Paul Worsfold

Movement and physiological match demands of elite rugby league using portable global positioning systems

Abstract Twelve elite players from an English Super League club consented to participate in the present study using portable global positioning system (GPS) devices to assess position-specific demands. Distances covered at low-intensity running, moderate-intensity running, high-intensity running, very high-intensity running, and total distance were significantly (P < 0.05) lower in forwards compared with outside backs and adjustables. Metres per minute was higher in adjustables and forwards, owing to higher values for relative distance in medium-intensity running and a rise in high-intensity running from previous absolute values. Sprint distance, sprint frequency, and peak speed were higher in outside backs than both adjustables and forwards. A moderate, significant correlation (r = 0.62, P = 0.001) was apparent between session ratings of perceived exertion and summated heart rate. Results support the requirement for position-specific conditioning and provide preliminary evidence for the use of session ratings of perceived exertion as a measure of match load.

Concurrent validity and test–retest reliability of a global positioning system (GPS) and timing gates to assess sprint performance variables

Abstract There has been no previous investigation of the concurrent validity and reliability of the current 5 Hz global positioning system (GPS) to assess sprinting speed or the reliability of integrated GPS–accelerometer technology. In the present study, we wished to determine: (1) the concurrent validity and reliability of a GPS and timing gates to measure sprinting speed or distance, and (2) the reliability of proper accelerations recorded via GPS–accelerometer integration. Nineteen elite youth rugby league players performed two over-ground sprints and were simultaneously assessed using GPS and timing gates. The GPS measurements systematically underestimated both distance and timing gate speed. The GPS measurements were reliable for all variables of distance and speed (coefficient of variation [CV] = 1.62% to 2.3%), particularly peak speed (95% limits of agreement [LOA] = 0.00 ± 0.8 km · h−1; CV = 0.78%). Timing gates were more reliable (CV = 1% to 1.54%) than equivalent GPS measurements. Accelerometer measurements were least reliable (CV = 4.69% to 5.16%), particularly for the frequency of proper accelerations (95% LOA = 1.00 ± 5.43; CV = 14.12%). Timing gates and GPS were found to reliably assess speed and distance, although the validity of the GPS remains questionable. The error found in accelerometer measurements indicates the limits of this device for detecting changes in performance.

The movement characteristics of English Premiership rugby union players

Abstract The purpose of this investigation was to quantify the movement characteristics of elite rugby union players during competitive play and identify whether position-related differences exist. Ninety-eight elite players from eight English Premiership Clubs were tracked using global positioning systems (GPS) during 44 competitive matches throughout the 2010/2011 season. Player positions were defined as: (1) Backs or Forwards; (2) Front, Second and Back Rows, Scrum Half, Inside and Outside Backs; (3) 15 individual positions (numbers 1–15). Analysis revealed the game is predominantly played at low speeds with little distance covered ‘sprinting’ by either the Backs (50 ± 76 m) or the Forwards (37 ± 64 m). The Backs travelled greater (P < 0.05) absolute and relative distances than the Forwards. The Scrum Half covered the greatest total distance during a match (7098 ± 778 m) and the Front Row the least (5158 ± 200 m). The Back Row covered the greatest distances at ‘sprinting’ speeds, particularly the number 8 position (77 m). These findings reflect notable differences in the movement characteristics displayed by elite rugby union players in specific positional roles, and reinforce the contemporary view that training programmes for such players ought to be structured with this in mind.

The relationship between physical abilities, ball-carrying and tackling among elite youth rugby league players

Abstract This study investigated the relationship between the physical abilities of adolescent rugby league players and tackling and ball-carrying skills performed during matches, across three seasons (under-15 to under-17). The players were measured each season for acceleration (10–30 m), peak and mean speed (10–30 m), sprinting force (10–30 m), aerobic power, counter-movement jump (CMJ) height and jumping power. The matches were filmed and analysed for ball-carrying and tackling frequency per minute (successful and unsuccessful outcomes). There were strong relationships between successful carries∙min–1 and 10 m force in the under-15 (R = 0.61, P < 0.001), under-16 (R = 0.69, P < 0.001) and under-17 groups (R = 0.64, P < 0.001). There were also strong and moderate relationships between predicted vertical power and successful carries∙min–1 in the under-15 (R = 0.63, P = 0.011) and under-17 group (R = 0.40, P = 0.030), respectively. There were no relationships between carries or tackles and any other performance indicators. These findings suggest that acceleration, in accordance with gains in body mass, support ball-carrying but not tackling performance. Performance measurements, such as CMJ or aerobic power, do not support ball-carrying ability among youth rugby league players.

Differences in the Game Specific Skills of Elite and Sub-Elite Youth Football Players: Implications for Talent Identification

The concept of multidimensional talent modelling offers a recent attempt to objectively identify sporting talent in adolescents, of which game specific skill assessment has become a significant dimension. Previous studies have used closed skill testing to assess ‘open’ skills in youth football players, often finding such measures to discriminate between elite and sub-elite groups. The current study used an example performance analysis template to; 1) Identify differences in performance indicators between pre-determined groups of elite and sub-elite performers during an open match environment; 2) Identify differences in performance indicators between positional groups of elite and sub-elite performers at separate levels of competition; 3) Individually identify sub-elite players compared to a normative profile of elite positional counterparts. Results from Mann-Whitney U testing suggested that elite players are significantly higher (p<0.0028) performers within 9 of 18 performance indicators. Comparisons refined by position and round of competition found only one indicator to distinguish between elite and sub-elite players. The use of a normative profiling method demonstrated how sub-elite players may be analysed relative to elite counterparts. Results are discussed in relation to the advantages of performance analysis as a preferred measure of game specific skills in the talent identification process.

Changes in anthropometry and performance, and their interrelationships, across three seasons in elite youth rugby league players.

Abstract Waldron, M, Worsfold, P, Twist, C, and Lamb, K. Changes in anthropometry and performance, and their interrelationships, across three seasons in elite youth rugby league players. J Strength Cond Res 28(11): 3133–3141, 2014—This study investigated the changes in anthropometry and performance, and their interrelationships, across 3 consecutive seasons (under-15 to under-17 age groups) in elite youth rugby league players. Each player participated in annual anthropometrical and performance assessments, comprising measurements of stature; body mass; limb lengths and circumference; skinfolds; predicted muscle cross-sectional area (CSA); 20-m speed, countermovement jump height, vertical power, and aerobic power. Lean body mass percentage changed (p ⩽ 0.05) between the under-15 (70.9 ± 5.9%), under-16 (72.0 ± 5.8%), and the under-17 age groups (74.1 ± 5.7%). Likewise, predicted quadriceps muscle CSA also changed (p ⩽ 0.05) between each age group (under-15 = 120.9 ± 37.8 cm2; under-16 = 133.2 ± 36.0 cm2; under-17 = 154.8 ± 28.3 cm2). Concomitant changes between the under-15 and under-16 groups were found for 20-m speed (3.5 ± 0.1 cf. 3.4 ± 0.2 seconds; p = 0.008) and predicted jumping power (3,611.3 ± 327.3 W cf. 4,081.5 ± 453.9 W; p = 0.003). Both lean body mass and quadriceps muscle CSA consistently, related to both 20-m sprint time and jumping power, with r values ranging between −0.39 and −0.63 (20-m sprint time) and 0.55 to 0.75 (jumping power). Our findings demonstrate the importance of gains in lean body mass across later adolescence that support the ability to generate horizontal speed and predicted vertical power. This information informs the expectations and subsequent training programs of elite rugby league practitioners.

A three-season comparison of match performances among selected and unselected elite youth rugby league players

Abstract This study compared technical actions, movements, heart rates and perceptual responses of selected and unselected youth rugby league players during matches (under-15 to under-17 age groups). The players’ movements and heart rates were assessed using 5 Hz Global Positioning Systems (GPSs), while their technical actions were analysed using video analysis. The maturity of each player was predicted before each season for statistical control. There were no differences (P > 0.05) between selected and unselected players in the under-15 or the under-17 age group for any variables. However, in the under-16 age group, the selected players (57.1 ± 11.9 min) played for longer than the unselected players (44.1 ± 12.3 min; P = 0.017; ES = 1.08 ± CI = 0.87), and covered more distance (5181.0 ± 1063.5 m cf. 3942.6 ± 1108.6 m, respectively; P = 0.012; ES = 1.14 ± CI = 0.88) and high-intensity distance (1808.8 ± 369.3 m cf. 1380.5 ± 367.7 m, respectively; P = 0.011; ES = 1.16 ± CI = 0.88). Although successful carries per minute was higher in the selected under-15 age group, there were no other differences (P > 0.05) in match performance relative to playing minutes between groups. Controlling for maturity, the less mature, unselected players from the under-16 age group performed more high-intensity running (P < 0.05). Our findings question the use of match-related measurements in differentiating between selected and unselected players, showing that later maturing players were unselected, even when performing greater high-intensity running during matches.

Predicting 30 m timing gate speed from a 5 Hz Global Positioning System (GPS) device

The measurement of over-ground human locomotion using global positioning systems (GPS) has many potential research applications, one of which is the assessment of linear sprint performance. Although recent studies have reported 5 Hz systems to underestimate speed determined by infra-red timing gates, which are commonly used to assess linear speed over brief 10 to 30 m intervals, the magnitude and direction of error are yet to be clarified. Therefore, the purpose of this study was to (i) evaluate the concurrent validity between a 5 Hz GPS and timing gates for measuring mean speed over 30 m and (ii) examine whether regression analysis could yield an accurate model to predict over-ground speed from GPS values. Sixty elite team sport participants (age: 14.2 ± 0.67 years; stature: 171.6 ± 9.8 cm; body mass: 66.1 ± 12.9 kg) performed one maximal sprint over a 30 m distance and were concurrently measured using a 5 Hz GPS device and infra-red timing gates. Analysis of the mean speeds calculated revealed a significant correlation (r = 0.85, P<0.05) between the measures, but a systematic underestimation of 1.96 km·h-1 (P<0.05) by the GPS (20.89 km·h-1) of the values from the timing gates (22.85 km·h-1). Multiple linear regression analysis, incorporating mean and peak GPS speeds as independent variables, yielded an adjusted R2 of 0.84 (SEE = 0.49 km·h-1) and the equation; timing gate speed = 2.869 + [(0.246 × mean GPS speed) + (0.497 × peak GPS speed)]. On this basis, it is suggested that amongst sportsmen such as these, the current GPS prediction model can provide a valid alternative to timing gates in the assessment of sprint performance over 30 m.

The Reliability of Functional Movement Screening and In-Season Changes in Physical Function and Performance Among Elite Rugby League Players.

Abstract Waldron, M, Gray, A, Worsfold, P, and Twist, C. The reliability of functional movement screening and in-season changes in physical function and performance among elite rugby league players. J Strength Cond Res 30(4): 910–918, 2016—This study aimed to (a) assess the reliability of the functional movement screening (FMS) protocol and (b) to establish changes in both FMS and tests of physical performance throughout a season. The reliability of the FMS components (12 in total) was assessed through a nonparametric statistical approach, based on 2 trials, separated by 1 week. Score on the FMS, strength (3 repetition maximum full squat, 1 repetition maximum [1 RM] bench press), running speed (10 and 40 m), and jump height of 12 elite male under-19 rugby league players was monitored at pre-, mid-, and late-season periods. There was no bias (p > 0.05) found between trials for the FMS, with the majority of components reaching 100% “perfect agreement,” reflecting the good reliability of the FMS tool. There were no effects (p > 0.05) of season stage on any of the FMS components; however, an improvement (p ⩽ 0.05) between the pre- and both mid- and late-season periods was apparent in every component of fitness, such as 1 RM bench press (112.92 ± 24.54 kg; 125.83 ± 21.41 kg; 125.98 ± 24.48 kg) and 40-m sprint time (5.69 ± 0.35 seconds; 5.62 ± 0.31 seconds; 5.64 ± 0.27 seconds). Our findings demonstrate that the FMS can be reliably administered to elite rugby league players but will not change in accordance with physical performance across a competitive season. Our findings should not necessarily deter practitioners from using the FMS but begin to question the specific qualities that are being assessed through its administration.

The observational analysis of elite coaches within youth soccer: The importance of performance analysis

The study investigated the observational capabilities of experienced elite coaches whilst focusing upon soccer specific actions and playing positions within elite youth soccer. Six soccer coaches assessed the performances of 10 youth soccer players (across 8 matches) on their short/long passing, tackling, shooting, heading and dribbling. Analysis was undertaken on an overall, quality and positional grouping basis. Mean observational accuracy was 38.8%, with successful shooting (78.6%) and passing (29.9%) illustrating the range. The limited effective observation of dribbling (37.2%), often considered a separating factor within talent identification, highlights the need for objective measures to aid such processes. Positional grouping analysis elicited ∼20% more effective observation for unsuccessful compared with successful actions. The poor level of observational accuracy identified herein has significant implications on talent identification assessments devoid of post-performance analyses. The findings reinforce the importance of performance analysis in the provision of highly accurate and comprehensive augmented feedback within the coaching process.