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

A Plyometric Warm-Up Protocol Improves Running Economy in Recreational Endurance Athletes

This study explored the impact of two differing warm-up protocols (involving either resistance exercises or plyometric exercises) on running economy (RE) in healthy recreationally active participants. Twelve healthy university students [three males, nine females, age 20 ± 2 years, maximal oxygen uptake (38.4 ± 6.4 ml min–1 kg–1)] who performed less than 5 h per week of endurance exercise volunteered to participant in this study. All participants completed three different warm-up protocols (control, plyometric, and resistance warm-up) in a counterbalanced crossover design with trials separated by 48 h, using a Latin-square arrangement. Dependent variables measured in this study were RE at four running velocities (7, 8, 9, and 10 km h–1), maximal oxygen uptake; heart rate; respiratory exchange rate; expired ventilation; perceived race readiness; rating of perceived exertion, time to exhaustion and leg stiffness. The primary finding of this study was that the plyometric warm-up improved RE compared to the control warm-up (6.2% at 7 km h–1, ES = 0.355, 9.1% at 8 km h–1, ES = 0.513, 4.5% at 9 km h–1, ES = 0.346, and 4.4% at 10 km h–1, ES = 0.463). There was no statistically significant difference in VO2 between control and resistance warm-up conditions at any velocity. There were also no statistically significant differences between conditions in other metabolic and pulmonary gas exchange variables; time to exhaustion; perceived race readiness and maximal oxygen uptake. However, leg stiffness increased by 20% (P = 0.039, ES = 0.90) following the plyometric warm-up and was correlated with the improved RE at a velocity of 8 km h–1 (r = 0.475, P = 0.041). No significant differences in RE were found between the control and resistance warm-up protocols. In comparison with the control warm-up protocol, an acute plyometric warm-up protocol can improve RE in healthy adults

The effects of single versus twice daily short term heat acclimation on heat strain and 3000 m running performance in hot, humid conditions

Endurance performances are impaired under conditions of elevated heat stress. Short term heat acclimation (STHA) over 4-6 days can evoke rapid adaptation, which mitigate decrements in performance and alleviate heat strain. This study investigated the efficacy of twice daily heat acclimation (TDHA) compared to single session per day heat acclimation (SDHA) and normothermic training, at inducing heat acclimation phenotype and its impact upon running performance in hot, humid conditions.Twenty one, moderately trained males were matched and assigned to three groups; SDHA (mean±SD) (peak oxygen consumption [V˙O2peak] 45.8±6.1 mL kg-1 min-1, body mass 81.3±16.0 kg, stature 182±3 cm), TDHA (46.1±7.0 mL kg-1 min-1, 80.1±11.9 kg, 178±4 cm) or control (CON) (47.1±3.5 mL kg-1 min-1, 78.6±16.7 kg, 178±4 cm). Interventions consisted of 45 min cycling at 50% V˙O2peak, once daily for 4d (SDHA) and twice daily for 2d (TDHA), in 35 °C, 60% relative humidity (RH), and once daily for 4 days (CON) in 21 °C, 40% RH. Participants completed a pre- and post-intervention 5 km treadmill run trial in 30 °C, 60% RH, where the first 2 km were fixed at 40% V˙O2peak and the final 3 km was self-paced.No statistically significant interaction effects occurred within- or between-groups over the 2-4 days intervention. While within-group differences were found in physiological and perceptual measures during the fixed intensity trial post-intervention, they did not statistically differ between-groups. Similarly, TDHA (-36±34 s [+3.5%]) and SDHA (-26±28 s [+2.8%]) groups improved 3 km performances (p=0.35), but did not differ from CON (-6±44 s [+0.6%]).This is the first study to investigate the effects of HA twice daily and compare it with traditional single session per day STHA. These STHA protocols may have the ability to induce partial adaptive responses to heat stress and possibly enhance performance in environmentally challenging conditions, however, future development is warranted to optimise the administration to provide a potent stimuli for heat adaptation in athletic and military personnel within a rapid regime

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

Standardisation of acceleration zones in professional field sport athletes

Running acceleration data provides important information about the physical demands placed on field sport athletes. However, the absence of clearly defined acceleration zones has contributed to the minimal examination of this variable. This study aimed to develop a standardised set of acceleration zones and determine any differences in accelerations between elite and sub-elite Australian footballers. Thirty-nine professional male Australian footballers performed a 30 m sprint from a standing start. Timing lights were placed at 0, 10, 20 and 30 m to calculate accelerations over 0-10, 10-20 and 20-30 m splits. The accelerations over these splits were 3.27 m·s-2, 1.81 m·s-2 and 0.33 m·s-2. The differences between the elite and sub-elite groups for time, velocity and acceleration over the splits were examined using independent t-tests and effect sizes. Acceleration zones were determined by using maximal acceleration to establish the subsequent acceleration zones. In this case 20%, 45% and 85% of maximum acceleration were used to develop low (0.65-1.46 m·s-2), moderate (1.47-2.77 m·s-2) and high (>2.78 m·s-2) zones. No differences between the elite and sub-elite athletes for each acceleration category were found. The development of standardised acceleration zones will assist with the assessment and understanding of accelerations in field sport athletes. This has the potential to improve the implementation of training programs and recovery sessions. Further, these accelerations zones are seemingly applicable for both elite and sub-elite field sport athletes

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