Influence of gait speed on free vertical moment during walking

Functional significance of vertical free moment for generation of human bipedal walking

In human bipedal walking, the plantar surface of the foot is in contact with the floor surface, so that a vertical free moment (VFM), a torque about a vertical axis acting at the centre-of-pressure due to friction between the foot and the ground, is generated and applied to the foot. The present study investigated the functional significance of the VFM in the mechanics and evolution of human bipedal walking by analysing kinematics and kinetics of human walking when the VFM is selectively eliminated using point-contact shoes. When the VFM was selectively eliminated during walking, the thorax and pelvis axially rotated in-phase, as opposed to normal out-of-phase rotation. The amplitudes of the axial rotation also significantly increased, indicating that the VFM greatly contributes to stable and efficient bipedal walking. However, such changes in the trunk movement occurred only when arm swing was restricted, suggesting that the VFM is critical only when arm swing is restrained. Therefore, the human plantigrade foot capable of generating large VFM is possibly adaptive for bipedal walking with carrying food, corroborating with the so-called provisioning hypothesis that food carrying in the early hominins is a selective pressure for the evolution of human bipedalism.

Free moment induced by oblique transverse tarsal joint: investigation by constructive approach

The human foot provides numerous functions that let humans deal with various environments. Recently, study of the structure of the human foot and adjustment of an appropriate reaction force and vertical free moment during bipedal locomotion has gained attention. However, little is known about the mechanical (morphological) contribution of the foot structure to the reaction force and free moment. It is difficult to conduct a comparative experiment to investigate the contribution systematically by using conventional methods with human and cadaver foot experiments. This study focuses on the oblique transverse tarsal joint (TTJ) of the human foot, whose mechanical structure can generate appropriate free moments. We conduct comparative experiments with a rigid foot, a non-oblique joint foot (i.e. mimicking only the flexion/extension of the midfoot), and an oblique joint foot. Axial loading and walking experiments were conducted with these feet. The axial loading experiment demonstrated that the oblique foot generated free moment in the direction of internal rotation, as observed in the human foot. The walking experiment showed that the magnitude of the free moment generated with the oblique foot is significantly lower than that with the rigid foot during the stance phase. Using this constructive approach, the present study demonstrated that the oblique axis of the TTJ can mechanically generate free moments. This capacity might affect the transverse motion of bipedal walking.

Walking speed measurement technology: A review

Purpose of review

This article presents an overview of the main technologies used to estimate gait parameters, focusing on walking speed (WS).

Recent findings

New wearable and environmental technologies to estimate WS have been developed in the last five years. Wearable technologies refer to sensors attached to parts of the patient's body that capture the kinematics during walking. Alternatively, environmental technologies capture walking patterns using external instrumentation. In this review, wearable and external technologies have been included.From the different works reviewed, external technologies face the challenge of implementation outside controlled facilities; an advantage that wearable technologies have, but have not been fully explored. Additionally, systems that can track WS changes in daily activities, especially at-home assessments, have not been developed.

Summary

Walking speed is a gait parameter that can provide insight into an individual's health status. Image-based, walkways, wearable, and floor-vibrations technologies are the most current used technologies for estimating WS. In this paper, research from the last five years that explore each technology's capabilities on WS estimation and an evaluation of their technical and clinical aspects is presented.

Do humans exploit the metabolic and mechanical benefits of arm swing across slow to fast walking speeds?

Humans naturally select conditions to minimize their net cost of transport (COT) during walking. One way to do this is by exploiting the mechanical benefit of arm swing which reduces whole-body rotation about the vertical axis and thus, minimizes the free vertical moment (FVM) that the foot applies to the ground. Humans appear to exploit these benefits of arm swing at speeds that are considered optimal, but we sought to determine if these benefits are conserved across slow to fast walking speeds. If true, arm swing may be a key feature that helps to minimize the net COT regardless of one's walking speed. We hypothesized that at all speeds, walking with arm swing would be less costly compared to walking without arm swing. As a secondary aim, we also explored if reductions in the peak FVM could explain the metabolic benefits of arm swing. Twenty-one young, healthy subjects walked with and without arm swing at speeds ranging from 0.50 to 2.00 m/s while we recorded metabolic, kinematic and kinetic data. At slow speeds (≤1.00 m/s), net COT was similar when walking with or without arm swing (p > 0.05). However, at intermediate and fast speeds (≥1.00 m/s), arm swing reduced the net COT by ~7-13% (all p's < 0.05). Additionally, peak FVM magnitudes decreased with arm swing, suggesting that it may partially explain the metabolic benefit of arm swing. Overall, we find that arm swing provides a net metabolic benefit during walking, but this benefit is constrained to intermediate and fast walking speeds.

Age-related changes in the control of whole-body angular momentum during stepping

BACKGROUND

Appropriate control of whole-body angular momentum (H) is crucial to maintain dynamic balance and thus avoid falling during daily activities. Poor H control ability during locomotion has been found in people with an increased risk of falling, such as post-stroke patients and amputees. In contrast, little is known about the control of H during locomotion in the elderly. The aim of this study was to investigate whether and how aging influences three-dimensional H control during initiation of stepping.

METHODS

Twenty-two healthy old and 22 healthy young individuals were instructed to perform a series of initiation of stepping with their dominant leg and at their self-selected preferred pace. Two force plates and a motion capture system were used to record H, the net external moment about the body's center of mass and components of this net external moment (moment arms and ground reaction forces) during the double support and step execution phases of stepping.

RESULTS

In the double support phase, older participants exhibited smaller peak-to-peak ranges of H in the sagittal and transversal planes compared to their younger counterparts. These results were explained by decreased net external moments in both planes in the older participants. Conversely, during the step execution phase, older adults had higher peak-to-peak ranges of H in the frontal and sagittal planes compared to the younger adults. These higher ranges of H were associated with a longer duration of the step execution phase. Furthermore, in the sagittal plane, a higher external moment also contributed to increasing peak-to-peak ranges of H in older adults.

CONCLUSION

The current study revealed that older and younger adults exhibit different control strategies of H during initiation of stepping. The age-related changes, which may emphasize a higher difficulty to control H in the older adults, could impose a higher challenge for balance control and a potentially higher risk of falling during the step execution phase in this population.