Power requirements and mechanical efficiency of treadmill walking

The instantaneous energy levels of body segments are computed from kinematic measurements on a level treadmill at various speeds with freely chosen step rates and a constant speed with different imposed step rates. The changes in the energy levels of segments are combined to compute the average work rate required to accelerate the total body (positive internal work). This work is compared to total metabolic power consumption to obtain a minimal estimate of mechanical efficiency. The efficiency increases rapidly from 9% to 0.84 m/sec to a maximum of 23% at 1.70 m/sec. Thereafter, the efficiency slowly decreases with speed to 18% at 2.35 m/sec. When different step rates are imposed at one constant speed, the average positive work rate remains constant. This work rate level is identical to that required for walking at the same speed with self-determined (free) step rate. Thus, maximum gross efficiency results at the free step rate.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24523/1/0000802.pd

Kinematic prediction of intersegment loads and power at the joints of the leg in walking

The left and right ground reactions are predicted from computed absolute motion data with the aid of some simple assumptions regarding symmetry between the forward shear forces during the double support phase and the rate at which support is transferred from one leg to the other. The computed ground forces are then used to evaluate forces, moments and power at the joints of the lower limb. The power supplied at the joints of the lower limbs is found to agree well with the power required to increase the energy level of the body.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24573/1/0000855.pd

Computer generation of human gait kinematics

The paper describes a computer program that generates absolute motion variables of human gait from predetermined relative motions. Relative displacements are measured over a range of step rates during both free (self-determined step rate at different speeds) and forced (forced step rate at a constant speed) walking, converted into harmonic coefficients and stored in an array as a function of step rate. Only six variable identifiers need to be specified to compute any absolute variable or its derivatives at any desirable step rate. The paper displays some examples of measured relative motions and reconstituted absolute variables.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23673/1/0000641.pd

A simple model predicts energetically optimised jumping in dogs

© 2018. Published by The Company of Biologists Ltd. It is generally accepted that animals move in a way that minimises energy use during regular gait and there is evidence that the principle might extend more generally to locomotor behaviour and manoeuvres. Jumping during locomotion is a useful manoeuvre that contributes to the versatility of legged locomotion and is within the repertoire of many terrestrial animals. We describe a simple ballistic model that can be used to identify a single unique trajectory of the body s centre of mass that minimises the mechanical work to initiate a jump, regardless of the approach velocity or take-off position. The model was used to show that domestic dogs (Canis lupus familiaris) demonstrate complex anticipatory control of locomotor behaviour by systematically using jump trajectories close to those that minimised the mechanical energy of jumps over raised obstacles. It is unclear how the dogs acquired the complex perception and control necessary to exhibit the observed behaviour. The model may be used to investigate whether animals adopt energetically optimised behaviour in any similarly constrained ballistic task

Pilot investigation of the oxygen demands and metabolic cost of incremental shuttle walking and treadmill walking in patients with cardiovascular disease

Objective: To determine if the metabolic cost of the incremental shuttle-walking test protocol is the same as treadmill walking or predicted values of walking-speed equations. Setting: Primary care (community-based cardiac rehabilitation). Participants: Eight Caucasian cardiac rehabilitation patients (7 males) with a mean age of 67±5.2 years. Primary and secondary outcome measures: Oxygen consumption, metabolic power and energy cost of walking during treadmill and shuttle walking performed in a balanced order with 1 week between trials. Results: Average overall energy cost per metre was higher during treadmill walking (3.22±0.55 J kg/m) than during shuttle walking (3.00±0.41 J kg/m). There were significant post hoc effects at 0.67 m/s (p<0.004) and 0.84 m/s (p<0.001), where the energy cost of treadmill walking was significantly higher than that of shuttle walking. This pattern was reversed at walking speeds 1.52 m/s (p<0.042) and 1.69 m/s (p<0.007) where shuttle walking had a greater energy cost per metre than treadmill walking. At all walking speeds, the energy cost of shuttle walking was higher than that predicted using the American College of Sports Medicine walking equations. Conclusions: The energetic demands of shuttle walking were fundamentally different from those of treadmill walking and should not be directly compared. We warn against estimating the metabolic cost of the incremental shuttle-walking test using the current walking-speed equations

Investigating the correlation between paediatric stride interval persistence and gross energy expenditure

<p>Abstract</p> <p>Background</p> <p>Stride interval persistence, a term used to describe the correlation structure of stride interval time series, is thought to provide insight into neuromotor control, though its exact clinical meaning has not yet been realized. Since human locomotion is shaped by energy efficient movements, it has been hypothesized that stride interval dynamics and energy expenditure may be inherently tied, both having demonstrated similar sensitivities to age, disease, and pace-constrained walking.</p> <p>Findings</p> <p>This study tested for correlations between stride interval persistence and measures of energy expenditure including mass-specific gross oxygen consumption per minute (<inline-formula><graphic file="1756-0500-3-47-i1.gif"/></inline-formula>), mass-specific gross oxygen cost per meter (<it>VO</it>₂) and heart rate (HR). Metabolic and stride interval data were collected from 30 asymptomatic children who completed one 10-minute walking trial under each of the following conditions: (i) overground walking, (ii) hands-free treadmill walking, and (iii) handrail-supported treadmill walking. Stride interval persistence was not significantly correlated with <inline-formula><graphic file="1756-0500-3-47-i1.gif"/></inline-formula> (p > 0.32), <it>VO</it>₂(p > 0.18) or HR (p > 0.56).</p> <p>Conclusions</p> <p>No simple linear dependence exists between stride interval persistence and measures of gross energy expenditure in asymptomatic children when walking overground and on a treadmill.</p

Biomechanical implications of walking with indigenous footwear

Objectives This study investigates biomechanical implications of walking with indigenous “Kolhapuri” footwear compared to barefoot walking among a population of South Indians. Materials and methods Ten healthy adults from South India walked barefoot and indigenously shod at voluntary speed on an artificial substrate. The experiment was repeated outside, on a natural substrate. Data were collected from (1) a heel‐mounted 3D‐accelerometer recording peak impact at heel contact, (2) an ankle‐mounted 3D‐goniometer (plantar/dorsiflexion and inversion/eversion), and (3) sEMG electrodes at the m. tibialis anterior and the m. gastrocnemius medialis. Results Data show that the effect of indigenous footwear on the measured variables, compared to barefoot walking, is relatively small and consistent between substrates (even though subjects walked faster on the natural substrate). Walking barefoot, compared to shod walking yields higher impact accelerations, but the differences are small and only significant for the artificial substrate. The main rotations of the ankle joint are mostly similar between conditions. Only the shod condition shows a faster ankle rotation over the rapid eversion motion on the natural substrate. Maximal dorsiflexion in late stance differs between the footwear conditions on an artificial substrate, with the shod condition involving a less dorsiflexed ankle, and the plantar flexion at toe‐off is more extreme when shod. Overall the activity pattern of the external foot muscles is similar. Discussion The indigenous footwear studied (Kolhapuri) seems to alter foot biomechanics only in a subtle way. While offering some degree of protection, walking in this type of footwear resembles barefoot gait and this type of indigenous footwear might be considered “minimal”