Definition of Terms


Concentric activity refers to the shortening of a muscle as it contracts, as in the bending portion of a biceps curl or extension of the elbow when lifting an object overhead.


Eccentric activity refers to the lowering phase of an exercise, when the muscle lengthens, as in lowering the weight to the chest during the bench press or lowering oneself into a chair. Eccentric muscle activity is seen in many mobility-related functional tasks.


The kinetic chain refers to all the muscles and joints that are involved in producing a given movement. For example, in the movement of arising from a chair, the kinetic chain consists of the trunk, hip, knee, and ankle. Most exercises involve more than one muscle group and joint, which work simultaneously to produce the movement. Exercises in the kinetic chain can be performed two ways, open and closed, referred to as open chain and closed chain.


Open chain exercises are performed such that the distal end of the kinetic chain is free to move. An example of an open chain activity is quadriceps knee extension sitting on a plinth where the leg moves from 90° of flexion to full extension.


Closed chain exercises are performed with the distal end of the kinetic chain fixed. An example of a closed chain exercise for the quadriceps is squatting. The knee is again moving through 90° of movement but the leg is fixed in place and the thigh is moving over the fixed leg.



Elbow Flexion Test


The elbow flexion test is an example of how to use free weights to determine maximal muscle strength. In this instance the biceps, brachialis, and pronator teres are the muscles that will be challenged, particularly the biceps and brachialis. This test can easily discern side-to-side differences and whether strength is adequate for lifting during work.




Testing Procedure:

Based on the patient’s answers to prescreening questions (such as, can you lift a gallon of milk?), the therapist should pick a weight that is reasonably challenging. Normative strength is approximately 25% of body weight for women and 33% of body weight for men.6 Another way to determine a starting point for less fit individuals is to ask the patient if he can easily carry a large bag of groceries (approximately 10 pounds). If the patient responds affirmatively, begin the test with 15 pounds of weight. The patient’s elbow should be straight, with arm at the side. Put the 15-pound weight in the patient’s hand and have the patient flex the elbow through full range of motion (Figure 8-5). If this movement is easy, select a 20-pound weight for the next repetition. After 20 pounds have been successfully lifted through full range of motion, select a 25-pound weight for the next repetition. If this movement is successful but difficult, increase the weight by 2.5 pounds. When the weight cannot be lifted through full range in a controlled manner, or if muscle failure occurs, the test is terminated and the last weight that was successfully lifted is the patient’s 1-RM. Recall that 30 to 60 seconds of rest should be provided between repetitions.


image
FIGURE 8-5

If this movement is easy, increase weight for the next repetition by 5 to 10 pounds. If this movement is successful but difficult, increase the weight by 2.5 pounds.


When the weight cannot be lifted through full range in a controlled manner or if muscle failure occurs, the test is terminated 30 to 60 seconds of rest should be provided between repetitions.







Bench Press Test


The bench press is one of the most popular tests of upper extremity strength because it provides a composite value for a large number of muscles, similar to the leg press.




Testing Procedure:

The patient is positioned supine on a low testing bench with a testing bar overhead. The patient’s nipple line should be below the weight bar. Based on prescreening, two free weights are selected and one weight is placed at each end of the bench press bar and locked in place.


Hand placement should be gripping the bar with both hands placed slightly wider than shoulder width and the forearms in pronation (Figure 8-6). The bench press bar is lifted until the elbows are fully extended and the shoulders are at 90° of flexion. After the patient successfully completes the test, additional weight in 5- to 10-pound increments is added. Provide the patient 30 to 60 seconds of rest between lifts. Test failure is observed when the patient is unable to complete full range of motion.


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FIGURE 8-6

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Relevance and Limitations of Manual Muscle Testing Ready Reference Anatomy Testing the Muscles of the Neck Testing Functional Performance Testing the Muscles of the Trunk and Pelvic Floor Testing the Muscles of the Upper Extremity

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Aug 25, 2016 | Posted by in RHEUMATOLOGY | Comments Off on Alternatives to Manual Muscle Testing

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