Rugby league football is played in several countries worldwide. A rugby league team consists of 13 players (6 forwards and 7 backs), with matches played over two 40-minute halves separated by a 10-minute rest interval. Several studies have documented the physiological capacities of rugby league players and the physiological demands of competition, with the physiological capacities of players and the physiological demands of competition increasing as the playing level is increased. However, there is also evidence to suggest that the physiological capacities of players may deteriorate as the season progresses, with reductions in muscular power and maximal aerobic power and increases in skinfold thickness occurring towards the end of the rugby league season, when training loads are lowest and match loads and injury rates are at their highest. Player fatigue and playing intensity have been suggested to contribute to injuries in rugby league, with a recent study reporting a significant correlation (r=0.74) between match injury rates and playing intensity in semi-professional rugby league players. Studies have also reported a higher risk of injury in players with low 10-m and 40-m speed, while players with a low maximal aerobic power had a greater risk of sustaining a contact injury. Furthermore, players who completed <18 weeks of training prior to sustaining their initial injury were at greater risk of sustaining a subsequent injury. These findings provide some explanation for the high incidence of fatigue-related injuries in rugby league players and highlight the importance of speed and endurance training to reduce the incidence of injury in rugby league players. To date, most, but not all, studies have investigated the movement patterns and physiological demands of rugby league competition, with little emphasis on how training activities simulate the competition environment. An understanding of the movement patterns and physiological demands of specific individual positions during training and competition would allow the development of strength and conditioning programmes to meet the specific requirements of these positions. In addition, further research is required to provide information on the repeated effort demands of rugby league. A test that assesses repeated effort performance and employs distances, tackles and intensities specific to rugby league, while also simulating work-to-rest ratios similar to rugby league competition, is warranted.

The aim of this study was to analyse movement patterns of professional rugby league players during matches played as part of Australia's National Rugby League (NRL) competition. The movement patterns of one player from each of the three positional groups (hit-up forwards, adjustables, and outside backs) during three competition matches were examined using time-motion analysis. Positional groups differed in distances covered (P = 0.001), and covered shorter distances than those described in earlier research. The mean exercise-to-rest ratio was 1:6 for the outside backs and hit-up forwards and 1:5 for the adjustables. However, such ratios did not reflect the most demanding periods of the game, which included repeated high-intensity efforts interspersed with recovery periods of short duration. These periods of repeated high-intensity exercise often occurred at crucial phases of the game, when players were either attacking or defending the try-line. Furthermore, patterns of movement during repeated high-intensity periods of play differed among positional groups. To prepare for the most highly intense periods of match-play, professional rugby league players should adopt position-specific training that includes the highest and lowest exercise-to-rest ratios likely to be experienced in competition.

These findings suggest that GNSS devices may be more sensitive than GPS devices in quantifying the physical demands of team-sport movements, but further study into the accuracy of GNSS devices is required.

Laser communication using free-space optics is an important element of the proposed US Department of Defense (DoD) Transformational Communication System. It offers data rates on the order of several Gigabits per second, resists electromagnetic jamming and interference, and enjoys low probability of intercept and detection. This paper describes an investigation, carried out using a computer simulation, to analyze the performance of the laser beam steering control system consisting of two gimbals, a fast steering mirror, the global positioning system (GPS), and attitude sensors. Two different application scenarios were simulated: ground-to-air and air-to-air. The simulation evaluated several control system parameters such as pointing accuracy, tracking capabilities and bandwidth requirements. The results of the simulation elucidated the impact of the system bandwidth on the performance and functionality of the ground or air-to-air laser communication system. The results also showed close correlation between pointing and tracking error with the uncertainties of the system due to GPS and attitude sensor measurements.

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