Introduction
Methods
Measurement of Muscle Function
Muscle Strength
Grip Strength
Definition
How to Measure Grip Strength in Clinical Practice?
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Procedure The measurement is easy to perform, the device is portable, with an acceptable cost, and does not require a specialist trained user. Because of the ease of its application, grip strength measurement can be used in clinical practice, and thus, can be applied in a large sample of older adults, symptomatic or asymptomatic, to identify those with low muscle strength. It is recommended to use standardized measurement protocols such the Southampton protocol, proposed by Roberts et al. [13, 14] for the measurement of grip strength. Briefly, standardized conditions for the test include seating the subject in a standard chair with forearms resting flat on the chair arms. The testing nurse or physician should demonstrate the use of the dynamometer and show that gripping very tightly registers the best score. Six measures should be taken, 3 with each arm. Ideally, the patients should be encouraged to squeeze as hard and as tightly as possible during 3–5 s during each of the 6 trials; usually the highest reading of the 6 measurements is reported as the final result.
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Time of administration 5 min.
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Equipment A well-calibrated handheld dynamometer. Different features exist such as hydraulic dynamometer [e.g. Jamar, which is usually considered as the gold reference for this measurement, with units in kilograms (kg) or pounds (lbf)], pneumatic [e.g. Martin vigorimeter with units in millimetres of mercury (mmHg) or pounds per square inch (psi)] which measure grip pressure, mechanical [e.g. Harpenden dynamometer with units in kg or lbf) and strain dynamometer (with units in Newtons of force (N)]. Dynamometers have to be calibrated appropriately by manufacturer prior using it [15].
Performance Characteristics
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Highly feasible [16].
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Floor effects For patients with upper extremity impairment and/or affected by rheumatoid arthritis, hand osteoarthritis or carpal tunnel syndrome, grip strength measure may not be an accurate reflection of muscle strength and may lead to underestimations. The design of the Jamar dynamometer may be the reason for this [22] and a pneumatic dynamometer may be a good alternative for these patients. With the Martin vigorimeter for example, patients try to squeeze rubber balls (available in three sizes) following the same protocol as that described for the Jamar dynamometer. However, the comparison between these two devices is limited given the different unit of measure provided by them.
Reference Range
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Variety of normative data have been proposed, ranging from 16 to 21 kg for women and 26 to 30 kg for men [10, 26‐29]. It should also be noted that values adjusted for BMI or height also exists. For example, the EWGSOP [27] proposed general values for grip strength (< 30 kg for men and < 20 kg for women) but also BMI dependent value (e.g. ≤ 29 kg for men with a BMI ≤ 24 kg/m2; ≤ 30 kg for men with a BMI between 24.1 and 28 kg/m2; ≤ 32 kg for men with a BMI > 28 kg/m2; ≤ 17 kg for women with a BMI ≤ 23 kg/m2; ≤ 17.3 kg for women with a BMI between 23.1 and 26 kg/m2; ≤ 18 kg for women with a BMI between 26.1 and 29 kg/m2 and finally ≤ 21 kg for women with a BMI > 29 kg/m2).
Muscle power
Measurement of Physical Performance
Gait Speed Test
Short Walk Measures of Usual Gait Speed
Definition
How to Measure Gait Speed Test in Clinical Practice?
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Procedure short-distance walk tests are applicable in clinics and in GPs offices but some training for the testing staff is required. This measure is also highly acceptable for participants and health professionals [43, 44]. Some tentative recommendations for a protocol of administration have been proposed following a systematic review [45]: (1) use a static start with timing commencing when the foot touches the floor the first time after the line; (2) usual or comfortable pace to be used as the standard, with fast pace used as appropriate for specific research questions. (3) Walking protocol to be reported in detail including pace instructions, verbal or other encouragement, and specific timing procedures.
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Time of administration 95 ± 20 s.
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Equipment 4-m long flat floor devoid of obstacles and a chronograph. This test can therefore be administered in restricted areas.
Performance Characteristics
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Test–retest reliability excellent test–retest reliability on 4- and 10-m distance has been shown for healthy older adults (ICC values ranging from 0.96 to 0.98) [46]. Test–retest reliability of gait speed has also been assessed in populations with comorbidities such as in patients with stroke [47], COPD [48], in cardiac rehabilitation [49], etc. It has been demonstrated to be highly reliable in each of these populations.
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Responsiveness the 4-m gait speed is responsive to clinically meaningful changes with 0.05 m/s denoting a small change (i.e. clinically detectable, potentially important) and 0.1 m/s indicating a substantial change (clinically detectable, definitely important) [51].
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Floor effect A floor effect is obvious in subjects unable to walk. However, as it has been shown in a systematic review, there is a broad range of people for whom timed walking is a valid and sensitive outcome measure (patients with cancer, neurological problems, osteoarthritis, fractures, etc.) [45]. A ceiling effect has also been reported in certain populations. For example, it is doubtful whether a potential increase of muscle mass will result in an improvement in gait speed in well-functioning subjects with a high baseline walking speed.
Reference Range
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Timed usual gait has been shown to be highly predictive for future care dependence [52], for other adverse health events such as severe mobility limitation or mortality [53]. But it has also been demonstrated that poor performance in other tests of lower extremity function (standing balance test and chair rise test) had comparable prognostic value [54].
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Cut-off < 0.8 m/s for 4-m distance identifies subjects with poor physical performance [10]. A systematic review including 3 studies with 3261 participants revealed a very high sensitivity for the < 0.8 m/s cut-off for identifying frailty (Se = 0.99), as well as high negative predictive value (NPV = 0.99), but also a moderate specificity (Sp = 0.64) and a low positive predictive value (PPV = 0.26) [55].
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Cut-off < 1 m/s for a 6-m distance identifies older persons at high risk of health-related negative events [54].
Chair Stand Test
Definition
How to Measure the 30-s CST Test in Clinical Practice?
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Procedure: Classically, the 30-s CST consists of manually counting the number of total sit-stand-sit cycles completed during the 30 s of the test. This test is highly feasible in clinical practice and may therefore be recommended as a measure of physical performance.
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Time of administration 1–2 min.
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Equipment A chair with a straight back without arm rests and a stopwatch.
Performance Characteristics
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Inter-rater reliability limited data available but very strong inter-rater reliability on older adults in nursing home with mild to moderate dementia (perfect ICC of 1) [64].
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Responsiveness Very limited data available. Only a minimal detectable change (MDC) value of 3.49 in older people with dementia [66] has been defined. Then, an improvement in more than 3.49 sit-stand-sit cycles during the 30-s chair stand test is considered to be a true change in performance with 95% confidence.
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Floor effect this test is not impacted by floor effect, as it is the case of the five sit-to-stand test, since subjects unable to perform it are attributed a score of 0. Some authors argue that the 30-s CST protocol makes it possible to assess wider variations in ability levels of individuals compared to the five-time sit-to-stand test as it avoid potential floor effects [67].
Reference Range
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Limited data in literature.
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One author report an association between the test and the risk of falling in a population of older nursing home residents [68].
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Normative values have been proposed for two particular populations: Hong Kong older adults and US older adults. Normative value for Hong Kong older adults 70–74 years for example is a mean of 10.1 ± 3.8 stands during 30-s and 13 stands during 30 s for US norms [69].
Short Physical Performance Battery (SPPB)
Definition
How to Measure SPPB Test in Clinical Daily Practice?
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Time of administration 10 min.
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Equipment a 4-m track, ground marks, a chronometer and straight-backed chair.
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Procedure applicable in research and in clinics as well as in GPs offices but training is required. The full detailed instructions can be downloaded for free from the web (https://sppbguide.com/) but are summarized here below. This test is longer to apply compared to chair rising test alone or to gait speed test alone but is nevertheless feasible and can be recommended as a screening test for poor physical performance and risk of sarcopenia.
Performance Characteristics
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Test–retest reliability has been shown to be good to excellent (ICC ranging from 0.83 to 0.92 for measures made 1 week apart) [71‐73]. The reproducibility of the SPPB, already very good, can nevertheless be enhanced through the use of standardized equipment and an appropriate standard operating procedure.
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Inter-rater reliability has been shown to be excellent (ICC 0.91) among acutely admitted older medical patients [16]. Data on healthy populations are limited.
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Ceiling effects it may have ceiling effects for high functioning and very fit older adults (who will score 12 points). For research, a more challenging SPPB has been proposed, for example, in the Health, Aging and Body Composition (Health ABC) Study, with time to walk 400 m measured instead of 4-m distance, and by extending the times from 10 to 30 s for the three standard balance tests [54]. This approach is relevant to assess the wide range of functioning at baseline among fit older participant of cohort studies but is unlikely to be useful in clinical practice.
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Floor effects it is still not clear how to score a subject unable to walk and therefore unable to perform the SPPB test correctly. Floor effects of 0 points may be observed in this specific case.
Reference Range
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Cut-off point of ≤ 10 points has been shown to be a strong predictor of the loss of ability to walk 400 meters with a sensitivity of 0.69 and a specificity of 0.84 [42].
Timed-Get-Up-and-Go Test
Definition
How to Measure the TUG Test in Clinical Daily Practice?
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Procedure Applicable in clinical settings and GPs offices and on different populations (with frailty, Parkinson’s disease, cognitive impairment, recent joint surgery, osteoarthritis, etc.); little training is necessary.
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TUG requires the subject to stand up from a chair, walk three meters, turn around, return and sit down again. The stopwatch is started on the word “go” and stopped at the moment the subject sits down. The person wears regular footwear, uses his/her customary walking aid and walks at her/his usual pace. No physical assistance is given. A practice trial is given first, and the average time of two consecutive trials is recorded.
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Complete instructions can be downloaded in the following website: http://foxrehab.org/uploads/pdf/2008_AssitedLivingConsult_TUGTest.pdf. A video provided by the Center for Disease Control and Prevention (CDC) is also available on the following website: https://www.youtube.com/watch?v=BA7Y_oLElGY.
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Time of administration 2–3 min.
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Equipment Chair with armrest, 3-m track, ground marks, stopwatch.
Performance Characteristics
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Responsiveness not well defined in older populations. A reduction in time greater than or equal to 0.8, 1.4 and 1.2 s on the TUG has been determined to be the Minimal Important Clinical Change score (MCID) for patients suffering from hip osteoarthritis [83].
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Floor and ceiling effects the TUG does not suffer from ceiling effects [84]. Floor effects are observed, as for each test involving a person’s walking ability.
Reference Range
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The time to perform the task is compared to normative values for age, gender, and research-based guidelines that measure increased risk of falls and functional decline. The performance of the patient can also be summarized into a five-point scaled score [85].
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A TUG score of 14 s is sensitive (87%) and specific (87%) for identifying older individuals who are at risk for falls [82].
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In the systematic review of Clegg et al. [55]., assessing, among others, the accuracy of the TUG test for identifying frailty, a sensitivity of 0.93 has been shown for the cut-off of > 10 points (with a negative predictive value of 0.99), with a specificity of 0.62 (with a positive predictive value of only 0.17).