Effectiveness of a Variable-Speed Control Based on Auditory Feedback: Is It Possible?

PURPOSE: Variable-speed control in the field is challenging for motion science. Tests were performed to evaluate speed, Froude number, and oxygen consumption if these varied when using the same frequency of steps. The objective of this study was to evaluate the use of auditory feedback to control variable speed on the treadmill and track during acceleration cycles around the transition speed. METHODS: Twenty-four trained men participated. The protocol was based on 5 ramps of 50 seconds each around 80%, 90%, 100%, 110%, and 120% of the walking-running transition speed, recording the frequency of steps with a mobile phone during the treadmill test. The tests were replicated on the track using auditory feedback. RESULTS: When evaluating each speed of the protocols separately for the same frequency of steps, the average speed on the track was always higher on average at 54.7% compared to the laboratory (P < .050), and on the track, it was 16.2% higher than in the laboratory (P > .050). CONCLUSIONS: It cannot be considered that the same frequency of steps is equivalent to the same speed in the laboratory and on the track. These results point to the importance of reliable speed control during open field tests.

Maximum downward slope of sleep slow waves as a potential marker of attention-deficit/hyperactivity disorder clinical phenotypes.

BACKGROUND: Attention-Deficit/Hyperactivity Disorder (ADHD) is a highly heterogeneous diagnostic category, encompassing several endophenotypes and comorbidities, including sleep problems. However, no predictor of clinical long-term trajectories or comorbidity has yet been established. Sleep EEG has been proposed as a potential tool for evaluating the synaptic strength during development, as well as the cortical thickness, which is presumed to be altered in ADHD. We investigated whether the slope of the Slow Waves (SWs), a microstructural parameter of the sleep EEG, was a potential predictive parameter for psychiatric comorbidities and neuropsychological dimensions in ADHD. METHODS: 70 children (58 m; 8.76 ± 2.77 y) with ADHD who underwent psychiatric and neurologic evaluations and a standard EEG recording during naps were investigated. After sleep EEG analysis, we grouped the extracted SWs in bins of equal amplitude and then measured the associations, through generalized linear regression, between their maximum downward slopes (MDS) and the individual scores obtained from clinical rating scales. RESULTS: The presence of Multiple Anxiety Disorders was positively associated with MDS of medium amplitude SWs in temporo-posterior left areas. The Child Behavior Checklist scores showed negative associations in the same areas for small SWs. The presence of autistic traits was positively associated with MDS of high amplitude SWs in bilateral anterior and temporal left areas. The WISC-IV Processing Speed Index showed negative associations with MDS of small-to-medium SWs in anterior and temporal right areas, while positive associations in posterior and temporal left areas. CONCLUSIONS: Consistency of association clusters' localization on the scalp suggests that variations in the local MDS, revealing alterations of local synaptic strength and/or in daytime use of certain cortical circuits, could underlie specific neurodevelopmental trajectories resulting in different ADHD clinical phenotypes.

Compensatory recruitment allows amphibian population persistence in anthropogenic habitats.

Habitat anthropization is a major driver of global biodiversity decline. Although most species are negatively affected, some benefit from anthropogenic habitat modifications by showing intriguing life-history responses. For instance, increased recruitment through higher allocation to reproduction or improved performance during early-life stages could compensate for reduced adult survival, corresponding to "compensatory recruitment". To date, evidence of compensatory recruitment in response to habitat modification is restricted to plants, limiting understanding of its importance as a response to global change. We used the yellow-bellied toad (Bombina variegata), an amphibian occupying a broad range of natural and anthropogenic habitats, as a model species to test for and to quantify compensatory recruitment. Using an exceptional capture-recapture dataset composed of 21,714 individuals from 67 populations across Europe, we showed that adult survival was lower, lifespan was shorter, and actuarial senescence was higher in anthropogenic habitats, especially those affected by intense human activities. Increased recruitment in anthropogenic habitats fully offset reductions in adult survival, with the consequence that population growth rate in both habitat types was similar. Our findings indicate that compensatory recruitment allows toad populations to remain viable in human-dominated habitats and might facilitate the persistence of other animal populations in such environments.

Brain's Energy After Stroke: From a Cellular Perspective Toward Behavior.

Stroke is a neurological condition that impacts activity performance and quality of life for survivors. While neurological impairments after the event explain the performance of patients in specific activities, the origin of such impairments has traditionally been explained as a consequence of structural and functional damage to the nervous system. However, there are important mechanisms related to energy efficiency (trade-off between biological functions and energy consumption) at different levels that can be related to these impairments and restrictions: first, at the neuronal level, where the availability of energy resources is the initial cause of the event, as well as determines the possibilities of spontaneous recovery. Second, at the level of neural networks, where the "small world" operation of the network is compromised after the stroke, implicating a high energetic cost and inefficiency in the information transfer, which is related to the neurological recovery and clinical status. Finally, at the behavioral level, the performance limitations are related to the highest cost of energy or augmented energy expenditure during the tasks to maintain the stability of the segment, system, body, and finally, the behavior of the patients. In other words, the postural homeostasis. In this way, we intend to provide a synthetic vision of the energy impact of stroke, from the particularities of the operation of the nervous system, its implications, as one of the determinant factors in the possibilities of neurological, functional, and behavioral recovery of our patients.

Electromyographical and Physiological Correlation in Patient with Heart Disease

Abstract 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.

Common motor patterns of asymmetrical and symmetrical bipedal gaits.

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 muscle activation in the trailing leg for landing could be the key distinctive event of unilateral skipping.

Sleep EEG microstructure in children and adolescents with attention deficit hyperactivity disorder: a systematic review and meta-analysis.

Attention deficit hyperactivity disorder (ADHD) is commonly associated with sleep problems, possibly due to shared pathophysiology. Microstructural sleep electroencephalographic (EEG) alterations may likely represent markers of disordered cortical maturation in ADHD, although literature data are still conflicting, deserving further assessment. After having systematically reviewed the literature, we included 11 studies from 598 abstracts, and assessed 23 parameters of cyclic alternating pattern (CAP), four parameters of sleep EEG power and one parameter of sleep graphoelements through 29 meta-analyses and, when possible, univariate meta-regressions. Slow wave activity (SWA) in ADHD was significantly higher in early childhood and lower in late childhood/adolescence compared to controls, with an inversion point at 10 years. Total CAP rate and CAP A1 index in non-rapid eye movement (NREM) stage 2 sleep, and CAP A1 rate in NREM sleep were significantly lower in ADHD patients than controls. SWA and CAP A1 changes are therefore possible markers of altered cortical maturation in ADHD, consistently with the neuropsychological deficits characterizing the disorder, likely fostering earlier detection of at-risk/milder conditions, and more tailored therapeutic interventions.

Giant steps: adhesion and locomotion in theraphosid tarantulas.

Theraphosid tarantulas are large spiders that bear dense hairy adhesive pads on the distal parts of their legs: scopula and claw tufts. These structures allow them to climb on vertical smooth surfaces and contribute to prey capture. While adult females and juveniles remain most of the time in their burrows, adult males actively walk searching for females during the reproductive period. Adhesion and locomotion thus play important roles in the ecology and reproduction of these animals. In this paper, we review the current state of the knowledge on adhesion and locomotion in tarantulas, focusing on functional and evolutionary morphology.

Locomoción humana: modelos y variables biomecánicas / Human locomotion: models and biomechanical variables

Resumen La locomoción con miembros implica diferentes desafíos de tipo mecánico: en cada ciclo, los segmentos deben reposicionarse anatómicamente, con fases de aceleración y deceleración y 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 humano. En específico, la carrera es una actividad muy estudiada por las ciencias del deporte, medicina, fisioterapia o kinesiología, ingeniería y biología, por el alto impacto articular y muscular que genera, ya que esta trae consigo lesiones y alteraciones en el rendimiento de los pacientes y deportistas. El constante estudio de la locomoción ha 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, con sus modelos mecánicos. Finalmente, los autores esperan que este texto sea un aporte para docentes y estudiantes para la comprensión de la locomoción en idioma español.

Abstract Limbed locomotion involves different mechanical challenges: in each cycle, limbs must be repositioned anatomically, with acceleration and deceleration phases and the consequent raising and lowering of the center of mass. As part of human locomotion, walking and running are fundamental activities throughout the life cycle. In particular, running has been highly studied by sports sciences, medicine, physiotherapy, kinesiology, engineering, and biology due to the high joint and muscular impact it generates, commonly causing injuries and alterations in the performance of patients and athletes. The constant study of locomotion has brought to light the different physiological and mechanical challenges when explaining and analyzing phenomena. Using classical texts, this article aims to clarify concepts considered basic and important to understand further research. In addition, different parameters needed to understand locomotion, both in human and animal studies, are explained. The objective of this paper is to review the literature focused on the mechanical and energetic aspects of locomotion, the effect of size, and the different locomotion patterns and mechanical models. Finally, this paper is presented as a contribution for teachers and students to understand locomotion in the Spanish language.

Resumo A locomoção com membros implica diferentes desafios do tipo mecânico: em cada ciclo, os segmentos devem ser reposicionados anatomicamente, com fases de aceleração e desaceleração e a subsequente elevação e descenso do centro de massa. Dentro da locomoção humana, a marcha e a corrida são atividades fundamentais em todo o ciclo vital humano. Especificamente, a corrida é uma atividade muito estudada pelas ciências do esporte, medicina, fisioterapia ou cinesiologia, engenharia e biologia, devido à geração de alto impacto articular e muscular, trazendo consigo lesões e alterações no rendimento dos pacientes e esportistas. O constante estudo da locomoção reconheceu diferentes desafios de tipo fisiológico e mecânico, tanto na explicação de fenômenos como na análise destes. Este artigo busca aclarar conceitos através de textos clássicos, considerados básicos e importantes para entender as pesquisas posteriores. Além disso, são explicados diferentes parâmetros que servem para compreender a locomoção, tanto em estudos com humanos quanto com animais. O objetivo deste trabalho é fazer uma revisão da literatura, que se enfoca nos aspectos mecânicos, energéticos, no efeito do tamanho e nos diferentes padrões da locomoção, com seus modelos mecânicos. Finalmente, os autores esperam que este texto, em espanhol, seja uma contribuição para docentes e estudantes para a compreensão da locomoção.

Kinematics of male Eupalaestrus weijenberghi (Araneae, Theraphosidae) locomotion on different substrates and inclines.

BACKGROUND: The mechanics and energetics of spider locomotion have not been deeply investigated, despite their importance in the life of a spider. For example, the reproductive success of males of several species is dependent upon their ability to move from one area to another. The aim of this work was to describe gait patterns and analyze the gait parameters of Eupalaestrus weijenberghi (Araneae, Theraphosidae) in order to investigate the mechanics of their locomotion and the mechanisms by which they conserve energy while traversing different inclinations and surfaces. METHODS: Tarantulas were collected and marked for kinematic analysis. Free displacements, both level and on an incline, were recorded using glass and Teflon as experimental surfaces. Body segments of the experimental animals were measured, weighed, and their center of mass was experimentally determined. Through reconstruction of the trajectories of the body segments, we were able to estimate their internal and external mechanical work and analyze their gait patterns. RESULTS: Spiders mainly employed a walk-trot gait. Significant differences between the first two pairs and the second two pairs were detected. No significant differences were detected regarding the different planes or surfaces with respect to duty factor, time lags, stride frequency, and stride length. However, postural changes were observed on slippery surfaces. The mechanical work required for traversing a level plane was lower than expected. In all conditions, the external work, and within it the vertical work, accounted for almost all of the total mechanical work. The internal work was extremely low and did not rise as the gradient increased. DISCUSSION: Our results support the idea of considering the eight limbs functionally divided into two quadrupeds in series. The anterior was composed of the first two pairs of limbs, which have an explorative and steering purpose and the posterior was more involved in supporting the weight of the body. The mechanical work to move one unit of mass a unit distance is almost constant among the different species tested. However, spiders showed lower values than expected. Minimizing the mechanical work could help to limit metabolic energy expenditure that, in small animals, is relatively very high. However, energy recovery due to inverted pendulum mechanics only accounts for only a small fraction of the energy saved. Adhesive setae present in the tarsal, scopulae, and claw tufts could contribute in different ways during different moments of the step cycle, compensating for part of the energetic cost on gradients which could also help to maintain constant gait parameters.

Effect of walking speed in heart failure patients and heart transplant patients.

BACKGROUND: Chronic heart failure patients present higher cost of transport and some changes in pattern of walking, but the same aspects have not yet been investigated in heart transplant patients. METHODS: The aim of this study was to investigate both metabolic and mechanicals parameters, at five different walking speeds on treadmill, in chronic heart failure and heart transplant patients. Twelve chronic heart failure patients, twelve healthy controls and five heart transplant patients participated in the study. Tridimensional kinematics data and oxygen uptake were collected simultaneously. FINDINGS: In both experimental groups the self-selected walking speed was lower than in controls, and lower than the expected optimal walking speed. At that speed all groups showed the best ventilatory efficiency. On contrary, chronic heart failure and heart transplant patients reached the minimum cost of transport and the maximum recovery at greater speeds than the self-selected walking speed. Their mechanical efficiency was lower than in controls, while their metabolic cost and mechanical work were on average larger. INTERPRETATION: We conclude that actions, like a physical training, that could increase the self-selected walking speed in these patients, could also increase their economy and optimize the mechanical parameters of walking. We propose a rehabilitation index, based on the theoretical optimal walking speed, to measure the improvements during a physical rehabilitation therapy. These results have an important clinical relevance and can help to improve the quality of life of heart failure and transplant patients.

Electromyography and economy of walking in chronic heart failure and heart transplant patients.

Background Patients with chronic heart failure frequently report intolerance to exercise and present with changes in walk pattern, but information about heart transplant patients is lacking. Alterations of the gait pattern are related to interaction changes between the metabolism, neurological system and the mechanical demands of the locomotor task. The aim of this study was to investigate the electromyographic cost, coactivation and cost of transport of walking of chronic heart failure and heart transplant patients. Design This research was of an exploratory, cross-sectional design. Methods Twelve chronic heart failure patients, twelve healthy controls and five heart transplant patients participated in the study. Electromyographic data and oxygen uptake were collected simultaneously at five walking speeds. Results In the experimental groups, the electromyographic cost, percentage of coactivation in the leg and cost of transport were higher than in controls. The electromyographic cost was in line with the cost of transport. The minimum electromyographic cost matched with the self-selected walking speed in controls, while in chronic heart failure and heart transplant patients, it was reached at speeds higher than the self-selected walking speed. Conclusion The largest postural isometric activation and antagonist activation resulted in the highest metabolic demand. These findings are of great clinical relevance because they support the concept that interventions in order to improve the muscle performance in these patients can increase the self-selected walking speed and therefore the metabolic economy of walking.

Skipping vs. running as the bipedal gait of choice in hypogravity.

Hypogravity challenges bipedal locomotion in its common forms. However, as previously theoretically and empirically suggested, humans can rely on "skipping," a less common gait available as a functional analog (perhaps a vestigium) of quadrupedal gallop, to confidently move when gravity is much lower than on Earth. We set up a 17-m-tall cavaedium (skylight shaft) with a bungee rubber body-suspension system and a treadmill to investigate the metabolic cost and the biomechanics of low-gravity (Mars, Moon) locomotion. Although skipping is never more metabolically economical than running, the difference becomes marginal at lunar gravities, with both bouncing gaits approaching values of walking on Earth (cost ≈ 2 J · kg(-1)· m(-1)). Nonmetabolic factors may thus be allowed to dominate the choice of skipping on the Moon. On the basis of center of pressure measurements and body segments kinetics, we can speculate that these factors may include a further reduction of mechanical work to move the limbs when wearing space suits and a more effective motor control during the ground (regoliths)-boot interaction.

Biomechanical determinants of transverse and rotary gallop in cursorial mammals.

Transverse and rotary gallop differ in the placement of the leading hindfeet and forefeet: ipsilateral in the former gait, contralateral in the latter. We analysed 351 filmed sequences to assess the gallop type of 89 investigated mammalian species belonging to Carnivora, Artiodactyla and Perissodactyla orders. Twenty-three biometrical, ecological and physiological parameters were collected for each species both from literature data and from animal specimens. Most of the species showed only one kind of gallop: transverse (42%) or rotary (39%), while some species performed rotary gallop only at high speed (19%). In a factorial analysis, the first principal component (PC), which accounted for 40% of the total variance, was positively correlated to the relative speed and negatively correlated to size and body mass. The second PC was correlated to the ratio between distal and proximal limb segments. Large size and longer proximal limb segments were associated with transverse gallop, while rotary and speed-dependent species showed higher metacarpus/humerus and metatarsus/femur length ratio and faster relative speeds. The resulting limb excursion angles were proportional to the square-root of the Froude number, and significantly higher in rotary gallopers. The gait pattern analysis indicated significant differences between transverse and rotary gallop in forelimb and hindlimb duty factor (t-test; P<0.001), and in duration of the forelimb contact (t-test; P=0.045). Our results show that an exclusive gallop gait is adopted by a large number of mammalian species, and indicate that the gallop pattern depends on diverse environmental, morphometrical and biomechanical characters.

Biomechanics of octopedal locomotion: kinematic and kinetic analysis of the spider Grammostola mollicoma.

Despite the abundance of octapodal species and their evolutionary importance in originating terrestrial locomotion, the locomotion mechanics of spiders has received little attention so far. In this investigation we use inverse dynamics to study the locomotor performance of Grammostola mollicoma (18 g). Through 3-D kinematic measurements, the trajectory of the eight limbs and cephalothorax or abdomen allowed us to estimate the motion of the body centre of mass (COM) at different speeds. Classic mechanics of locomotion and multivariate analysis of several variables such as stride length and frequency, duty factor, mechanical external work and energy recovery, helped to identify two main gaits, a slow (speed <11 cm s(-1)) one and a fast one characterised by distinctive 3-D trajectories of COM. The total mechanical work (external + internal) calculated in the present study and metabolic data from the literature allowed us to estimate the locomotion efficiency of this species, which was less than 4%. Gait pattern due to alternating limb support, which generates asymmetrical COM trajectories and a small but consistent energy transfer between potential and kinetic energies of COM, is discussed both in terms of coordination indices and by referring to the octopod as formed by two quadrupeds in series. Analogies and differences of the newly obtained parameters with the allometric data and predictions are also illustrated.