Effects of Fatigue Intervention on Biomechanics of Lower Extremity during a Stretch-Shortening Cycle Movement / 中国运动医学杂志

Objectives To explore the effect of fatigue intervention on biomechanics of lower extremity and performance during the stretch-shortening cycle(SSC) movement-drop jumps(DJ).Methods The Vicon motion capture system and 3D Kistler force plates were used to collect sagittal plane kinematics and ground reaction force data synchronously of a total of fifteen trained male athletes under pre-and post-fatigue conditions with shuttle running + vertical jumping fatigue protocol.The joint angle,joint moment,power,work,and leg/joint stiffness were compared before and after fatigue.Results After fatigue,the maximum height of DJ decreased(P＜0.05),while the touchdown angle and the range of motion(△θ) of knee and ankle joints,as well as the occurrence time for the eccentric,concentric and total phase increased(P＜0.05).However,the maximum push-off moment and power of knee reduced(P＜ 0.05).The stiffness of knee and ankle joints during the eccentric phase reduced,resulting in the reduction of the leg stiffness(P＜0.05).Moreover,the energy absorption and net energy of the ankle joint decreased;meanwhile,the energy contribution of the knee joint decreased during the eccentric phase of a DJ task.Conclusion Fatigue changes the movement pattern,decreasing the control ability of the lower extremity especially in the knee and ankle joint,and results in decreased performance.Moreover,the decrease of leg,ankle and knee stiffness and the corresponding energy can be used as sensitive indexes to evaluate the performance of drop jumps in a fatigued condition.

Grupo e trabalho coletivo na escola: trocando olhares, mudando práticas / Joint group and work in school: exchanging looks, changing practices

O presente artigo trata do trabalho desenvolvido por um grupo de formação instituído em uma escola de ensino fundamental da Rede Municipal de Campinas-SP, no período de 2004 a 2005, cujo objetivo foi a redefinição do trabalho com as classes de alfabetização. Uma das inquietações do grupo foi a não-aprendizagem de alguns dos alunos das primeiras séries no tempo que a escola seriada estipula. Em função disso, as professoras promoveram uma mudança significativa ao assumir a responsabilidade pela aprendizagem de todos os alunos dessas séries que precisavam de "outros tempos". Enfatizo, neste texto, a potencialidade do trabalho conjunto dessas professoras quando decidiram mudar a prática do reforço já instituída na escola, prática solitária professora-aluno. A prática coletiva do reforço estabeleceu novas formas de organização que possibilitaram aos alunos vivenciar o trabalho com outras professoras, bem como proporcionar-lhes a possibilidade de trocar olhares sobre um mesmo aluno.

The work developed by an educational group of an Elementary School in the Municipal Schools of Campinas (SP) during 2004-2005, aiming at restructuring the teaching of reading classes is reported. One of the group issues was the learning deficiency of some first-grade students in relation to the expectancy standard. Thus, the teachers furthered a deep change, responsible as they were for the development of all those who needed "some other time" to learn. These teachers´ joint work potentialities are emphasized as they change the traditional reinforcement classes at school, a solitary teacher-student practice, contrasting to the collective reinforcement practice which established new forms of organization that enabled students to interact with different teachers, and created the opportunity for teachers to exchange varying points of view about one same student.