Neuromuscular factors affecting stretch-induced torque loss

The mechanisms underpinning the immediate torque loss induced by acute, static muscle stretching are still not clear. The current research was designed to examine the neuromuscular factors influencing this torque loss. In Study 1, the contributions of central versus peripheral factors to the stretch-induced torque loss were investigated. Measures of central drive, including the EMG amplitude normalised to the muscle compound action potential amplitude (EMG:M), percent voluntary activation (%VA) and first volitional wave amplitude (V:M), and measures of peripheral function, including the twitch peak torque and 20:80 Hz tetanic torque ratio were made before, and immediately and 15 min after a 5-min continuous plantar flexor stretch. There was a 15.7% (p Alternatively, intermittent (i.e. repeated) stretching commonly performed by athlete and clinical populations causes cycles of ischaemia-reperfusion, increasing the likelihood of contractile failure. Therefore, Study 2 was designed to determine whether intermittent stretch might cause greater torque loss when compared to continuous stretch, and to quantify the potentially greater peripheral effect. The main findings were that intermittent stretch induced a greater torque loss (-23.8%; p Central drive failure can clearly be of spinal origin, and it is reasonable to speculate that muscle stretch might affect the afferent-mediated motor neurone facilitatory system. Thus, in Study 3 a vibration-stimulation protocol (vib+stim) was used to elicit reflexmediated muscular contractions during two experiments. In Experiment 1, vib+stim was imposed with the ankle joint plantar flexed (+10°), neutral (0°) and dorsiflexed (-10°). Torque and EMG amplitudes during vibration and during the self-sustained torque period after vib+stim were greater in dorsiflexion, providing method validation. In Experiment 2, vib+stim was imposed twice before (Control) and immediately, 5, 10 and 15 min after a 5-min intermittent stretch protocol. Torque and EMG amplitude were depressed immediately after stretching during both vibration (-60% and –41%, respectively;

As atividades lúdicas no desenvolvimento de crianças em fase pré-escolar

A criança, em todas as épocas e culturas, utiliza grande parte de seu tempo com brincadeiras. É consenso entre vários teóricos do desenvolvimento (Piaget,1975; Wallon, 1989; Vigotski,2003;) a respeito da importância do brincar no desenvolvimento infantil. É brincando, de acordo com Piaget (1934, 1975, 1978) a criança constrói o significado de si mesma, dos outros, das situações e do mundo em que vive, pois a brincadeira é o meio que a criança usa para explorar o mundo. Então, para este autor, brincar é construir significados. Debortoli (2003) coloca que brincar é interagir com o mundo. Ao brincar, combinamos regras, fantasiamos, imaginamos e nos relacionamos com o outro. Isso faz com que demos novos significados ao mundo, pois podemos expressar objetivamente o significado de tudo que nos cerca através da fala, além de podermos fazer interações simbólicas através da expressão corporal. O objetivo este estudo centrou-se na verificação da importância da brincadeira para o desenvolvimento cognitivo e sócio-afetivo da criança na fase escolar. Buscou-se conhecer também, quais são as brincadeiras mais utilizadas e que finalidades elas alcançam. Foi realizada a pesquisa qualitativa, utilizando para coleta de dados a observação participante de situações de atividades lúdicas de crianças interagindo no contexto escolar. Foram registradas as formas e ações no brincar, as quais foram analisadas e categorizadas. Os resultados demonstraram o quanto é importante a brincadeira no contexto da pré-escola, favorecendo a construção do conhecimento, permitindo a criança desenvolver em sua totalidade, como apontam as teorias e os autores que estudam o desenvolvimento infantil

O PAPEL DO ALONGAMENTO NA PREVENÇÃO DE LESÕES: uma análise crítica

resum

A voz dos olhares que percorrem a periferia: o território sob as lentes do adolescente

The outskirts of São Paulo is marked by situations of social inequality, violence and poverty. It is a fertile territory full of vulnerabilities and potentialities, aspects that only their residents can identify them. Adolescence is marked by the search for new experiences of pleasure and feelings of belonging to a social group are actors ideal for photographing the potentialities and weaknesses of the territory in which they live and structure your daily life. Thus, this exploratory qualitative study, which used the photography as a methodological resource, sought to investigate the perception that adolescents residents in a slum have over the territory in which they live. So cameras were distributed to the participants, who in turn photographed dimensions related to leisure, socializing, sports and entertainment found in space, as well as recorded aspects that need more government attention, such as garbage and rubble placed on sidewalks, polluted springs and finally, valued the organization maintenance and revitalization of squares and the soccer field, showing that the Their youth are attentive to the complex issues of the territory in which they live.A periferia de São Paulo é marcada por situações de desigualdade social, violência e pobreza. É um território fértil e repleto de vulnerabilidades e potencialidades, aspectos que somente seus moradores conseguem identificar. A adolescência é marcada pela busca de novas experiências, de prazer e sensações de pertencimento a um grupo social, são atores ideais para fotografar as potencialidades e fragilidades do território em que vivem no qual estruturam seu cotidiano. Desta forma, este estudo qualitativo exploratório, que utilizou a fotografia como recurso metodológico, buscou investigar a percepção que os adolescentes residentes em uma favela têm sobre o território em que vivem. Sendo assim, câmeras fotográficas foram distribuídas aos participantes, que por sua vez, fotografaram dimensões relacionadas ao lazer, convívio, esporte e entretenimento encontrados no espaço, assim como registraram aspectos que necessitam de maior atenção do governo, como é o caso do lixo e entulhos colocados nas calçadas, nascentes poluídas e por fim, valorizaram a organização comunitária na manutenção e revitalização de praças e do campo de futebol, mostrando que a juventude mostra-se atenta à questões complexas do território em que habitam.Dados abertos - Sucupira - Teses e dissertações (2019

Cartografia do cotidiano do sujeito em situações de rua no Distrito Federal

Monografia (graduação)—Universidade de Brasília, Faculdade de Ceilândia, Terapia Ocupacional, 2013.Introdução: São diversos os motivos que levam as pessoas às situações de rua e independente destes, essas pessoas materializam todo o seu cotidiano nos espaços da rua, sendo assim, torna-se necessário compreender como os sujeitos endereçam suas significações pelo território e como tecem suas redes de apoio. Objetivos: Compreender como o sujeito em situações de rua organiza sua existência; Descrever como o sujeito organiza suas atividades cotidianas na rua; Revelar o significado dos recursos utilizados para operacionalizar as atividades cotidianas realizadas pelo sujeito em situações de rua. Metodologia: O presente trabalho apresenta uma leitura etnográfica das vivências resultadas de um acompanhamento realizado com um sujeito em situações de rua e seus desdobramentos. O trabalho mescla aspectos de um estudo de caso, orientado por uma análise etnográfica e subsidiados pela observação participante, na qual uma entrevista foi gravada e transcrita, sendo analisada posteriormente com o auxílio do diário de campo. Análise dos resultados: A pesquisa resultou na análise de 8 categorias relacionando o sujeito com seu cotidiano, são elas: O carrinho da existência; Rede, circuitos e pessoas; Atitudes conflitivas, ameaças e violência encenadas no cotidiano da rua; Encontros e desencontros; O corpo que anda todo arrumadinho; O guardião; Dinheiro e prazer; Atividades e ocupações, o sentido se materializa e significa a vida. Discussões: É na rua que o sujeito em destaque mescla elementos de ambientes privados, que são historicamente e socialmente construídos, com elementos que são públicos, dessa forma, atividades íntimas e privadas são realizadas em ambientes públicos, onde o sujeito tece suas próprias estratégias para concretizá-las. Considerações finais: É dessa forma que o sujeito se encontrando imerso em uma constante esperança equilibrista, equilibrando estratégias para viver e sobreviver, existir e resistir nos espaços da rua. ____________________________________________________________________________ ABSTRACTIntroduction: There are several reasons that lead people to street situations and independent of them, these people embody all your everyday activities on the streets, so it is necessary to understand how the subject address their meanings and how to weave their territory support networks. Objectives: To understand how the person in street situations organizes its existence; Describe how the person organizes their daily activities on the street; Reveal the significance of the resources used to operationalize the daily activities performed by the subject in street situations. Methodology: This paper presents an ethnographic reading of experiences of monitoring undertaken with a subject in street situations and their consequences. The work blends aspects of a case study, guided by an ethnographic analysis and subsidized by participant observation, in which an interview was recorded, transcribed, and analyzed later with the aid of a field journal. Results: The search resulted in the analysis of 8 categories relating the subject to their daily life, they are: The cart of existence; Network, circuits and persons, conflicting attitudes, threats and violence staged in everyday street; Encounters and clashes; The body who walks around tidy; The guardian; Money and pleasure; Activities and occupations, the effect materializes and means life. Discussion: On the street merges elements highlighted in private environments, which are historically and socially constructed, with elements that are public, thus intimate and private activities are held in public places, where the subject weaves their own strategies for achieving them. Final Thoughts: This is how the subject lying immersed in a constant tightrope hope, balancing strategies to live and survive, exist and resist in the space of the street

Facilitation–inhibition control of motor neuronal persistent inward currents in young and older adults

A well-coordinated facilitation–inhibition control of motor neuronal persistent inward currents (PICs) via diffuse neuromodulation and local inhibition is essential to ensure motor units discharge at required times and frequencies. Present best estimates indicate that PICs are reduced in older adults; however, it is not yet known whether PIC facilitation–inhibition control is also altered with ageing. We investigated the responses of PICs to (i) a remote handgrip contraction, which is believed to diffusely increase serotonergic input onto motor neurones, and (ii) tendon vibration of the antagonist muscle, which elicits reciprocal inhibition, in young and older adults. High-density surface electromyograms were collected from soleus and tibialis anterior of 18 young and 26 older adults during triangular-shaped plantar and dorsiflexion contractions to 20 % (handgrip experiments) and 30 % (vibration experiments) of maximum torque (rise-decline rate of 2 % / s). A paired-motor-unit analysis was used to calculate ∆F, which is assumed to be proportional to PIC strength. ΔF increased in both soleus (0.55 peaks per second (pps), 16.0 %) and tibialis anterior (0.42 pps, 11.4 %) after the handgrip contraction independent of age. Although antagonist tendon vibration reduced ΔF in soleus (0.28 pps, 12.6 %) independent of age, less reduction was observed in older (0.42 pps, 10.7 %) than young adults (0.72 pps, 17.8 %) in tibialis anterior. Our data indicate a preserved ability of older adults to amplify PICs following a remote handgrip contraction, during which increased serotonergic input onto the motor neurones is expected, in both lower leg muscles. However, PIC deactivation in response to reciprocal inhibition was impaired with ageing in tibialis anterior despite being preserved in soleus. (Figure presented.). Key points: Motor neuronal persistent inward currents (PICs) are facilitated via diffuse neuromodulation and deactivated by local inhibition to ensure motor units discharge at required times and frequencies, allowing normal motor behaviour. PIC amplitudes appear to be reduced with ageing; however, it is not known whether PIC facilitation–inhibition control is also altered. Remote handgrip contraction, which should diffusely increase serotonergic input onto motor neurones, facilitated PICs similarly in both soleus and tibialis anterior of young and older adults. Antagonist tendon vibration, which induces reciprocal inhibition, reduced PICs in soleus in both young and older adults but had less effect in tibialis anterior in older adults. Data from lower-threshold motor units during low-force contractions suggest that PIC facilitation is preserved with ageing in soleus and tibialis anterior. However, the effect of reciprocal inhibition on the contribution of PICs to motor neurone discharge seems reduced in tibialis anterior but preserved in soleus

Ageing reduces persistent inward current contribution to motor neurone firing: Potential mechanisms and the role of exercise

Nervous system deterioration is a primary driver of age-related motor impairment. The motor neurones, which act as the interface between the central nervous system and the muscles, play a crucial role in amplifying excitatory synaptic input to produce the desired motor neuronal firing output. For this, they utilise their ability to generate persistent (long-lasting) depolarising currents that increase cell excitability, and both amplify and prolong the output activity of motor neurones for a given synaptic input. Modulation of these persistent inward currents (PICs) contributes to the motor neurones’ capacities to attain the required firing frequencies and rapidly modulate them to competently complete most tasks. Thus, PICs are crucial for adequate movement generation. Impairments in intrinsic motor neurone properties can impact motor unit firing capacity, with convincing evidence indicating that the PIC contribution to motor neurone firing is reduced in older adults. Indeed, this could be an important mechanism underpinning the age-related reductions in strength and physical function. Furthermore, resistance training has emerged as a promising intervention to counteract age-associated PIC impairments, with changes in PICs being correlated with improvements in muscular strength and physical function after training. In this review, we present the current knowledge of the PIC magnitude decline during ageing and discuss whether reduced serotonergic and noradrenergic input onto the motor neurones, voltage-gated calcium channel dysfunction or inhibitory input impairments are candidates that: (i) explain age-related reductions in the PIC contribution to motor neurone firing and (ii) underpin the enhanced PIC contribution to motor neurone firing following resistance training in older adults. (Figure presented.)

Neuromuscular factors contributing to reductions in muscle force after repeated, high-intensity muscular efforts

Multiple neuromuscular processes contribute to the loss of force production following repeated, high-intensity muscular efforts; however, the relative contribution of each process is unclear. In Experiment 1, 16 resistance trained men performed six sets of unilateral isometric plantar flexor contractions of the right leg (3 s contraction/2 s rest; 85% maximal voluntary contraction torque; 90-s inter-set rest) until failure with and without caffeine ingestion (3 mg kg-1) on two separate days. Corticospinal excitability and cortical silent period (cSP) were assessed before and immediately, 10 and 20 min after the exercise. In Experiment 2, electrically evoked tetanic force and persistent inward current (PIC)-mediated facilitation of the motor neuron pool (estimated using neuromuscular electrical stimulation with tendon vibration) were assessed before and after the same exercise intervention in 17 resistance trained men. Results showed decreases in peak plantar flexion torque (Experiment 1: -12.2%, Experiment 2: -16.9%), electrically evoked torque (20 Hz -15.3%, 80 Hz -15.3%, variable-frequency train -17.9%), and cSP (-3.8%; i.e., reduced inhibition) post-exercise which did not recover by 20 min. Electromyographic activity (EMG; -6%), corticospinal excitability (-9%), and PIC facilitation (-24.8%) were also reduced post-exercise but recovered by 10 min. Caffeine ingestion increased torque and EMG but did not notably affect corticospinal excitability, PIC amplification, or electrically evoked torque. The data indicate that a decrease in muscle function largely underpins the loss of force after repeated, high-intensity muscular efforts, but that the loss is exacerbated immediately after the exercise by simultaneous decreases in corticospinal excitability and PIC amplitudes at the motor neurons

Acute effects of three different stretching protocols on the Wingate test performance

The purpose of this study was to examine the acute effects of different stretching exercises on the performance of the traditional Wingate test (WT). Fifteen male participants performed five WT; one for familiarization (FT), and the remaining four after no stretching (NS), static stretching (SS), dynamic stretching (DS), and proprioceptive neuromuscular facilitation (PNF). Stretches were targeted for the hamstrings, quadriceps, and calf muscles. Peak power (PP), mean power (MP), and the time to reach PP (TP) were calculated. The MP was significantly lower when comparing the DS (7.7 ± 0.9 W/kg) to the PNF (7.3 ± 0.9 W/kg) condition (p \u3c 0.05). For PP, significant differences were observed between more comparisons, with PNF stretching providing the lowest result. A consistent increase of TP was observed after all stretching exercises when compared to NS. The results suggest the type of stretching, or no stretching, should be considered by those who seek higher performance and practice sports that use maximal anaerobic power