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César Gallo-Salazar, Francisco Areces, Javier Abián-Vicén, Beatriz Lara, Juan José Salinero, Cristina Gonzalez-Millán, Javier Portillo, Victor Muñoz, Daniel Juarez and Juan Del Coso

The aim of this study was to investigate the effectiveness of a caffeinated energy drink to enhance physical performance in elite junior tennis players. In 2 different sessions separated by 1 wk, 14 young (16 ± 1 y) elite-level tennis players ingested 3 mg caffeine per kg body mass in the form of an energy drink or the same drink without caffeine (placebo). After 60 min, participants performed a handgrip-strength test, a maximal-velocity serving test, and an 8 × 15-m sprint test and then played a simulated singles match (best of 3 sets). Instantaneous running speed during the matches was assessed using global positioning (GPS) devices. Furthermore, the matches were videotaped and notated afterward. In comparison with the placebo drink, the ingestion of the caffeinated energy drink increased handgrip force by ~4.2% ± 7.2% (P = .03) in both hands, the running pace at high intensity (46.7 ± 28.5 vs 63.3 ± 27.7 m/h, P = .02), and the number of sprints (12.1 ± 1.7 vs 13.2 ± 1.7, P = .05) during the simulated match. There was a tendency for increased maximal running velocity during the sprint test (22.3 ± 2.0 vs 22.9 ± 2.1 km/h, P = .07) and higher percentage of points won on service with the caffeinated energy drink (49.7% ± 9.8% vs 56.4% ± 10.0%, P = .07) in comparison with the placebo drink. The energy drink did not improve ball velocity during the serving test (42.6 ± 4.8 vs 42.7 ± 5.0 m/s, P = .49). The preexercise ingestion of caffeinated energy drinks was effective to enhance some aspects of physical performance of elite junior tennis players.

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Blake D. McLean, Cloe Cummins, Greta Conlan, Grant Duthie and Aaron J. Coutts

Global positioning systems (GPS) that are embedded in microtechnology devices have previously been shown to be reliable for measuring the activity profiles of field-based team-sport athletes. 1 In addition to GPS data, these microtechnology devices contain accelerometers that provide information

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Eduardo A. Abade, Bruno V. Gonçalves, Nuno M. Leite and Jaime E. Sampaio


To provide the time–motion and physiological profile of regular training sessions (TS) performed during the competitive season by under-15 (U15), under-17 (U17), and under-19 (U19) elite-level Portuguese soccer players.


One hundred fifty-one elite players of U15 (age 14.0 ± 0.2 y, n = 56), U17 (age 15.8 ± 0.4 y, n = 66), and U19 (age 17.8 ± 0.6 y, n = 29) participated in the study during a 9-wk period. Time–motion and body-impact data were collected using GPS technology (15 Hz) across 38 randomly selected TS that resulted in a total of 612 samples. In addition, heart rate (HR) was continuously monitored (1 Hz) in the selected TS.


The total distances covered (m) were higher in U17 (4648.3 ± 831.9), followed by U19 (4212.5 ± 935.4) and U15 (3964.5 ± 725.4) players (F = 45.84, P < .001). Total body impacts and relative impacts were lower in U15 (total: 490.8 ± 309.5, F = 7.3, P < .01), but no differences were identified between U17 (total: 584.0 ± 363.5) and U19 (total: 613.1 ± 329.4). U19 players had less high- and very-high-intensity activity (above 16 km/h; F = 11.8, P < .001) and moderate-intensity activity (10.0–15.9 km/h; F = 15.07, P < .001). HR values showed significant effects of zone (F = 575.7, P < .001) and interaction with age group (F = 9.7, P < .001), with pairwise differences between all zones (zone 1, <75%; zone 2, 75–84.9%; zone 3, 85–89.9%; zone 4, ≥90%). All players spent most of their time below 75% HRmax (U15, ~50%; U17, ~42%; U19, ~50%).


Results showed high variability between TS, refraining from identifying meaningful trends when measuring performance, although different demands were identified according to age group. The U15 TS were less physiologically demanding, probably because of increased focus on small-sided games to develop basic tactical principles and technical skills. The focus on game-like situations imposed higher external and internal workloads on U17 and U19 players.

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Catherine Mason and Matt Greig

segmental forces, 8 but these methods offer limited ecological validity. Contemporary means of quantifying lumbar spine loading is provided by applications in global positioning system (GPS) technology, which enable measurement in the clinical or sporting context. Typical GPS analysis metrics include

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Matt Greig and Benjamin Child

potential for wearable microtechnology devices as a means of prescribing and monitoring bowling workload. The microtechnology described typically refers to a triaxial accelerometer embedded within a global positioning satellite (GPS) unit. This unit is typically worn in a customized vest that positions the

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Adam Jones, Chris Brogden, Richard Page, Ben Langley and Matt Greig

causal effect in the field given the complexity of lower-extremity injury mechanics and the relative lack of ecological validity in laboratory trials. Contemporary developments in the microelectromechanical systems (MEMS) integrated within global positioning system (GPS) technology provide an in vivo

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Mitchell J. Henderson, Bryna C.R. Chrismas, Christopher J. Stevens, Aaron J. Coutts and Lee Taylor

tournament within the stadium WBGT peak was 37.5°C, with expectations that tournament day one would see similar WBGT values; however, conditions on the day were surprisingly mild (≤20°C WBGT; Table  2 ). Activity profiles during matches were measured using 10 Hz GPS devices (EVO; GPSports, Canberra

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Jade A.Z. Haycraft, Stephanie Kovalchik, David B. Pyne and Sam Robertson

activity profiles for each player were measured for 1, 2, or 3 games within each participant’s competitive season, with an average of 67 (80) days between physical testing and game. Data were recorded using a global positioning system (GPS) device (OptimEye S5; Catapult Innovations, Melbourne, Australia

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Patrick G. Campbell, Jonathan M. Peake and Geoffrey M. Minett

.8 [5.0] min·wk −1 ) unit skills, captain’s run (15.2 [7.9] min·wk −1 ), and modified game periods (20.4 [7.2] min·wk −1 ). Eleven injury-free Premier Grade squad players were randomly selected for involvement each week to accommodate the limited global positioning system (GPS) devices available to

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Phillip M. Bellinger, Cameron Ferguson, Tim Newans and Clare L. Minahan

In team sports, the use of microtechnology, including global positioning systems (GPS) and triaxial accelerometers, is now important to monitor training and match movement patterns. 1 , 2 For example, information on athletes’ activity profiles, such as total distance traveled and the magnitude of