Understanding gait alterations: trunk flexion and its effects on walking neuromechanics.

Evolutionary and functional adaptations of morphology and postural tone of the spine and trunk are intrinsically shaped by the field of gravity in which humans move. Gravity also significantly impacts the timing and levels of neuromuscular activation, particularly in foot-support interactions. During step-to-step transitions, the centre of mass velocity must be redirected from downwards to upwards.

Biomechanics of human locomotion in the wind.

In laboratory settings, human locomotion encounters minimal opposition from air resistance. However, moving in nature often requires overcoming airflow. Here, the drag force exerted on the body by different headwind or tailwind speeds (between 0 and 15 m·s) was measured during walking at 1.

Kinematics and mechanical changes with step frequency at different running speeds.

Purpose: Running at a given speed can be achieved by taking large steps at a low frequency or on the contrary by taking small steps at a high frequency. The consequences of a change in step frequency, at a fixed speed, affects the stiffness of the lower limb differently. In this study, we compared the running mechanics and kinematics at different imposed step frequencies (from 2 step s to 3.

Modification of the locomotor pattern when deviating from the characteristic heel-to-toe rolling pattern during walking.

Purpose: Humans are amongst few animals that step first on the heel, and then roll on the ball of the foot and toes. While this heel-to-toe rolling pattern has been shown to render an energetic advantage during walking, the effect of different foot contact strategies, on the neuromuscular control of adult walking gaits has received less attention. We hypothesised that deviating from heel-to-toe rolling pattern affects the energy transduction and weight acceptance and re-propulsive phases in gait along with the modification of spinal motor activity.

Neuromuscular Age-Related Adjustment of Gait When Moving Upwards and Downwards.

Locomotor movements are accommodated to various surface conditions by means of specific locomotor adjustments. This study examined underlying age-related differences in neuromuscular control during level walking and on a positive or negative slope, and during stepping upstairs and downstairs. Ten elderly and eight young adults walked on a treadmill at two different speeds and at three different inclinations (0°, +6°, and -6°).

Postural control in the elephant.

As the largest extant legged animals, elephants arguably face the most extreme challenge for stable standing. In this study, we investigated the displacement of the centre of pressure of 12 elephants during quiet standing. We found that the average amplitude of the oscillations in the lateral and fore-aft directions was less than 1.

Mechanical work as a (key) determinant of energy cost in human locomotion: recent findings and future directions.

New Findings: What is the topic of this review? This narrative review explores past and recent findings on the mechanical determinants of energy cost during human locomotion, obtained by using a mechanical approach based on König's theorem (Fenn's approach). What advances does it highlight? Developments in analytical methods and their applications allow a better understanding of the mechanical-bioenergetic interaction. Recent advances include the determination of 'frictional' internal work; the association between tendon work and apparent efficiency; a better understanding of the role of energy recovery and internal work in pathological gait (amputees, stroke and obesity); and a comprehensive analysis of human locomotion in (simulated) low gravity conditions.

Intra-limb and muscular coordination during walking on slopes.

Purpose: Intra-limb and muscular coordination during gait are the result of the organisation of the neuromuscular system, which have been widely studied on a flat terrain. Environmental factors, such as the inclination of the terrain, is a challenge for the postural control system to maintain balance. Therefore, we hypothesised that the central nervous system flexibly modifies its control strategies during locomotion on slopes.

The bouncing mechanism of running against hindering, or with aiding traction forces: a comparison with running on a slope.

Purpose: Much like running on a slope, running against/with a horizontal traction force which either hinders/aids the forward motion of the runner creates a shift in the positive and negative muscular work, which in turn modifies the bouncing mechanism of running. The purpose of the study is to (1) investigate the energy changes of the centre of mass and the storage/release of energy throughout the step during running associated with speed and increasing hindering and aiding traction forces; and (2) compare these changes to those observed when running on a slope.

Methods: Ground reaction forces were measured on eight subjects running on an instrumented treadmill against different traction forces at different speeds.

Neuromechanical adjustments when walking with an aiding or hindering horizontal force.

Purpose: Walking against a constant horizontal traction force which either hinders or aids the motion of the centre of mass of the body (COM) will create a discrepancy between the positive and negative work being done by the muscles and may thus affect the mechanics and energetics of walking. We aimed at investigating how this imbalance affects the exchange between potential and kinetic energy of the COM and how its dynamics is related to specific spatiotemporal organisation of motor pool activity in the spinal cord. To understand if and how the spinal cord activation may be associated with COM dynamics, we also compared the neuromechanical adjustments brought on by a horizontal force with published data about those brought on by a slope.

Differential activation of lumbar and sacral motor pools during walking at different speeds and slopes.

Organization of spinal motor output has become of interest for investigating differential activation of lumbar and sacral motor pools during locomotor tasks. Motor pools are associated with functional grouping of motoneurons of the lower limb muscles. Here we examined how the spatiotemporal organization of lumbar and sacral motor pool activity during walking is orchestrated with slope of terrain and speed of progression.

Effect of walking speed on the intersegmental coordination of lower-limb segments in elderly adults.

Background: Ageing brings profound changes in walking gait. For example, older adults reduce the modification of pelvic and trunk kinematics with walking speed. However, the modification of the coordination between lower-limb segments with age has never been investigated across various controlled speeds.

Running on a slope: A collision-based analysis to assess the optimal slope.

When running, energy is lost during stance to redirect the center of mass of the body (COM) from downwards to upwards. The present study uses a collision-based approach to analyze how these energy losses change with slope and speed. Therefore, we evaluate separately the average collision angle, i.

Kinematic patterns while walking on a slope at different speeds.

During walking, the elevation angles of the thigh, shank, and foot (i.e., the angle between the segment and the vertical) covary along a characteristic loop constrained on a plane.

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

When ascending (descending) a slope, positive (negative) work must be performed to overcome changes in gravitational potential energy at the center of body mass (COM). This modifies the pendulum-like behavior of walking. The aim of this study is to analyze how energy exchange and mechanical work done vary within a step across slopes and speeds.

The mechanics of head-supported load carriage by Nepalese porters.

In the Everest valley of Nepal, because of the rugged mountain terrain, roads are nothing more than dirt paths and all material must be conveyed on foot. The Nepalese porters routinely carry head-supported loads, which often exceed their body mass, over long distances up and down the steep mountain footpaths. In Africa, women transport their loads economically thanks to an energy-saving gait adaptation.

Human motor control of landing from a drop in simulated microgravity.

Landing on the ground on one's feet implies that the energy gained during the fall be dissipated. The aim of this study is to assess human motor control of landing in different conditions of fall initiation, simulated gravity, and sensory neural input. Six participants performed drop landings using a trapdoor system and landings from self-initiated counter-movement jumps in microgravity conditions simulated in a weightlessness environment by different pull-down forces of 1-, 0.

The rebound of the body during uphill and downhill running at different speeds.

When running on the level, muscles perform as much positive as negative external work. On a slope, the external positive and negative work performed are not equal. The present study analysed how the ratio between positive and negative work modifies the bouncing mechanism of running.

Observation of Gravitational Waves from a Binary Black Hole Merger.

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21).

Motor control of landing from a countermovement jump in simulated microgravity.

Landing from a jump implies proper positioning of the lower limb segments and the generation of an adequate muscular force to cope with the imminent collision with the ground. This study assesses how a hypogravitational environment affects the control of landing after a countermovement jump (CMJ). Eight participants performed submaximal CMJs on Earth (1-g condition) and in a weightlessness environment with simulated gravity conditions generated by a pull-down force (1-, 0.

Motor Control of Landing from a Jump in Simulated Hypergravity.

On Earth, when landing from a counter-movement jump, muscles contract before touchdown to anticipate imminent collision with the ground and place the limbs in a proper position. This study assesses how the control of landing is modified when gravity is increased above 1 g. Hypergravity was simulated in two different ways: (1) by generating centrifugal forces during turns of an aircraft (A300) and (2) by pulling the subject downwards in the laboratory with a Subject Loading System (SLS).