The correlation between metabolic and individual leg mechanical power during walking at different slopes and velocities

Abstract

During level-ground walking, mechanical work from each leg is required to redirect and accelerate the center of mass. Previous studies show a linear correlation between net metabolic power and the rate of step-to-step transition work during level-ground walking with changing step lengths. However, correlations between metabolic power and individual leg power during step-to-step transitions while walking on uphill/downhill slopes and at different velocities are not known. This basic understanding of these relationships between metabolic demands and biomechanical tasks can provide important information for design and control of biomimetic assistive devices such as leg prostheses and orthoses. Thus, we compared changes in metabolic power and mechanical power during step-to-step transitions while 19 subjects walked at seven slopes (0°, +/−3°, +/−6°, and +/−9°) and three velocities (1.00, 1.25, and 1.50 m/s). A quadratic model explained more of the variance (R 2 =0.58-0.61) than a linear model (R 2 =0.37-0.52) between metabolic power and individual leg mechanical power during step-to-step transitions across all velocities. A quadratic model explained more of the variance (R 2 =0.57-0.76) than a linear model (R 2 =0.52-0.59) between metabolic power and individual leg mechanical power during step-to-step transitions at each velocity for all slopes, and explained more of the variance (R 2 =0.12-0.54) than a linear model (R 2 =0.07-0.49) at each slope for all velocities. Our results suggest that it is important to consider the mechanical function of each leg in the design of biomimetic assistive devices aimed at reducing metabolic costs when walking at different slopes and velocities.

Pendular energy transduction within the step during human walking on slopes at different speeds

“…Functionally, a longer T4 indicates that the COM is still rising when its forward velocity starts to increase (Figs 1 , 2 & 3 ). Walking uphill on steeper slopes involves a greater during double support and this positive work is done both by the leading and the trailing legs [ 43 , 44 ]. Our results show that, a significant part of the positive external work performed during the step is generated during T4 and T1 and that this work increases when speed increases ( Fig 10 ).…”

Individual Leg and Joint Work during Sloped Walking for People with a Transtibial Amputation Using Passive and Powered Prostheses

“…We iteratively tuned the BiOM prosthesis to match the average biological ankle sagittal plane range of motion, peak moment, peak power, and net work from 20 non-amputees at each slope (Jeffers et al, 2015). Though subjects used the same tuning parameters, prosthetic components, and alignment established in the tuning sessions for all experimental sessions, they likely modified the way that they walked while using the BiOM during the final experimental session compared to the tuning sessions (Figure 2).…”

“…To objectively tune the BiOM, we calculated prosthetic ankle angles, moments, powers, and net mechanical work normalized to body mass, including prosthetic mass using Visual 3D software (C-Motion, Germantown, MD, USA) after each 45-s trial and compared these data with averages from 20 non-amputees walking at the same speed and slopes (Jeffers et al, 2015). Similar to Ventura et al (2011), we did not adjust the rigid segment model foot or shank in Visual 3D and used inertial properties inherent in the Visual 3D anatomical model due to the similar weight of the BiOM and an anatomical foot and shank (21.6 N).…”

Use of a powered ankle–foot prosthesis reduces the metabolic cost of uphill walking and improves leg work symmetry in people with transtibial amputations

“…To objectively tune the powered prosthesis at each slope, we calculated prosthetic ankle angles, moments, powers and work normalized to subject mass with the prosthesis during each 45 s trial using Visual 3D (C-Motion, Germantown, MD, USA) and compared these data with averages from 20 non-amputees walking at the same speed and slope on the same equipment [21]. We then iteratively tuned the powered prosthesis for each slope using a tablet with software provided by the manufacturer (BionX Medical Technologies).…”