Abstract
BACKGROUND:
Muscle weakness is a common impairment accompanying stroke.
OBJECTIVE:
Describe isokinetic testing procedures and clinimetric findings associated with the testing of older individuals with weakness following stroke.
METHODS:
Relevant articles were identified by an electronic PubMed search using the search string “isokinet
RESULTS:
Seventy-six relevant articles were found. The articles largely support the validity and reliability of isokinetic strength testing of older patients with stroke. Little data are available that provides specific information on the responsiveness for such measures.
CONCLUSIONS:
Isokinetic dynamometry is a valid and reliable measure of muscle strength after stroke. However, it is not particularly practical and information is lacking regarding its responsiveness.
Introduction
Stroke is the most common neurological disorder in the world today. The World Stroke Organization has estimated that the worldwide incidence of stroke is 15 million per year and that stroke is the second leading cause of death for adults older than 60 years [1]. Although numerous impairments can result directly from stroke, muscle weakness is probably the most common and obvious [2]. Several options are available for measuring muscle strength after stroke, among them are self-report [3] manual muscle testing [4], field tests such as sit-to-stand [5], hand-held dynamometry [6], hand-grip dynamometry [7], and isokinetic dynamometry [8]. This review focuses on isokinetic dynamometry. Specifically, it seeks to describe the isokinetic testing procedures that have been applied to older individuals with stroke and the findings obtained using the procedures.
Methods
Potentially relevant articles were identified by a search of PubMed on February 10, 2019. The search string used was “isokinet
Summary of studies describing the isokinetic measurement of strength after stroke
Summary of studies describing the isokinetic measurement of strength after stroke
The PubMed search identified 161 potentially relevant articles. An additional 3 possibly relevant articles were identified by hand searches. Ultimately, 76 articles were found that met inclusion and exclusion criteria. Relevant information from those articles is summarized alphabetically by author in Table 1 [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83].
The summarized information shows that isokinetic dynamometers have been used extensively to measure strength in individuals with stroke, most often older adults (mean/median age of 48.3 to 74.0 years) with chronic stroke. Isokinetic testing of individuals with stroke has been conducted in at least 15 different countries, but testing is reported most widely in North America and Europe. Utilization of some model of 7 different dynamometers has been described in the literature, with some type of Biodex described most frequently, followed by some model of Cybex or KinCom. Most articles that specified the type of measurement obtained documented concentric torque. Some articles however were inspecific or reported the measurement of eccentric or isometric torque with isokinetic dynamometers. A few articles reported torque normalized against body weight, the nonparetic side, or healthy controls [8, 9, 11, 16, 20, 22, 23, 35, 40, 43, 44, 53, 56, 58, 64, 65, 69, 73], or measures of work, power, or velocity [13, 40, 45, 63, 68, 69, 79]. The speed of concentric and eccentric testing ranged from 15 to 240
The clinimetric properties of isokinetic testing of individuals with stroke is generally well-supported. Validity has been demonstrated most often by differences in known groups and known conditions. Specifically, numerous studies have demonstrated that individuals with stroke are weaker, often significantly (SGNF), than controls in both the paretic [11, 17, 19, 28, 38, 55, 63, 64] and nonparetic [11, 17, 23, 28, 35, 38, 55, 61, 63, 71, 74, 78] limbs, that individuals with stroke are weaker (almost always SGNF) on their paretic side than on their nonparetic side [10, 13, 14, 15, 16, 20, 22, 23, 27, 28, 30, 31, 33, 34, 35, 36, 38, 40, 41, 43, 45, 47, 54, 55, 67, 68, 70, 72, 75, 77], that men tend to be SGNF stronger than women [79], that ambulatory individuals tend to be SGNF stronger than nonambulatory individuals [59], and that community ambulators are SGNF stronger than household ambulators [41]. Validity is also supported by correlations between isokinetically measured strengths of different muscle actions [26, 48] and between isokinetic strength measures at different speeds [14, 62, 81]. Most studies examining the correlation between isokinetic measurements of the lower limbs and mobility [13, 17, 31, 38, 39, 43, 47, 48, 54, 56, 62, 70, 74, 76, 77, 83] and other important variables [20, 60] have also reported SGNF results.
Numerous studies have used intraclass correlation coefficients (ICCs) to describe the relative reliability of strength measures obtained from individuals with stroke tested with isokinetic dynamometers. One study reported ICCs for inter-tester reliability of 0.61 to 0.96 [69]. All other studies addressing reliability focused on the test-retest consistency of measures obtained over periods of 1 day to 6 weeks. With the exception of a few results reported by Hsu et al. [40] and Kim et al. [45] virtually all test-retest ICCs reported exceeded 0.80 [8, 19, 22, 25, 27, 32, 40, 45, 67, 69]. The absolute reliability of isokinetic measures obtained from patients with stroke has received little attention. However, a few studies have reported a wide range of smallest real differences of 1.5 to 85.1% [19, 25, 15, 32], which also reflect on responsiveness. No studies were found that used minimal detectable changes or minimal clinically important differences to reflect responsiveness. What was found in abundance were studies showing a wide range of increases in isokinetic strength, some SGNF in response to strengthening and other interventions as well as the natural course of stroke recovery [11, 16, 18, 21, 24, 29, 30, 33, 34, 37, 44, 46, 49, 50, 51, 52, 53, 61, 65, 71, 72, 73, 76, 80, 81, 82]. Whether described using ICCs, smallest real difference or some other indication of reliability the magnitude of summary descriptions is dependent on the sensitivity of the isokinetic measurement, the time between measurements, the natural course of stroke recovery, and the effectiveness of any intervention applied between measurements.
In spite of precedence and evidence supporting the use of isokinetic testing of strength following stroke, the information in this nonsystematic review is limited. Most notably, a single bibliographic database (PubMed) was used. While it is doubtful that the inclusion of additional databases would have markedly altered the results, such expansion may have added to the evidence for the conclusions presented herein. A more systematic review may have also allowed for a meta-analysis of some variables and for a quality assessment of included articles.
Conclusion
There is considerable research support for measuring the isokinetic strength of older individuals who have experienced a stroke. That noted, the data are mostly limited to the young old and information on responsiveness is limited.
Footnotes
Conflict of interest
The author declares no conflict of interest.
