Objective: To measure muscle strength and motor fatigue with a knee dynamometer and to assess the intra-rater reliability of measurements for maximal isometric extensor and flexor torques and the reliability of a new fatigue index (FI) in patients with mild to moderate multiple sclerosis (MS).
Design: Repeated assessments with one-week intervals.
Setting: The Masku Neurological Rehabilitation Centre, Masku, and the Social Insurance Institution, Research Department, Turku, Finland.
Subjects: Twenty-eight MS patients.
Outcome measures: Maximal isometric torque during 5 s and fatigue of knee flexors and extensors during isometric contractions of 30 s were assessed. A new FI was established and compared with the two previously used indices (FI1 and FI2). All three indices are based on the calculated area under the force versus time curve (AUFC), with FI1 using the 30-s recording time in its entirety and F2 omitting the initial 5 s in the calculation. In the new fatigue index (FI3), the time point of maximum (TPM) torque achieved by the subject is used as the starting point in the calculation. The patient's subjective fatigue was measured by Fatigue Severity Scale (FSS).
Results: The intraclass correlation coefficient (ICC) was 0.97 in maximal isometric torque measurements. FI3 showed good intra-rater reliability (ICC 0.68-0.86). None of the fatigue indices correlated with FSS.
Conclusions: Maximal isometric torque and motor fatigue of knee flexor and extensor muscles can be reliably measured using a knee dynamometer in MS patients. The new FI proved to be a reliable model for MS patients.
References
1.
1 Rice CL, Vollmer TL, Bigland-Ritchie B. Neuromuscular responses of patients with multiple sclerosis. Muscle Nerve1992; 15: 1123–1132.
2.
2 Schwid SR, Thornton CA, Pandya S et al. Quantitative assessment of motor fatigue and strength in MS. Neurology1999; 53: 743–750.
3.
3 Freal JE, Kraft GH, Coryell JK. Symptomatic fatigue in multiple sclerosis. Arch Phys Med Rehabil1984; 65:135–138.
5 Fisk JD, Pontefract A, Ritvo PG, Archibald CJ, Murray TJ. The impact of fatigue in patients with multiple sclerosis. Can J Neurol Sci1994; 21:9–14.
6.
6 Vercoulen JHMM, Hommes OR, Swanink CMA et al. The measurement of fatigue in patients with multiple sclerosis: a multidimensional comparison with patients with chronic fatigue syndrome and healthy subjects. Arch Neurol1996; 53: 642–649.
7.
7 Krupp LB, Christodoulou C. Fatigue in multiple sclerosis. Curr Neurol Neurosci Rep2001; 1: 294–298.
8.
8 Miller RG, Moussavi RS, Green AT, Carson PJ, Weiner MW. The fatigue of rapid repetitive movements. Neurology1993; 43: 755–761.
9.
9 Djaldetti R, Ziv I, Achiron A, Melamed E. Fatigue in multiple sclerosis compared with chronic fatigue syndrome. A quantitative assessment. Neurology1996; 46: 632–635.
10.
10 Kurtzke JF. Rating neurologic impairment in multiple sclerosis. An expanded disability status scale (EDSS). Neurology1983; 33: 1444–1452.
11.
11 Poser C, Paty DW, Scheinberg L et al. New diagnostic criteria for multiple sclerosis: guidelines for research protocols. Ann Neurol1983; 13: 227–231.
12.
12 Krupp LB, LaRocca NG, Muir-Nash J, Steinberg AD. The fatigue severity scale: application to patients with multiple sclerosis and systemic lupus erythematosus. Arch Neurol1989; 46:1121–1123.
13.
13 Fleiss JL. The design and analysis of clinical experiments. New York: Wiley, 1986.
14.
14 Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet1986; 8: 307–310.
15.
15 Bigland-Richie B, Johansson R, Lippold OC, Woods JJ. Contractile speed and EMG changes during sustained maximal voluntary contractions. J Neurophysiol1983; 50: 313–324.
16.
16 Maugham R, Gleeson M, Greenhaff PL. Bio-chemistry of exercise and training. Oxford: Oxford University Press, 1997: 12–13.
17.
17 Sharma KR, Kent-Braun J, Mynher MA, Weiner MW, Miller RG. Evidence of an abnormal intramuscular component of fatigue in multiple sclerosis. Muscle Nerve1995; 18: 1403–1411.
18.
18 Sheean GL, Murray NMF, Rothwell JC, Miller DH, Thompson AJ. An electrophysiological study of the mechanism of fatigue in multiple sclerosis. Brain1997; 120: 299–315.
19.
19 Iriarte J, De Castro P. Correlation between symptom fatigue and muscular fatigue in multiple sclerosis. Eur J Neurol1998; 5: 579–585.
20.
20 Schwid SR, Covington M, Segal BM, Goodman AD. Fatigue in multiple sclerosis: current understanding and future directions. J Rehabil Res Dev2002; 39: 211–224.
