Human Locomotion

Surprisingly, despite millions of years of bipedal walking evolution, the gravity-related pendulum mechanism of walking does not seem to be implemented at the onset of independent walking, requiring each toddler to develop it. We discuss the precursor of the mature locomotor pattern in infants as an optimal starting point strategy for gait maturation.

Multibody system dynamics is an essential part of computational dynamics a topic more generally dealing with kinematics and dynamics of rigid and flexible systems, finite elements methods, and numerical methods for synthesis, optimization and control including nonlinear dynamics approaches. The theoretical background of multibody dynamics is presented, the efficiency of recursive algorithms is shown, methods for dynamical analysis are summarized, and applications to vehicle dynamics and biomechanics are reported. In particular, the wear of railway wheels of high-speed trains and the metabolical cost of human locomotion is analyzed using multibody system methods.

This review aims to provide both researchers and coaches with a comprehensive overview of race walking biomechanics and to point out new viable route for future analyses. The examined literature has been divided into three categories according to the method of analysis: kinematics, ground reaction forces and joint power/efficiency. From an overall view, race walking athletes seem to adhere to the ‘straightened knee’ rule, but at race speed they do not observe the ‘no-flight time’ rule. The coach-oriented analysis highlights that stride length (SL) is more important than stride frequency (SF) for increasing speed and it is mainly obtained by ankle and hip joint power. Moreover, kinematic differences (SF, SL and flight time) between male and female athletes were shown. Also, we found that the maximal speed prediction according to dynamic similarity theory with walking (Froude number) is not applicable as the 3D trajectory of the body centre of mass does not follow an arc of circumference as in walking. The analysed literature shows some shortcomings: (1) the data collection is often unreliable because of the mixture of gender and performance level and (2) the analysis has sometimes been performed on a limited number of strides and speeds. These limitations lead to a scattered and incomplete gait description and a biased application of the results. The research strategy adopted so far is promising but further rigorous analyses need to be approached to obtain a fully comprehensive picture of race walking and to provide coaches with consistent results and reference values.

The objective of this study is to develop a computational framework for investigating the dynamic behavior and the internal loading conditions of the human foot complex during locomotion. A subject-specific dynamic finite element model in the sagittal plane was constructed based on anatomical structures segmented from medical CT scan images. Three-dimensional gait measurements were conducted to support and validate the model. Ankle joint forces and moment derived from gait measurements were used to drive the model. Explicit finite element simulations were conducted, covering the entire stance phase from heel-strike impact to toe-off. The predicted ground reaction forces, center of pressure, foot bone motions and plantar surface pressure showed reasonably good agreement with the gait measurement data over most of the stance phase. The prediction discrepancies can be explained by the assumptions and limitations of the model. Our analysis showed that a dynamic FE simulation can improve the prediction accuracy in the peak plantar pressures at some parts of the foot complex by 10%-33% compared to a quasi-static FE simulation. However, to simplify the costly explicit FE simulation, the proposed model is confined only to the sagittal plane and has a simplified representation of foot structure. The dynamic finite element foot model proposed in this study would provide a useful tool for future extension to a fully muscle-driven dynamic three-dimensional model with detailed representation of all major anatomical structures, in order to investigate the structural dynamics of the human foot musculoskeletal system during normal or even pathological functioning.

The question of how the central nervous system coordinates muscle activity is central to an understanding
of motor control. The authors argue that motor programs may be considered as a characteristic timing of
muscle activations linked to specific kinematic events. In particular, muscle activity occurring during human
locomotion can be accounted for by five basic temporal components in a variety of locomotion conditions.
Spatiotemporal maps of spinal cord motoneuron activation also show discrete periods of activity. Furthermore,
the coordination of locomotion with voluntary tasks is accomplished through a superposition of motor
programs or activation timings that are separately associated with each task. As a consequence, the selection
of muscle synergies appears to be downstream from the processes that generate activation timings.

Uner Tan was born in Unye, Ordu in Turkey on 1 May 1937 and attended high school in Izmir Turkey, followed by medical school at the Egean University in Izmir. He moved to Germany to attend Goettingen University, where he earned his medical doctorate. He received his PhD from the Max-Planck Institute for Medical Research in Goettingen.

Tan returned to Turkey in 1969 and worked as lecturer and then associate professor at Hacettepe and Ataturk universities in Turkey. He was head of the Department of Physiology at Ataturk University from 1973 to 1999 and BlackSea Technical University until 2002. He was head of the Neurophysiology Unit at Cukurova University in Adana until 2004. He remains at Cukurova University as senior researcher.

Tan’s many research interests include the spinal and cerebral motor systems, epilepsy, sex differences in cerebral lateralization and cognition, and Uner Tan Syndrome, which involves habitual quadrupedalism. Tan’s publications include around 180 papers in the Science Citation Index and almost 2000 citations since 1966.

Tan’s memberships include the American Academy of Neuropsychology, World Innovation Foundation, the American Psychological Association and Honorary Membership of the Turkish Academy of Sciences. Tan also belongs to the New York Academy of Sciences, the European Neuroscience Association, and several other professional associations.

Tan has served as editor or member of editorial boards for journals such as the International Journal of Neuroscience and Perceptual and Motor Skills. He is currently on the editorial board of the Journal of Neuroquantology, and acts as reviewer for various scientific periodicals.

Tan has won many awards, including Turkish awards such as the Dorothea Morton First Prize for Neurological Sciences (1980) and Science award from Turkish Technical and Scientific Council. His USA awards include Einstein Medals for Science and Peace (1986), Medal of Honor (1987), and Nobel Medals for Science and Peace (1991).

Uner Tan is married with four children. His hobbies include playing the violin (he was once first violinist), and stamp collecting.

OBJECTIVE: To describe a method to obtain a profile of the duration and intensity (speed) of walking periods over 24 hours in women under free-living conditions. DESIGN: A new method based on accelerometry was designed for analyzing walking activity. In order to take into account interindividual variability of acceleration, an individual calibration process was used. Different experiments were performed to highlight the variability of acceleration vs walking speed relationship, to analyze the speed prediction accuracy of the method, and to test the assessment of walking distance and duration over 24-h. SUBJECTS: Twenty-eight women were studied (mean AE s.d.) age: 39.3 AE 8.9 y; body mass: 79.7 AE 11.1 kg; body height: 162.9 AE 5.4 cm; and body mass index (BMI) 30.0 AE 3.8 kg=m 2 . RESULTS: Accelerometer output was significantly correlated with speed during treadmill walking (r ¼ 0.95, P < 0.01), and short unconstrained walks (r ¼ 0.86, P < 0.01), although with a large inter-individual variation of the regression parameters. By using individual calibration, it was possible to predict walking speed on a standard urban circuit (predicted vs measured r ¼ 0.93, P < 0.01, s.e.e. ¼ 0.51 km=h). In the free-living experiment, women spent on average 79.9 AE 36.0 (range: 31.7 -168.2) min=day in displacement activities, from which discontinuous short walking activities represented about 2=3 and continuous ones 1=3. Total walking distance averaged 2.1 AE 1.2 (range: 0.4 -4.7) km=day. It was performed at an average speed of 5.0 AE 0.5 (range: 4.1 -6.0) km=h. CONCLUSION: An accelerometer measuring the anteroposterior acceleration of the body can estimate walking speed together with the pattern, intensity and duration of daily walking activity.

Darstellungen  von  Transport  und  Fortbewegung  sind  in
Ägypten bereits seit frühester Zeit belegt. Gerade der Pharao
auf dem Streitwagen ist ein gängiges Bild. Auch Frauen in
Sänften und auf Streitwagen sind vereinzelt nachzuweisen. Noch
seltener sind die Darstellungen, die die Fortbewegung von
Kindern zeigen. Sie geben wieder, wie die Kinder z.B. von
ihren Müttern fortbewegt wurden bzw. zeigen, wie sich die
Kinder selbst fortbewegten.

While walking, human beings continuously adjust step length (SpL), step time (SpT), step speed (SpS = SpL/SpT) and step width (SpW) by integrating both feedforward and feedback mechanisms. These motor control processes result in correlations of gait parameters between consecutive strides (statistical persistence). Constraining gait with a speed cue (treadmill) and/or a rhythmic auditory cue (metronome), modifies the statistical persistence to anti-persistence. The objective was to analyze whether the combined effect of treadmill and rhythmic auditory cueing (RAC) modified not only statistical persistence, but also fluctuation magnitude (standard deviation, SD), and stationarity of SpL, SpT, SpS and SpW. Twenty healthy subjects performed 665 min. walking tests at various imposed speeds on a treadmill instrumented with foot-pressure sensors. Freely-chosen walking cadences were assessed during the first three trials, and then imposed accordingly in the last trials with a metronome. Fluctuation magnitude (SD) of SpT, SpL, SpS and SpW was assessed, as well as NonStationarity Index (NSI), which estimates the dispersion of local means in the times series (SD of 20 local means over 10 steps). No effect of RAC on fluctuation magnitude (SD) was observed. SpW was not modified by RAC, what is likely the evidence that lateral foot placement is separately regulated. Stationarity (NSI) was modified by RAC in the same manner as persistent pattern: Treadmill induced low NSI in the time series of SpS, and high NSI in SpT and SpL. On the contrary, SpT, SpL and SpS exhibited low NSI under RAC condition. We used relatively short sample of consecutive strides (100) as compared to the usual number of strides required to analyze fluctuation dynamics (200 to 1000 strides). Therefore, the responsiveness of stationarity measure (NSI) to cued walking opens the perspective to perform short walking tests that would be adapted to patients with a reduced gait perimeter.

The aim of this study was to investigate the contribution of proprioceptive feedback to the amplitude modulation of the soleus muscle activity during human walking. We have previously shown that slow-velocity, small-amplitude ankle dorsiflexion enhancements and reductions applied during the stance phase of the step cycle generate, respectively, increments and decrements on the ongoing soleus activity. We have also shown that the increments in soleus activity are at least partially mediated by feedback from group Ia fibres. In the present study, we further investigated the afferent-mediated contribution from muscle group II afferents, cutaneous and proprioceptive afferents from the foot, and load-sensitive afferents to the soleus EMG. Slow-velocity, small-amplitude ankle trajectory modifications were combined with the pharmaceutical depression of group II polysynaptic pathways with tizanidine hydrochloride, anaesthetic blocking of sensory information from the foot with injections of lidocaine hydrochloride, and modulation of load feedback by increasing and decreasing the body load. The depression of the group II afferents significantly reduced the soleus response to the ankle trajectory modifications. Blocking sensory feedback from the foot did not have an effect on the soleus muscle activity. Changes in body load affected the ongoing soleus activity level; however, it did not affect the amplitude of the soleus EMG responses to the ankle trajectory modifications. These results suggest that the feedback from group II afferents, and possibly from load-sensitive afferents, contribute to the amplitude modulation of the soleus muscle activity during the stance phase of the step cycle. However, feedback from cutaneous afferents and instrinsic proprioceptive afferents from the foot does not seem to contribute to this muscle activation.

Differences in thorax shape between humans and the great apes are well documented, with the narrow upper thorax and wide lower thorax of apes contrasting with the opposite pattern in fossil Homo and extant humans.  Interestingly, current reconstructions of thoraces in small-bodied hominins, such as the Australopithecus afarensis A.L. 288-1, may feature a smaller, more apelike pulmonary thorax (upper thorax), while its larger-bodied conspecific KSD-VP-1/1 is suggested to be more human with a relatively expanded upper thorax.  Toward understanding this dichotomy, we examine the relationship between body size and thorax shape, and model trajectories of the upper limb relative to differently shaped thoraces.

We show that variation in thorax shapes facilitate or constrain certain locomotor patterns, as a small upper with an expanded lower thorax facilitates knuckle-walking, orienting the upper limb close to the sagittal midline and center of gravity during locomotion, and confers efficient scapular movement around the ribcage.  Conversely, an expanded upper and small lower thorax better facilitates bipedality, facilitating more efficient arm swing and energy return from upper limb momentum, while lower thoracic expansion constrains arm swing in bipedal locomotion. 
Since lung volume and body mass scale isometrically, increases in lung capacity (and concomitant expansion of the thorax) would be best apportioned to the lower thorax in knuckle-walkers.  By contrast, increases in lung capacity and thorax expansion in bipeds are best apportioned superiorly. Thus, locomotor constraints, in concert with the isometric relationship between body size and lung size, may explain thoracic shape variation in early hominins.

Background: On Earth only a few legged species, such as water strider insects, some aquatic birds and lizards, can run on water. For most other species, including humans, this is precluded by body size and proportions, lack of appropriate appendages, and limited muscle power. However, if gravity is reduced to less than Earth's gravity, running on water should require less muscle power. Here we use a hydrodynamic model to predict the gravity levels at which humans should be able to run on water. We test these predictions in the laboratory using a reduced gravity simulator.

Il problema del dispositivo e l’impressione di realtà ad esso correlata hanno le loro origini negli studi estetici e psicologici sulla locomozione umana che si sviluppano verso la fine del XIX secolo. L’articolo segue l’opera dell’estetologo francese Paul Souriau, L’esthétique du mouvement (1889), con il fine di analizzare le condizioni materiali in cui sorge concretamente la disposizione dello spettatore cinematografico, sottolineando le implicazioni ontologiche e politiche relative a questo fenomeno. Una particolare attenzione è posta in questo senso sull’incrocio che si crea tra le ricerche della teoria della rappresentazione e la nascita di dispositivi pre-cinematografici che fungono da strumento scientifico nel processo di oggettivazione e controllo del movimento umano.

Background Motorized treadmills are widely used in research or in clinical therapy. Small kinematics, kinetics and energetics changes induced by Treadmill Walking (TW) as compared to Overground Walking (OW) have been reported in literature. The purpose of the present study was to characterize the differences between OW and TW in terms of stride-to-stride variability. Classical (Standard Deviation, SD) and non-linear (fractal dynamics, local dynamic stability) methods were used. In addition, the correlations between the different variability indexes were analyzed. Methods Twenty healthy subjects performed 10 min TW and OW in a random sequence. A triaxial accelerometer recorded trunk accelerations. Kinematic variability was computed as the average SD (MeanSD) of acceleration patterns among standardized strides. Fractal dynamics (scaling exponent α) was assessed by Detrended Fluctuation Analysis (DFA) of stride intervals. Short-term and long-term dynamic stability were estimated by computing the maximal Lyapunov exponents of acceleration signals. Results TW did not modify kinematic gait variability as compared to OW (multivariate T2, p = 0.87). Conversely, TW significantly modified fractal dynamics (t-test, p = 0.01), and both short and long term local dynamic stability (T2 p = 0.0002). No relationship was observed between variability indexes with the exception of significant negative correlation between MeanSD and dynamic stability in TW (3 × 6 canonical correlation, r = 0.94). Conclusions Treadmill induced a less correlated pattern in the stride intervals and increased gait stability, but did not modify kinematic variability in healthy subjects. This could be due to changes in perceptual information induced by treadmill walking that would affect locomotor control of the gait and hence specifically alter non-linear dependencies among consecutive strides. Consequently, the type of walking (i.e. treadmill or overground) is important to consider in each protocol design.

af Klint R, Nielsen JB, Sinkjaer T, Grey MJ. Sudden drop in ground support produces force-related unload response in human overground walking. . Humans maneuver easily over uneven terrain. To maintain smooth and efficient gait the motor system needs to adapt the locomotor output to the walking environment. In the present study we investigate the role of sensory feedback in adjusting the soleus muscle activity during overground walking in 19 healthy volunteers. Subjects walked unrestrained over a hydraulically actuated platform. On random trials the platform was accelerated downward at 0.8 g, unloading the plantar flexor muscles in midstance or late stance. The drop of the platform resulted in a significant depression of the soleus muscle activity of Ϫ17.9% (SD 2) and Ϫ21.4% (SD 2), with an onset latency of 49 ms (SD 1) and 45 ms (SD 1) in midstance and late stance, respectively. Input to the vestibular apparatus (i.e., the head acceleration) occurred at a latency 10.0 ms (SD 2.4) following the drop and ankle dorsiflexion velocity was decreased starting 22 ms (SD 15) after the drop. To investigate the role of length-and velocity-sensitive afferents on the depression in soleus muscle activity, the ankle rotation was arrested by using an ankle foot orthotic as the platform was dropped. Preventing the ankle movement did not significantly change the soleus depression in late stance [Ϫ18.2% (SD 15)], whereas the depression in midstance was removed [ϩ4.9% (SD 13)]. It is concluded that force feedback from ankle extensors increases the locomotor output through positive feedback in late stance. In midstance the effect of force feedback was not observed, suggesting that spindle afferents may have a more significant effect on the output during this phase of the step cycle.

The aim of this study was to investigate the contribution of feedback from large-diameter sensory fibers to the adaptation of soleus muscle activity following small ankle trajectory modifications during human walking. Small-amplitude and slow-velocity ankle dorsiflexion enhancements and reductions were applied during the stance phase of the gait cycle in order to mimic the normal variability of the ankle trajectory during walking.

Humans maneuver easily over uneven terrain. To maintain smooth and efficient gait the motor system needs to adapt the locomotor output to the walking environment. In the present study we investigate the role of sensory feedback in adjusting the soleus muscle activity during overground walking in 19 healthy volunteers. Subjects walked unrestrained over a hydraulically actuated platform. On random trials the platform was accelerated downward at 0.8 g, unloading the plantar flexor muscles in midstance or late stance. The drop of the platform resulted in a significant depression of the soleus muscle activity of -17.9% (SD 2) and -21.4% (SD 2), with an onset latency of 49 ms (SD 1) and 45 ms (SD 1) in midstance and late stance, respectively. Input to the vestibular apparatus (i.e., the head acceleration) occurred at a latency 10.0 ms (SD 2.4) following the drop and ankle dorsiflexion velocity was decreased starting 22 ms (SD 15) after the drop. To investigate the role of length- and velo...

Background: Walking is an economic activity, the more efficient the mechanical contribution, the less metabolic energy is necessary to keep walking. Patients with chronic heart failure and heart transplant present peripheral musculoskeletal disorders, dyspnea, and fatigue in their activities. Objective: In this scenario, the present study sought to verify the correlations between metabolic and electromyographic variables in chronic heart failure, heart transplant patients, and healthy controls. Methods: Regression and correlation between cost of transport and electromyographic cost, as well as correlation between oxygen consumption and muscle coactivation in patients and controls at five different walking speeds have been performed, with alpha = 0.05. Results: Strong correlation values (r controls: 0.99; chronic heart failure: 0.92; heart transplant: 0.88) indicate a linear relationship between the cost of transport and electromyographic cost. Oxygen consumption was significantly correlated to muscle activation in all groups. Conclusion: These results suggested that dynamic muscle coactivation was an important factor, especially for CHF and HT. These data support the idea that peripheral muscle limitations play an important role in people with CHF and HT. These findings indicate a strong relation between metabolic and electromyographic variables. For chronic heart failure and heart transplant patients, it can help to explain some difficulties in daily activities and aid in physical rehabilitation.

Force field adaptation of locomotor muscle activity is one way of studying the ability of the motor control networks in the brain and spinal cord to adapt in a flexible way to changes in the environment. Here, we investigate whether the corticospinal tract is involved in this adaptation. We measured changes in motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in the tibialis anterior (TA) muscle before, during, and after subjects adapted to a force field applied to the ankle joint during treadmill walking. When the force field assisted dorsiflexion during the swing phase of the step cycle, subjects adapted by decreasing TA EMG activity. In contrast, when the force field resisted dorsiflexion, they increased TA EMG activity. After the force field was removed, normal EMG activity gradually returned over the next 5 min of walking. TA MEPs elicited in the early swing phase of the step cycle were smaller during adaptation to the assistive force field and larger during adaptation to the resistive force field. When elicited 5 min after the force field was removed, MEPs returned to their original values. The changes in TA MEPs were larger than what could be explained by changes in background TA EMG activity. These effects seemed specific to walking, as similar changes in TA MEP were not seen when seated subjects were tested during static dorsiflexion. These observations suggest that the corticospinal tract contributes to the adaptation of walking to an external force field.

The purpose of this study was to investigate the relationship between anthropometric parameters and the preferred transition speed (PTS) in human locomotion, in both genders. Previous studies exploring body measures as possible determinants of the PTS were biased toward longitudinal body dimensions, while the relationship between the PTS and transverse body dimensions has so far not been examined. Longitudinal and transverse anthropometric parameters were measured in 48 physical education students (21 males, 27 females), and an exercise test was performed for determination of the PTS. The relationship between the PTS and the anthropometric variables was determined using Pearson product-moment correlations and stepwise multiple regression analysis. Weak to moderate correlations between several body size and body shape variables and the PTS were found. In males, significant negative correlations (p < .05) between transverse body dimensions scaled to body height (calf girth, shoulder, bicristal and bitrochanteric diameters) and the PTS were found (r = À.51 to À.63). In females, calf girth and thigh girth scaled to height were significantly negatively correlated with the PTS (r = À.61 and À.42, respectively; p < .05). The results of the study suggest that gait transition speed in humans is related to both transverse and longitudinal body dimensions, and that sexual dimorphism in body size and shape should be taken into consideration for a proper interpretation of the PTS.

A fundamental change associated with bipedalism was the evolution of a lumbar lordosis, a dorsally concave curvature that enhances the stability of the spine and places the center of gravity over the hips. Recent research suggests that unlike early hominins and modern humans, Neandertals were hypolordotic (Been et al., 2012). Absence of a lumbar lordosis in Neandertals is surprising given both the evolutionary and biomechanical relevance of the lumbar curve in bipedal locomotion. To better understand the function of the reduced lumbar lordosis in Neandertals, two studies were performed: a morphological analysis of human and Neandertal lumbopelvic regions and a kinematic assessment of human subjects walking with an experimentally reduced lordosis. The morphological analysis examined lumbopelvic variables in thirty-nine modern humans and three Neandertal skeletal specimens to determine whether hypolordotic humans and Neandertals share a similar lumbopelvic complex. In the kinematic analysis, 34 subjects posteriorly tilted the pelvis to achieve a reduced lordotic curve, simulating the Neandertal hypolordosis. Walking gait was then examined to determine the effects of walking with hypolordosis.

The morphological study revealed that hypolordotic modern humans have significantly longer and more ventrocaudally oriented transverse processes (p < 0.05) than normal or hyperlordotic humans, although Neandertals expressed a different pattern. Hypolordotic modern humans and Neandertals
also featured a wide sacral shape index (p = 0.0292) compared to other lordosis groups. These skeletal characteristics present in hypolordotic subjects enhance lumbar stability and robusticity, which are advantageous for stressful physical activity.

In the kinematic study, subjects achieved a posterior pelvic tilt (normal mean 8.22º, experimental mean -1.76º, p < 0.0001) and a reduced lordosis (normal mean 24.48º, experimental mean 14.80º, p < 0.0001) in quiet stance. Overall, posterior tilt was associated with no change in lordosis during walking. It appears that a reduction in lordosis is difficult to sustain during locomotion, hinting at the fundamental need for the lumbar lordosis. Hypolordotic strides were reduced in length in females and associated with a flexed knee in both sexes (p < 0.0001).

The gait kinematics of experimentally induced hypolordosis in modern bipeds, combined with the relatively short legs of Neandertals, suggest that Neandertals may have been less efficient locomotors over flat terrain than modern humans. However, the Neandertal specimens featured a dorsolaterally positioned hip joint and a lumbopelvic complex uniquely adapted for hypolordosis, which may have alleviated the gait deviations seen in modern hypolordotic subjects. Lumbopelvic adaptations may have also given Neandertals a unique advantage during physically stressful activities such as lifting, so hypolordosis was likely an adaptation to both glacial climates and high activity levels.

Numerous animal and human studies have shown that afferent information from the periphery contributes to the control of walking. In particular, recent studies have consistently shown that load receptor input is an important element of the locomotion control mechanism. The objective of this study was to investigate the contribution of load receptor feedback to the compensatory stretch re¯ex response. We examined the contribution of load receptor feedback to the magnitude of the short and medium latency components of the ankle plantar¯exor stretch re¯ex responses following an unexpected dorsi¯exion perturbation during human walking. Three body load conditions were investigated: normal body load, a 30% increase in body load, and a 30% decrease in body load. Healthy subjects walked on a treadmill at~3.6 km/h with the left ankle attached to a portable stretching device. Dorsi¯exion perturbations (8°; 350±425°/s) were generated during the late stance phase of gate (~400 ms following heel contact). Electromyographic activity was recorded from the soleus, tibialis anterior, medial gastrocnemius, rectus femoris, and biceps femoris muscles using bipolar surface electrodes. Stretch re¯ex responses were observed in the soleus and gastrocnemius muscles for all of the body load conditions; however, increasing or decreasing the body load did not affect the timing and magnitude of the responses. This study provides evidence that load receptor input does not contribute strongly to the corrective response of the stretch re¯ex in the plantar¯exor muscles during walking.

A vast amount of research has been carried out inspired by the motion event typology established by Talmy (1985, 2000), that of, verb-framed and satellite-framed languages. However, hardly any research has been devoted to either deeply analyse motion verb lexicons or to explore manner-of-motion verb granularity between languages typologically different or similar (cf. Slobin, 2003, 2006). This paper concentrates on an important subdomain of motion, i.e., human locomotion, and examines the way Spanish and English lexicalise it in verbs. The first part of the paper focuses on the semantics of human locomotion verbs with special attention to the sort of fine-grained manner information that each language encodes. In the second part, an empirical study on how Spanish and English monolinguals categorise human locomotion verbs into three motor pattern categories (Walk – Run – Jump) is reported.

The present study was designed to explore how the interaction between the fascicles and tendinous tissues is involved in storage and utilization of elastic energy during human walking. Eight male subjects walked with a natural cadence (1.4 +/- 0.1 m/s) on a 10-m-long force plate system. In vivo techniques were employed to record the Achilles tendon force and to scan real-time fascicle lengths for two muscles (medial gastrocnemius and soleus). The results showed that tendinous tissues of both medial gastrocnemius and soleus muscles lengthened slowly throughout the single-stance phase and then recoiled rapidly close to the end of the ground contact. However, the fascicle length changes demonstrated different patterns and amplitudes between two muscles. The medial gastrocnemius fascicles were stretched during the early single-stance phase and then remained isometrically during the late-stance phase. In contrast, the soleus fascicles were lengthened until the end of the single-stance ph...

Force field adaptation of locomotor muscle activity is one way of studying the ability of the motor control networks in the brain and spinal cord to adapt in a flexible way to changes in the environment. Here, we investigate whether the corticospinal tract is involved in this adaptation. We measured changes in motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in the tibialis anterior (TA) muscle before, during, and after subjects adapted to a force field applied to the ankle joint during treadmill walking. When the force field assisted dorsiflexion during the swing phase of the step cycle, subjects adapted by decreasing TA EMG activity. In contrast, when the force field resisted dorsiflexion, they increased TA EMG activity. After the force field was removed, normal EMG activity gradually returned over the next 5 min of walking. TA MEPs elicited in the early swing phase of the step cycle were smaller during adaptation to the assistive force field and larger during adaptation to the resistive force field. When elicited 5 min after the force field was removed, MEPs returned to their original values. The changes in TA MEPs were larger than what could be explained by changes in background TA EMG activity. These effects seemed specific to walking, as similar changes in TA MEP were not seen when seated subjects were tested during static dorsiflexion. These observations suggest that the corticospinal tract contributes to the adaptation of walking to an external force field.

RESUMEN La locomoción con miembros implica diferentes desafíos de tipo mecánico: en cada ciclo los segmentos tienen que ser reposicionados anatómicamente, con fases de aceleración y deceleración, con la consiguiente elevación y descenso del centro de masa. Dentro de la locomoción humana la marcha y la carrera son actividades fundamentales en todo el ciclo vital de las personas. En específico la carrera es una actividad muy estudiada por las ciencias del deporte, medicina, fisioterapia o kinesiología, ingeniería y biólogos, por el alto impacto articular y muscular que genera, ya que esto trae consigo lesiones y alteraciones en el rendimiento de los pacientes y deportistas. El constante estudio de la locomoción a reconocido diferentes desafíos de tipo fisiológico y mecánico tanto en la explicación de fenómenos como en el análisis de estos. Este artículo busca aclarar conceptos a través de textos clásicos, que se consideran básicos e importantes para entender las investigaciones posteriores. Además, se explican diferentes parámetros que sirven para comprender la locomoción, tanto en estudios con humanos como en animales. El objetivo de este trabajo es hacer una revisión de la literatura, que se enfoca en los aspectos mecánicos, energéticos, el efecto del tamaño y los diferentes patrones de la locomoción, PENSAR EN MOVIMIENTO. Artículo descargado de www.revistas.ucr.ac.cr/index.php/pem/ para uso personal únicamente. Este manuscrito Recién Horneado es la versión aceptada para publicación previa a diagramación y correcciones; habrá algunas diferencias con la versión final. Por favor citar como: Massimo Biancardi, C., Bona, R.L., y Lagos Hausheer, L. Locomoción humana: modelos y variables biomecánicas. PensarMov (2020).

Over the last century, numerous techniques have been developed to analyze the movement of humans while walking and running. The combined use of kinematics and kinetics methods, mainly based on high speed video analysis and forceplate, have permitted a comprehensive description of locomotion process in terms of energetics and biomechanics. While the different phases of a single gait cycle are well understood, there is an increasing interest to know how the neuro-motor system controls gait form stride to stride. Indeed, it was observed that neurodegenerative diseases and aging could impact gait stability and gait parameters steadiness. From both clinical and fundamental research perspectives, there is therefore a need to develop techniques to accurately track gait parameters stride-by-stride over a long period with minimal constraints to patients. In this context, high accuracy satellite positioning can provide an alternative tool to monitor outdoor walking. Indeed, the high-end GPS receivers provide centimeter accuracy positioning with 5-20 Hz sampling rate: this allows the stride-by-stride assessment of a number of basic gait parameterssuch as walking speed, step length and step frequency -that can be tracked over several thousand consecutive strides in free-living conditions. Furthermore, long-range correlations and fractal-like pattern was observed in those time series. As compared to other classical methods, GPS seems a promising technology in the field of gait variability analysis. However, relative high complexity and expensiveness -combined with a usability which requires further improvement -remain obstacles to the full development of the GPS technology in human applications.

Force field adaptation of locomotor muscle activity is one way of studying the ability of the motor control networks in the brain and spinal cord to adapt in a flexible way to changes in the environment. Here, we investigate whether the corticospinal tract is involved in this adaptation. We measured changes in motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) in the tibialis anterior (TA) muscle before, during, and after subjects adapted to a force field applied to the ankle joint during treadmill walking. When the force field assisted dorsiflexion during the swing phase of the step cycle, subjects adapted by decreasing TA EMG activity. In contrast, when the force field resisted dorsiflexion, they increased TA EMG activity. After the force field was removed, normal EMG activity gradually returned over the next 5 min of walking. TA MEPs elicited in the early swing phase of the step cycle were smaller during adaptation to the assistive force field and larger during adaptation to the resistive force field. When elicited 5 min after the force field was removed, MEPs returned to their original values. The changes in TA MEPs were larger than what could be explained by changes in background TA EMG activity. These effects seemed specific to walking, as similar changes in TA MEP were not seen when seated subjects were tested during static dorsiflexion. These observations suggest that the corticospinal tract contributes to the adaptation of walking to an external force field.

In this paper the development of a low-cost and easy wearable mechatronic system for the measurement of ground reaction forces (GRF) for the biomechanical analysis of the human locomotion is presented. The system consists of an insole, a conditioning device for the signals produced by the sensors applied to the insole and a data acquisition system connected to a USB portable storage. The sensors applied to the insole can measure the reaction forces in the horizontal and vertical directions during locomotion. The prototype was validated by comparing the data from the sensors with the values obtained using a force platform.

We investigated the contribution of afferent feedback to the soleus (SOL) muscle activity during the stance phase of walking in patients with spastic stroke. A total of 24 patients with hemiparetic spastic stroke and age-matched healthy volunteers participated in the study. A robotic actuator attached to the foot and leg was used to apply 3 types of ankle perturbations during treadmill walking. First, fast dorsiflexion perturbations were applied to elicit stretch reflexes in the SOL muscle. The SOL short-latency stretch reflex was facilitated in the patients (1.4 +/- 0.3) compared with the healthy volunteers (1.0 +/- 0.3, P = .05). Second, fast plantar flexion perturbations were applied during the stance phase to unload the plantar flexor muscles, thus, removing the afferent input from these muscles to the SOL motoneurons. These perturbations produced a distinct decrease in SOL activity that was significantly smaller in the patients (-30 +/- 3%) compared with the control subjects (-...

During human walking, a sudden trip may elicit a Ia afferent fibre mediated short latency stretch reflex. The aim of this study was to investigate soleus (SOL) muscle mechanical behaviour in response to dorsiflexion perturbations, and to relate this behaviour to short latency stretch reflex responses. Twelve healthy subjects walked on a treadmill with the left leg attached to an actuator capable of rapidly dorsiflexing the ankle joint. Ultrasound was used to measure fascicle lengths in SOL during walking, and surface electromyography (EMG) was used to record muscle activation. Dorsiflexion perturbations of 6 deg were applied during mid-stance at walking speeds of 3, 4 and 5 km h(-1). At each walking speed, perturbations were delivered at three different velocities (slow: approximately 170 deg s(-1), mid: approximately 230 deg s(-1), fast: approximately 280 deg s(-1)). At 5 km h(-1), fascicle stretch amplitude was 34-40% smaller and fascicle stretch velocity 22-28% slower than at 3 k...

To maintain smooth and efficient gait the motor system must adjust for changes in the ground on a step-to-step basis. In the present study we investigated the role of sensory feedback as 19 able-bodied human subjects walked over a platform that mimicked an uneven supporting surface. Triceps surae muscle activation was assessed during stance as the platform was set to different inclinations (+/-3 deg, +/-2 deg and 0 deg rotation in a parasagittal plane about the ankle). Normalized triceps surae muscle activity was significantly increased when the platform was inclined (2 deg: 0.153 +/- 0.051; 3 deg: 0.156 +/- 0.053) and significantly decreased when the platform was declined (-3 deg: 0.133 +/- 0.048; -2 deg: 0.132 +/- 0.049) compared with level walking (0.141 +/- 0.048) for the able-bodied subjects. A similar experiment was performed with a subject who lacked proprioception and touch sensation from the neck down. In contrast with healthy subjects, no muscle activation changes were obs...

Neuroprosthetic technology and robotic exoskeletons are being developed to facilitate stepping, reduce muscle efforts, and promote motor recovery. Nevertheless, the guidance forces of an exoskeleton may influence the sensory inputs, sensorimotor interactions and resulting muscle activity patterns during stepping. The aim of this study was to report the muscle activation patterns in a sample of intact and injured subjects while walking with a robotic exoskeleton and, in particular, to quantify the level of muscle activity during assisted gait. We recorded electromyographic (EMG) activity of different leg and arm muscles during overground walking in an exoskeleton in six healthy individuals and four spinal cord injury (SCI) participants. In SCI patients, EMG activity of the upper limb muscles was augmented while activation of leg muscles was typically small. Contrary to our expectations, however, in neurologically intact subjects, EMG activity of leg muscles was similar or even larger...

Background. Synergy modules have been used to describe activation of lower limb muscles during locomotion and hence to understand how the system controls movement. Walking and running have been shown shared synergy patterns suggesting common motor control of both symmetrical gaits. Unilateral skipping, an equivalent gait to the quadrupedal gallop in humans, has been defined as the third locomotion paradigm but the use by humans is limited due to its high metabolic cost. Synergies in skipping have been little investigated. In particular, to the best of our knowledge, the joint study of both trailing and leading limbs has never been addressed before. Research question. How are organized muscle activation patterns in unilateral skipping? Are they organized in the same way that in symmetrical gaits? If yes, which are the muscle activation patterns in skipping that make it a different gait to walking or running? In the present research, we investigate if there are shared control strategies for all gaits in locomotion. Addressing these questions in terms of muscle synergies could suggest possible determinants of the scarce use of unilateral skipping in humans. Methods. Electromyographic data of fourteen bilateral muscles were collected from volunteers while performing walking, running and unilateral skipping on a treadmill. Also, spatiotemporal gait parameters were computed from 3D kinematics. The modular composition and activation timing extracted by non-negative matrix factorization were analyzed to detect similarities and differences among symmetrical gaits and unilateral skipping. Results. Synergy modules showed high similarity throughout the different gaits and between trailing and leading limbs during unilateral skipping. The synergy associated with the propulsion force operated by calf muscles was anticipated in bouncing gaits. Temporal features of synergies in the leading leg were very similar to those observed for running. The different role of trailing and leading legs in unilateral skipping was reflected by the different timing in two modules. Activation for weight acceptance was anticipated and extended in the trailing leg, preparing the body for landing impact after the flight phase. A different behaviour was detected in the leading leg, which only deals with a pendular weight transference. Significance. The evidence gathered in this work supports the hypothesis of shared modules among symmetrical and asymmetrical gaits, suggesting a common motor control despite of the infrequent use of unilateral skipping in humans. Unilateral skipping results from phase-shifted activation of similar muscular groups used in symmetrical gaits, without the need for new muscular groups. The high and anticipated How to cite this article Pequera G, Ramírez Paulino I, Biancardi CM. 2021. Common motor patterns of asymmetrical and symmetrical bipedal gaits.

The concept of body schema has been introduced and widely discussed in the literature to explain various clinical observations and distortions in the body and space representation. Here we address the role of body schema related information in multi-joint limb motion. The processing of proprioceptive information may differ significantly in static and dynamic conditions since in the latter case the control system may employ specific dynamic rules and constraints. Accordingly, the perception of movement, e.g., estimation of step length and walking distance, may rely on a priori knowledge about intrinsic dynamics of limb segment motion and inherent relationships between gait parameters and body proportions. The findings are discussed in the general framework of space and body movement representation and suggest the existence of a dynamic locomotor body schema used for controlling step length and path estimation.