The relationship between isokinetic and isometric knee muscle strength and maximal step-up height after stroke: A pilot study

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Article type: Research Article

Authors: Carlsson, Håkan^{a; *} | Lexell, Jan^{a; b} | Brogårdh, Christina^{a; b}

Affiliations: [a] Department of Neurology and Rehabilitation Medicine, Skåne University Hospital, Lund, Sweden | [b] Department of Health Sciences, Lund University, Lund, Sweden

Correspondence: [*] Corresponding author: Håkan Carlsson, Department of Neurology and Rehabilitation Medicine, Skåne University Hospital, Orupssjukhuset, 221 85 Lund. Sweden. Tel.: +46 413 55 66 51; Fax: +46 413 55 66 77; E-mail:Hakan.Carlsson@skane.se

Abstract: BACKGROUND: A novel way to evaluate muscle strength and functioning in the lower limbs is to measure how high a person could step up on a platform, the so called Maximal Step-up Test (MST). Studies of healthy persons and overweight women have shown that the maximal step-up height (MSH) is associated with both muscle strength and physical function, but no study has assessed persons after stroke. OBJECTIVE: To evaluate the relationship between isokinetic and isometric knee muscle strength and maximal step-up height after stroke. METHODS: A convenience sample of 21 ambulatory persons with stroke (13 men and eight women; mean age 63 ± 12 years; mean time since stroke onset 26 ± 36 months). Isokinetic concentric knee extension and knee flexion strength at 60°/s and isometric knee extension strength at 90° were measured for both lower limbs with a Biodex dynamometer. Maximal step-up height was measured using a 40 cm × 60 cm platform, which could be raised from 3 cm to 45 cm with 3 cm intervals. The relationship between knee muscle strength (normalized to body weight) and the maximal step-up height was analysed with the Pearson's correlation coefficient (r). RESULTS: There were significant but only moderate relationships between the paretic isokinetic knee extension, and flexion, strength and maximal step-up height, r= 0.49; p < 0.05, and r= 0.57; p < 0.01, respectively. CONCLUSION: These moderate relationships indicate that muscle weakness is only partially associated with maximal step-up height after stroke. The MST may therefore have limited value in the assessment of muscle strength after stroke.

Keywords: Stroke, knee muscle strength, maximal step-up

DOI: 10.3233/IES-150574

Journal: Isokinetics and Exercise Science, vol. 23, no. 3, pp. 143-149, 2015