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The assessment of biological maturation is a central topic in pediatric exercise sciences. Skeletal age (SA) reflects changes in each bone of the hand and wrist from initial ossification to the adult state. This study examined intra-observer and inter-examiner agreement is Greulich-Pyle (GP) assessments of SA in 97 male tennis players 8.6–16.8 years of age. Two observers independently examined all films on two occasions using the GP method. The SA of each bone was evaluated. The mean and median of SAs assigned for each bone was the individual SA for each participant. The calculation was exclusively based on the bones that were not skeletally mature. Intra-observer mean differences were significant for several bones with better results by the experienced examiner (observer B). Comparisons between SA values of the two independent observers indicated significant differences for the ulna, metacarpals II and III, and distal phalanx V. Nevertheless, the magnitude of the bone-specific differences was small, perhaps trivial. Differences in individual SA values of the tennis players based on the non-mature bones of the hand-wrist were negligible based on the mean (0.04±0.39, t = 0.321, p = 0.749) or the median (0.05±0.58, t = 0.007, p = 0.994). Nevertheless, the current study confirmed examiners as a source of error in the estimation of SA using the Greulich-Pyle method and highlighted the importance of calculating SAs based on non-mature bones among adolescent players. [ABSTRACT FROM AUTHOR]

Background: The digit ratio (2D:4D), the ratio of the lengths of second (2D) to the fourth (4D) fingers, is a proxy indicator of prenatal androgen exposure. On average, males display lower 2D:4D than females. Previous studies have shown that lower 2D:4D ratios were associated with better sports and physical abilities. Aim: To assess whether a challenge condition, imposed by intense exercise, could increase handgrip strength (HGS) associated with 2D:4D. Methods: This cross‐sectional experimental study included 90 healthy young Polish adults (40 males, 50 females). They underwent intense physical exercise, before (7 days) and after which they were measured for HGS and 2D:4D. Height and weight were also measured. Analyses of Covariance were employed to delineate associations. Results: 2D:4D had significant predictive effects on the differences in HGS (DHGS) measured in two occasions, without and after, physical exercises. The lower was the 2D:4D, the higher the DHGS, particularly, for the left hand. Conclusion: The results reconfirmed that the link between prenatal testosterone exposure (indicated by 2D:4D) and physical strength depends on the context, such as a challenged condition. [ABSTRACT FROM AUTHOR]

Objective: To estimate the associations between height, weight, and three estimates of skeletal age (SA) and the strength and motor performance of male soccer players in two chronological age (CA) groups, 9–12 (n = 60) and 13–16 (n = 52) years. Methods: Height, weight, strength (grip), speed (5 m, 20 m sprints), acceleration (time at crossing 10 m in 20 m sprint), agility (figure‐of‐eight run), power (vertical jump), and endurance (intermittent shuttle run) were measured. SA was assessed with the TW2 RUS, TW3 RUS, and Fels methods; each SA was expressed as the standardized residual of the regression of SA on CA (SAsr). Hierarchical multiple regression was used. Results: Body size accounted for ≥50% of the variance in grip strength in both CA groups; the body size × SAsr for each method and SAsr alone added little to the explained variance. Body size, body size × SAsr interactions, and SAsr per se with each method accounted for small percentages of variance in motor tasks among players 9–12 years, while body size explained a larger proportion of variance in motor tasks (except the endurance run) among players 13–16 years; body size × SAsr interactions for TW2 and TW3 more so than Fels added to the explained variances. For the endurance run, only SAsr per se with each method accounted for significant portions of the variance. Conclusion: Body size and the three estimates of SA significantly influenced strength and motor performance, but the explained variance varied between CA groups and among SA methods and performance tasks. [ABSTRACT FROM AUTHOR]

The contributions of height, weight and skeletal age (SA) to strength and motor performances of male soccer players 9–12 (n = 60) and 13–16 (n = 52) years were estimated. SA was assessed with the Fels method, and was expressed as the standardized residual of the regression of SA on chronological age CA (SAsr). Static strength (right + left grip), speed (5 m, 20 m sprints), acceleration (10 to 20 m), agility (figure-of-eight run), explosive strength (vertical jump) and endurance (yo–yo intermittent shuttle run, 13–16 years only) were measured. Hierarchical multiple regression was used. The interaction of SAsr with body size (height and height x weight interaction) explained most of the variance in strength in both age groups, 9–12 years (51.6%) and 13–16 years (56.7%), and in speed (31.4%, 38.7%), acceleration (39.6%), and explosive strength (32.6%) among players 13–16 years. In contrast, SAsr alone explained limited amounts of variance in strength, speed, acceleration and vertical jump among players 9–12 years (1.4–4.5%) and 13–16 years (0–0.5%). Results for agility varied with CA group, while SAsr per se was the primary contributor to endurance among players 13–16 years (18.5% of the variance). Although the influence of body size and skeletal maturity status on performances was significant, the explained variance differed among tasks and between CA groups, and suggested a role for other factors affecting performances of the soccer players. [ABSTRACT FROM AUTHOR]

Background: The objective of the study was to evaluate secular changes in the physical fitness of rural school youth, 7–15 years, in west-central Poland between 1986 and 2016. Methods: The fitness of cross-sectional samples of school youth resident in the same 10 communities was evaluated in 4 decennial surveys: 1986—1417 boys/1326 girls; 1996—979 boys/947 girls; 2006—871 boys/843 girls; and 2016—1189 boys/1105 girls. Five tests evaluated speed (5-m run), agility (figure 8 run), explosive power (vertical jump), flexibility (stand and reach), and cardiovascular fitness (modified Harvard step test). Age- and sex-specific descriptive statistics were calculated by survey, while differences among surveys were compared in 3 broad age groups (7–9, 10–12, and 13–15 y) using analysis of variance with age and age squared as covariates. Results: Speed and flexibility declined, while the jump and step test index changed variably across surveys. Although agility improved across surveys, the major improvement occurred between 1986 and 1996. Conclusions: Performances of rural school youth on 5 tests of physical fitness changed significantly, but, variably, between 1986 and 2016. The results were generally consistent with other studies of Polish school youth that spanned a similar interval. [ABSTRACT FROM AUTHOR]

Featured Application: When using the prone plank exercise as part of core stabilisation training, clinicians, physiotherapists, and fitness professionals should consider the demonstrated increase in abdominal activation during head flexion and no change in core muscle activity during head extension, when compared to neutral. Additionally, they should consider that the cranio-cervical segment modulates participants' exertion rating and intensify the perceived neuromuscular fatigue when the plank differs from neutral performance. These findings may provide physical therapists and fitness professionals with new guidelines that should be considered when using this exercise as part of core stabilisation training in rehabilitation and sports programmes. This study aimed to investigate the influence of head position on the electromyographical activity of the core muscles during the prone plank exercise. Twenty healthy participants were enrolled in this study. Muscle activation was registered using surface electromyography in the rectus abdominis, external oblique, internal oblique, and the lumbar portion of erector spinae. Three plank conditions were randomly evaluated, varying the position of the cranio-cervical segment during the plank performance (neutral, flexion and extension). The activation of each individual examined muscle and the overall core muscle activity (Total Intensity), as well as the ratings of perceived exertion were analysed with statistical significance set at p < 0.05. Flexion revealed significantly higher Total Intensity values compared to neutral and extension (p < 0.001; effect size (ES) > 0.90). The rectus abdominis presented larger activation in flexion compared to the other variations (p < 0.05; ES > 0.70). Flexion elicited a greater response for both sides of external oblique when compared to neutral and extension, and also for both sides of internal oblique compared to the other conditions (p < 0.05; ES > 0.70). Both flexion and extension reported higher exertion rating values compared to neutral (p < 0.05; ES > 0.90). Head position influenced the electromyographical activation of core musculature, showing highest values when performing the plank in a head flexion. [ABSTRACT FROM AUTHOR]

External workloads associated Hockey 5 s, the new version of youth field hockey, were evaluated in 31 elite U16 male field players (15.4 ± 0.7 years) from three national teams. Mixed-longitudinal observations for the 31 players provided complete data for 33 forwards and 43 defenders. Activities of the players during games were monitored with the GPSports SPI Elite System with a sampling frequency of 10 Hz and were analysed with GPSports Team AMS (version R1 2015.14, Australia). Observed variables did not differ between forwards and defenders, and the three periods of play were differentiated only by maximal speed in the second and third periods. The greatest distances covered were in speed zone 3 (10.0–15.9 km h−1; 35.5–38.2%) and the smallest in speed zones 4 (16.0–22.9 km h−1; 14.8–15.6%) and 5 (> 23 km h−1; 0.4–1.4%). The trends indicated high intensity levels for the entire match and by position and periods. Active time of forwards and defenders accounted for about one-half of a game's duration (~ 15.7 of 30 min). Overall, the Hockey 5s format was highly demanding of players and included relatively short intervals for recovery. The results emphasize the need for preparation that includes specific mixed anaerobic and aerobic training and also the importance of recovery during breaks. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine intra- and inter-observer agreement for the three skeletal ages derived from the TW2 method among male pubertal soccer players. The sample included 142 participants aged 11.0–15.3 years. Films of the left hand-wrist were evaluated twice by each of two observers. Twenty bones were rated and three scoring systems used to determine SA adopting the TW2 version: 20-bone, CARPAL and RUS. Overall agreement rates were 95.1% and 93.8% for, respectively, Observer A and Observer B. Although, agreement rates between observers differed for 13 bones (5 carpals, metacarpal-I, metacarpal-III, metacarpal-V, proximal phalanges-I, III and V, distal phalanx-III), intra-class correlationa were as follows: 0.990 (20-bone), 0.969 (CARPAL), and 0.988 (RUS). For the three SA protocols, BIAS was negligible: 0.02 years (20-bone), 0.04 years (CARPAL), and 0.03 years (RUS). Observer-associated error was not significant for 20-bone SA (TEM = 0.25 years, %CV = 1.86) neither RUS SA (TEM = 0.31 years, %CV = 2.22). Although the mean difference for CARPAL SAs between observers (observer A: 12.48±1.18 years; observer B: 12.29±1.24 years; t = 4.662, p<0.01), the inter-observer disagreement had little impact (TEM: 0.34 years: %CV: 2.78). The concordance between bone-specific developmental stages seemed was somewhat more problematic for the carpals than for the long bones. Finally, when error due to the observer is not greater than one stage and the replicated assignments had equal probability for being lower or higher compared to initial assignments, the effect on SAs was trivial or small. [ABSTRACT FROM AUTHOR]

A maturity-associated gradient among adolescent athletes in many sports tends to favour early maturing participants. This study was aimed to describe inter-individual variance in growth and skeletal maturation among male youth table tennis. The sample included 99 players registered in competitive clubs for at least 2 years. Chronological age (CA) ranged 10.00–14.63 years. Stature and body mass were plotted relative to US references. Skeletal age (SA) was estimated with the Fels method. Maturity status was given as SA minus CA. Somatic maturation was derived from predicted age at peak height velocity. Mean values for stature and weight were above the reference medians from 10 to 13 years and at the median in the oldest group. In general, SA was in advance to CA (CA: 12.45 ± 1.28 years; SA: 13.44 ± 2.37 years). The majority of the players were early maturing according to SA (52%) and average maturing based on the somatic indicator (80%). The results suggested that table tennis tends to retain taller and heavier participants who are somewhat advanced in skeletal maturity. Participation in youth table tennis and opportunities to win need to consider age- and maturity-associated variations, particularly regarding bands for competitions. [ABSTRACT FROM AUTHOR]

Konarski, JM, Konarska, A, Strzelczyk, R, Skrzypczak, M, and Malina, RM. Internal and external loads during Hockey 5's competitions among U16 players. J Strength Cond Res 35(11): 3199–3206, 2021—The purpose of the study was to characterize the external and internal loads associated with Hockey 5's, the modified small-sided format of competition for U16 field hockey introduced in 2014. Subjects were 10 males, 15.2–16.3 years, who were field players on the U16 Polish National Team. A GPSports Athlete Tracking System was used to estimate external loads (sprints, total distance), and a Polar Team2 unit was used to monitor internal loads (heart rate [HR] and energy expenditure [EE]) during active time of play for 8 field players in 2 international matches. Players covered, on average, a distance of 2,217 ± 178 m during a match including 614 ± 12 m sprinting at 8.1 ± 0.8 km·h−1 with a speedmax of 23.1 ± 1.1 km·h−1. HRmean was 170.5 ± 6.6 b·min−1, whereas HRmax was 184.9 ± 6.4 b·min−1. Speed, sprinting, and distance covered did not differ among periods, whereas HR was greater during the second and third periods. HRmax, %HRmax, and EE varied between forwards and defenders, and among periods. Effort expended by field players during Hockey 5's games can be characterized as heavy. The results highlight the need for preparation in both aerobic and anaerobic activities, which include a major speed component and adequate time for rapid recovery to facilitate the adaptation of youth players to the demands of the modified game. Although not directly comparable, comparison of internal loads during Hockey 5's and 11-a-side matches suggests more intensive activity of field players in the former. [ABSTRACT FROM AUTHOR]

Objective: To evaluate secular changes in the heights and weights of rural school youth in west‐central Poland across decennial surveys of the same communities spanning 1986 and 2016. Methods: Heights and weights of school youth 7 to 15 years in 10 rural communities in the vicinity of the city of Poznań were measured in 1986 (1417 boys, 1326 girls), 1996 (979 boys, 947 girls), 2006 (871 boys, 843 girls), and 2016 (1189 boys, 1105 girls). Descriptive statistics for sex‐specific single year chronological age groups were calculated by survey, while the sample was partitioned into three age groups (7‐9, 10‐12, 13‐15 years) for detailed analysis of changes across surveys using sex‐specific ANCOVA with age and age2 as covariates. Pairwise post hoc comparisons between specific surveys, adjusted for multiple comparisons (Bonferroni), were evaluated. Results: Heights and weights of rural school youth increased significantly between 1986 and 2016, but estimated secular gains between adjacent surveys were variable and not linear over time. Conclusion: Significant secular changes occurred in the heights and weights of rural school children in the 10 rural communities between 1986 and 2016, but estimated rates of change across sequential decennial surveys were variable. The results were generally consistent with corresponding studies of Polish youth. [ABSTRACT FROM AUTHOR]

Studies of age at menarche in Poland have a long history and consistently show an urban-rural gradient. The objectives of the study were to to estimate the age at menarche among school girls resident in ten rural communities of the Greater Poland province in 2016 and to compare ages at menarche by weight status and by population growth. The sample included 1146 girls, 7–16 years of age, resident in ten rural communities. Menarcheal status was obtained via interview. Heights and weights were measured; the BMI was calculated. Based on the latter, the girls were classified as thin, normal weight and overweight (including the obese) relative to IOTF criteria. Population growth between 1986 and 2016 in each community was estimated from local records. Ages at menarche were estimated with the probit regression protocol (SPSS) using the logistic model with log 10 transformation for the total sample and for the subsamples by weight status and population growth. The median age at menarche for the total sample of rural girls was 13.25±0.20 years. Menarche was earlier among Overweight (13.06±0.32 years) compared to Normal Weight (13.25±0.37 years) and Thin (13.81±0.41 years), and among girls resident in communities with Major population growth (12.58±0.44 years) compared to Little/No growth (13.65±0.14 years). Results of the present survey were generally consistent with recent surveys of age at menarche among rural girls in Poland and among girls classified by weight status. Corresponding comparative data relating menarche to population growth are lacking. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Interrelationships among skeletal maturity status, body size, ventilator thresholds (VT) and peak oxygen uptake (VO2peak) were considered in 47 adolescent male soccer players aged 12.5–15.4 years. Body mass, stature, and the triceps and subscapular skinfolds were measured. The latter were used to estimate fat mass and fat-free mass. Skeletal age was assessed with the Fels method. VO2peak and VO2 at the first (VT1) and second (VT2) ventilatory thresholds were determined during an incremental maximal exercise test on a motorized treadmill. Ratio standards and allometric models were used in the analysis. Scaling exponents suggested linearity for all combinations between size descriptors and physiological variables, except between log-transformed values of VT1 and body mass (mL·kg-0.801·min, 95%CI: 0.649 to 0.952). Early maturing players attained greater values than players classified as “on-time” in skeletal maturity for the three ventilatory parameters expressed in absolute terms (d ranged from 0.65 to 0.71). The differences were attenuated after normalizing for mass descriptors using ratio standards and scaled variables (d ranged from 0.00 to 0.31). The results suggested significant variability between maturity groups when moving from VT1 to maximal metabolic conditions expressed by unit of stature (VT1: t = -2.413, p = 0.02, d = 0.60; VT2: t = -2.488, p = 0.02, d = 0.65; VO2peak: t = -2.475, p = 0.02, d = 0.65). Skeletal maturity status and associated variation in overall body size affects VT1, VT2 and VO2peak. The observed scaling of ventilatory outputs for body size may be related to the better running economy and smaller body size of average maturing athletes. [ABSTRACT FROM AUTHOR]

Background: Comparisons of physical fitness in normal weight and overweight/obese youth generally highlight the negative consequences of an elevated BMI. In contrast, several studies of children and adolescents highlight the importance of variation in indicators of physical fitness across the full spectrum of BMIs from low through high. Aim: The purpose of the study was to evaluate relationships between specific physical fitness items and the BMI among youth. Subjects and methods: Height, weight and six physical fitness tests were measured in 1239 males and 903 females, aged 13-16 years; BMI (kg/m2) was calculated. Fitness tests were compared by weight status using sex-specific MANCOVAs, controlling for age. Sex-specific quadratic regressions of each fitness item on the BMI were also calculated. Results: The sprint, standing long jump and shuttle run indicated better performances in normal than in thin and overweight/obese boys; the latter groups did not differ. Thin and normal weight boys performed better than overweight/obese boys in sit-ups and distance run. Among girls, sit-ups differed as follows: normal > thin > overweight/obese. Thin and normal weight girls performed better than overweight/obese girls in the jump, distance run and shuttle run. Normal weight girls were faster in the sprint than the overweight/obese. The quadratic regressions indicated significant non-linear relationships between the BMI and all fitness items among boys and in four items among girls. Conclusion: Performances on fitness tests varied with weight status. Relationships between performances and the BMI were curvilinear except for the distance run and flexibility in girls. [ABSTRACT FROM AUTHOR]

Introduction. The aim of the study was to determine the changes in selected motor parameters of highly skilled field hockey players during the training macrocycle. It was assumed that the changes in the parameters examined in the study would correspond with the hypothesised variation related to the adaptive changes that were expected to take place. Material and methods. The study involved eleven field hockey players from the KS AZS-AWF Poznań club (age = 22.3 ± 1.1 years; height = 176.5 ± 4.0 cm; weight = 75.2 ± 6.3 kg; %FM = 12.2 ± 3.9%; VO2max = 55.4 ± 4.85 ml/kg/min). The dates of the measurements were agreed on with the trainers, who played an active role in the study, and were consistent with the cycle of planned measurements that were aimed at assessing the implementation of training/competition loads (two measurements during the preparatory period and one during the competition period). We examined the fundamental elements of motor preparation that are considered important in field hockey, that is speed endurance, running speed, and aerobic endurance. These assessments were supplemented by the measurements of lactate concentration in capillary blood as well as those of jumping ability and agility. Results. In most cases, the changes in the actual results corresponded with the hypothesised values adopted for the training. The relationships between the levels of particular parameters of the players' motor skills were adequate to a great extent. Conclusion. The effects of the training observed both for the entire team and for individual players were generally in line with the goals of the training/ competition loads implemented. Any discrepancies that were found were identified and corrected by regulating individual exercise loads and were monitored in subsequent measurements. [ABSTRACT FROM AUTHOR]

This study presents a detailed analysis of sprinting activities and distance covered by professional soccer players in two seasons of the Europa League competition. The investigation considered such variables as the mean sprinting distance covered, duration of the rest pause between sprinting activities and maximal running speed recorded during the match. The study involved 147 soccer players participating in 10 matches played at one ground in the 2008-2009 and 2010-2011 Europa League seasons. Players' performance data were divided into two halves of matches and five playing positions. The study was carried out using data from Amisco Pro (version 1.0.2.). Results indicate wide variations in the analyzed variables, depending on the playing position on the pitch and tactical tasks. Individualization of training speed and endurance loads will help to optimize the training process of soccer players at different levels of their athletic skills. [ABSTRACT FROM AUTHOR]