Impaired economy of gait and decreased six-minute walk distance in Parkinson's disease

Abstract

Changes in the biomechanics of gait may alter the energy requirements of walking in Parkinson's Disease (PD). This study investigated economy of gait during submaximal treadmill walking in 79 subjects with mild to moderate PD and the relationship between gait economy and 6-minute walk distance (6 MW). Oxygen consumption (VO(2)) at the self-selected treadmill walking speed averaged 64% of peak oxygen consumption (VO(2) peak). Submaximal VO(2) levels exceeded 70% of VO(2) peak in 30% of the subjects. Overall the mean submaximal VO(2) was 51% higher than VO(2) levels expected for the speed and grade consistent with severe impairment in economy of gait. There was an inverse relationship between economy of gait and 6MW (r = -0.31, P < 0.01) and with the self-selected walking speed (r = -0.35, P < 0.01). Thus, the impairment in economy of gait and decreased physiologic reserve result in routine walking being performed at a high percentage of VO(2) peak.

Figure 1

Submaximal VO₂ measured at self-selected walking speed during the last 40 seconds of the first 2-minute stage of treadmill test versus walking speed in mph. Diamonds show measured values, where solid line shows expected value (VO₂ mL/kg/min predicted = 0.1 × 26.8 speed in mph + 3.5). The vast majority of subjects had measured values higher than the predicted values indicative of poor economy of gait.

Figure 2

Relationship between the Hoehn and Yahr stage and economy of gait (ratio of measured VO₂ to predicted VO₂). Higher values of the ratio of measured VO₂ to predicted VO₂ are indicative of impaired economy of gait.

Figure 3

There was an inverse relationship between the distance covered during the 6 min walk (6 MW) and the amount of oxygen subjects consumed at their self-selected walking speed during the first stage of the treadmill expressed as a percentage of their VO₂ peak.