ABSTRACT Alterations in gait biomechanics are common during early stages of Parkinson’s disease (PD), potentially elevating energy requirements of walking and leading to impaired economy of gait. Although gait economy is traditionally assessed during treadmill walking with simultaneous ox-ygen consumption (VO2) monitoring, treadmill gait mechanics, particularly in PD, may be different from over-ground walking mechanics, possibly providing a distorted picture of true gait economy. Currently, no studies have directly examined the energy cost of over-ground walking in PD patients. The purpose of this study was to test the feasibility of measuring energy expenditure during over-ground walking in mild to moderate PD using portable gas exchange monitoring technology. Additionally, we sought to determine whether energy expenditure, as assessed through VO2 measures, related to disease severity for PD. Seventeen PD patients underwent separate 6-minute walk (6MW) tests both with and without the COSMED K4b2 portable oxygen monitoring system. Gait economy was calculated as measured VO2 during 6MW divided by the predicted VO2 for non-PD age-matched subjects, according to a standard estimation equation utilizing ground speed. Distance covered during the 6MW with the portable system (420 ± 12 meters) was highly correlated (r = 0.96, p < 0.001) to distance without the system (442 ± 135 meters) indicating that the lightweight equipment did not confound walking ability in these participants. Mean VO2 during the 6MW (16.0 ± 5.5 mL/kg/min) was 74% of mean VO2 peak for this sample, and 16 out of 17 subjects had impaired gait economy. The degree of gait economy impairment was not related to scores on either UPDRS total or motor. Our results demonstrate that PD patients use extraordinarily high percentage of VO2 peak for normal floor walking, and show impaired gait economy relative to prediction equations. Interestingly, the degree of elevated energy expenditure during gait did not relate to disease severity.
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Stookey, A. , Ivey, F. , Hammers, J. , Shulman, L. , Anderson, K. and Katzel, L. (2012) Over-ground walking in Parkinson’s disease: A pilot study utilizing a portable metabolic analyzer. Health, 4, 1127-1132. doi: 10.4236/health.2012.431170.
 Brusse, K.J., Zimdars, S., Zalewski, K.R. and Steffen, T.M. (2005) Testing functional performance in people with Parkinson disease. Physical Therapy, 85, 134-141.
 Hausdorff, J.M. (2009) Gait dynamics in Parkinson’s disease: Common and distinct behavior among stride length, gait variability, and fractal-like scaling. Chaos, 19, 1-14. doi:10.1063/1.3147408
 Bloem, B.R., Hausdorff, J.M., Visser, J.E. and Giladi, N. (2004) Falls and freezing of Gait in Parkinson’s disease: A review of two interconnected, episodic phenomena. Movement Disorders, 19, 871-884.
 Waters, R.L. and Mulroy S. (1999). The energy expenditure of normal and pathological gait. Gait Posture, 9, 207- 231. doi:10.1016/S0966-6362(99)00009-0
 Frenkel-Toledo, S., Giladi, N., Peretz, C., Herman, T., Gruendlinger, L. and Hausdorff, J.M. (2005) Treadmill walking as an external pace-maker to improve gait rhythm and stability in Parkinson’s dis-ease. Movement Disorders, 20, 1109-1114. doi:10.1002/mds.20507
 Hoehn, M.M. and Yahr, M.D. (1967) Parkisonism: Onset, progression and mortality. Neurol-ogy, 17, 427-442.
 Fahn, S., Elton, R.L. and Committee, U.D. (1987) Unified Parkinson’s disease rating scale. In: Fahn, S., Marsden, C.D., Calne, D. and Goldstein, M., Eds., Recent Developments in Parkinson’s Disease. Macmillan Health-care Information, Florham Park, New York, 153-163.
 Folstein, M.F., Folstein, S.E. and McHugh, P.R. (1975) Mini mental state: A practical method for grading the cognitive state of patients for the clinician. Journal of Psychiatric Research, 12, 189-198.
 Katzel, L.I., Ivey, F.M., Sorkin, J.D., Macko, R.F., Smith, B. and Shulman, L.M. (2012) Impaired economy of gait and decreased six-minute walk distance in Parkinson’s disease. Parkinson’s Disease, 241754.
 Whaley, M.H., Brubaker, P.H. and Otoo, R.M. (2006) Metabolic calculations, in ACSM’s Guidelines for Exercise Testing and Prescription. 7th Edition, Lipinncott Williams and Wilkins, Philadelphia.
 Christiansen, C.L., Schenkman, M.L., McFann, K., Wolfe, P. and Kohrt, W.M. (2009) Walking economy in people with Parkinson’s disease. Movement Disorders, 30, 1481- 1487. doi:10.1002/mds.22621
 Arnett, S.W., Laity, J.H., Agrawal, S.K. and Cress, M.E. (2008) Aerobic reserve and physical functional performance in older adults. Age and Ageing, 37, 384-389.
 Kazel, L.I., Sorkin, J.D., Macko, R.F., Smith, B., Ivey, F.M. and Shulman, L.M. (2011) Repeatability of aerobic capacity measurements in Parkinson Disease. Medicine & Science in Sports & Exercise, 43, 2381-2387.
 Rosen, M.J., Sorkin, J.D., Goldberg, A.P., Hagberg, J.M. and Katzel, L.I. (1998) Predictors of age-associated decline in maximal aerobic capacity: A comparison of four statistical models. Journal of Applied Physiology, 84, 2163-2170.
 Falvo, M.J. and Ear-hart, G.M. (2009) Reference equation for 6-minute walk in individuals with Parkinson disease. Journal of Rehabilitation Research and Development, 46, 1121-1126. doi:10.1682/JRRD.2009.04.0046
 Enrichi, P.L. and Sherrill, D.L. (1998) Reference equation for the six-minute walk in healthy adults. American Journal of Respiratory and Critical Care Medicine, 158, 1384-1387.
 Martin, P.E. and Morgan, D.W. (1992) Biomechanical considerations for economical walking and running. Medicine & Science in Sports & Exercise, 24, 467-474.