Keith Lyons

Identification of Cross-Country Skiing Movement Patterns Using Micro-Sensors

This study investigated the potential of micro-sensors for use in the identification of the main movement patterns used in cross-country skiing. Data were collected from four elite international and four Australian athletes in Europe and in Australia using a MinimaxX™ unit containing accelerometer, gyroscope and GPS sensors. Athletes performed four skating techniques and three classical techniques on snow at moderate velocity. Data from a single micro-sensor unit positioned in the centre of the upper back was sufficient to visually identify cyclical movement patterns for each technique. The general patterns for each technique were identified clearly across all athletes while at the same time distinctive characteristics for individual athletes were observed. Differences in speed, snow condition and gradient of terrain were not controlled in this study and these factors could have an effect on the data patterns. Development of algorithms to process the micro-sensor data into kinematic measurements would provide coaches and scientists with a valuable performance analysis tool. Further research is needed to develop such algorithms and to determine whether the patterns are consistent across a range of different speeds, snow conditions and terrain, and for skiers of differing ability.

Movement profiles of elite women soccer players during international matches and the effect of opposition’s team ranking

Abstract Movement patterns in elite men’s soccer have been reported in depth, but less research exists for women’s soccer. Aims of the study were to identify the movement profiles of elite women soccer players in international competition and examine the effect the level of opposition, based on Federation Internationale de Football Association (FIFA) rankings, had on the physical demands of the game. MinimaxX athlete tracking devices were used by 15 players during 13 international matches against opponent teams of varying ability. Total distance covered averaged 9292 ± 175 m. There was a decrease in high-intensity running (HIR) in the 60- to 75-min and 75- to 90-min periods compared to the 0- to 15-min period of 22.4% and 26.1%, respectively (P = 0.022, P = 0.004) although sprint distances remained unchanged across game periods. HIR distances covered were significantly greater for midfielders versus defenders, while defenders had lower sprinting compared to both midfielders and attackers. Stronger opponents elicited less HIR and greater low-speed activity (LSA) compared to playing teams of similar or lower ranking. These results are important to coaches to prepare players for international competition and show the differing demands required depending on the ability of the opponents.

Accuracy of an UWB-based position tracking system used for time-motion analyses in game sports

Abstract The main aim of this study was to determine the accuracy of the ultra-wideband (UWB)-based positioning system Ubisense, which is used for time-motion analysis in sports. Furthermore, some alternatives for positioning the systems transponders on the atheletes, as well as the accuracy depending on the location of measurement, were tested. Therefore, in a pre-study, some basic issues were examined (measurement assumptions and consistency and location of the systems transponder used for position detection), and position measurements at the borders and in the centre of a basketball field were performed. In the main study, 13 male basketball players (15.8 years ± 0.6; 187.9 height ± 3.4; 77.5 weight ± 3.7), equipped with a Ubisense transponder mounted on top of their heads, handled a trundle wheel during simulated match play. The players with the trundle wheel participated passively in the match by following one of the ten competing players. The distance measurements of the trundle wheel were used as reference values and compared to the Ubisense distance estimations. Best results were found with the measurements of a single mounted transponder on top of the athletes heads. No differences were detectable in the accuracy between measurements in the centre and at the borders of the basketball field. The (Ubisense) systems difference to the (trundle wheel) reference was 3.45 ± 1.99%, resulting in 95% limits of agreement of −0.46–7.35%. The study indicates the examined systems sufficient accuracy for time-motion analysis in basketball.

The volume of goal shooting during training can predict shoulder soreness in elite female water polo players

OBJECTIVES Examine the association between measures shoulder soreness and the goal shooting volume in high performance womens water polo. DESIGN Seven national level female water polo players were monitored across two training camps (squad selection and team game-based). METHODS Performance analysis coded all shots for each athlete during the training camps and the shoulder soreness information was gathered through an athlete self-rating survey. Residual maximal likelihood analysis was used to predict shoulder soreness. RESULTS It was shown that 74% (p=0.013) of shoulder soreness was explained by the volume of goal shooting during training (R(2) 0.743) with greater soreness associated with less rest time between shots (p=0.032). Greater levels of shoulder soreness were reported in the squad selection training camp compared to team game-based camp (p=0.002) with 29% of this shoulder soreness prediction based on individual athlete differences. CONCLUSIONS Shoulder soreness increased with a greater number of shots in conjunction with less rest. Monitoring athletes on an individual basis seemed the most appropriate method of identifying increased shoulder soreness.

Effective Defensive Strategies at the Ruck Contest in Rugby Union

Performance analysis examined the association between defensive strategies and ruck outcomes in rugby union. Defensive tactics at the ruck contest were coded (n = 8563) during 60 games of the 2011 Super Rugby competition. Variables described attacking width, territory gained by the attack, defensive strategy used at the ruck, and ruck outcome. Chi-squared analysis showed that both early counter ruck (competing for the ball without hands) and jackal (competing for the ball with hands) were effective at turning over possession of the ball behind the advantage line (60% and 39% of turnovers, respectively). Early counter ruck was also effective at turning over possession when the ruck contest occurred in the wide attacking channels (18% of turnovers) whilst a jackal was used at ruck contests occurring in central field areas (13% of turnover). Late counter ruck was a poor strategy and was likely to concede penalties without an association with turnovers.

Attacking Strategies That Lead to Goal Scoring Opportunities in High Level Women's Football

This study identified the attacking strategies that lead to goal scoring opportunities in womens football (soccer). All regular season games (n = 34) of the 2010/2011 W-League football competition were coded using performance analysis. Variables described the attacking strategies employed by teams and their association with goal scoring. It was shown that 24% (p < .001) of goals were the result of a cross (a distribution made from a wide area to a central area in front of goal). Further analysis demonstrated that 26% of corner kicks resulted in a shot at goal (p < .001). It was concluded that attacking through the wide areas of the field followed by a cross into a central zone inside the 18-yard box was the most effective strategy for creating goal scoring opportunities in womens football.

Using micro-sensor data to quantify macro kinematics of classical cross-country skiing during on-snow training

Abstract Micro-sensors were used to quantify macro kinematics of classical cross-country skiing techniques and measure cycle rates and cycle lengths during on-snow training. Data were collected from seven national level participants skiing at two submaximal intensities while wearing a micro-sensor unit (MinimaxX™). Algorithms were developed identifying double poling (DP), diagonal striding (DS), kick-double poling (KDP), tucking (Tuck), and turning (Turn). Technique duration (T-time), cycle rates, and cycle counts were compared to video-derived data to assess system accuracy. There was good reliability between micro-sensor and video calculated cycle rates for DP, DS, and KDP, with small mean differences (Mdiff% = −0.2 ± 3.2, −1.5 ± 2.2 and −1.4 ± 6.2) and trivial to small effect sizes (ES = 0.20, 0.30 and 0.13). Very strong correlations were observed for DP, DS, and KDP for T-time (r = 0.87–0.99) and cycle count (r = 0.87–0.99), while mean values were under-reported by the micro-sensor. Incorrect Turn detection was a major factor in technique cycle misclassification. Data presented highlight the potential of automated ski technique classification in cross-country skiing research. With further refinement, this approach will allow many applied questions associated with pacing, fatigue, technique selection and power output during training and competition to be answered.

Full course macro-kinematic analysis of a 10 km classical cross-country skiing competition

In this study micro-sensors were employed to analyse macro-kinematic parameters during a classical cross-country skiing competition (10 km, 2-lap). Data were collected from eight male participants during the Australian championship competition wearing a single micro-sensor unit (MinimaxX™, S4) positioned on their upper back. Algorithms and visual classification were used to identify skiing sub-techniques and calculate velocities, cycle lengths (CL) and cycle rates (CR) over the entire course. Double poling (DP) was the predominant cyclical sub-technique utilised (43 ± 5% of total distance), followed by diagonal stride (DS, 16 ± 4%) and kick double poling (KDP, 5 ± 4%), with the non-propulsive Tuck technique accounting for 24 ± 4% of the course. Large within-athlete variances in CL and CR occurred, particularly for DS (CV% = 25 ± 2% and CV% = 15 ± 2%, respectively). For all sub-techniques the mean CR on both laps and for the slower and faster skiers were similar, while there was a trend for the mean velocities in all sub-techniques by the faster athletes to be higher. Overall velocity and mean DP-CL were significantly higher on Lap 1, with no significant change in KDP-CL or DS-CL between laps. Distinct individual velocity thresholds for transitions between sub-techniques were observed. Clearly, valuable insights into cross-country skiing performance can be gained through continuous macro-kinematic monitoring during competition.

A strategic analysis of goals scored in open play in four FIFA World Cup football championships between 2002 and 2014

This study analyzed game events leading up to the goals in four FIFA World Cups. Three categories of goals are presented: (a) from passing the ball behind the opposing defense or to a player level with the last defender who could either shoot or take the ball forwards or pass to a team mate to score, (b) from in front of the opposing defense or from dribbling past the last line of defense, referred to as ‘Other Methods’, and (c) from Crosses. The field of play was divided into seven zones to determine the origin of passes for goals in category (a) and (c) and three equal areas lengthwise to determine where possession was regained. The study concludes that the most dominant method of scoring goals in Open Play was from category (a), followed by category (b) and (c). Most goals in category (a) were from passes in the area referred to as Zone 14+ and the majority of goals in all categories came from regained possessions in the middle third.