02061nas a2200157   4500000000100000008004100001260001700042100002600059700001200085700001500097700001200112245010400124250001500228520161400243020004601857       2012                            d  c-357263871641 aSherrington Catherine1 aPaul S.1 aCanning C.1 aFung V.00aReduced muscle strength is the major determinant of reduced leg muscle power in Parkinson's disease  a2012/06/123 a<p>
BACKGROUND: Reduced muscle power (speed x strength) is associated with increased fall risk and reduced walking speed in people with Parkinson's disease (PD) as well as in the general older population. This study aimed to determine the relative contribution of motor impairments (bradykinesia, tremor, rigidity and weakness) to reduced leg muscle power in people with PD. METHODS: Eighty-two people with PD were tested while "on" medication. Leg extensor muscle strength and muscle power were measured using pneumatic variable resistance equipment. Lower limb bradykinesia, rigidity and tremor were measured using the Movement Disorders Society-sponsored Unified Parkinson's Disease Rating Scale. Associations between motor impairments and leg muscle power were examined using linear regression. RESULTS: Univariate models revealed that muscle strength (R(2) = 0.84), bradykinesia (R(2) = 0.05) and rigidity (R(2) = 0.05) were significantly associated with leg muscle power, while tremor was not. A multivariate model including bradykinesia, tremor, rigidity, muscle strength, age and gender explained 89% of the variance in leg muscle power. This model revealed reduced muscle strength to be the major determinant of reduced muscle power (beta = 0.7), while bradykinesia was a minor contributor to reduced muscle power (beta = -0.1), even when accounting for age and gender. CONCLUSIONS: The findings that reduced strength and bradykinesia contribute to reduced muscle power in people with PD tested "on" medication suggest that these impairments are potential targets for physical interventions.
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