Ages at peak height velocity in male soccer players 11-16 years: relationships with skeletal age and comparisons among longitudinal studies

Estimated ages at take-off (TO) and at peak height velocity (PHV) based on two models and maturity status based upon age at PHV and skeletal age (SA) were compared in a longitudinal sample of male soccer players. In addition, estimated ages at PHV in 13 longitudinal samples of soccer players were compared. The longitudinal height records of 58 players of European ancestry, measured annually on four or five occasions between 11 and 16 years, were modeled with Superimposition by Translation and Rotation (SITAR) and Functional Principal Component Analysis (FPCA) to estimate ages at TO and PHV. SAs were assessed with the Fels method. Ages at PHV in 13 longitudinal samples of soccer players (Europe 7, Japan 6) were evaluated with meta-analysis. Estimated ages at TO, 11.2 ± 0.8 (SITAR) and 11.0 ± 0.8 (FCPA) years, and at PHV, 13.6 ± 0.9 (SITAR) and 13.7 ± 0.0 (FCPA) years, were similar. An earlier age at PHV was associated with advanced skeletal maturity status (rho = -0.77 at ~14 years). Ages at PHV among European players indicated a north (later) - south (earlier) gradient, and were later than ages at PHV among Japanese players. In summary, ages at TO and PHV were similar with SITAR and FPCA, and ages at PHV were most strongly correlated with SA at ~14 years. Mean ages at PHV showed a north-south gradient among European samples, and were later compared to Japanese samples.

Observed and predicted ages at peak height velocity in soccer players

The purpose of the study was to evaluate predicted maturity offset (time before age at PHV) and age at PHV (chronological age [CA] minus maturity offset) in a longitudinal sample of 58 under-13 club level soccer players in central Portugal for whom ages at PHV were estimated with the SITAR model. Two maturity offset prediction equations were applied: the original equation which requires CA sitting height, estimated leg length, height and weight, and a modified equation which requires CA and height. Predicted maturity offset increased, on average, with CA at prediction throughout the age range considered, while variation in predicted maturity offset and ages at PHV within CA groups was considerably reduced compared to variation in observed ages at offset and at PHV. Predicted maturity offset and ages at PHV were consistently later than observed maturity offset and age at PHV among early maturing players, and earlier than observed in late maturing players. Both predicted offset and ages at PHV with the two equations were, on average, later than observed among players maturing on time. Intra-individual variation in predicted ages at PHV with each equation was considerable. The results for soccer players were consistent with similar studies in the general population and two recent longitudinal studies of soccer players. The results question the utility of predicted maturity offset and age at PHV as valid indicators of maturity timing and status.

Bio-Banding in Youth Sports: Background, Concept, and Application

Inter-individual differences in size, maturity status, function, and behavior among youth of the same chronological age (CA) have long been a concern in grouping for sport. Bio-banding is a recent attempt to accommodate maturity-associated variation among youth in sport. The historical basis of the concept of maturity-matching and its relevance to youth sport, and bio-banding as currently applied are reviewed. Maturity matching in sport has often been noted but has not been systematically applied. Bio-banding is a recent iteration of maturity matching for grouping youth athletes into 'bands' or groups based on characteristic(s) other than CA. The percentage of predicted young adult height at the time of observation is the estimate of maturity status of choice. Several applications of bio-banding in youth soccer have indicated positive responses from players and coaches. Bio-banding reduces, but does not eliminate, maturity-associated variation. The potential utility of bio-banding for appropriate training loads, injury prevention, and fitness assessment merits closer attention, specifically during the interval of pubertal growth. The currently used height prediction equation requires further evaluation.

Players' Physical Performance Decreased After Two-Thirds of the Season: Results of 3 Consecutive Seasons in the German First Bundesliga

The study aimed to: (1) investigate physical and technical performance among players during six consecutive phases of a competitive season, (2) determine if levels of match running and technical performance between the 1st and 6th phases of a season can be maintained, (3) and determine which phase features the lowest and highest values for variables assessed. Seventy out of 556 outfield players who played at least 80% of the matches in each phase of the Bundesliga seasons were analysed. Each season was divided into 6 phases: phase 1 (matches 1-6), phase 2 (7-11), phase 3 (12-17), phase 4 (18-23), phase 5 (24-28) and phase 6 (29-34). Thirteen variables were selected to quantify the physical and technical activity of players. Our results showed that by reducing the distances covered at intensities below 11 km·h^-1, players were able to cover greater distances at intensities in the range of 11-13.99 and 21-23.99 km·h^-1 in subsequent phases of a season. Players' capacity to maintain match running and technical performance between the first and sixth phases of the season has been demonstrated, though the 4th phase of the season showed a breakthrough point as regards the maintenance of exercise capacity among players participating in the Bundesliga.

Biological maturation of youth athletes: assessment and implications

The search for talent is pervasive in youth sports. Selection/exclusion in many sports follows a maturity-related gradient largely during the interval of puberty and growth spurt. As such, there is emphasis on methods for assessing maturation. Commonly used methods for assessing status (skeletal age, secondary sex characteristics) and estimating timing (ages at peak height velocity (PHV) and menarche) in youth athletes and two relatively recent anthropometric (non-invasive) methods (status-percentage of predicted near adult height attained at observation, timing-predicted maturity offset/age at PHV) are described and evaluated. The latter methods need further validation with athletes. Currently available data on the maturity status and timing of youth athletes are subsequently summarised. Selection for sport and potential maturity-related correlates are then discussed in the context of talent development and associated models. Talent development from novice to elite is superimposed on a constantly changing base-the processes of physical growth, biological maturation and behavioural development, which occur simultaneously and interact with each other. The processes which are highly individualised also interact with the demands of a sport per se and with involved adults (coaches, trainers, administrators, parents/guardians).

Longitudinal field test assessment in a Basque soccer youth academy: a multilevel modeling framework to partition effects of maturation

The purpose of the study was to examine the effect of age on short-term performance indicators applying multilevel regression modeling, and whether changes induced by age were affected by maturation. The study applied a mixed longitudinal approach with 8 measurement points over a period of 4 years. Anthropometry, predicted adult stature, countermovement jump, 15-m sprint and agility test from 38 under-11 young soccer players were considered. Early maturing players were 3% taller compared to late maturers. A substantial effect of age was present in all performance indicators (P<0.05). Parameters showed improvements in performance, even when accounting for interindividual variation in somatic maturity. Vertical jump tended to be stable in early maturers during the first year, presenting an exponential increase thereafter (16%, P<0.05). Additionally, early maturing boys had lower vertical jump scores but a substantial higher rate of development with age (3% per year). Performance tends to plateau during the first 3 years following the improvements in agility (9.1%, P<0.05). In the running tests, early maturers had better performances (19%, P<0.05), while a higher rate of improvement of 1% was observed for the late maturers. Young soccer players should be expected to have substantial improvements in short-term performance, influenced by independent variation between players in maturity status.

Maturity-associated variation in change of direction and dribbling speed in early pubertal years and 5-year developmental changes in young soccer players

AIM

The purpose of the current study was to assess the developmental changes in change of direction and dribbling speed in youth soccer players taking into account skeletal age (SA), maturity status, body size, estimated fat mass, aerobic endurance, lower limb explosive strength and annual volume of training.

METHODS

Eighty-three male soccer players aged 10-15 years (SA) at baseline were annually followed over 5 years, resulting in an average 4.4 observations per player. After testing for multicollinearity, multi-level regression modeling was used to examine the longitudinal developmental changes on change of direction and dribbling speed.

RESULTS

Maturity-associated variability was significant in change of direction and also dribbling speed among young soccer players aged 12-14 years with better scores being performed by late maturers. Moreover, the predicted longitudinal scores for change of direction and dribbling speed improved with SA (P<0.01), SA2 (P<0.01) and skeletal maturity status entered as an additional developmental predictor (P<0.05). Estimated fat-free mass (P<0.01), aerobic endurance (P<0.01) and lower limb strength (P<0.01) were additional predictors in both models. The soccer-specific skill, dibbling speed, was also explained by annual volume of training (P<0.05).

CONCLUSION

Skeletal maturity status explains inter-individual variability on maximal short-term run performances with and without the ball possession at early ages of participation in competitive soccer. The effects tend to persist across ages combined with longitudinal changes in body composition and functional fitness. In the particular case of the ball test, annual volume of training was also a longitudinal performance predictor.

Anthropometric characteristics, physical fitness and technical performance of under-19 soccer players by competitive level and field position

Anthropometric characteristics, physical fitness and technical skills of under-19 (U19) soccer players were compared by competitive level (elite, n=95; non-elite, n=85) and playing position (goalkeeper, central defender, fullback, midfield, forward). Fitness tests included 5- and 30-m sprints, agility, squat jump (SJ) and countermovement jump (CMJ), strength and Yo-Yo intermittent endurance test level 2 (Yo-Yo IE2). Soccer-specific skills included ball control and dribbling. Independent of position, elite players presented more hours of training per year than non-elite players (d>1.2). Stature and body mass discriminated elite from non-elite players among goalkeepers and central defenders (d>0.6). Major differences were noted between elite and non-elite goalkeepers for SJ, CMJ, Yo-Yo IE2, and ball control (d>1.2). Elite central defenders performed better than their non-elite counterparts in SJ and ball control tests (d>1.2). Elite players presented better agility and Yo-Yo IE2 performances than non-elite players within all positional roles (d>0.6). In conclusion, U19 players differed in anthropometric characteristics, physical fitness and technical skills by competitive level within field positions.

Modelling developmental changes in repeated-sprint ability by chronological and skeletal ages in young soccer players

This study investigated the influence of chronological (CA) and skeletal ages (SA), anthropometry, aerobic endurance and lower limb explosive strength on developmental changes in repeated-sprint ability (RSA) in soccer players aged 11-17 years. Participants were annually followed over 5 years, resulting in 366 measurements. Multilevel regression modelling analysed longitudinal data aligned by CA and SA (Model 1 and 2, respectively). After diagnosing for multicollinearity, it was possible to predict RSA with 2-level hierarchical models [Model 1 (CA as Level 2 predictor): Log-Likelihood=1,515.29, p<0.01; Model 2 (SA as Level 2 predictor): Log-Likelihood=1,513.89, p<0.01]. Estimating sum of sprints for young soccer players are given by equations: sum of sprints=84.47 - 1.82 × CA + 0.03 × CA2 - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength -0.09 × fat-free mass + 0.13 × fat mass (Model 1); 73.58 - 0.43 × SA - 0.05 × aerobic endurance - 0.10 × lower limb explosive strength - 0.08 × fat-free mass - 0.45 × training experience + 0.13 × fat mass (Model 2). The models produced performance curves that may be used to estimate individual performance across adolescent years. Finally, the validity of each model was confirmed based on corresponding measurements taken on an independent cross-sectional sample.

Concurrent validation of estimated activity energy expenditure using a 3-day diary and accelerometry in adolescents

Estimates of daily energy expenditure are important to studies of physical activity and energy balance. Objective measures are not always feasible and further research is needed to validate survey instruments and diaries. The study validates estimated activity energy expenditure (AEE) based on a 3-day diary protocol relative to AEE derived from uniaxial accelerometry in adolescents, 265 girls and 227 boys (12.5-16.4 years). Participants completed the diary and wore a GT1M Actigraph accelerometer on the same days. Height and weight were measured. Correlations between protocols were significant (P<0.001) but moderate, r=0.65 in males and r=0.69 in females. The highest correlation occurred among males on Friday, r=0.74 (P<0.01). Controlling for body mass, partial correlations between protocols decreased to 0.44 and 0.35 in males and females, respectively. About 97% of the cases fell within the limits of agreement in a Bland-Altman plot. The criterion of inclusion for the accelerometer excluded 18% of the initial sample. In summary, the 3-day diary was completed without any major problems and provided a reasonably valid alternative for assessing AEE. Concordance between methods was slightly lower for individuals with higher values of AEE.

Growth, maturation, functional capacities and sport-specific skills in 12-13 year-old- basketball players

AIM

The influence of maturity status on body size, functional capacities and basketball-specific skills was evaluated and multivariate relationships between domains of variables were examined in 80 male basketball players 12.0-13.9 years.

METHODS

Height, body mass and two skinfolds were measured. Stage of pubic hair (PH) was assessed clinically. Functional capacity was assessed with the vertical jump (squat jump, countermovement jump), 2-kg medicine ball throw, hand grip strength, 60-second sit-ups and endurance shuttle run. Performances on four basketball skills were tested: shooting, passing, dribbling and defensive movements. Analysis of covariance with age as the covariate was used to test differences among players by stage of puberty. Associations among body size, adiposity, functional capacities and skills were evaluated with canonical correlation analysis.

RESULTS

Maturity status explained a significant portion of variance in body size (F=50.13, P<0.01, h2=057, for height; F=13.47, P<0.01, h2=0.26, for weight). The effect of pubertal status was significant for the jumps and upper limb strength, but not for sit-ups or aerobic endurance. Canonical correlations showed an inverse relationship of height and adiposity with skill tests, and a positive relationship between skills and a combination of abdominal muscular strength (sit-ups) and aerobic endurance.

CONCLUSION

Skill appeared to be independent of pubertal status and the tallest group of basketball players did not attain better scores in basketball-specific skill tests.

Histological alterations found in the ureter during organ preservation and early phases of renal transplantation

INTRODUCTION

There are no studies on the phenomena that occur on the ureter during organ preservation and immediately after transplantation.

MATERIAL AND METHODS

We studied ureteral fragments obtained during organ harvesting in the cadaver (n = 9), after cold preservation period (n = 18), and immediately after kidney graft reperfusion (n = 126). In addition to the histological analysis, we evaluated the risk factors for the development of lesions and their relation to the evolution of the transplant.

RESULTS

Alterations were detected in 120 of the 126 fragments studied after graft reperfusion. Global cellular infiltration was considered to be normal, mild, and moderate to severe in 34.9%, 41.3%, and 23.8%, respectively, consisting mainly of CD8(+) T lymphocytes. Urothelial exfoliation and cell vacuolization were detected in 42% and 52.4% of the cases, respectively. There was an inverse relationship between donor ventilation time and the intensity of the cellular infiltration. Seven and three of the nine fragments obtained during organ harvesting showed mild cellular infiltration of the chorion and urothelium, respectively. Cold storage promoted minor histological changes. After reperfusion, there was increased urothelial infiltration in 11 of the 18 cases. There was no relation between the lesions encountered and human leukocyte antigen compatibilities, renal rejections episodes, or the evolution of the graft itself.

CONCLUSIONS

Consequences of brain death mechanical ventilation were detected at the ureteral level, with abnormal lymphocytic infiltration in most cases. Cold storage did not produce any major histological changes. The lesions detected after graft reperfusion do not seem to involve immunological phenomena.

Ureteric lesions detected in normally functioning kidney allografts: risk factors and clinical implications

INTRODUCTION

We characterized the alterations in ureteral biopsies from normally functioning kidney allografts to study risk factors.

MATERIALS AND METHODS

We studied 55 ureteral fragments from kidney grafts obtained during cystoscopy for routine double-J stent extraction. We evaluated the type and severity of the lesions, the risk factors for their occurrence, and their relation to the evolution of the transplant, including the occurrence of renal rejection episodes or ureteral complications.

RESULTS

Borderline or rejection lesions were detected in 21 of the 55 fragments. Rejection lesions were more common among biopsies performed in the first 80 days (54.6%) than during the 120 days afterward (15.4%, P = .043). Similarly, urothelium reactivity was detected in 71.4% and 30.7% of the biopsies performed up to and after 4 months, respectively (P = .008). Urothelial atrophy was detected in 20% of the fragments, the age of the donors being higher in these cases (P = .026). There was a trend to the association of borderline or rejection lesions in the ureteral biopsies and a history of an acute renal rejection episode (P = .053). There were no detectable relations between those findings and the evolution of the transplant.

CONCLUSIONS

Thirty-eight percent of the biopsed ureters showed rejection or borderline lesions, these lesions were more common among biopsies done in the first months after transplantation. These findings are similar to the ones found in routine renal biopsies. We did not find any significant relation between the nature of the lesions encountered on the ureteral biopsies and the evolution of the transplant.

Are transrectal ultrasonically guided biopsies required for the accurate diagnosis of carcinoma of the prostate? Can digitally guided systematic biopsies offer an acceptable alternative?

OBJECTIVE

To compare the diagnostic yield of ultrasonically guided and digitally guided systematic biopsies of the prostate.

PATIENTS AND METHODS

Fifty two patients with suspected but unproven carcinoma of the prostate underwent simultaneous transrectal ultrasonography (TRUS)-guided and digitally guided systematic biopsies of the prostate. A mean of 12 cores was obtained from each patient. On average more cores were obtained with TRUS guidance (mean 6.7) than with digital guidance (mean 5.3).

RESULTS

Cancer was detected in 19 patients and the diagnosis was made by both techniques in 16. Two patients had tumour detected only with TRUS guidance and one only with digital guidance. No complications occurred.

CONCLUSION

This study indicates that there is no significant difference between TRUS guidance and digital guidance to direct systematic biopsies of the prostate. The use of routine TRUS in screening programmes is now in doubt.