Michael G. Hughes

Talent Identification in Soccer: The Role of Maturity Status on Physical, Physiological and Technical Characteristics

The purpose of this paper is to provide a review around talent identification in soccer using physiological and technical testing procedures, and to summarise the issues associated with this process. The current research in soccer talent identification, among other sports, demonstrates a systematic bias in selection towards players born early in the year (i.e., relative age effect) and early maturers. From the studies investigating the physiological (e.g., power) and technical (e.g., dribbling) characteristics of players of different maturity status, early maturers had the tendency to perform better in these tests and therefore were likely to be more influential on the game and be recognised as more talented. When considering the current level of play and future success, elite youth and future professional players scored better in physiological and technical testing than recreational youth and future non-professional players, independently of maturity status. However, these testing procedures were not sensitive enough to distinguish youth elite from sub-elite or future national team from professional club players. Collectively, these studies demonstrated the need to use estimates of maturity status and subsequent appropriate analysis of data obtained from physiological and technical testing. When maturity is taken into account, these testing procedures can provide an indication of responsiveness to training load in youth players and an evaluation of potential to become a successful soccer player. However, these testing procedures should not be used as a marker of selection before full maturity is attainted and should be part of a multidimensional approach of talent identification considering the importance of other facets of the game at the highest level (e.g., perceptive-cognitive skills).

Reliability and validity of field-based measures of leg stiffness and reactive strength index in youths

Abstract The aim of the study was to assess the reliability of a mobile contact mat in measuring a range of stretch–shortening cycle parameters in young adolescents. Additionally, vertical leg stiffness using contact mat data was validated against a criterion method using force–time data. The reliability study involved 18 youths completing a habituation and three separate test sessions, while 20 youths completed a single test session for the validity study. Participants completed three trials of a squat jump, countermovement jump, and maximal hopping test and a single trial of repeated sub-maximal hopping at 2.0 Hz and 2.5 Hz. All tests were performed on the contact mat. Reliability statistics included repeated-measures analysis of variance, intraclass correlation coefficient, and coefficient of variation (CV), while the correlation coefficient (r) and typical error of estimate (TEE) were reported for the validity study. Squat jump height was the most reliable measure (CV = 8.64%), while leg stiffness during sub-maximal hopping, and reactive strength index produced moderate reliability (CV = 10.17–13.93% and 13.98% respectively). Measures of leg stiffness obtained from contact mat data during sub-maximal hopping were in agreement with the criterion measure (r = 0.92–0.95; TEE = 6.5–7.5%), but not during maximal hopping (r = 0.59; TEE = 41.9%). The contact mat was deemed a valid tool for measuring stretch–shortening cycle ability in sub-maximal but not maximal hopping. Although reliability of performance was generally moderate, the tests offer a replicable assessment method for use with paediatric populations.

Caffeine is ergogenic after supplementation of oral creatine monohydrate

PURPOSE The purpose of this investigation was to assess the acute effects of caffeine ingestion on short-term, high-intensity exercise (ST) after a period of oral creatine supplementation and caffeine abstinence. METHODS Fourteen trained male subjects performed treadmill running to volitional exhaustion (T(lim)) at an exercise intensity equivalent to 125% VO(2max). Three trials were performed, one before 6 d of creatine loading (0.3 g x kg x d(-1) baseline), and two further trials after the loading period. One hour before the postloading trials, caffeine (5 mg x kg(-1)) or placebo was orally ingested in a cross-over, double-blind fashion. Four measurements of rating of perceived exertion were taken, one every 30 s, during the first 120 s of the exercise. Blood samples were assayed for lactate, glucose, potassium, and catecholamines, immediately before and after exercise. RESULTS Body mass increased (P < 0.05) over the creatine supplementation period, and this increase was maintained for both caffeine and placebo trials. There was no increase in the maximal accumulated oxygen deficit between trials; however, total VO(2) was significantly increased in the caffeine trial in comparison with the placebo trial (13.35 +/- 3.89 L vs 11.67 +/- 3.61 L). In addition, caffeine T(lim) (222.1 +/- 48.9 s) was significantly greater (P < 0.05) than both baseline (200.8 +/- 33.4 s) and placebo (198.3 +/- 45.4 s) T(lim). RPE was also lower at 90 s in the caffeine treatment (13.8 +/- 1.8 RPE points) in comparison with baseline (14.6 +/- 1.9 RPE points). CONCLUSION As indicated by a greater T(lim), acute caffeine ingestion was found to be ergogenic after 6-d of creatine supplementation and caffeine abstinence.

Rating of perceived exertion during high-intensity treadmill running

PURPOSE The purpose of this investigation was 1) to evaluate the time course of the rating of perceived exertion (RPE; 6-20 Borg scale) during short-term, high-intensity, constant-load running (ST); and 2) to determine the reproducibility of RPE during ST. METHODS Fifteen well-trained males (VO2max = 58.0 +/- 4.6 mL x kg(-1) x min(-1), mean +/- SD) performed treadmill running (i.e., between 3 and 4 m.s-1 at 10.5% incline) to volitional exhaustion (Tlim) at an exercise intensity equivalent to 125% VO2max. A total of four RPE measurements were taken during each test, one every 30 s during the first 120 s of the exercise. The tests were repeated at the same time of day on three occasions within a 3-wk period. RESULTS Tlim for the three tests was 197.6 +/- 34.8 s. RPE was linearly related with exercise time (mean +/- SD for the three tests: RPE at 30 s = 10.8 +/- 2.2; RPE at 60 s = 12.6 +/- 1.8; RPE at 90 s = 14.5 +/- 1.7; RPE at 120 s = 16.0 +/- 1.9; RPE = 9.06 + (0.06 x time (s)); r = 0.71, SEE = 2.0, P < 0.01). Repeated ANOVA revealed no systematic bias between the three tests for RPE, and other measures of reliability were also favorable. These included intraclass correlation coefficients ranging from 0.78 to 0.87 and sample coefficients of variation of between 4.4% and 6.0%. The 95% limits of agreement ranged between 0.0 +/- 2.3 and 0.0 +/- 2.5. CONCLUSION ST RPE displays a positive linear response during the first 2 min. The measurement of ST RPE appears to be reliable and could thus add a new dimension to ST investigations.

The Influence of Recovery Duration on Multiple Sprint Cycling Performance

The purpose of this study was to examine the influence of recovery duration on various measures of multiple sprint cycling performance. Twenty-five physically active men completed 2 maximal multiple sprint (20 x 5 seconds) cycling tests with contrasting recovery periods (10 or 30 seconds). The mean +/- SD values for age, height, and body mass were 20.6 +/- 1.5 years, 177.2 +/- 5.4 cm, and 78.2 +/- 8.2 kg, respectively. All tests were conducted on a friction-braked cycle ergometer. Longer (30 seconds) recovery periods resulted in significantly (p < 0.05) higher measures of maximum (approximately 4%) and mean (approximately 26%) power output, the former appearing to result from a potentiation effect during the first few sprints. Thirty-second recovery periods also corresponded with significantly lower measures of fatigue (absolute difference: 16.1%; 95% likely range: 14.1-18.2%), heart rate, respiratory exchange ratio, and oxygen uptake. Blood lactate and ratings of perceived exertion (6-20 scale) increased progressively throughout both protocols and were significantly lower with 30-second recovery periods. The results of this study illustrate the considerable influence of recovery duration on various measures of multiple sprint work. Although the precise mechanisms of this response require further investigation, coaches and sport scientists should consider these findings when attempting to develop or evaluate the performance capabilities of athletes involved in multiple sprint sports.

the Reliability and Validity of Fatigue Measures During Short-duration Maximal-intensity Intermittent Cycling

&NA; Glaister, M., M.H. Stone, A.M. Stewart, M. Hughes, and G.L. Moir. The reliability and validity of fatigue measures during short‐duration maximal‐intensity intermittent cycling. J. Strength Cond. Res. 18(3):459–462. 2004.—The purpose of the present study was to assess the reliability and validity of fatigue measures, as derived from 4 separate formulae, during tests of repeat sprint ability. On separate days over a 3‐week period, 2 groups of 7 recreationally active men completed 6 trials of 1 of 2 maximal (20 × 5 seconds) intermittent cycling tests with contrasting recovery periods (10 or 30 seconds). All trials were conducted on a friction‐braked cycle ergometer, and fatigue scores were derived from measures of mean power output for each sprint. Apart from formula 1, which calculated fatigue from the percentage difference in mean power output between the first and last sprint, all remaining formulae produced fatigue scores that showed a reasonably good level of test‐retest reliability in both intermittent test protocols (intraclass correlation range: 0.78–0.86; 95% likely range of true values: 0.54–0.97). Although between‐protocol differences in the magnitude of the fatigue scores suggested good construct validity, within‐protocol differences highlighted limitations with each formula. Overall, the results support the use of the percentage decrement score as the most valid and reliable measure of fatigue during brief maximal intermittent work.

Notational analysis – a mathematical perspective.

The role of feedback is central in the performance improvement process, and by inference, so is the need for accuracy and precision of such feedback. The provision of this accurate and precise feedback can only be facilitated if performance and practice is subjected to a vigorous process of analysis. Recent research has reformed our ideas on reliability, performance indicators and performance profiling in notational analysis – also statistical processes have come under close scrutiny, and have generally been found wanting. These are areas that will continue to develop to the good of the discipline and the confidence of the sports scientist, coach and athlete. If we consider the role of a performance analyst in its general sense in relation the to the data that the analyst is collecting, processing and analysing, then there a number of mathematical skills that will be required to facilitate the steps in the processes:- i) defining performance indicators, ii) establishing the reliability of the data collected, iii) ensuring that enough data have been collected to define stable performance profiles, iv) determining which are important, v) comparing sets of data, vi) modelling performances and vii) prediction. The mathematical and statistical techniques commonly used and required for these processes will be discussed and evaluated in this paper.

An Exploration of Team Sport as a Dynamical System.

At the heart of this paper is the concept of open (complex) systems; a theory which seeks to explain how regularity emerges from within a system that consists of many degrees of freedom in constant flux. Theoretically dynamic patterns are founded on, and greatly inspired by the pioneering work of Hermann Haken, who introduced the concept of non-equilibrium phase transitions within natural patterns (Haken, 1983). At the heart of this theory is how patterns are formed in complex systems with small changes to the system prompting large (nonlinear) changes in the system. Kelso, Turvey and colleagues have been instrumental in applying these types of theory to the experimental analysis of perception and action (for a review, see Kelso, 1995). In these patterns, contents aren’t contained but are revealed by the systems dynamics. Understanding of these theories within sports behaviour has opened up an entirely new research avenue, including synergies, cooperation, and control and order parameters. The current paper discusses and reviews the application of dynamical systems theory within performance analysis of soccer, before beginning to apply this knowledge within the development of a new framework. Data are presented as team profiles composed of perturbations, territory, possession and momentum data from English League Football. It is hypothesized that application of similar strategies on differing scales may enable researchers to efficiently spot the periods of play which are critical to success, therefore negating the pitfalls of traditional notation research. These concepts may also enable players and coaches to understand the components of ‘game control’ and therefore improve the standards of their game through feedback, tactical interventions, player and coach psychology and pattern prediction.

The Effects of 4-Weeks of Plyometric Training on Reactive Strength Index and Leg Stiffness in Male Youths

Abstract Lloyd, RS, Oliver, JL, Hughes, MG, and Williams, CA. The effects of 4-weeks of plyometric training on reactive strength index and leg stiffness in male youths. J Strength Cond Res 26(10): 2812–2819, 2012—Although previous pediatric research has reported performance improvements in muscular power, agility, speed, and rate-of-force development after exposure to plyometric training, the effects on reactive strength index (RSI) and leg stiffness remain unclear. One hundred and twenty-nine boys from 3 different age groups (9, 12, and 15 years) participated and were divided into either an experimental (EXP) or control (CON) group within their respective age groups. The EXP groups followed a twice-weekly, 4-week plyometric training program, whereas the CON groups participated in their normal physical education lessons. Preintervention and postintervention measures were collected for RSI (during maximal hopping) and leg stiffness (during submaximal hopping). Both 12- and 15-year-old EXP groups made significant improvements in both absolute and relative leg stiffness (p < 0.05). The 9-year-old EXP group and CON groups for all ages did not make significant changes in leg stiffness. The 12-year-old EXP cohort also made significant improvements in RSI (p < 0.05). Both 15- and 9-year-old EXP cohorts, and CON groups for all ages, failed to show any significant improvements in RSI. The study concludes that improvements in RSI and leg stiffness after a 4-week plyometric training program are age dependent during childhood.

The influence of chronological age on periods of accelerated adaptation of stretch-shortening cycle performance in pre and postpubescent boys.

Lloyd, RS, Oliver, JL, Hughes, MG, and Williams, CA. The influence of chronological age on periods of accelerated adaptation of stretch-shortening cycle performance in pre and postpubescent boys. J Strength Cond Res 25(7): 1889-1897, 2011—Although it is suggested that periods of naturally occurring accelerated adaptation may exist for various physical parameters, it would appear that no such evidence exists for stretch-shortening cycle (SSC) development. Two hundred and fifty male youths aged 7-17 years were tested for squat (SJ) and countermovement jump (CMJ) height, reactive strength index (RSI), and leg stiffness, with analyses of variance used to establish any significant between-group differences. Additionally, to ascertain the existence of periods of accelerated adaptation, inferences were made about the magnitudes of change between consecutive chronological age groups in relation to the smallest worthwhile change. The largest mean differences (±90% confidence limits) occurred between age groups 10 and 11 (G10-G11) for squat jump (SJ) height (21.61 ± 12.08-31.94%), CMJ height (20.80 ± 11.1-44.1%), and RSI (26.51 ± 11.07-44.10%); and between G12 and G13 for SJ (15.31 ± 7.47-23.73%) and CMJ (16.09 ± 7.50-25.38%) height. Negative mean differences occurred between G11 and G12 for SJ height (−1.32 ± −9.30 to 7.37%), CMJ jump height (−7.68 ± −15.15 to 0.45%) and RSI (−11.48 ± −22.21 to 0.74%); and between G10 and G11 for leg stiffness (−8.87 ± −18.85 to 2.34%). It would appear almost certain that windows of accelerated adaptation may exist for SJ and CMJ height and RSI in male youths; however, leg stiffness results would suggest that fast-SSC function may follow a different developmental trend.