Ted Polglaze

Anthropometric and fitness characteristics of elite australian female water polo players

Tan, FHY, Polglaze, T, Dawson, B, and Cox, G. Anthropometric and fitness characteristics of elite Australian female water polo players. J Strength Cond Res 23(5): 1530-1536, 2009-The purpose of this study was to investigate the anthropometric and fitness characteristics of elite female water polo players and examine the differences between players of different competition levels (national and international) and playing positions (center and perimeter). Twenty-six female water polo players (National League, n = 12, and National Squad, n = 14) underwent measurements of standard anthropometry (height, body mass, and sum of 7 skinfolds), lower-body muscular power (in-water vertical jump), speed (10-m maximal sprint swim), and aerobic fitness (multistage shuttle swim test). No goalkeepers were involved. The National Squad players were taller (173.7 ± 5.5 vs. 169.6 ± 4.4 cm; p < 0.05) and heavier (74.6 ± 8.0 vs. 65.8 ± 8.4 kg; p < 0.05) and had better jumping (139.0 ± 7.0 vs. 129.7 ± 4.6 cm; p < 0.001), sprinting (5.96 ± 0.21 vs. 6.26 ± 0.34 seconds; p < 0.05), and endurance swimming abilities (652 ± 84 vs. 449 ± 124 m; p < 0.001) compared with the National League players. Perimeter players had lower-body mass (70.2 ± 3.8 vs. 82.5 ± 7.4 kg; p < 0.001) and skinfold levels (88.7 ± 14.1 vs. 118.6 ± 22.2 mm; p < 0.01) and better sprinting (5.88 ± 0.19 vs. 6.10 ± 0.19 seconds; effect size [ES] = 1.16, p > 0.05) and endurance swimming abilities (678 ± 65 vs. 606 ± 102 m; ES = 0.84, p > 0.05) compared with center players. These findings demonstrate that anthropometric and fitness characteristics can discriminate between players of different competition levels and playing positions. These water polo-specific field tests may assist coaches in profiling players and evaluating adaptations to training.

Postexercise Cooling Rates in 2 Cooling Jackets

CONTEXT Cooling jackets are a common method for removing stored heat accumulated during exercise. To date, the efficiency and practicality of different types of cooling jackets have received minimal investigation. OBJECTIVE To examine whether a cooling jacket containing a phase-change material (PC17) results in more rapid postexercise cooling than a gel cooling jacket and a no-jacket (control) condition. DESIGN Randomized, counterbalanced design with 3 experimental conditions. SETTING Participants exercised at 75% V o(2)max workload in a hot climate chamber (temperature = 35.0 +/- 1.4 degrees C, relative humidity = 52 +/- 4%) for 30 minutes, followed by postexercise cooling for 30 minutes in cool laboratory conditions (ambient temperature = 24.9 +/- 1.8 degrees C, relative humidity = 39% +/- 10%). PATIENTS OR OTHER PARTICIPANTS Twelve physically active men (age = 21.3 +/- 1.1 years, height = 182.7 +/- 7.1 cm, body mass = 76.2 +/- 9.5 kg, sum of 6 skinfolds = 50.5 +/- 6.9 mm, body surface area = 1.98 +/- 0.14 m(2), V o(2)max = 49.0 +/- 7.0 mLxkg(-1)xmin(-1)) participated. INTERVENTION(S) Three experimental conditions, consisting of a PC17 jacket, a gel jacket, and no jacket. MAIN OUTCOME MEASURE(S) Core temperature (T(C)), mean skin temperature (T(Sk)), and T(C) cooling rate ( degrees C/min). RESULTS Mean peak T(C) postexercise was 38.49 +/- 0.42 degrees C, 38.57 +/- 0.41 degrees C, and 38.55 +/- 0.40 degrees C for the PC17 jacket, gel jacket, and control conditions, respectively. No differences were observed in peak T(C) cooling rates among the PC17 jacket (0.038 +/- 0.007 degrees C/min), gel jacket (0.040 +/- 0.009 degrees C/min), and control (0.034 +/- 0.010 degrees C/min, P > .05) conditions. Between trials, no differences were calculated for mean T(Sk) cooling. CONCLUSIONS Similar cooling rates for all 3 conditions indicate that there is no benefit associated with wearing the PC17 or gel jacket.

Gold Standard or Fool’s Gold? The Efficacy of Displacement Variables as Indicators of Energy Expenditure in Team Sports

Over recent decades, the use of player tracking technology to monitor physical work output has become established practice in many team sports. Early tracking systems were manual in nature, relying on subjective assessments and arbitrary classifications of movement intensity. Poor spatial and temporal resolution meant that only gross displacement measures could be used to infer energy demands. However, the advent and evolution of automated systems, with higher sampling rates and improved accuracy, have enabled data collection to occur on a mass scale, and served as a catalyst for extensive research into the demands of team sport activity, including comparisons between different groups of athletes, and the effects of various interventions on performance. The inherent assumption with this research is that, based on steady-state models where energy cost is independent of speed, total distance and average speed are indicative of the amount and rate of work done, respectively. This assumption could be justified if the activity was performed at a constant speed in a straight line. However, team sport movement involves continual changes in both speed and direction, both of which increase energy cost. Accordingly, new models have emerged that incorporate both speed and acceleration to determine metabolic power. This provides a more complete measure of energy expenditure in intermittent activity, and is potentially more suitable than displacement variables for research into the demands of team sports.

Validity and reliability of GPS and LPS for measuring distances covered and sprint mechanical properties in team sports

This study aimed to investigate the validity and reliability of global (GPS) and local (LPS) positioning systems for measuring distances covered and sprint mechanical properties in team sports. Here, we evaluated two recently released 18 Hz GPS and 20 Hz LPS technologies together with one established 10 Hz GPS technology. Six male athletes (age: 27±2 years; VO2max: 48.8±4.7 ml/min/kg) performed outdoors on 10 trials of a team sport-specific circuit that was equipped with double-light timing gates. The circuit included various walking, jogging, and sprinting sections that were performed either in straight-lines or with changes of direction. During the circuit, athletes wore two devices of each positioning system. From the reported and filtered velocity data, the distances covered and sprint mechanical properties (i.e., the theoretical maximal horizontal velocity, force, and power output) were computed. The sprint mechanical properties were modeled via an inverse dynamic approach applied to the center of mass. The validity was determined by comparing the measured and criterion data via the typical error of estimate (TEE), whereas the reliability was examined by comparing the two devices of each technology (i.e., the between-device reliability) via the coefficient of variation (CV). Outliers due to measurement errors were statistically identified and excluded from validity and reliability analyses. The 18 Hz GPS showed better validity and reliability for determining the distances covered (TEE: 1.6–8.0%; CV: 1.1–5.1%) and sprint mechanical properties (TEE: 4.5–14.3%; CV: 3.1–7.5%) than the 10 Hz GPS (TEE: 3.0–12.9%; CV: 2.5–13.0% and TEE: 4.1–23.1%; CV: 3.3–20.0%). However, the 20 Hz LPS demonstrated superior validity and reliability overall (TEE: 1.0–6.0%; CV: 0.7–5.0% and TEE: 2.1–9.2%; CV: 1.6–7.3%). For the 10 Hz GPS, 18 Hz GPS, and 20 Hz LPS, the relative loss of data sets due to measurement errors was 10.0%, 20.0%, and 15.8%, respectively. This study shows that 18 Hz GPS has enhanced validity and reliability for determining movement patterns in team sports compared to 10 Hz GPS, whereas 20 Hz LPS had superior validity and reliability overall. However, compared to 10 Hz GPS, 18 Hz GPS and 20 Hz LPS technologies had more outliers due to measurement errors, which limits their practical applications at this time.

Metabolic power and energy expenditure in an international men’s hockey tournament

ABSTRACT The purpose of this study was to ascertain the typical metabolic power characteristics of elite men’s hockey, and whether changes occur within matches and throughout an international tournament. National team players (n = 16), divided into 3 positional groups (strikers, midfielders, defenders), wore Global Positioning System devices in 6 matches. Energetic (metabolic power, energy expenditure) and displacement (distance, speed, acceleration) variables were determined, and intensity was classified utilising speed, acceleration and metabolic power thresholds. Midfielder’s average metabolic power (11.8 ± 1.0 W · kg−1) was similar to strikers (11.1 ± 1.3 W · kg−1) and higher than defenders (10.8 ± 1.2 W · kg−1, P = 0.001). Strikers (29.71 ± 3.39 kJ · kg−1) expended less energy than midfielders (32.18 ± 2.67 kJ · kg−1, P = 0.014) and defenders (33.23 ± 3.96 kJ · kg−1, P < 0.001). Energetic variables did not change between halves or across matches. Across all positions, over 45% of energy expenditure was at high intensity (>20 W · kg−1). International hockey matches are intense and highly intermittent; however, intensity is maintained throughout matches and over a tournament. In isolation, displacement measures underestimate the amount of high-intensity activity, whereas the integration of instantaneous speed and acceleration provides a more comprehensive assessment of the demands for variable-speed activity typically occurring in hockey matches.

Variability of metabolic power data in elite soccer players during pre-season matches

Abstract This study aimed to determine the within-subject variability of GPS-derived metabolic power data in elite soccer players across several pre-season matches and compare the variability of high metabolic power, velocity, acceleration and deceleration running. Additionally, differences in metabolic power data among playing positions and relationships with various physical abilities were also investigated. Metabolic power data from 12 outfield starting players competing in the German Bundesliga were collected during five pre-season matches using GPS-technology (10 Hz). The players were also tested for speed, agility, power and intermittent endurance. Variability of global metabolic power data such as energy expenditure (CV = 2.2-7.0%) was lower than that for high-intensity including time ≥20 W·kg-1 (CV = 14.0-26.2%). Variability of high metabolic power (≥20 W·kg-1; CV = 14.1 ± 3.5%) was comparable to that of high velocity (≥15.5 km·h-1; CV = 17.0 ± 6.2%), acceleration (≥3 m·s-2; CV = 11.1 ± 5.1%) and deceleration running (≤-3 m·s-2; CV = 11.9 ± 4.5%) (p > 0.05, ES < 0.2). Defenders had a largely higher overall energy expenditure than midfielders and attackers (p < 0.01, ES > 0.6). Overall energy expenditure and cost were largely to very largely correlated with 5 m speed and 22 m agility sprint time and counter movement jump height (r = -0.70-0.69, p < 0.05). The detected variability indicates that global GPS-derived metabolic power data in elite soccer players from a single preseason match should be preferably used for practical applications. Contrary, high-intensity indicators should be interpreted cautiously and repeated match observations are recommended to establish meaningful high-intensity profiles of the players. Differences among playing positions and relationships with explosive physical abilities indicate that metabolic power analyses can provide new insights into the mechanics and energetics of soccer.

A comparison of displacement and energetic variables between three team sport GPS devices

ABSTRACT This study compared the outputs of three different commercially-available GPS player-tracking devices for a range of commonly used displacement and energetic variables in activities replicating team sport movements. Professional male soccer players (n = 7), simultaneously wore three GPS devices (Catapult OptimEye S5, GPExe Pro 1, StatSport ViperPod) whilst completing four separate drills, comprising progressively more complex changes in speed and direction. Displacement (distance, speed) and energetic (energy cost, metabolic power, energy expenditure) variables were compared for each device. All three devices tended to under-estimate distance compared to the known value for each drill, with only minor and inconsistent differences between devices. There were no differences between devices for average speed. For energetic variables, substantial differences were found between each device, and these differences magnified as movement tasks became more erratic. Given that energetic variables are derived from measures of instantaneous speed, and also incorporate the magnitude and direction of change between successive data points, these differences may be attributable to disparities in raw data quality, filtering techniques and calculation methods. In order to provide comparable estimates of energetic variables in team sports, player-tracking devices must be capable of accurately recording instantaneous velocity in activities comprising frequent changes in speed and direction.