Influence of arm swing on cost of transport during walking

Role of raising the upper limb of the non-rising side when performing rising movements from bed

Rising movements from bed comprise an important aspect of recovery from the bedridden state; however, they have not been sufficiently investigated using motion analysis studies. In particular, the effect of using the upper limb of the non-rising side before waist flexion on rising movements remains to be analyzed; this study aimed to clarify this effect. Accordingly, motion analyses were performed on rising movements under two constraint conditions, namely raising the upper limb of the non-rising side (upper limb use-condition) and keeping it in contact with the pelvis (upper limb non-use-condition); subsequently, the kinematics and kinematics parameters were compared. In comparison with the upper limb use-condition, in the upper limb non-use-condition, the distance traveled by the center of mass of the body (CoM trajectory, p < 0.01) increased while switching from the half-side-lying to on-hand postures, horizontal body movement (movement speed (Normalized time/total time), p < 0.01 and weight of center of body mass (CoM momentum in horizontal plane), p < 0.05) during the same period increased, and the half-side-lying time approached the peak value of the waist flexion angular velocity (Time lag between from half-side-lying to waist angler peak velocity, p < 0.05). The compensatory movement that occurred due to the upper limb non-use-condition denoted an increase in body momentum in the horizontal direction, rather than in the sagittal plane. Therefore, the upper limb on the non-rising side contributed to the smooth movement of the body in the horizontal direction. Moreover, this study demonstrated that asymmetrical rising movement in the diagonal direction is a characteristic movement wherein the horizontal movement of the body constitutes the main movement.

Regulation of whole-body angular momentum during human walking

In human walking, whole-body angular momentum (WBAM) about the body centre-of-mass is reportedly maintained in a small range throughout a gait cycle by the intersegmental cancellation of angular momentum. However, the WBAM is certainly not zero, which indicates that external moments applied from the ground due to ground reaction forces (GRFs) and vertical free moments (VFMs) counteract the WBAM. This study provides a complete dataset of the WBAM, each segmental angular momentum, and the external moments due to GRFs and VFMs during human walking. This is done to test whether (1) the three components of the WBAM are cancelled by coordinated intersegmental movements, and whether (2) the external moments due to GRFs and VFMs contribute only minimally to WBAM regulation throughout a gait cycle. This study demonstrates that WBAM is regulated in a small range not only by the segment-to-segment cancellation, but also largely through contributions by the GRFs. The magnitude of VFM is significantly smaller than the peak vertical moment generated by the GRFs; however, in the single-support phase during walking, the VFM is possibly critical for coping with the change in the vertical WBAM due to force perturbations and arm or trunk movements.

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.

Humans trade off whole-body energy cost to avoid overburdening muscles while walking

Metabolic cost minimization is thought to underscore the neural control of locomotion. Yet, avoiding high muscle activation, a cause of fatigue, often outperforms energy minimization in computational predictions of human gait. Discerning the relative importance of these criteria in human walking has proved elusive, in part, because they have not been empirically decoupled. Here, we explicitly decouple whole-body metabolic cost and 'fatigue-like' muscle activation costs (estimated from electromyography) by pitting them against one another using two distinct gait tasks. When experiencing these competing costs, participants (n = 10) chose the task that avoided overburdening muscles (fatigue avoidance) at the expense of higher metabolic power (p < 0.05). Muscle volume-normalized activation more closely models energy use and was also minimized by the participants' decision (p < 0.05), demonstrating that muscle activation was, at best, an inaccurate signal for metabolic energy. Energy minimization was only observed when there was no adverse effect on muscle activation costs. By decoupling whole-body metabolic and muscle activation costs, we provide among the first empirical evidence of humans embracing non-energetic optimality in favour of a clearly defined neuromuscular objective. This finding indicates that local muscle fatigue and effort may well be key factors dictating human walking behaviour and its evolution.

The Influence of the Relative Timing between Pole and Heel Strike on Lower Limb Loading among Young and Older Naïve Pole Walkers

Current research is unclear with respect to whether pole walking (PW) reduces lower limb loading when compared to regular walking (RW). Contradictory findings in the literature may be related to the relative timing between pole and foot contact events, which were examined in the current study among naïve pole walkers. Fourteen young (4 F; 25.3 ± 5.4 years) and 8 older adults (4 F; 68.5 ± 3.2 years) performed PW and RW trials along a force plate embedded walkway at two different visits. The time difference between pole and foot contact during both the onset of ground contact and the peak force application was calculated. Several kinetic measures were calculated for the lower limbs and poles. A significant decrease during PW, compared to RW, was found for foot impulse (2.1%; p < 0.01), peak vertical ground reaction force (vGRF) (3.4%; p < 0.01), rate of loading (5.2%; p=0.02), and peak push-off vGRF (2.1%; p=0.01). No difference in pole loading was found between age groups and visits. No significant correlations were found between the relative timing and foot loading measures. Significant low-to-moderate negative correlations were found between peak foot and pole vGRFs (p=0.04), peak foot vGRF and pole strike impulse (p=0.01), peak foot vGRF and pole impulse (p=0.02), and peak foot push-off vGRF and pole impulse (p=0.01), suggesting that as pole loading increased, foot loading decreased. Findings suggest timing between pole and heel contact may not be related to unloading the lower limbs but may be related to other aspects of pole use since PW reduced lower limb loading.

Coordination variability during running in adolescents with autism spectrum disorder

LAY ABSTRACT

Walking and running are popular forms of physical activity that involve the whole body (pelvis/legs and arms/torso) and are coordinated by the neuromuscular system, generally without much conscious effort. However, autistic persons tend not to engage in sufficient amounts of these activities to enjoy their health benefits. Recent reports indicate that autistic individuals tend to experience altered coordination patterns and increased variability during walking tasks when compared to non-autistic controls. Greater stride-to-stride coordination variability, when the task has not changed (i.e. walking at same speed and on same surface), is likely indicative of motor control issues and is more metabolically wasteful. To date, although, research examining running is unavailable in any form for this population. This study aimed to determine if coordination variability during running differs between autistic adolescents and age, sex, and body mass index matched non-autistic controls. This study found that increased variability exists throughout the many different areas of the body (foot-leg, left/right thighs, and opposite arm-opposite thigh) for autistic adolescents compared to controls. Along with previous research, these findings indicate autistic persons exhibit motor control issues across both forms of locomotion (walking and running) and at multiple speeds. These findings highlight issues with motor control that can be addressed by therapeutic/rehabilitative programming. Reducing coordination variability, inherently lessening metabolic inefficiency, may be an important step toward encouraging autistic youth to engage in sufficient physical activity (i.e. running) to enjoy physiological and psychological benefits.

Amble Gait EEG Points at Complementary Cortical Networks Underlying Stereotypic Multi-Limb Co-ordination

Background

Walking is characterized by stable antiphase relations between upper and lower limb movements. Such bilateral rhythmic movement patterns are neuronally generated at levels of the spinal cord and brain stem, that are strongly interconnected with cortical circuitries, including the Supplementary Motor Area (SMA).

Objective

To explore cerebral activity associated with multi-limb phase relations in human gait by manipulating mutual attunement of the upper and lower limb antiphase patterns.

Methods

Cortical activity and gait were assessed by ambulant EEG, accelerometers and videorecordings in 35 healthy participants walking normally and 19 healthy participants walking in amble gait, where upper limbs moved in-phase with the lower limbs. Power changes across the EEG frequency spectrum were assessed by Event Related Spectral Perturbation analysis and gait analysis was performed.

Results

Amble gait was associated with enhanced Event Related Desynchronization (ERD) prior to and during especially the left swing phase and reduced Event Related Synchronization (ERS) at final swing phases. ERD enhancement was most pronounced over the putative right premotor, right primary motor and right parietal cortex, indicating involvement of higher-order organization and somatosensory guidance in the production of this more complex gait pattern, with an apparent right hemisphere dominance. The diminished within-step ERD/ERS pattern in amble gait, also over the SMA, suggests that this gait pattern is more stride driven instead of step driven.

Conclusion

Increased four-limb phase complexity recruits distributed networks upstream of the primary motor cortex, primarily lateralized in the right hemisphere. Similar parietal-premotor involvement has been described to compensate impaired SMA function in Parkinson’s disease bimanual antiphase movement, indicating a role as cortical support regions.

The effects of forearm movements on human gait during walking with various self-selected speeds

The forearms significantly contribute to the upper extremity movements and, consequently, whole-body responses during locomotion. The purpose of this study is to provide a more in-depth understanding of the mechanism controlling forearm movements during walking by comprehensively investigating the effects of the forearms on the lower and upper limb movements. Such an understanding can provide critical information for the design and control of robotic upper-limb prostheses. Twelve healthy young participants were recruited to compare their gait during (1) natural walking, (2) walking while wearing a pair of artificial passive forearms and having their actual forearms restrained by orthopedic braces, and (3) walking with only having their forearms restrained by the braces (i.e., no artificial forearms). While the passive forearms in condition 2 were to determine if the forearm movements were passively or actively controlled, condition 3 was to account for the effects of restraining the forearms in condition 2. The participants' lower-limb joint angles and spatiotemporal parameters remained unchanged across the three conditions while walking at their normal and fast self-selected gait speeds. However, significant decreases were observed in the shoulder and trunk angles, the interlimb coordination, and the shoulder-trunk correlations when walking with the artificial forearms. These observations were in tandem with the increased muscle activity of the biceps, trapeziuses, and posterior deltoids, which controlled the shoulder motion and trunk rotation during walking with the artificial forearms across both normal and fast self-selected speeds. Although not significant, the metabolic energy analysis of five participants revealed an increase during walking with artificial forearms. The results support the idea that the body actively controls the forearm movements through the shoulder and trunk rotations to mitigate the undesired disturbances induced by the passive forearm movements during locomotion.

The Relationship Between Walking Speed and the Energetic Cost of Walking in Persons With Multiple Sclerosis and Healthy Controls: A Systematic Review

BACKGROUND

Persons with multiple sclerosis (pwMS) experience walking impairments, characterized by decreased walking speeds. In healthy subjects, the self-selected walking speed is the energetically most optimal. In pwMS, the energetically most optimal walking speed remains underexposed. Therefore, this review aimed to determine the relationship between walking speed and energetic cost of walking (Cw) in pwMS, compared with healthy subjects, thereby assessing the walking speed with the lowest energetic cost. As it is unclear whether the Cw in pwMS differs between overground and treadmill walking, as reported in healthy subjects, a second review aim was to compare both conditions.

METHOD

PubMed and Web of Science were systematically searched. Studies assessing pwMS, reporting walking speed (converted to meters per second), and reporting oxygen consumption were included. Study quality was assessed with a modified National Heart, Lung and Blood Institute checklist. The relationship between Cw and walking speed was calculated with a second-order polynomial function and compared between groups and conditions.

RESULTS

Twenty-nine studies were included (n = 1535 pwMS) of which 8 included healthy subjects (n = 179 healthy subjects). PwMS showed a similar energetically most optimal walking speed of 1.44 m/s with a Cw of 0.16, compared with 0.14 mL O₂/kg/m in healthy subjects. The most optimal walking speed in treadmill was 1.48 m/s, compared with 1.28 m/s in overground walking with a similar Cw.

CONCLUSION

Overall, the Cw is elevated in pwMS but with a similar energetically most optimal walking speed, compared with healthy subjects. Treadmill walking showed a similar most optimal Cw but a higher speed, compared with overground walking.

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.

A low-cost method for carrying loads during human walking

Humans often perform tasks that require them to carry loads, but the metabolic cost of carrying loads depends on where the loads are positioned on the body. We reasoned that carrying loads at the arms' center of mass (COM) during walking might be cheap because arm swing is thought to be dominated by passive pendulum dynamics. In contrast, we expected that carrying loads at the leg COM would be relatively expensive because muscular actuation is necessary to initiate and propagate leg swing. Therefore, we hypothesized that carrying loads at the arm COM while swinging would be cheaper than carrying loads at the leg COM. We further hypothesized that carrying loads at the arm COM while swinging would be more expensive than carrying loads at the waist, where the mass does not swing relative to the body. We measured net metabolic power, arm and leg motion, and the free vertical moment while subjects (n=12) walked on a treadmill (1.25 m s-1) without a load, and with 8 kg added to the arms (swinging versus not swinging), legs or waist. We found that carrying loads on the arms or legs altered arm swinging amplitude; however, the free vertical moment remained similar across conditions. Most notably, the cost of carrying loads on the swinging arms was 9% less than carrying at the leg COM (P<0.001), but similar to that at the waist (P=0.529). Overall, we found that carrying loads at the arm COM is just as cheap as carrying loads at the waist.

First person – Myriam de Graaf and Juul Hubert

First Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Myriam de Graaf and Juul Hubert are co-first authors on ‘Influence of arm swing on cost of transport during walking’, published in BiO. Myriam and Juul are both (research) master's students in the lab of Andreas Daffertshofer and Raôul Oudejans–John van der Kamp at the Faculty of Behavioural and Human Movement Sciences, Vrije Universiteit, Amsterdam, investigating human movement sciences. Myriam's interest lies predominantly in motor control, neuroscience and biomechanics, while Juul is focused on applications in (elite) sport.