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).

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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.

1The purpose of this study was to examine the natural development of the mechanical 2 features of sprint performance in relation to maturation within a large cohort of boys. 3Three hundred and thirty-six boys (11-15 years) were assessed for sprint performance 4 and maturation. Maximal speed, stride length (SL), stride frequency (SF), flight time 5 (FT) and contact time (CT) were assessed during the sprint. Five maturation groups 6 (G1-5) were established based on age from peak height velocity (PHV). G1 were 7 early pre-PHV, G2 pre-PHV, G3 approaching-PHV, G4 around-PHV and G5 post-8PHV. There was no difference in maximal speed between G1-3 but those in G4 and 9 G5 were significantly faster (p<0.05) than G1-3. Significant increases (p<0.05) in SL 10 were observed across G1-3, but no significant (p>0.05) improvements in SL were 11 observed between boys G4-5. SF decreased whilst CT increased (both p<0.05) 12 between G1-2, but no changes were observed for either variable between boys in G3-13 5. While boys pre-PHV (G1-3) improved their SL concomitant decreases in SF and 14 increases in CT prevented them from improving maximal speed. Maximal sprint 15 speed appears to develop around and post-PHV as SF and CT begin to stabilize, with 16 improvements in maximal sprint speed in maturing boys underpinned by improving 17 SL.

Short-term, high-altitude (HA) exposure raises pulmonary artery systolic pressure (PASP) and decreases left-ventricular (LV) volumes. However, relatively little is known of the long-term cardiac consequences of prolonged exposure in Sherpa, a highly adapted HA population. To investigate short-term adaptation and potential long-term cardiac remodeling, we studied ventricular structure and function in Sherpa at 5,050 m (n = 11; 31 ± 13 yr; mass 68 ± 10 kg; height 169 ± 6 cm) and lowlanders at sea level (SL) and following 10 ± 3 days at 5,050 m (n = 9; 34 ± 7 yr; mass 82 ± 10 kg; height 177 ± 6 cm) using conventional and speckle-tracking echocardiography. At HA, PASP was higher in Sherpa and lowlanders compared with lowlanders at SL (both P < 0.05). Sherpa had smaller right-ventricular (RV) and LV stroke volumes than lowlanders at SL with lower RV systolic strain (P < 0.05) but similar LV systolic mechanics. In contrast to LV systolic mechanics, LV diastolic, untwisting velocity was significantly lower in Sherpa compared with lowlanders at both SL and HA. After partial acclimatization, lowlanders demonstrated no change in the RV end-diastolic area; however, both RV strain and LV end-diastolic volume were reduced. In conclusion, short-term hypoxia induced a reduction in RV systolic function that was also evident in Sherpa following chronic exposure. We propose that this was consequent to a persistently higher PASP. In contrast to the RV, remodeling of LV volumes and normalization of systolic mechanics indicate structural and functional adaptation to HA. However, altered LV diastolic relaxation after chronic hypoxic exposure may reflect differential remodeling of systolic and diastolic LV function.