Estimation of body density based on hydrostatic weighing without head submersion in young Japanese adults

Abstract

The aim of this study was to evaluate the effect of a soccer-training season on the anthropometric and performance characteristics of elite youth soccer players.

Two groups (age: 14.4 years) participated in this study: 1) 24 soccer players training 8 to 10 hours per week and 2) 26 non-athletic boys used as controls. Anthropometric measurements, aerobic (Yo-Yo Intermittent Recovery test level 1) and anaerobic (counter-movement-jump (CMJ), squat-jump (SqJ), five-jump-test (5JT), and speed (T5m, 10 m, 30 m)) performances were assessed twice during 8 months (T0: October; T1: May) of the competitive season.

Data showed significant differences in height and weight at T0 between the two groups (P < 0.05), while no difference in the percentage of body fat (%BF) was observed. However, the soccer players were significantly taller and had lower %BF than age-matched controls at T1.

Compared to the controls, the soccer players attained better results in the physical fitness test (P < 0.05) at T0 and T1 except in (T5m) sprinting speed. Hence, significant improvements (P < 0.05) in physical parameters were observed between T0 and T1 only in soccer players.

The results demonstrate that soccer-training season was able to provide maturation free improvement in anthropometric and performance characteristics in young soccer players during the training season.     

Academic performance and self-regulatory skills in elite youth soccer players

Abstract

Although elite athletes have been reported to be high academic achievers, many elite soccer players struggle with a stereotype of being low academic achievers. The purpose of this study was to compare the academic level (pre-university or pre-vocational) and self-regulatory skills (planning, self-monitoring, evaluation, reflection, effort, and self-efficacy) of elite youth soccer players aged 12–16 years (n = 128) with those of 164 age-matched controls (typical students). The results demonstrate that the elite youth soccer players are more often enrolled in the pre-university academic system, which means that they are high academic achievers, compared with the typical student. The elite players also report an increased use of self-regulatory skills, in particular self-monitoring, evaluation, reflection, and effort. In addition, control students in the pre-university system had more highly developed self-regulatory skills than those in the pre-vocational system, whereas no difference was observed within the soccer population. This suggests that the relatively stronger self-regulatory skills reported by the elite youth soccer players may be essential for performance at the highest levels of sport competition and in academia.     

Biomechanical mechanisms of jumping performance in youth elite female soccer players

ABSTRACT

We aimed to determine key biomechanical parameters explaining age-related jumping performance differences in youth elite female soccer players. Multiple biomechanical parameters from countermovement (CMJ) squat (SJ) and drop (DJ) jump testing of elite female soccer players (n = 60) within the same national training centre were analysed across ages 9-11y, 12-14y and 15-19y. Effects of age group and jump type on jump height were found, with the older jumping higher than the younger groups in all jumps (P < 0.05). For DJ, higher reactive strength index was found for older, compared to each younger group (P < 0.001). For CMJ and SJ, peak power was the most decisive characteristic, with significant differences between each group for absolute peak power (P < 0.0001) and body-weight-normalised peak power in CMJ (57 ± 7W/kg, 50 ± 7W/kg, 44.7 ± 5.5W/kg; P < 0.05) and between the older and each younger group in SJ (56.7 ± 7.1W/kg, 48.9 ± 7.1W/kg, 44.6 ± 6W/kg; P < 0.01). Age-related differences in jumping performance in youth elite female soccer players appear to be due to power production during standing jumps and by the ability to jump with shorter ground contact times during reactive jumps.     

Stress hormonal analysis in elite soccer players during a season

PurposeThe purpose of this study was to evaluate the changes in some hormonal parameters (cortisol, testosterone, ratio of testosterone/cortisol (T/C)) in professional soccer players during a season.MethodsFifteen professional players from a soccer club of the first division of the Greek soccer league participated. All sport medical examinations were conducted four times: before the re-building period, post re-building period, mid-season, and after finishing the competition phase.ResultsFor testosterone, significant differences were observed between the end season and post re-building period (11.6%; p < 0.05) and mid-season (12.1%; p < 0.05). The cortisol concentration increased at mid-season by approximately 23%, and this change differed significantly from all other measurements for this hormone. The T/C ratio increased at the post re-building period and decreased at the middle of the season.ConclusionThese hormones and their ratios could be used as stress and recovery state indicators. Coaches can use these parameters in combination with other indicators to optimize workloads, and to avoid overreaching and overtraining.     

Body composition of English Premier League soccer players: Influence of playing position,international status,and ethnicity

Abstract

Body composition is a key consideration in the physical make-up of professional soccer players. The aims of the present study were to determine whether the body composition of professional soccer players varied according to playing position, international status or ethnicity, and to establish which variables best distinguished the soccer players from a reference group. Body composition was assessed using dual-energy X-ray absorptiometry in 64 male professional soccer players. Measured variables included bone mineral density and the relative amounts of lean and fat mass. Data were analysed using analysis of variance and stepwise discriminant function. The soccer players recorded better values than a reference group (n = 24) for all body composition compartments. Percent lean mass and bone mineral density were the variables best able to identify the soccer players (95.5% correctly classified). Differences in body composition were evident between goalkeepers and outfield players, but not between outfield playing positions. No differences were found on the basis of international status. The non-Caucasian players demonstrated significantly lower percent body fat (9.2 ± 2.0%) than the Caucasian players (10.7 ± 1.8%). It was concluded that body composition is important for elite soccer players, but that homogeneity between players at top professional clubs results in little variation between individuals.     

Influence of different sports on bone mass in growing girls

The aim of this study was to analyse whether there are differences in bone mass in girls playing different sports. Two hundred girls (10.6 ± 1.5 years old, Tanner stages I–III) participated in the study and were divided into groups of 40 (swimmers, soccer players, basketball players, handball players and controls). Bone mineral content and bone mineral density (BMD) (whole body and hip) were measured using dual-energy X-ray absorptiometry. The degree of sexual development was determined using Tanner test, and physical activity habits were recorded through a questionnaire designed ad hoc for this research. Girls were divided by pubertal stage and the type of sport. In the prepubertal group, intertrochanteric BMD was significantly higher in both handball and soccer players compared with the control group (P < 0.05). Furthermore, in the pubertal group, total BMD, mean arms BMD, pelvis BMD, femoral neck BMD, intertrochanteric BMD and Ward’s triangle BMD were significantly higher in soccer and handball players compared with the control group (P < 0.05), and the swimmers showed significantly higher values in the mean arms BMD compared with the control group (P < 0.01). Our data suggest that sport practice during puberty, especially in activities that support the body weight, may be an important factor in achieving a high peak bone mass and improving bone health in girls.     

Isokinetic imbalance of hip muscles in soccer players with osteitis pubis

Abstract

In this study, we compared the isokinetic torques of hip flexors/extensors and abductors/adductors in soccer players suffering from osteitis pubis (OP), with normal soccer players. Twenty soccer male athletes with OP and 20 normal soccer athletes were included in this study. Peak torque/body weight (PT/BW) was recorded from hip flexor/extensor and abductor/adductor muscles during isokinetic concentric contraction modes at angular velocity of 2.1 rad · s^?1, for both groups. The results showed a significant difference between the normal and OP groups for hip flexors (P < 0.05). The normal group had significant, lower PT/BW value than the OP group for their hip flexors (P < 0.05). The hip flexor/extensor PT ratio of OP affected and non-affected limbs was significantly different from that of normal dominant and non-dominant limbs. There were no significant differences between the normal and OP groups for hip extensor, adductor and abductor muscles (P > 0.05). Regarding the hip adductor/abductor PT ratio, there was no significant difference between the normal and OP groups of athletes (P > 0.05). The OP group displayed increase in hip flexor strength that disturbed the hip flexor/extensor torque ratio of OP. Therefore, increasing the hip extensor strength should be part of rehabilitation programmes of patients with OP.     

Yo-Yo IR2 testing of elite and sub-elite soccer players: Performance,heart rate response and correlations to other interval tests

Abstract

We examined performance, heart rate response and construct validity of the Yo-Yo IR2 test by testing 111 elite and 92 sub-elite soccer players from Norway and Denmark. VO₂max, Yo-Yo IR1 and repeated sprint tests (RSA) (n = 51) and match-analyses (n = 39) were also performed. Yo-Yo IR2 and Yo-Yo IR1 performance was 41 and 25% better (P < 0.01) for elite than sub-elite players, respectively, and heart rate after 2 and 4 min of the Yo-Yo IR2 test was 20 and 15 bpm (9 and 6% HRmax), respectively, lower (P < 0.01) for elite players. RSA performance and VO₂max was not different between competitive levels (P > 0.05). For top-teams, Yo-Yo IR2 performance (28%) and sprinting distance (25%) during match were greater (P < 0.05) than for bottom-teams. For elite and sub-elite players, Yo-Yo IR2 performance was correlated (P < 0.05) with Yo-Yo IR1 performance (r = 0.74 and 0.76) and mean RSA time (r = ?0.74 and ?0.34). We conclude that the Yo-Yo IR2 test has a high discriminant and concurrent validity, as it discriminates between players of different within- and between-league competitive levels and is correlated to other frequently used intermittent elite soccer tests.     

Reliability and validity of the Yo-Yo intermittent recovery test level 1 in young soccer players

Abstract

The present study investigated the test-retest reliability from the Yo-Yo IR1 (distance and heart rate responses), and the ability of the Yo-Yo IR1 to differentiate between elite and non-elite youth soccer players. A total of 228 youth soccer players (11–17 years) participated: 78 non-elite players to examine the test-retest reliability within 1 week, added with 150 elite players to investigate the construct validity. The main finding was that the distance covered was adequately reproducible in the youngest age groups (U13 and U15) and highly reproducible in the oldest age group (U17). Also, the physiological responses were highly reproducible in all age groups. Moreover, the Yo-Yo IR1 test had a high-discriminative ability to distinguish between elite and non-elite young soccer players. Furthermore, age-related standards for the Yo-Yo IR1 established for elite and non-elite groups in this study may be used for comparison of other young soccer players.     

Association of different types of playing surfaces with bone mass in growing girls

The aim of this cross-sectional study was to compare bone mass in young female athletes playing ball games on different types of playing surfaces. About 120 girls, 9–13 years of age (10.6 ± 1.5 years old Tanner I–III) were recruited and divided into prepubertal and pubertal groups. The sample represented 3 groups of athletes: soccer (N = 40), basketball (N = 40), and handball (N = 40); and 6 different playing surfaces (soccer – ground, soccer – artificial turf, basketball – synthetic, basketball – parquet, handball – synthetic, and handball – smooth concrete). Total and regional body composition (bone mass, fat mass, and lean mass) were measured by dual-energy X-ray absorptiometry (DXA). The mechanical properties of the surfaces (force reduction, vertical deformation, and energy return) were measured with the Advanced Artificial Athlete (Triple A) method. The degree of sexual development was determined using Tanner test. The pubertal group showed that soccer players on the ground, basketball players on synthetic, and handball players on smooth concrete had higher values of bone mineral content (BMC) and bone mineral density (BMD) (P < 0.05) than the soccer players on the artificial turf, basketball players on parquet, and handball players on synthetic. In conclusion, a hard playing surface, with less vertical deformation and force reduction, and greater energy return, is associated with higher levels of BMD and BMC in growing girls, regardless of the sport they practice.     

Metabolic impact of a soccer match on female players

The aim of this study was to examine the metabolic effect of a female soccer match in elite and sub-elite teams. Blood samples were taken (24 h before, immediately after and 18 h after official soccer matches) to determine haematological, electrolytic and hormonal variables, as well as the levels of cell damage and oxidative stress in 14 elite and 14 sub-elite players. Our results show increases in white blood cell count (P < 0.001) and the percentage of neutrophils (P < 0.001), and decreases in the percentage of lymphocytes (P < 0.05), eosinophils (P < 0.001), monocytes (P < 0.001) and basophils (P < 0.05) immediately post-match. Increases were also found in lactate dehydrogenase activity (P < 0.001), uric acid (P < 0.001), albumin (P < 0.001), total antioxidant status (P < 0.001) and free testosterone levels (P < 0.01). Creatine kinase activity significantly increased 18 h post-match (P < 0.01) and the concentrations of several ions, glucose and proteins were found to be altered immediately post-match. Overall, our results show that playing a soccer match exerts specific metabolic effects on female players, resulting in muscle damage, oxidative stress and biochemical and hormonal variations. On the basis of some interesting correlations, we also suggest that exercise-induced cell breakdown may enhance antioxidant capacity of the soccer players.     

Comparative efficacy of active recovery and cold water immersion as post-match recovery interventions in elite youth soccer

ABSTRACT

The current study compared cold-water immersion (CWI) and active recovery (AR) to static stretching (SS) on muscle recovery post-competitive soccer matches in elite youth players (n = 15). In a controlled crossover design, participants played a total of nine competitive soccer games, comprising three 80 minute games for each intervention (SS, CWI and AR). Muscle oedema, creatine kinase (CK), countermovement jump performance (CMJA) and perceived muscle soreness (PMS) were assessed pre-, immediately post-, and 48 hours post-match and compared across time-intervals and between interventions. Following SS, all markers of muscle damage remained significantly elevated (P < 0.05) compared to baseline at 48 hours post-match. Following AR and CWI, CMJA returned to baseline at 48 hours post-match, whilst CK returned to baseline following CWI at 48 hours post-match only. Analysis between recovery interventions revealed a significant improvement in PMS (P < 0.05) at 48 hours post-match when comparing AR and CWI to SS, with no significant differences between AR and CWI observed (P > 0.05). Analysis of %change for CK and CMJA revealed significant improvements for AR and CWI compared to SS. The present study indicated both AR and CWI are beneficial recovery interventions for elite young soccer players following competitive soccer matches, of which were superior to SS.     

The adolescent motor performance development of elite female soccer players: A study of prognostic relevance for future success in adulthood using multilevel modelling

ABSTRACT

Considering the scarce empirical evidence regarding talent predictors in female youth soccer, the present study aimed to investigate the long-term prognostic validity of elite female soccer players’ adolescent motor performance for future success in adulthood. Additionally, the three-year development of highly talented girls’ motor performance and the predictive value of this motor development for reaching a professional adult performance level (APL) was analysed.

Overall, N = 737 female players participated in nationwide motor diagnostics (sprinting, agility, dribbling, ball control, shooting) within the German Soccer Association’s talent identification and development programme at least twice between the age groups Under-12 (U12) and U15. Based on their APL at least four years later, participants were assigned to a professional (first German division, 6.2%) or non-professional group (lower divisions, 93.8%).

Multilevel regression analyses revealed a general prognostic relevance for the investigated parameters with respect to players’ APL. In addition, there was a non-linear improvement in participants’ motor performance across all variables from U12 to U15. However, non-significant interactions between APL and these improvements indicate motor performance development itself cannot adequately predict players’ future success in adulthood. Findings provide insightful information that can help coaches foster optimal support for young female soccer players’ development.     

High-intensity endurance capacity assessment as a tool for talent identification in elite youth female soccer

ABSTRACT

Talent identification and development programmes have received broad attention in the last decades, yet evidence regarding the predictive utility of physical performance in female soccer players is limited. Using a retrospective design, we appraised the predictive value of performance-related measures in a sample of 228 youth female soccer players previously involved in residential Elite Performance Camps (age range: 12.7–15.3 years). With 10-m sprinting, 30-m sprinting, counter-movement jump height, and Yo-Yo Intermittent Recovery Test Level 1 (IR1) distance as primary predictor variables, the Akaike Information Criterion (AIC) assessed the relative quality of four penalised logistic regression models for determining future competitive international squads U17–U20 level selection. The model including Yo-Yo IR1 was the best for predicting career outcome. Predicted probabilities of future selection to the international squad increased with higher Yo-Yo IR1 distances, from 4.5% (95% confidence interval, 0.8 to 8.2%) for a distance lower than 440 m to 64.7% (95% confidence interval, 47.3 to 82.1%) for a score of 2040 m. The present study highlights the predictive utility of high-intensity endurance capacity for informing career progression in elite youth female soccer and provides reference values for staff involved in the talent development of elite youth female soccer players.     

Is an elevated submaximal heart rate associated with psychomotor slowness in young elite soccer players?

Abstract

The aim of the present study was to find early markers for overreaching that are applicable in sport practice. In a group of elite soccer players aged 15–18, the stress–recovery balance and reaction times before and after exercise were assessed. Overreaching was indicated by an elevated submaximal heart rate during a sport-specific field test. Submaximal changes in heart rate were prospectively monitored by means of monthly Interval Shuttle Run Tests during two competitive seasons. Out of 94 players, seven players with an elevated heart rate of at least one month could be included in the study, together with seven controls, matched for age, body composition, training and performance level. The stress–recovery balance was assessed with the Dutch version of the Recovery Stress Questionnaire (RESTQ-Sport). The soccer players with an elevated heart rate reported a disturbed stress–recovery balance (Mann–Whitney test, P<0.05). An ANOVA for repeated measures of reaction times revealed a significant main effect of time (F _1,12=13.87, P<0.01) indicating an improvement of psychomotor speed. No differences between groups were found. We conclude that soccer players with an elevated submaximal heart rate of at least one month share a disturbed stress–recovery balance, but they could not be distinguished from controls based on reaction time after strenuous exercise.     

Power training in elite young soccer players: Effects of using loads above or below the optimum power zone

ABSTRACT

This study aimed to examine the effects of two jump squat (JS) training programs involving different loading ranges in under-20 soccer players during a preseason period. Twenty-three elite young soccer players performed sprint speed (at 5-, 10-, and 20-m), change-of-direction (COD) speed, JS peak-power (PP), and countermovement jump (CMJ) tests pre and post four weeks of training. Athletes were pair-matched in two groups according to their optimum power loads (OPL) as follows: lower than OPL (LOPL; athletes who trained at a load 20% lower than the OPL) and higher than OPL (HOPL; athletes who trained at a load 20% higher than the OPL). Magnitude-based inferences were used to compare pre- and post-training measures. Meaningful increases in the PP JS were observed for both groups. Likely and possible improvements were observed in the 5- and 10-m sprint velocity in the LOPL group. Meanwhile, possible and likely improvements were observed in the CMJ, 5- and 10-m sprint velocity, and COD speed in the HOPL group. Overall, both training schemes induced positive changes in athletic performance. Soccer coaches and sport scientists can implement the JS OPL-based training schemes presented here, either separately or combined, to improve the physical performance of youth soccer players.     

The scientific foundations and associated injury risks of early soccer specialisation

ABSTRACT

Early specialisation is characterised by formal participation in a single sport at the exclusion of others. Limited data are available to support this approach in the development of soccer players who attain elite status later in life. Of growing concern is the associated increased risk of injury and suggestions that single sport specialisation is a risk factor independent of age, growth, biological maturation and training volumes. In the United Kingdom, elite soccer organisations have recently adopted an early sport specialisation approach following the introduction of the Elite Player Performance Plan. A key tenet of this programme is increased opportunities for training through a marked rise in the specified on-pitch hours per week. The accumulation of high training hours may be less of a relevant marker for success, and the impact of such a significant increase in training volume for young athletes who are experiencing a range of growth and maturational processes is currently unknown. This critical commentary includes an evidence-based discussion of the effectiveness of early sport specialisation and the potential injury risks associated with such programmes placing a specific focus on elite male youth soccer players. Available data indicate that modifications to the existing Elite Player Performance Plan framework could enhance players’ development and reduce injury risk. Proposed alterations include reduced volume of soccer-specific training at key stages of growth and maturation and guidelines for the provision of a greater variety of physical activities that are integrated within other programme components.     

Prevalence of disordered eating in elite female athletes in team sports in Greece

ABSTRACT

The purpose of the study was to assess (a) the prevalence of disordered eating (DE) in elite female team sports players compared to non-athletes and (b) to compare DE prevalence in elite female players in basketball, volleyball and water polo. One hundred and seventy-five females were recruited (age 23.10?±?5.4, BMI 21.85?±?2.3?kg/m²), 53 were elite basketball players, 42 were elite volleyball players, 34 were elite water polo players and 46 were non-athletes. Participants completed the Eating Disorders Questionnaire (EDE-Q) and a physical activity questionnaire. The EDE-Q incorporates 36 statements which relate to the occurrence and frequency of key behaviours of eating disorders, under the following four subscales: Restraint, eating concern, shape concern and weight concern and a global score of disordered eating. No differences were found in the EDE-Q subscale score and global score between athletes and non-athletes. Only 6.2% of the total number of participants exhibited DE using the global score >2.3. Water polo players had significantly higher scores in the ‘eating concern’ subscale and in the frequency of key behavioural features of DE such as binge eating episodes and objective and subjective bulimic episodes, compared to volleyball and basketball players. In conclusion, team sport elite female players do not exhibit greater prevalence of DE compared to non-athletes. Water polo, a sport that emphasises leanness and control of body weight for international distinctions, is associated with a higher tendency to exhibit DE, when compared to other team sports.