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Reliability of isokinetic normalized peak torque assessments for knee muscles in post-stroke hemiparesis
Gait & Posture 27 (2008) 715–718 www.elsevier.com/locate/gaitpost
Short communication
Reliability of isokinetic normalized peak torque assessments for knee muscles in post-stroke hemiparesis Shohreh Noorizadeh Dehkordi a,1, Saeed Talebian a,*, Gholamreza Olyaei a,1, Ali Montazeri b a
Tehran University of Medical Sciences, Rehabilitation Faculty, Department of Physiotherapy, Enghelab Avenue, Piche Shemiran, P.O. Box 11365-1683, Tehran, Iran b Iranian Institute for Health Sciences Research, P.O. Box 13185-1488, Tehran, Iran Received 12 February 2007; received in revised form 17 July 2007; accepted 22 July 2007
Abstract The purpose of this study was to establish test–retest reliability of measurement procedures for quantifying isokinetic concentric peak torque (PT) at the knee using normalization methods post-stroke. A second aim was to estimate the change required to show clinically significant improvements in knee muscles strength. The isokinetic normalized PT (NPT) values for the knee extensors and flexors were measured in each participant at two different angular velocities during two sessions 1 day apart. Thirty participants with mild to moderate hemiparesis after stroke who were able to walk were tested. The normalized PT measures for the knee muscles of the affected lower extremity were highly reliable (intraclass correlation coefficients ranged from 0.85 to 0.98; p < 0.05). Size of relative changes (the percent smallest real difference, SRD%) for extensors NPT (ranged from 22.35% to 25.68%) were lower than flexors NPT (ranged from 74.01% to 76.31%), indicating that the affected isokinetic knee flexors had more random variation than the knee extensors. This study supports the use of isokinetic dynamometers for the assessment of knee muscle strength in participants with chronic mild to moderate post-stroke hemiparesis and to measure clinical improvements. Established measurement error and smallest real differences in normalized PT will aid interpretation of real changes in muscle strength in this clinical population. # 2007 Elsevier B.V. All rights reserved. Keywords: Hemiparesis; Reliability; Weakness; Stroke
1. Introduction Muscle weakness is a primary source of motor impairment amongst stroke survivors [1]. It is associated with reductions in peak muscle torque, decreases in the velocity of force development, lack of sustaining force output, rapid onset of fatigue and ineffective force production within the context of a task [1,2]. In addition, several studies have shown weakness of the ipsilesional side as early as 1 week following stroke [3,4]. Isokinetic * Corresponding author. Tel.: +98 21 77533939; fax: +98 21 77534133. E-mail addresses: [email protected] (S. Noorizadeh Dehkordi), [email protected] (S. Talebian), [email protected] (G. Olyaei), [email protected] (A. Montazeri). 1 Tel.: +98 21 77533939; fax: +98 21 77534133. 0966-6362/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2007.07.013
dynamometers are frequently used to assess muscle strength at different velocities in both health and disease. There is preliminary evidence of high relative test–retest reliability of repeated measures of knee muscles strength in patients more than 6 months post-stroke [5–10]. Nevertheless, few studies demonstrated measurement errors and systematic changes in the mean for peak torque (PT) in isokinetic dynamometers [5,7]. No studies have quantified the smallest real difference (SRD) in PT measures quantified with the normalization methods at angular velocities of 608/s and 1208/s for the lower limbs using isokinetic dynamometry. The objectives of this study were therefore to: (i) determine values of concentric PT quantified with the normalization method in the affected and unimpaired knee flexors and extensors, (ii) establish the relative and absolute reliability of concentric knee extensors and flexors PT within
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S. Noorizadeh Dehkordi et al. / Gait & Posture 27 (2008) 715–718
2. Methods
maximal warm up trials, they performed three maximal knee extensions and flexions at velocity of 608/s with a 30 s rest between trials. After 2 min rest, the test was continued with five maximal contractions at velocity of 1208/s. After a further 10 min rest, the procedure was repeated for the other limb. On the next day the same protocol was followed. The primary researcher (SND) performed all measurements on two separate sessions 1 day apart at the same time of the day.
2.1. Design and participants
2.3. Statistical analyses
For the test–retest reliability study, 42 participants post-stroke were recruited from October 2005 to November 2006. Of the 42 participants screened, 30 participants (19 male and 11 female) were included in the study. The mean age was 61.5 years (S.D. = 11.75) and the mean body mass indexes were 26.48 kg/ m2 (S.D. = 4.31). The average post-onset period was 18.4 months (S.D. = 12.52). The average motor function score of the affected lower extremity using the Fugl–Meyer assessment [11] was 54.9 (S.D. = 26.1). To be included the first stroke needed to occur between 6 and 60 months earlier. Other inclusion criteria were: over 40 years of age, and able to walk independently for a minimum of 40 m with or without using an assistive device on a level surface. The diagnoses needed to be confirmed by MRI or CT-scan. They were excluded if they had disorders that compromised muscle strength and if they scored less than 23 on the Folstein Mini-Mental Status Test [12]. The ethic committee of the Tehran University of Medical Sciences approved the study (Ref. number: 260-306). Informed consent was obtained from all the participants.
From the considerable amount of data that Biodex System software provided, PT and normalized peak torque (NPT) values were selected to keep analysis simple. The a level was set at 0.05 for all analyses. Agreement between two sessions was assessed by intraclass correlation coefficients (ICC). Systematic changes in the mean of the knee extensors and flexors strength values around the zero line were assessed using the Bland–Altman analysis. This included the calculation of the mean difference between the two test sessions (p), standard error of p and 95% confidence intervals for p. Absolute reliability of NPT measurements was also assessed using the standard error of measurement (SEM). The smallest change in flexors and extensors NPT that indicates a real improvement for a group of individuals and for a single participant was represented using the SEM% and SRD%, respectively [13].
two angular velocities in post-stroke hemiparesis individuals, and (iii) determine SRD in the affected knee muscles strength, as this represents the minimum difference to clarify any significant clinical changes.
3. Results
2.2. Procedure The Biodex isokinetic dynamometer was used to measure isokinetic concentric muscle strength for bilateral knee flexors and extensors at angular velocities of 608/s and 1208/s. Each participant was positioned on the dynamometer in a supported semi-reclining position with knee over the edge of the chair. In that position, the hip joint angle was adjusted at 558 with forward inclination from the horizontal plane by changing the backrest of the chair. The leg was positioned so that the lateral knee joint line was aligned with the dynamometer center of rotation. The range was set from 808 to 208 flexion. Each participant was given a familiarization trial before the first test session. During the first assessment, each participant performed a total of 11 trials during the strength test for each limb. After completing the first three sub
All participants were able to complete the test protocols at both angular velocities except four, who showed zero torque for the affected knee flexors in two velocities. Table 1 shows that the mean PT and NPT values in the affected lower limbs indicate statistically significant lower values than the unimpaired side ( p < 0.01). As seen in Table 2, the ICC between two sessions for PT and NPT ranged from 0.85 to 0.99, p < 0.01. All p values were close to zero with acceptable 95% confidence intervals (CI). In addition, all SEM values were below 3.3. The percent SEM in the affected knee extensors and flexors were below 9.29% and 30.71%, respectively. The percent SRD ranged from 18.73% to 85.11%.
Table 1 Means and S.D. of peak torque (PT) and normalized peak torque (NPT) measurements for the knee muscle groups in Nm and Nm/kg in two angular velocities in chronic post-stroke hemiparesis Muscle groups
Mean (S.D.) Affected side
Unimpaired side
PT
NPT
PT
NPT
Knee extensors 608/s 1208/s
35.80 (28.15) 31.89 (25.14)
50.98 (37.70) 41.30 (27.23)
67.82 (36.93) 54.25 (30.01)
98.50 (45.23) 77.45 (37.01)
Knee flexors 608/s 1208/s
10.39 (9.38) 8.81 (7.25)
14.21 (12.52) 12.05 (9.02)
28.50 (17.96) 26.01 (16.09)
40.44 (20.85) 33.73 (20.00)
S. Noorizadeh Dehkordi et al. / Gait & Posture 27 (2008) 715–718
717
Table 2 Test–retest reliability of the affected peak torques (PT) and normalized peak torques (NPT) measurements in Nm and Nm/kg Knee muscles
ICC
95% CI for ICC
95% CI for p
SEM
SEM%
SRD%
95% CI for SRD
PT extension 608/s 1208/s
0.99 0.99
0.98–0.99 0.98–0.99
0.62 1.02
2.16 to 0.92 2.61 to 0.56
3.3 2.19
9.14 6.76
25.34 18.73
9.77 to 8.53 7.09 to 5.05
PT flexion 608/s 1208/s
0.90 0.88
0.82–0.95 0.78–0.94
0.53 0.29
0.89 to 1.95 1.01 to 1.59
3.08 2.75
30.42 30.71
84.36 85.11
8.01 to 9.07 7.33 to 7.91
NPT extension 608/s 1208/s
0.98 0.97
0.96–0.99 0.94–0.98
0.46 1.73
2.40 to 3.32 4.20 to 0.74
2.92 3.01
8.09 9.29
22.35 25.68
8.69 to 7.45 9.34 to 7.3
NPT flexion 608/s 1208/s
0.85 0.86
0.71–0.92 0.72–0.93
1.23 0.68
1.14 to 3.60 1.04 to 2.40
2.71 2.47
26.78 27.6
74.01 76.31
6.96 to 8.02 6.54 to 7.12
p
ICC: intraclass coefficient; CI: confidence interval; p: the mean difference between the two test sessions; SEM: standard error of measurement; SRD: smallest real difference.
4. Discussion
Acknowledgments
All of the normalized isokinetic strength measures for the affected knee extensors and flexors were found to be highly reliable. However, the affected isokinetic knee flexors had more random variation than the knee extensors. Previous studies have shown the mean of muscles strength of the affected limb to be lower than the unimpaired limb [5,6,9]. This may be due to compromised neural activation [14], inactivity [1], and impaired muscular activation [15]. The ICC values for all concentric measurements in this study were high. These observations are consistent with previously conducted work in stroke at velocities of 608/s and 1208/s [5–7,9]. In this study, SEM values for the affected knee muscle strengths were small (ranged from 2.19 to 3.3) whereas Flansbjer et al. [7] reported the SEM values ranging from 6.3 to 10.6. These differences might be due to different measurement protocols and samples. In the current study, size of relative changes (SRD% and SEM%) for extensors PT were lower than the level reported by Clark et al. and Flansbjer et al. [5,7]. However, SRD% and SEM% for flexors PT were greater than the level that was reported by Flansbjer et al. [7]. This discrepancy could be related to differences in sample size, population, research methodologies, and differences in the degree of post-stroke muscle weakness. Thus, the findings of this study should be interpreted with caution. To conclude, this study supports the use of isokinetic dynamometers for the assessment of knee muscles strength in participants with chronic mild to moderate post-stroke hemiparesis and to measure clinical improvements. When quantifying muscle strength, the normalization of PT related to the body weight may be a useful procedure to distinguish small changes after rehabilitation. Nevertheless, the measurements in this study were limited to the two angular velocities of the knee that limits the generalizability of the findings.
The authors would like to thank the Deputy of Research Affairs of Tehran University of Medical Sciences and Reza Keyhani for the statistical consultancy. The helpful comments and suggestions of the anonymous reviewers were greatly appreciated. Finally, we would like to thank Prof. M. Morris for her editorial corrections of the manuscript. Source of support: This work is supported by a grant from the Deputy of Research Affairs of Tehran University of Medical Sciences and Health Services. The ethic committee of the Tehran University of Medical Sciences, Rehabilitation Faculty (Ref. number: 260-306) approved the study and informed consent was obtained from all the participants.
Conflict of interest None.
References [1] Patten C, Lexell J, Brown HE. Weakness and strength training in persons with post-stroke hemiplegia. Rational, method, and efficacy. J Rehabil Res Dev 2004;41:293–312. [2] Canning CG, Ada L, O’Dwyer N. Slowness to develop force contributes to weakness after stroke. Arch Phys Med Rehabil 1999;80:66– 70. [3] Desrosiers J, Bourbonnais D, Bravo G, Roy PM, Guay M. Performance of the ‘‘unaffected’’ upper extremity of elderly stroke patients. Stroke 1996;27:1564–70. [4] Harris ML, Polkey MI, Bath PM, Moxham J. Quadriceps muscle weakness following acute hemiplegic stroke. Clin Rehabil 2001;15:274–81. [5] Clark DJ, Condliffe EG, Patten C. Reliability of concentric and eccentric torque during isokinetic knee extension in post-stroke hemiparesis. Clin Biomech (Bristol Avon) 2006;21:395–404. [6] Eng JJ, Kim CM, Macintyre DL. Reliability of lower extremity strength measures in persons with chronic stroke. Arch Phys Med Rehabil 2002;83:322–8.
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S. Noorizadeh Dehkordi et al. / Gait & Posture 27 (2008) 715–718
[7] Flansbjer UB, Holmback AM, Downham D, Lexell J. What change in isokinetic knee muscle strength can be detected in men and woman with hemiparesis after stroke? Clin Rehabil 2005;19: 514–22. [8] Hsu AL, Tang PF, Jan MH. Test–retest reliability of isokinetic muscle strength of the lower extremities in patients with stroke. Arch Phys Med Rehabil 2002;83:1130–7. [9] Pohl PS, Startzell JK, Duncan PW, Wallace D. Reliability of lower extremity isokinetic strength testing in adults with stroke. Clin Rehabil 2000;14:601–7. [10] Tripp EJ, Harris SR. Test–retest reliability of isokinetic knee extension and flexion torque measurements in persons with spastic hemiparesis. Phys Ther 1991;71:390–6.
[11] Sanford J, Moreland J, Swanson LR, Stratford PW, Gowland C. Reliability of the Fugl–Meyer assessment for testing motor performance in patients following stroke. Phys Ther 1993;73:447–54. [12] Folstein MF, Folstein SE, McHugh PR. ‘‘Mini-mental state’’. A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975;12:189–98. [13] Lexell JE, Downham DY. How to assess the reliability of measurements in rehabilitation. Am J Phys Med Rehabil 2005;84:719–23. [14] McComas AJ, Sica RE, Upton AR, Aguilera N. Functional changes in motoneurones of hemiparetic patients. J Neurol Neurosurg Psychiatry 1973;36:183–93. [15] Bourbonnais D, Vanden NS. Weakness in patients with hemiparesis. Am J Occup Ther 1989;43:313–9.
Short communication
Reliability of isokinetic normalized peak torque assessments for knee muscles in post-stroke hemiparesis Shohreh Noorizadeh Dehkordi a,1, Saeed Talebian a,*, Gholamreza Olyaei a,1, Ali Montazeri b a
Tehran University of Medical Sciences, Rehabilitation Faculty, Department of Physiotherapy, Enghelab Avenue, Piche Shemiran, P.O. Box 11365-1683, Tehran, Iran b Iranian Institute for Health Sciences Research, P.O. Box 13185-1488, Tehran, Iran Received 12 February 2007; received in revised form 17 July 2007; accepted 22 July 2007
Abstract The purpose of this study was to establish test–retest reliability of measurement procedures for quantifying isokinetic concentric peak torque (PT) at the knee using normalization methods post-stroke. A second aim was to estimate the change required to show clinically significant improvements in knee muscles strength. The isokinetic normalized PT (NPT) values for the knee extensors and flexors were measured in each participant at two different angular velocities during two sessions 1 day apart. Thirty participants with mild to moderate hemiparesis after stroke who were able to walk were tested. The normalized PT measures for the knee muscles of the affected lower extremity were highly reliable (intraclass correlation coefficients ranged from 0.85 to 0.98; p < 0.05). Size of relative changes (the percent smallest real difference, SRD%) for extensors NPT (ranged from 22.35% to 25.68%) were lower than flexors NPT (ranged from 74.01% to 76.31%), indicating that the affected isokinetic knee flexors had more random variation than the knee extensors. This study supports the use of isokinetic dynamometers for the assessment of knee muscle strength in participants with chronic mild to moderate post-stroke hemiparesis and to measure clinical improvements. Established measurement error and smallest real differences in normalized PT will aid interpretation of real changes in muscle strength in this clinical population. # 2007 Elsevier B.V. All rights reserved. Keywords: Hemiparesis; Reliability; Weakness; Stroke
1. Introduction Muscle weakness is a primary source of motor impairment amongst stroke survivors [1]. It is associated with reductions in peak muscle torque, decreases in the velocity of force development, lack of sustaining force output, rapid onset of fatigue and ineffective force production within the context of a task [1,2]. In addition, several studies have shown weakness of the ipsilesional side as early as 1 week following stroke [3,4]. Isokinetic * Corresponding author. Tel.: +98 21 77533939; fax: +98 21 77534133. E-mail addresses: [email protected] (S. Noorizadeh Dehkordi), [email protected] (S. Talebian), [email protected] (G. Olyaei), [email protected] (A. Montazeri). 1 Tel.: +98 21 77533939; fax: +98 21 77534133. 0966-6362/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.gaitpost.2007.07.013
dynamometers are frequently used to assess muscle strength at different velocities in both health and disease. There is preliminary evidence of high relative test–retest reliability of repeated measures of knee muscles strength in patients more than 6 months post-stroke [5–10]. Nevertheless, few studies demonstrated measurement errors and systematic changes in the mean for peak torque (PT) in isokinetic dynamometers [5,7]. No studies have quantified the smallest real difference (SRD) in PT measures quantified with the normalization methods at angular velocities of 608/s and 1208/s for the lower limbs using isokinetic dynamometry. The objectives of this study were therefore to: (i) determine values of concentric PT quantified with the normalization method in the affected and unimpaired knee flexors and extensors, (ii) establish the relative and absolute reliability of concentric knee extensors and flexors PT within
716
S. Noorizadeh Dehkordi et al. / Gait & Posture 27 (2008) 715–718
2. Methods
maximal warm up trials, they performed three maximal knee extensions and flexions at velocity of 608/s with a 30 s rest between trials. After 2 min rest, the test was continued with five maximal contractions at velocity of 1208/s. After a further 10 min rest, the procedure was repeated for the other limb. On the next day the same protocol was followed. The primary researcher (SND) performed all measurements on two separate sessions 1 day apart at the same time of the day.
2.1. Design and participants
2.3. Statistical analyses
For the test–retest reliability study, 42 participants post-stroke were recruited from October 2005 to November 2006. Of the 42 participants screened, 30 participants (19 male and 11 female) were included in the study. The mean age was 61.5 years (S.D. = 11.75) and the mean body mass indexes were 26.48 kg/ m2 (S.D. = 4.31). The average post-onset period was 18.4 months (S.D. = 12.52). The average motor function score of the affected lower extremity using the Fugl–Meyer assessment [11] was 54.9 (S.D. = 26.1). To be included the first stroke needed to occur between 6 and 60 months earlier. Other inclusion criteria were: over 40 years of age, and able to walk independently for a minimum of 40 m with or without using an assistive device on a level surface. The diagnoses needed to be confirmed by MRI or CT-scan. They were excluded if they had disorders that compromised muscle strength and if they scored less than 23 on the Folstein Mini-Mental Status Test [12]. The ethic committee of the Tehran University of Medical Sciences approved the study (Ref. number: 260-306). Informed consent was obtained from all the participants.
From the considerable amount of data that Biodex System software provided, PT and normalized peak torque (NPT) values were selected to keep analysis simple. The a level was set at 0.05 for all analyses. Agreement between two sessions was assessed by intraclass correlation coefficients (ICC). Systematic changes in the mean of the knee extensors and flexors strength values around the zero line were assessed using the Bland–Altman analysis. This included the calculation of the mean difference between the two test sessions (p), standard error of p and 95% confidence intervals for p. Absolute reliability of NPT measurements was also assessed using the standard error of measurement (SEM). The smallest change in flexors and extensors NPT that indicates a real improvement for a group of individuals and for a single participant was represented using the SEM% and SRD%, respectively [13].
two angular velocities in post-stroke hemiparesis individuals, and (iii) determine SRD in the affected knee muscles strength, as this represents the minimum difference to clarify any significant clinical changes.
3. Results
2.2. Procedure The Biodex isokinetic dynamometer was used to measure isokinetic concentric muscle strength for bilateral knee flexors and extensors at angular velocities of 608/s and 1208/s. Each participant was positioned on the dynamometer in a supported semi-reclining position with knee over the edge of the chair. In that position, the hip joint angle was adjusted at 558 with forward inclination from the horizontal plane by changing the backrest of the chair. The leg was positioned so that the lateral knee joint line was aligned with the dynamometer center of rotation. The range was set from 808 to 208 flexion. Each participant was given a familiarization trial before the first test session. During the first assessment, each participant performed a total of 11 trials during the strength test for each limb. After completing the first three sub
All participants were able to complete the test protocols at both angular velocities except four, who showed zero torque for the affected knee flexors in two velocities. Table 1 shows that the mean PT and NPT values in the affected lower limbs indicate statistically significant lower values than the unimpaired side ( p < 0.01). As seen in Table 2, the ICC between two sessions for PT and NPT ranged from 0.85 to 0.99, p < 0.01. All p values were close to zero with acceptable 95% confidence intervals (CI). In addition, all SEM values were below 3.3. The percent SEM in the affected knee extensors and flexors were below 9.29% and 30.71%, respectively. The percent SRD ranged from 18.73% to 85.11%.
Table 1 Means and S.D. of peak torque (PT) and normalized peak torque (NPT) measurements for the knee muscle groups in Nm and Nm/kg in two angular velocities in chronic post-stroke hemiparesis Muscle groups
Mean (S.D.) Affected side
Unimpaired side
PT
NPT
PT
NPT
Knee extensors 608/s 1208/s
35.80 (28.15) 31.89 (25.14)
50.98 (37.70) 41.30 (27.23)
67.82 (36.93) 54.25 (30.01)
98.50 (45.23) 77.45 (37.01)
Knee flexors 608/s 1208/s
10.39 (9.38) 8.81 (7.25)
14.21 (12.52) 12.05 (9.02)
28.50 (17.96) 26.01 (16.09)
40.44 (20.85) 33.73 (20.00)
S. Noorizadeh Dehkordi et al. / Gait & Posture 27 (2008) 715–718
717
Table 2 Test–retest reliability of the affected peak torques (PT) and normalized peak torques (NPT) measurements in Nm and Nm/kg Knee muscles
ICC
95% CI for ICC
95% CI for p
SEM
SEM%
SRD%
95% CI for SRD
PT extension 608/s 1208/s
0.99 0.99
0.98–0.99 0.98–0.99
0.62 1.02
2.16 to 0.92 2.61 to 0.56
3.3 2.19
9.14 6.76
25.34 18.73
9.77 to 8.53 7.09 to 5.05
PT flexion 608/s 1208/s
0.90 0.88
0.82–0.95 0.78–0.94
0.53 0.29
0.89 to 1.95 1.01 to 1.59
3.08 2.75
30.42 30.71
84.36 85.11
8.01 to 9.07 7.33 to 7.91
NPT extension 608/s 1208/s
0.98 0.97
0.96–0.99 0.94–0.98
0.46 1.73
2.40 to 3.32 4.20 to 0.74
2.92 3.01
8.09 9.29
22.35 25.68
8.69 to 7.45 9.34 to 7.3
NPT flexion 608/s 1208/s
0.85 0.86
0.71–0.92 0.72–0.93
1.23 0.68
1.14 to 3.60 1.04 to 2.40
2.71 2.47
26.78 27.6
74.01 76.31
6.96 to 8.02 6.54 to 7.12
p
ICC: intraclass coefficient; CI: confidence interval; p: the mean difference between the two test sessions; SEM: standard error of measurement; SRD: smallest real difference.
4. Discussion
Acknowledgments
All of the normalized isokinetic strength measures for the affected knee extensors and flexors were found to be highly reliable. However, the affected isokinetic knee flexors had more random variation than the knee extensors. Previous studies have shown the mean of muscles strength of the affected limb to be lower than the unimpaired limb [5,6,9]. This may be due to compromised neural activation [14], inactivity [1], and impaired muscular activation [15]. The ICC values for all concentric measurements in this study were high. These observations are consistent with previously conducted work in stroke at velocities of 608/s and 1208/s [5–7,9]. In this study, SEM values for the affected knee muscle strengths were small (ranged from 2.19 to 3.3) whereas Flansbjer et al. [7] reported the SEM values ranging from 6.3 to 10.6. These differences might be due to different measurement protocols and samples. In the current study, size of relative changes (SRD% and SEM%) for extensors PT were lower than the level reported by Clark et al. and Flansbjer et al. [5,7]. However, SRD% and SEM% for flexors PT were greater than the level that was reported by Flansbjer et al. [7]. This discrepancy could be related to differences in sample size, population, research methodologies, and differences in the degree of post-stroke muscle weakness. Thus, the findings of this study should be interpreted with caution. To conclude, this study supports the use of isokinetic dynamometers for the assessment of knee muscles strength in participants with chronic mild to moderate post-stroke hemiparesis and to measure clinical improvements. When quantifying muscle strength, the normalization of PT related to the body weight may be a useful procedure to distinguish small changes after rehabilitation. Nevertheless, the measurements in this study were limited to the two angular velocities of the knee that limits the generalizability of the findings.
The authors would like to thank the Deputy of Research Affairs of Tehran University of Medical Sciences and Reza Keyhani for the statistical consultancy. The helpful comments and suggestions of the anonymous reviewers were greatly appreciated. Finally, we would like to thank Prof. M. Morris for her editorial corrections of the manuscript. Source of support: This work is supported by a grant from the Deputy of Research Affairs of Tehran University of Medical Sciences and Health Services. The ethic committee of the Tehran University of Medical Sciences, Rehabilitation Faculty (Ref. number: 260-306) approved the study and informed consent was obtained from all the participants.
Conflict of interest None.
References [1] Patten C, Lexell J, Brown HE. Weakness and strength training in persons with post-stroke hemiplegia. Rational, method, and efficacy. J Rehabil Res Dev 2004;41:293–312. [2] Canning CG, Ada L, O’Dwyer N. Slowness to develop force contributes to weakness after stroke. Arch Phys Med Rehabil 1999;80:66– 70. [3] Desrosiers J, Bourbonnais D, Bravo G, Roy PM, Guay M. Performance of the ‘‘unaffected’’ upper extremity of elderly stroke patients. Stroke 1996;27:1564–70. [4] Harris ML, Polkey MI, Bath PM, Moxham J. Quadriceps muscle weakness following acute hemiplegic stroke. Clin Rehabil 2001;15:274–81. [5] Clark DJ, Condliffe EG, Patten C. Reliability of concentric and eccentric torque during isokinetic knee extension in post-stroke hemiparesis. Clin Biomech (Bristol Avon) 2006;21:395–404. [6] Eng JJ, Kim CM, Macintyre DL. Reliability of lower extremity strength measures in persons with chronic stroke. Arch Phys Med Rehabil 2002;83:322–8.
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S. Noorizadeh Dehkordi et al. / Gait & Posture 27 (2008) 715–718
[7] Flansbjer UB, Holmback AM, Downham D, Lexell J. What change in isokinetic knee muscle strength can be detected in men and woman with hemiparesis after stroke? Clin Rehabil 2005;19: 514–22. [8] Hsu AL, Tang PF, Jan MH. Test–retest reliability of isokinetic muscle strength of the lower extremities in patients with stroke. Arch Phys Med Rehabil 2002;83:1130–7. [9] Pohl PS, Startzell JK, Duncan PW, Wallace D. Reliability of lower extremity isokinetic strength testing in adults with stroke. Clin Rehabil 2000;14:601–7. [10] Tripp EJ, Harris SR. Test–retest reliability of isokinetic knee extension and flexion torque measurements in persons with spastic hemiparesis. Phys Ther 1991;71:390–6.
[11] Sanford J, Moreland J, Swanson LR, Stratford PW, Gowland C. Reliability of the Fugl–Meyer assessment for testing motor performance in patients following stroke. Phys Ther 1993;73:447–54. [12] Folstein MF, Folstein SE, McHugh PR. ‘‘Mini-mental state’’. A practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975;12:189–98. [13] Lexell JE, Downham DY. How to assess the reliability of measurements in rehabilitation. Am J Phys Med Rehabil 2005;84:719–23. [14] McComas AJ, Sica RE, Upton AR, Aguilera N. Functional changes in motoneurones of hemiparetic patients. J Neurol Neurosurg Psychiatry 1973;36:183–93. [15] Bourbonnais D, Vanden NS. Weakness in patients with hemiparesis. Am J Occup Ther 1989;43:313–9.