FUNCTIONAL ABILITY AND FUNCTIONAL CAPACITY IN PATIENTS WITH PARKINSON??S DISEASE

Abstract

Functional ability and the ability to carry out activities of daily living are integrally related to functional capacity. The Timed Up and Go test and the 6-Minute Walk are measures of functional ability commonly employed in the clinical setting, but there has been limited evaluation of how these tests compare with tests of functional capacity, particularly in patients with Parkinson's Disease. Seventeen male patients with Parkinson's Disease (Hoehn-Yahr stages 1–3; mean age 57 ± 12 years) completed 2 tests of functional ability: the 6-Minute Walk and the Timed Up and Go test, and underwent a maximal graded cycle ergometer exercise test with measurement of peak oxygen uptake (VO2peak) to measure functional capacity. The mean time for completion of the Timed Up and Go test was 6.1 ± 1.7 seconds and the average distance traveled during the 6-Minute Walk was 459 ± 119 meters. Peak oxygen uptake was 24.7 ± 8.6 ml.kg.−1min−1, with a peak respiratory exchange ratio of ≥ 1.1 in all patients, suggesting a maximal effort. The patients attained a peak heart rate of 147 ± 27 beats per minute (89% ± 12% of the predicted maximal heart rate) and a peak workload of 152 ± 50 watts during the cycle ergometer test. Pearson Product-Moment Correlations between the standardized scores on the 3 tests were evaluated, and all tests correlated significantly (p ≤ 0.05) with each other. There was an inverse, moderate correlation between the 6-Minute Walk and the Timed Up and Go test (r ≡ −0.55), suggesting that these tests measure different attributes of physical function. When compared with VO2peak, the Timed Up and Go correlated highly, but inversely (r ≡ 0.71), while the 6-Minute Walk correlated only modestly (r ≡ 0.40). A linear regression procedure was performed with VO2peak as the dependent variable and the 6-Minute Walk and the Timed Up and Go as the independent variables. The Timed Up and Go was the only significant predictor of the VO2peak (β ≡ −3.574, constant ≡ 46.5; p ≤ 0.001), with an adjusted R square of 0.47 and standard error of the estimate of 0.47. These results suggest that muscle strength and/or motor function are important determinants of functional capacity in patients with Parkinson's Disease. Conclusion: The Timed Up and Go Test is a good indicator of functional capacity in patients with Parkinson's Disease and may be preferable to the 6-Minute Walk in these patients. Further work evaluating the ability of these tests to reflect changes in functional capacity is needed.