Testing Functional Performance

In current clinical practice, there is a growing need to emphasize the relationship between strength and functional movement, especially in older adults. Each person has a threshold of strength that is minimal for the performance of activities of daily living (ADLs). The larger or taller the person is, for example, the more strength will be needed. Third-party payers are requiring that therapists show a relationship between strength and function in their patients and if their assessments fail to show this relationship, payment is often denied. It has always been important for therapists to show that patients have strength deficits, but it is now critical for them to show that strength deficits are tied to the patient’s ability, or lack thereof, to independently complete ADLs, perform a job task (such as bricklaying), or play with their children or grandchildren. This chapter presents a series of functional tasks, particularly relevant to older individuals, that can only be completed if strength is at a minimum threshold. Once an impairment is pinpointed, a strengthening program can be designed to help patients achieve their functional goals.

The functional assessment tests described in this chapter have been correlated to specific strength measures, and normative values are provided when available. The essential muscles involved in each movement are also identified. The list of muscles for each task is not comprehensive, but it provides a starting point for the beginning therapist to use in the design of exercises to improve task performance. In some cases, patients may be able to accomplish a task by compensating for a muscle weakness, but this weakness must be identified and corrected in order for the task to be performed successfully.

Introduction

Functional abilities represent a broad range of movements that require muscles to act in highly specific ways to achieve a desired purpose. These include ADLs such as dressing, eating, bathing, transferring, and walking, as well as other tasks of mobility such as rising from a chair, climbing stairs, lifting, writing, and rising from the floor. These functional activities are basic tasks of mobility that are required for all individuals to be independent in the home and community. Functional activity performance is especially important for older adults who may be at risk for institutionalization because of an inability to independently perform specific functional tasks. Higher level functional abilities such as those required for sports and work will not be discussed in this chapter.

The Nagi Model of Disablement ¹ as well as the newer International Classification of Functioning (ICF) disablement model² describe the impact of disease and pathology within the context of both function and societal roles and provide a conceptual model to guide clinical practice. In these models, diminished muscle strength is seen as an impairment that affects a person’s ability to perform functional tasks or to fulfill societal roles. Muscle strength testing takes place at the impairment level whereas testing performance of a functional task occurs at the function level. One goal of this chapter is to integrate impairment (strength deficit) and functional loss.

It is generally accepted that in the normal person, performance of basic functional tasks requires a relatively small amount of muscle strength in relation to the total amount of strength that existed before the injury, before a lifestyle of inactivity, or before the passage of years. The minimum amount of strength required is referred to as a “strength threshold.” If patients have strength above the required threshold amount, they are unlikely to show deficits in performance. The relationship of strength to function up to a specific threshold is illustrated in Figure 9-1. According to the principle illustrated in this graph, if we strengthen a patient sufficiently and bring his or her strength value to the point at which the curve flattens out, a patient should be strong enough to perform the task. For example, about 45% of one’s body weight is required to rise from a chair without using the arms.³ If a person is unable to rise from a chair unassisted because of weakness in the lower extremities, strengthening will help to improve that function. Further strengthening will allow the person to rise more quickly and efficiently and will create a strength reserve to help preserve the ability to perform the task in the future.

FIGURE 9-1 Conceptual diagram of curvilinear relationship between strength and function.

Functional Testing

An analysis of any functional task shows that movements are multiplanar and asymmetrical, incorporate rotation, and are speed and balance dependent. Therefore, simply testing a muscle’s maximum ability to generate force will not accurately represent its functional ability. Observation of the individual performing the functional task is the only way to accurately test functional ability. Such observation provides information about the quality of the performance, which in turn informs the therapist’s clinical decision making. Inferring that a specific muscle is functional without direct observation of the functional task is incorrect and should be avoided. Table 9-1 shows the key muscles required for some basic functional tasks.

Table 9-1

KEY MUSCLES ESSENTIAL FOR FUNCTIONAL MOVEMENTS

Functional Movement	Key Muscles
Bed mobility	Abdominals, erector spinae, gluteus maximus
Transfers and squats	Gluteus maximus, medius, and obturator externus, piriformis, quadriceps
Ambulation and stair climbing	Abdominals, erector spinae, gluteus maximus and medius, obturator externus, piriformis, quadriceps, and anterior tibialis and gastrocsoleus
Floor transfers	Abdominals, erector spinae, gluteus maximus and medius, obturator externus, piriformis, quadriceps and gastrocsoleus
Fast gait and jumping	Gastrocsoleus, gluteus maximus and medius, quadriceps

Measurement

Functional task performance is measured in several ways. Ordinal scales showing hierarchical levels of performance are commonly used in both manual muscle testing and in some functional tests. In ordinal scales, numbers are sequentially and hierarchically assigned in accordance with the difficulty of the task. However, ordinal scales are limited by their susceptibility to subjectivity and their lack of responsiveness to small changes in performance. Therefore, measuring individual patient performance using ratio scales, such as time, is the preferred method. Timing task performance provides a strong measure of reliability and responsiveness. However, when a functional task is timed, such as when a patient is instructed to rise from a chair as quickly as possible, it should be noted that power is an additional component to strength. Ratio measures such as time and distance allow the therapist to compare an individual patient’s performance against available normative data of similar individuals. This comparison aids in clinical decision-making.

Chair Stand

Helpful Hints

• Do not use a folding chair, a very soft chair, a deep chair, or a chair on wheels for the chair stand test. The chair should be placed against the wall for safety purposes.

• Allow the patient to perform the sit-to-stand movement first, without coaching. If the patient has difficulty rising, then offer tips such as scooting to the edge of the chair, leaning forward, etc.

• It is useful to observe the position of the hips while the patient is attempting to stand and sit. If the hips are adducted and/or internally rotated, this may indicate that the patient is primarily using the quadriceps to stand, rather than the gluteal muscles, and specific muscle testing is indicated, especially of the gluteus medius (Figure 9-4).

• Excessive bending forward of the trunk in order to stand may indicate that the patient has weak quadriceps (Figure 9-5).

• Although it is preferable to have the patient cross the arms over the chest, some patients may need to extend their arms forward to help them stand. If this occurs, it could indicate that the patient’s legs are weak and that the trunk is being used to aid in standing (Figure 9-6).

• For every 1-second increase in the timed 5-repetition chair stand test, the odds of being disabled increases 1.4 times; inability to rise five times increases the odds ratio 2.5 times for severe mobility difficulty within 12 months.⁸

• If you suspect the patient will not be able to complete five repetitions, the 30-second chair stand is the preferred test because the patient is required to only complete a minimum of one repetition for a successful test.

Table 9-2 shows normative ranges for physically active older men and women. For the 30-second chair stand, seven repetitions may indicate frailty in people with coronary artery disease.⁹ Likewise, eight repetitions may be the threshold for physical disability.⁵

Table 9-2

CHAIR STAND NORMS FOR PHYSICALLY ACTIVE OLDER ADULTS

CHAIR STAND TEST by AGE (MEN)⁵
Percentile Rank	60-64	65-69	70-74	75-79	80-84	85-89	90-94
95	23	23	21	21	19	19	16
90	22	21	20	20	17	17	15
85	21	20	19	18	16	16	14
80	20	19	18	18	16	15	13
75	19	19	17	17	15	14	12
70	19	18	17	16	14	13	12
65	18	17	16	16	14	13	11
60	17	16	16	15	13	12	11
55	17	16	15	15	13	12	10
50	16	15	14	14	12	11	10
45	16	15	14	13	12	11	9
40	15	14	13	13	11	10	9
35	15	13	13	12	11	9	8
30	14	13	12	12	10	9	8
25	14	12	12	11	10	8	7
20	13	11	11	10	9	7	7
15	12	11	10	10	8	6	6
10	11	9	9	9	7	5	5
5	9	8	8	8	6	4	3

CHAIR STAND TEST BY AGE (WOMEN)
Percentile Rank	60-64	65-69	70-74	75-79	80-84	85-89	90-94
95	21	19	19	19	18	17	16
90	20	18	18	17	17	15	15
85	19	17	17	16	16	14	13
80	18	16	16	16	15	14	12
75	17	16	15	15	14	13	11
70	17	15	15	14	13	12	11
65	16	15	14	14	13	12	10
60	13	13	14	13	12	11	9
55	15	14	13	13	12	11	9
50	15	14	13	12	11	10	8
45	14	13	12	12	11	10	7
40	14	13	12	12	10	9	7
35	13	12	11	11	10	9	6
30	12	12	11	11	9	8	5
25	12	11	10	10	9	8	4
20	11	11	10	9	8	7	4
15	10	10	9	9	7	6	3
10	9	9	8	8	6	5	1
5	8	8	7	6	4	4	0

Source of data for women: Rikli RE, Jones CJ. Senior Fitness Test Manual. Champaign, IL: Human Kinetics; 2001.

Table 9-3 shows normative ranges for moderately disabled women—that is, those who have difficulty performing two ADL tasks. The Women’s Health and Aging Study (of moderately to severely disabled women) found a mean time for ages 65 to 85 and older of 15.3 seconds.¹⁰ The more time required, the more likely it is that the individual is frail.¹¹

Table 9-3

CHAIR STAND PERFORMANCE FOR MODERATELY DISABLED WOMEN

5-Repetition Chair Stand	Total N = 1002	65-74 Y N = 388	75-84 Years N = 311	85+ Y N = 303
Unable to do (%)	25.2	17.8	25.9	44.9
Mean Time to rise 5 × (seconds)	15.3	14.7	15.7	16.3
5th percentile	24.5	21.9	25.5	24.1
25th percentile	17.4	16.7	17.5	18.5
50th percentile	14.2	13.9	14.4	15.0
75th percentile	12.3	12.1	12.4	12.7
95th percentile	10.0	9.6	10.3	10.0

Y, age in years.

Moderately disabled women were those with difficulty in two or more activities of daily living tasks.

Adapted from Ferrucci L, Guralnik JM, Bandeen-Roche KL, et al. Performance measures from the Women’s Health and Aging Study. http://www.grc.nia.nih.gov/branches/ledb/whasbook/chap4/chap4.htm. Accessed January 8, 2012.

Gait Speed

Purpose:

Gait speed is a functional test of one’s ability to walk at a comfortable (usual) speed. A fast-paced walk can demonstrate available reserve and the ability to accelerate rapidly, such as in the need to get across a street. Possible gait speed times range from the fastest sprinters to the slowest possible gait, often seen in individuals residing in nursing homes. Gait speed has been called the sixth vital sign because of its validity in predicting functional ability, frailty, nursing home placement, and the ability to walk in the community.¹⁵ It can be measured in any person who can walk, even those using assistive devices.

Essential Muscle Movements for Task Performance:

Hip extension and abduction, knee extension, ankle plantar flexion, and ankle dorsiflexion with inversion.¹² Hip flexion also contributes to walking velocity.¹³ The reader is referred to the gait section of this chapter for a more specific list of muscles that are imperative for smooth and normal gait.

Reliability:

r = 0.90 ¹⁴

Validity:

Gait speed is related to age (Figure 9-7).¹⁵ Gait speed at “usual pace” was found to be a consistent predictor of disability, cognitive impairment, institutionalizations, falls, and/or mortality.¹⁶ A speed of less than 0.8 meters per second (m/s) is a predictor of 8-year mortality in predisabled women 75 years or older¹⁷ and is considered pathologic.¹⁸ A speed of less than 1.0 m/s identifies well-functioning people at high risk of health-related outcomes¹⁹ and impaired function.²⁰ In one study, the mean gait speed used by 139 pedestrians was 1.32 (SD, 0.31) m/s.²¹ A cutoff score of 0.57 m/s can indicate that the person is in need of physical therapy.²²

FIGURE 9-7 Self-selected walking speed categorized by gender and age.

Equipment:

A 4- to 8-meter-long walkway and a stopwatch. It is helpful to have 2 meters or so before and after the 4-meter test course to allow for acceleration and deceleration. However, although this extra distance is desirable, it is not necessary to perform the test.

Testing Procedure:

First, describe the test clearly to the individual. Demonstrate the test if needed, taking care not to walk too fast. Then, have the patient perform two trials with adequate rest in between, scoring the faster one. Test both comfortable (usual) and fast gait speeds. Begin timing the individual when the first foot crosses the line at the beginning of the course (Figure 9-8,A) and stop timing when the first foot crosses the end line (Figure 9-8,B). Any part of the foot will do; it is just important to be consistent.

Position of Patient:

Standing, facing a marked-off walkway. Patient may use an assistive device if needed.

Position of Therapist:

Standing, holding the stopwatch perpendicular to the starting line. Therapist will walk with the patient to obtain an accurate view of when the first foot crosses the finish line. The therapist will begin timing when the first foot (or part of the first foot) crosses the start line of the 4-meter walkway (see Figure 9-8,A).

Instructions to Patient:

“First, walk at your usual and comfortable speed from this line to the other line on the floor (indicate which line). I will be timing you. The first trial is the practice trial and then we’ll test you twice. OK? Ready, Go!” (The same directions are given for the fast-paced walk, with the patient instructed to walk as quickly, but as safely, as possible.)

Scoring

The time taken to walk 4 meters is divided into 4 for a result in meters per second (m/s). There are many gait speed standards. Gait speeds of 1.75 m/s to 2.25 m/s are normal in high-functioning older adults, whereas gait speeds slower than 0.5 m/s are common in nursing home residents. Table 9-4 indicates some conversions from meters/second to feet/second and miles/hour. Tables 9-5, 9-6 and 9-7 list normative values for gait speed by age.

Table 9-4

CONVERSIONS FOR GAIT SPEED

Meters/Second	Feet/Second	Minutes/Mile	Miles/Hour
0.25	0.82	106.7	0.6
0.30	0.98	88.9	0.7
0.35	1.15	76.2	0.8
0.40	1.31	66.7	0.9
0.45	1.48	59.3	1.0
0.50	1.64	53.3	1.1
0.55	1.80	48.5	1.2
0.60	1.97	44.4	1.4
0.65	2.13	41.0	1.5
0.70	2.30	38.1	1.6
0.75	2.46	35.6	1.7
0.80	2.62	33.3	1.8
0.85	2.79	31.4	1.9
0.90	2.95	29.6	2.0
0.95	3.12	28.1	2.1
1.00	3.28	26.7	2.3
1.10	3.61	24.2	2.5
1.20	3.94	22.2	2.7
1.30	4.26	20.5	2.9
1.40	4.59	19.0	3.2
1.50	4.92	17.8	3.4
1.60	5.25	16.7	3.6
1.70	5.58	15.7	3.8
1.80	5.90	14.8	4.1
1.90	6.23	14.0	4.3
2.00	6.56	13.3	4.5

Table 9-5

MEAN USUAL GAIT SPEED TIME FOR MEN AND WOMEN AGE 20 YEARS AND OLDER

Sex/age	Comfortable Gait Speed (m/s)		Maximum Gait Speed (m/s)
Sex/age		SD		SD
Men
20s	1.39	0.15	2.53	0.29
30s	1.46	0.09	2.46	0.32
40s	1.46	0.16	2.46	0.36
50s	1.39	0.23	2.07	0.45
60s	1.36	0.21	1.93	0.36
70s	1.33	0.20	2.08	0.36
Women
20s	1.41	0.18	2.47	0.25
30 s	1.42	0.13	2.34	0.34
40s	1.39	0.16	2.12	0.28
50s	1.40	0.15	2.01	0.26
60s	1.27	0.21	1.77	0.25
70s	1.27	0.21	1.75	0.28

SD, standard deviation; x, mean.

Data from Bohannon RW. Comfortable and maximum walking speed of adults aged 20-79 years: reference values and determinants. Age Ageing. 1997;26(1):15-19.

Table 9-6

NORMS FOR USUAL GAIT SPEED TIME (M/S) FOR MODERATELY DISABLED WOMEN AGE 65 AND OLDER

	Total n = 1002	65-74	75-84	85+
Mean	0.6	0.7	0.6	0.4
5th percentile	0.2	0.3	0.2	0.1
25th percentile	0.4	0.5	0.4	0.3
50th percentile	0.6	0.6	0.6	0.6
75th percentile	0.7	0.7	0.8	0.6
95th percentile	1.1	1.1	1.1	0.8

M/s, meters per second; n, number of subjects.

Moderately disabled women were those with difficulty in two or more activities of daily living tasks.

Subjects were asked to walk at their usual and customary pace for 4 m.

Adapted from: Ferrucci L, Guralnik JM, Bandeen-Roche KL, et al. Performance measures from the women’s health and aging study. http://www.grc.nia.nih.gov/branches/ledb/whasbook/chap4/chap4.htm. Accessed January 8, 2012.

Table 9-7

NORMS FOR FAST GAIT SPEED TIME (M/S) FOR MODERATELY DISABLED WOMEN AGE 65 AND OLDER

	Total n = 1002	65-74	75-84	85+
Mean	0.9	1	0.9	0.7
5th percentile	0.2	0.4	0.3	0.2
25th percentile	0.6	0.8	0.6	0.4
50th percentile	0.9	1	0.9	0.7
75th percentile	1.1	1.3	1.1	0.9
95th percentile	1.7	1.7	1.7	1.3