Energy cost of spontaneous walking in Parkinson's disease patients.

In healthy subjects, comfortable walking minimizes the energy cost (E (c)) of locomotion. In Parkinson's disease (PD) patients walking is slower than in healthy subjects: this may increase E (c). Our aims were to analyze gait and E (c) in PD patients during walking, particularly at self-selected speed, and the possible pathological, mechanical, and cardiorespiratory limitations. Fourteen mild-to-moderate PD and 14 control subjects were enrolled. Subjects underwent 5-min walking tests at two speeds: self-selected and as-fast-as-possible speeds. Cardiopulmonary and gait parameters (heart rate, ventilation, gas exchanges, step count) were recorded. Velocity was reduced in PD compared to control subjects at both speeds (P < 0.05), and PD patients had shorter strides (P < 0.05) at both speeds and reduced cadence (P = 0.01) at fastest speed. No significant difference was found in E (c) at self-selected (0.12 ± 0.04 versus 0.11 ± 0.02 mLO(2) kg(-1) m(-1) in PD and control subjects, respectively) and maximal (0.14 ± 0.03 versus 0.15 ± 0.02 mLO(2) kg(-1) m(-1) in PD and control subjects, respectively) speed. However, the E (c) increment from self-selected to fastest velocity was significantly lower (P = 0.02) in PD patients. PD patients failed to walk at a self-selected speed, which minimizes the E (c). This could be mainly due to the inability to develop a wider stride. Cardiorespiratory adaptation was not affected, except for the possible reduced cardiac adaptation observed in some (28%) cases. Presumably, rehabilitation procedures that improve flexibility and step length may help maintain walking ability.