Análise geoestratégica de Portugal

Este artigo consiste numa breve caracterização de Portugal, nos planos físico, demográfico, cultural, político e económico. Enumera os objectivos geoestratégicos, distinguindo os objectivos permanentes e os objectivos actuais, identificando as ameaças e contemplando as chamadas novas ameaças. Destaca também alguns dos aspectos geoestratégicos julgados mais significativos, considerados em cinco dimensões espaciais: nacional, lusófona, oeste-europeia, norte-atlântica e globa

Padrões de coordenação neuromuscular associados ao movimento do braço e antebraço em acções de lançamento: contributos para a orientação do treino de força

Os lançamentos constituem uma família de gestos técnicos desportivos em que um objecto é arremessado a uma mão por cima da cabeça e incluem gestos como o serviço e smash no ténis e no badmington, o remate de andebol, o remate de voley, o arremesso no basebol ou o lançamento do dardo no atletismo. Caracteriza-se no essencial pelo mesmo padrão gestual, com uma sequência de movimentos articulares organizada numa sequência próximo-distal e sujeita ao princípio da somação de velocidades, e com aspectos comuns ao nível dos padrões de coordenação neuromuscular. Com base em registos EMG e cinemáticos de diferentes acções de lançamento são caracterizados os padrões neuromusculares com incidência nos grupos musculares com acção no braço e no antebraço. A partir dessa caracterização, concluímos com algumas considerações metodológicas relacionadas com a orientação dos processos de treino da força em atletas solicitados em acções de lançamento

COMPARATION OF ABDOMINAL WALL ACTIVATION DURING SIT- UP AND CURL- UP EXERCISES IN WOMEN

In order to carry out this study, fourteen healthy females performed series of sit-up and curl-up exercises, with and without fixation for the legs. Electrogoniometers were placed on the hip and dorsal spine. Surface EMG was recorded from the superior and inferior portions of the rectus abdominis, external oblique, internal oblique, and rectus femoris of both sides. Muscle patterns were compared to norrr.alized values of integrated EMG. The results showed that the sit-up exercise required higher activity of the abdominal muscles than the curl-up, when the exercises were performed with or without fixation of the legs. In the same way, the sit-up exercise required high activity of the rectus femoris, mainly with fixation for the legs

EMG AND CINEMATIC PATTERNS ON ELBOW EXTENSION DURING A THROWING TASK PERFORMED AT DIFFERENT SPEEDS

The myoelectric activity of agonist and antagonist muscles in fast human movements is characterized by a phasic pattern, normally composed by three bursts and known as the friphasicpatfern. The most important events of this pattern are the initial agonist activation (AGI) responsible for the initial limb acceleration, and the antagonist activation (AMI), coincident with the electrical silence of the agonist muscle. On last 15 years, a lot of experimental research was done to understand how the Central Nervous System programs ballistic movements performed at different speeds. The most part of these studies were done with single-joint movements, performed an laboratorial environments, which became more attractive as a paradigm for testing hypotheses but didn't allow direct applications to more complex and "natural" movements. Purposes of this study were (1) to characterize the activation pattern of agonist and antagonist muscles of elbow extension on a dart throw to a target, (2) to analyze the effects of movement velocity on EMG and cinematic parameters and (3) to compare the above mentioned variables on trained and untrained subjects. Experiments were performed on four skilled dart throwers and nine untrained subjects. The task was a dart throw to a concentric target at a distance of 3 m and 1,70 m of centre height. Each subject performed 30 trials on each of three different conditions. Subjects were instructed before each condition: (P) "try to reach the target centre", (C) "try to reach the target centre as fast as possible" and (V) '3ust try to be as fast as possible". Two electrogoniometers on shoulder and elbow joints were used to measure position and velocity movement parameters on each joint. Surface EMGs were recorded from triceps (vastus medialis) and biceps brachii with active bipolar electrodes. The EMG signals were filtered, fullwave rectified and smoothed. The angle, velocity and EMG signals were time normalized using the shortest movement time as a reference and averaged in blocks of 20 trials representatives of each condition. Then, the EMG bursts (AGI and ANT) were isolated for parameters determination. A laser system developed on our Faculty allowed the dart speed determination. The elbow extension on initial condition (P) were accomplished by a tri- or biphasic EMG pattern with a clear tendency for a reciprocal activation: the maximum peak of ANT was always coincident with the silent period between the two agonist bursts AG 1 was a short duration burst (90- 135 ms) which began before movement onset and ceased before the moment of elbow peak velocity. The antagonist pattern contained a phasic burst (ANT) which began before the end of AGl and presented its maximum peak near the end of the acceleration phase. This burst was normally preceded by a tonic activation which started near movement imitation. The results show that either the modulation on amplitude and timing of AGI can be seen together or separate when we compare different throwing conditions. The subjects adjusted the time and the size af the burst to the nature of the task with a possible individual predominance of one of these mechanisms. Nevertheless, the increase of the initial EMG slope, measured by the integrated EMG of the first 30 rns of AGI [iEMG30), revealed to be the most related variable with the elbow movement speed. This finding agrees with a "dual-strategy" model (Gottlieb et al., 1989a,b, 1990). The antagonist EMG presented identical timing structure between different throwing conditions, but revealed a general tendency to an increase on its intensity when subjects throw quickly. The similar behaviour of agonist and antagonist activation intensities suggests a common mechanism of magnitude control. The untrained subjects show longer acceleration phases and longer duration of EMG events (duration of AGl, time to agonist and antagonist EMG peak, time of antagonist onset) than the skilled throwers. Those trained subjects presented reduced variability on temporal structure among throwing conditions

Geopolítica e geoestratégia

Este artigo efetua uma revisão analítica dos conceitos de geopolítica e geoestratégia. Argumenta que a designação corrente de geopolítica aplica-se predominantemente a elaborações teóricas que são do domínio da geoestratégia. Esta derivação semântica abre caminho ao surgimento de uma nova forma de encarar a geopolítica que respeite os seus fundamentos conceptuais, enquanto disciplina que assenta na combinação da geografia e da política, mas invertendo a interação mútua destes elementos, passando-se de uma geografia como instrumento em benefício da política, a uma política como instrumento colocado ao serviço da geografia

Alterações estratégicas na África subsariana

Até à Conferência de Berlim (1884-1885) os actores em confl ito na África Subsariana, africanos em confrontos internos ou resistindo aos invasores europeus e europeus contra a resistência africana ou nas suas disputas para-imperiais, ainda não tinham atingido o patamar da “estratégia científi ca”, mantendo-se no da “estratégia instintiva”1 . Os princípios e métodos da estratégia científi ca, introduzidos por Carl Von Clausewitz, encarada como o emprego racional da coacção na gestão dos confl itos ao serviço da política, a oposição a um “outro” como essência do raciocínio estratégico, só chegaram ao continente africano através das guerras em que se confrontaram ambições coloniais das potências europeias, cujo início podemos situar na Guerra Anglo-Boer (1898-1902)

GROUND REACTION FORCES OF STEP EXERCISE DEPENDING ON STEP FREQUENCY AND BENCH HEIGHT

Step exercise is one of the most famous Fitness activities. Different music speeds and bench heights can be used in Step classes. During the step cycle the higher mechanical load is experienced when the first foot steps down. The purpose of this study was to determine the ground reaction forces (GRF) of the step-down phase, depending on step frequency and bench height. Two groups of subjects participated in this study: a) 20 female subjects, mean age of 25 years, skilled in Step exercise; and b) 15 female subjects, post menopause, mean age of 62 years. Kistler force plate signals were collected. Increasing step frequency and bench height leads to the increase of mechanical load, which appears trigger adaptations of the movement technique