Validity and interunit reliability of 10 Hz and 15 Hz GPS units for assessing athlete movement demands

The purpose of this study was to assess the validity and interunit reliability of 10 Hz (Catapult) and 15 Hz (GPSports) Global Positioning System (GPS) units and investigate the differences between these units as measures of team sport athlete movement demands. A team sport simulation circuit was completed by 8 trained male participants. The movement demands examined included: total distance covered (TD), average peak speed, and the distance covered, time spent, and the number of efforts performed low-speed running (0.00-13.99 km·h-1), high-speed running (14.00-19.99 km·h-1), and very highspeed running (>20.00 km·h-1). The degree of difference between the 10 Hz and the 15 Hz GPS units and validity was assessed using a paired samples t-test. Pearson's correlations were also used for validity assessment. Interunit reliability was established using percentage typical error of measurement (%TEM) and intraclass correlations. The findings revealed that 10 Hz GPS units were a valid (p > 0.05) and reliable (%TEM = 1.3%) measure of TD. In contrast, the 15 Hz GPS units exhibited lower validity for TD and average peak speed. Further, as the speed of movement increased the level of error for the 10 Hz and 15 Hz GPS units increased (% TEM = 0.8-19.9). The findings from this study suggest that comparisons should not be undertaken between 10 Hz and 15 Hz GPS units. In general, the 10 Hz GPS units measured movement demands with greater validity and interunit reliability than the 15 Hz units, however, both 10 Hz and 15 Hz units provided the improved measures of movement demands in comparison to 1 Hz and 5 Hz GPS units. © 2014 National Strength and Conditioning Association

The effect of plyometric training on distance running performance

Previous research has reported that plyometric training improves running economy (RE) and ultimately distance-running performance, although the exact mechanism by which this occurs remains unclear. This study examined whether changes in running performance resulting from plyometric training were related to alterations in lower leg musculotendinous stiffness (MTS). Seventeen male runners were pre- and post-tested for lower leg MTS, maximum isometric force, rate of force development, 5-bound distance test (5BT), counter movement jump (CMJ) height, RE,VO2max, lactate threshold (Th1a), and 3-km time. Subjects were randomly split into an experimental (E) group which completed 6 weeks of plyometric training in conjunction with their normal running training, and a control (C) group which trained as normal. Following the training period, the E group significantly improved 3-km performance (2.7%) and RE at each of the tested velocities, while no changes in VO2max or Th1a were recorded. CMJ height, 5BT, and MTS also increased significantly. No significant changes were observed in any measures for the C group. The results clearly demonstrated that a 6-week plyometric programme led to improvements in 3-km running performance. It is postulated that the increase in MTS resulted in improved RE. We speculate that the improved RE led to changes in 3-km running performance, as there were no corresponding alterations in VO2max or Th1a

Match-play movement and metabolic power demands of elite youth, sub-elite and elite senior Australian footballers

© 2019 Kelly et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Aims Currently minimal research has quantified physical requirement differences in match-play between youth and senior Australian football players. The aim of the current research was to describe and compare the movement profiles and energy cost of youth, sub-elite and elite senior Australian football match-play. Methods Fifty-seven Australian footballers playing in an elite senior 20, sub-elite senior 16 and elite youth competition 21 participated in this study. Distance, speed based indices and metabolic power measures recording via Global Positioning System (GPS) devices were compared across three competition tiers. Kicks and handballs were collected via a commercial statistics provider (Champion Data) and compared across the competition tiers. Results Youth players recorded less field time (elite: ES = 1.37/sub-elite: ES = 1.68), total distance (elite: ES = 1.64 /sub-elite: ES = 1.55) and high speed running (elite: ES = 0.90/sub-elite: ES = 0.26) compared to the elite and sub-elite players. The average energy cost of elite (ES = 2.19) and sub-elite (ES = 1.58) match-play was significantly higher that youth match-play. Conclusions A progressive increase regarding physical demands was evident across AF competition tiers. The findings suggest that sub-elite match-play can provide a viable pathway for youth players to develop physical capacity and technical skills before transitioning to elite senior match-play

Assessment of 5 Hz and 10 Hz GPS units for measuring athlete movement demands

This study aimed to assess the validity and inter-unit reliability of 5 Hz and 10 Hz global positioning system (GPS) units and determine the differences between these units as measures of team sport athlete movement demands. A team sport simulation circuit was completed by eight trained male participants to examine the following movement demands: total distance covered (TD), peak speed and the distance covered, time spent and number of efforts performed at different speed zones. Additionally, repeated high intensity efforts, player load and exertion index were investigated. The analysis using paired samples t-test and percentage typical error of measurement (%TEM) revealed that 10 Hz GPS units provided a valid and reliable measure of TD (p>0.05, %TEM=1.3). The 5 Hz units also displayed reliable measures of TD (%TEM=1.2). It was apparent that as the speed of movement increased, the level of GPS error increased for both 5 Hz and 10 Hz units (%TEM: 0- 14%). The updates in GPS firmware and increased sampling rates have further improved the validity and inter-unit reliability of GPS. Consequently, practitioners can more confidently rely on the data obtained from current GPS units during training and matches, however, caution is required when measuring high speed movements

Player acceleration and deceleration profiles in professional Australian football

This study aimed to determine the validity and reliability of global positioning system (GPS) units for measuring a standardized set of acceleration and deceleration zones and whether these standardized zones were capable of identifying differences between playing positions in professional Australian football. Eight well trained male participants were recruited to wear two 5 Hz or 10 Hz GPS units whilst completing a team sport simulation circuit to measure acceleration and deceleration movements. For the second part of this article 30 professional players were monitored between 1-29 times using 5 Hz and 10 Hz GPS units for the collection of acceleration and deceleration movements during the 2011 and 2012 Australian Football League seasons. Players were separated into four distinct positional groups - nomadic players, ixed defenders, ixed forwards and ruckman. The GPS units analysed had good to poor levels of error for measuring the distance covered (<19.7%), time spent (<17.2%) and number of efforts performed (<48.0%) at low, moderate and high acceleration and deceleration zones. The results demonstrated that nomadic players and ixed defenders perform more acceleration and deceleration efforts during a match than ixed forwards and ruckman. These studies established that these GPS units can be used for analysing the distance covered and time spent at the acceleration and deceleration zones used. Further, these standardized zones were proven to be capable of distinguishing between player positions, with nomadic players and ixed defenders required to complete more high acceleration and deceleration efforts during a match

Movement Profiles, Match Events, and Performance in Australian Football

© 2016 National Strength and Conditioning Association. Johnston, RJ, Watsford, ML, Austin, D, Pine, MJ, and Spurrs, RW. Movement profiles, match events, and performance in Australian football. J Strength Cond Res 30(8): 2129-2137, 2016 - This study examined the relationship between movement demands, match events, and match performance in professional Australian football. Data were collected from 19 players using global positioning system units during 2 Australian Football League seasons. A range of movement demands and instantaneous power measures were collected. The players were divided into high-caliber (HC, ≥17/20) and low-caliber (LC, ≤8/20) groups based on the rating score by their coaches. A Mann-Whitney U-test, independent samples t-test, and effect sizes were used to determine whether any differences existed between the 2 groups. The HC group had a significantly higher match duration (7.2%), higher total distance (9.6%), and covered more distance and spent more time high-speed running per minute (12.7 and 11.9%). Although not significant, the effect sizes revealed that the HC group tended to have a higher mean metabolic power output (2.6%) and spent more time at the high power zone (7.9%). For the match event data, the HC group had significantly more involvements with the football. The results demonstrated the higher physical demands placed on the HC group. The findings suggest that analyzing instantaneous power measures can provide valuable information about the physical demands placed on team sport athletes to coaches and conditioning staff

Movement demands and metabolic power comparisons between elite and subelite australian footballers

© 2015 National Strength and Conditioning Association. This study examined the differences in movement demands and metabolic power output of elite and subelite Australian football (AF) players and quantified the movement profiles of a subelite AF competition. Movement variables were collected from AF players using Global Positioning System devices over 2 AF League (elite) and North East Australian Football League (NEAFL, subelite) seasons. A total of 500 files were collected from 37 elite and subelite nomadic AF players. NEAFL players covered 13,547 m at an average speed of 124.5 m·min -1. Elite players performed more high-speed running (5.7-6.3%) and high acceleration and deceleration efforts (1.9-14.7%, p ≤ 0.05). The elite players had a higher mean metabolic power output (3.2%) and time spent at the very high power zone (15.9%, p ≤ 0.05). In contrast, elite players recorded a lower total match duration than the subelite players (4%, p ≤ 0.05). The contrasting amount of high-intensity activities performed by the 2 groups demonstrates the need to alter the training programs of subelite players to ensure they are capable of meeting the demands of elite football. The differences in match duration suggest that reducing subelite players' match time through increasing their rotations would assist the replication of movement profiles of elite players

An Examination of the Relationship between Movement Demands and Rating of Perceived Exertion in Australian Footballers

© 2015 National Strength and Conditioning Association. This study aimed to determine whether a relationship existed between movement demands, match events, and perceptual match load, as determined by rating of perceived exertion (RPE) in professional Australian footballers. The movement variables were collected between 1 and 22 times using global positioning system units from 21 players during the 2011 and 2012 Australian Football League seasons. A range of movement demands and match events were collected to obtain a complete insight into the physical demands and work rates of these athletes. These data were separated into the high-load (HL, ≥9) and low-load (LL, ≤8) RPE groups. A Mann-Whitney U-test, independent samples t-test, and effect sizes were used to determine whether any differences existed between the 2 groups and the size of the difference. The results revealed that the HL groups covered more distance, spent more time, and produced more efforts at the high deceleration zone (2.4-6.7%). Further, the HL group had more possessions and disposals of the football than the LL group (9.2-29.6%). The findings have highlighted the importance of monitoring accelerations, decelerations, and instantaneous power outputs to obtain a comprehensive insight into the physical demands placed on team sport athletes. Furthermore, the results demonstrate that training sessions should involve a focus on drills that are composed of both skill development and physical stimulus element

Phases of match-play in professional Australian Football: Descriptive analysis and reliability assessment

© 2017 Sports Medicine Australia Objectives: To examine the frequency and time spent in the phases of Australian Football (AF) match-play and to assess the intra-assessor reliability of coding these phases of match-play. Design: Observational, intra-reliability assessment. Methods: Video footage of 10 random quarters of AF match-play were coded by a single researcher. Phases of offence, defence, contested play, umpire stoppage, set shot and goal reset were coded using a set of operational definitions. Descriptive statistics were provided for all phases of match-play. Following a 6-month washout period, intra-coder reliability was assessed using typical error of measurement (TEM) and intra-class correlation coefficients (ICC). Results: A quarter of AF match-play involved 128 ± 20 different phases of match-play. The highest proportion of match-play involved contested play (25%), followed by offence (18%), defence (18%) and umpire stoppages (18%). The mean duration of offence, defence, contested play, umpire stoppage, set shot and goal reset were 14, 14, 10, 11, 28 and 47 s, respectively. No differences were found between the two coding assessments (p > 0.05). ICCs for coding the phases of play demonstrated very high reliability (r = 0.902–0.992). TEM of the total time spent in each phase of play represented moderate to good reliability (TEM = 1.8–9.3%). Coding of offence, defence and contested play tended to display slightly poorer TEMs than umpire stoppages, set shots and goal resets (TEM = 8.1 vs 4.5%). Conclusions: Researchers can reliably code the phases of AF match-play which may permit the analysis of specific elements of competition