Vertical displacement of the centre of mass during walking in people with diabetes and diabetic neuropathy does not explain their higher metabolic cost of walking

Influence of Diabetic Neuropathy on Gait Complexity

“…19 Thus, the highest entropy values found in subjects with PDN reflect a greater variability in CoM displacement, thus signaling an irregular system. 18 The statistically higher values of entropy reflect greater disturbance in CoM displacement in diabetics with PDN in the anteroposterior and mediolateral vectors, but not in the vertical vector. These differences merit attention, because both the increase in CoM 20 displacement and the decrease/absence of CoM 20,21 displacement increase the metabolic cost of walking (CoW).…”

“…Accordingly, it can be said that PDN influenced entropy from CoM displacement in the mediolateral and anteroposterior vectors, but not in the vertical vector, which is consistent with the literature where changes related to PDN lead to functional adaptations of gait, such as lower self-selected and maximum speed, shorter strides, and higher cadence. 18 Considering that PDN is characterized by sensory and motor deficit, 7 a decrease in the system's ability to adapt to changes in the environment in routine tasks has been pinpointed as a possible explanation for changes in gait.…”

“…This phenomenon is the opposite of that found in a system without adaptation restrictions. 18 In the gait cycle, CoM displacement can be represented as an inverted pendulum with a sine wave. 19 Thus, the highest entropy values found in subjects with PDN reflect a greater variability in CoM displacement, thus signaling an irregular system.…”

“…It is worth remembering that the sine wave is representative of the principle of conservation of mechanical energy 22 and the cost of walking (CoW). 18 The elevation and negative acceleration in the sine wave of CoM displacement found in the first half of the gait cycle support phase 19 is characterized by conversion of kinetic energy into gravitational potential, 23 whereas depression and positive acceleration in the second half of the support phase 19 are characterized by a conversion of gravitational potential energy into kinetic energy. 23 Therefore, an ideal CoM displacement must be produced in terms of its effect on the CoW, and deviations from this ideal indicate inefficiency in terms of energetic cost, which is consistent with the scenario expected in PDN.…”

“…However, the increased CoW is caused instead by the additional work undertaken to reorganize CoM oscillations during step-by-step transitions, as well as by the work needed to restore the lost energy. 18 Although in mechanical terms such an adjustment is multifaceted, the increased CoW is due to a complex interaction of sensory (impaired vibration and protective sensation), muscle and joint impairment (mobility), 24 which result in kinetic, EMG and kinematic changes. 24,25 For example, the debility characteristic of PDN would produce less incursion of the knee joints during the support phase, changing the stride length, and this would consequently cause greater disturbance in the fluctuation of CoM displacement and the CoW.…”