Percorrer por autor "Infante, Jorge"
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- Atividade física em contexto de contenção social COVID-19 e impacto na aptidão física dos Cadetes-Alunos do MICP/CFOP do ISCPSIPublication . Monteiro, Luís; Massuça, Luís; Infante, Jorge; Sequeira, Américo; Silva, TiagoEm 2020, a propagação da doença coronavírus (COVID-19) resultou numa pandemia mundial. Perante as medidas sociais implementadas em Portugal, o normal funcionamento das aulas nas Instituições de Ensino em geral, e no ISCPSI em particular, passaram de presenciais a síncronas. Este estudo teve como objetivos: (i) conhecer os comportamentos de atividade física dos cadetes-alunos do MICP/CFOP do ISCPSI em contexto de contenção social; e (ii) conhecer o impacto desse confinamento (de 3 a 4 meses) na aptidão física dos cadetes-alunos do MICP/CFOP do ISCPSI. Um total de 146 cadetes-alunos responderam a um inquérito (questionário online auto-preenchido) sobre a atividade física em contexto de contenção social (desenho de estudo observacional transversal), sendo consideradas as seguintes dimensões: (i) literacia em saúde; (ii) alimentação; e (iii) atividade física. Em complemento, 156 cadetes-alunos foram submetidos à avaliação da aptidão física em dois momentos (antes do COVID-19 e no regresso às aulas presenciais). Foi aplicada uma bateria de testes de avaliação da aptidão física (que contemplou: morfologia; impulsão horizontal; força de preensão manual; flexibilidade; força dos membros superiores; abdominais; velocidade; agilidade; vaivem), sendo os instrumentos utilizados e os procedimentos adotados, em conformidade com o Protocolo de Testes de Aptidão Física do ISCPSI. Os resultados do estudo sugerem que, na ausência/redução da atividade física sistemática, os cadetes-alunos tiveram um acréscimo significativo na % de massa gorda, e um decréscimo acentuado da capacidade aeróbia, força superior e potência. Ao referido, acresce o impacto negativo na saúde mental e na privação de liberdade. Assim, sugere-se que os cadetes-alunos, em situações futuras, evitem a interrupção prolongada do treino aeróbio, de força e da potência, atenuando o impacto negativo no desempenho e na saúde.
- Hamstring stiffness pattern during contraction in healthy individuals: analysis by ultrasound-based shear wave elastographyPublication . Mendes, Bruno; Firmino, Telmo; Oliveira, Raúl; Neto, Tiago; Infante, Jorge; Vaz, João R; Freitas, SandroPurpose To assess the stiffness of hamstring muscles during isometric contractions in healthy individuals, using ultrasoundbased shear wave elastography to (1) determine the intra- and inter-day assessment repeatability, (2) characterize the stiffness of semitendinosus (ST) and biceps femoris long head (BFlh) along the contraction intensity, and (3) characterize stiffness distribution among the hamstring muscles and inter-limb symmetry. Methods Two experiments were conducted. In experiment I (n = 12), the intra-day repeatability in assessing the BFlh and ST stiffness were determined at intensities between 10–60% of maximal voluntary isometric contraction (MVIC) in a single session. In experiment II (n = 11), the stiffness of the hamstring muscles of both thighs was assessed at 20% of MVIC in the first session; and retested (for one randomly chosen thigh) in a second session. Isometric contraction of knee flexors was performed with the knee flexed at 30° and with the hip in a neutral position. Results Moderate-to-very-high intra- and inter-day repeatability was found (ICC = 0.69–0.93). The BFlh/ST stiffness ratio increased with contraction intensity. At 20% of MVIC, the ST showed the highest stiffness among the hamstring muscles (p < 0.02), with no differences between the remaining hamstring muscles (p > 0.474). No differences were found between limbs (p = 0.12). Conclusions The stiffness distribution among the hamstring muscles during submaximal isometric contractions is heterogeneous, but symmetric between limbs, and changes depending on the contraction intensity. Shear wave elastography is a reliable tool to assess the stiffness of hamstring muscles during contraction.
- Muscle activation and intermuscular coordination adaptations to early strength training during maximal force productionPublication . Santos, Paulo D. G.; Vaz, João R.; Gomes, Miguel; Infante, Jorge; Pezarat-Correia, PedroPreviously untrained individuals tend to increase maximal and rapid strength during the initial resistance training stages. Muscle activation and coordination are neural mechanisms contributing to the increased mechanical output. However, how the force production characteristics are accompanied by changes in activation of agonist muscles as well as coordination of muscles with different functional roles is not fully understood. This study investigated the time course of adaptations following 6 weeks of resistance training, evaluating every two weeks a leg-press isometric maximum voluntary contraction. Peak force (PF), rate of force development (RFD), rate of EMG rise (RER) of the agonist muscles and intermuscular coherence between synergist or antagonist pairs of muscles were evaluated. In result of a dynamic squat program, the maximal and rapid leg-press isometric force increased after the 6-week period (p = 0.011 and p = 0.015, respectively), although improvements at specific intervals of RFD at specific time points were observed. Regarding knee extensor activation, generally decreased RER was observed only for rectus femoris and not for the monoarticular portions of quadriceps. Additionally, intermuscular coherence analysis revealed increased coupling between rectus femoris and the monoarticular portions of quadriceps after training, and adaptations between agonist muscles acting in different joints as well as between agonist and antagonist muscle at specific time points were observed concerning specific bands. This is the first study to characterize the time course of intermuscular coordination adaptations during the early phase of strength training in previously untrained individuals, bringing new insights into the neural mechanisms of muscle recruitment following resistance training in what concerns to coordinative strategies in the control of muscles with different functional roles.