Iraia Bidaurrazaga-Letona

Relationship between the relative age effect and anthropometry, maturity and performance in young soccer players

Abstract The presence of the relative age effect (RAE) has been widely reported; however, its underlying causes have not yet been determined. With this in mind, the present study examined if anthropometry and performance were different amongst older and younger soccer players born in the same year. Eighty-eight young soccer players participated in the study (age 9.75 ± 0.30). Anthropometric measurements, physical tests (sprint, agility, endurance test, jump and hand dynamometry) and the estimation of the maturity status were carried out. Most players (65.9%) were born in the first half of the year. Older players were taller (P < 0.05), had longer legs (P < 0.01) and a larger fat-free mass (P < 0.05). Maturity offset was smaller in the older boys (P < 0.05); however, age at peak height velocity was similar. Older boys performed better in velocity and agility (P < 0.05) and particularly in the overall score of performance (P < 0.01). Stepwise regression analysis revealed that chronological age was the most important variable in the agility test and the overall score, after the skinfolds (negative effect). We report differences in anthropometry and physical performance amongst older and younger pre-pubertal soccer players. These differences may underlie the RAE.

Talent identification and selection process of outfield players and goalkeepers in a professional soccer club

Abstract The aim of this study was to analyse the talent identification process of a professional soccer club. A preselection of players (n = 64) aged 9–10 years and a final selection (n = 21) were performed by the technical staff through the observation during training sessions and matches. Also, 34 age-matched players of an open soccer camp (CampP) acted as controls. All participants underwent anthropometric, maturity and performance measurements. Preselected outfield players (OFs) were older and leaner than CampP (P < 0.05). Besides, they performed better in velocity, agility, endurance and jump tests (P < 0.05). A discriminant analysis showed that velocity and agility were the most important parameters. Finally, selected OFs were older and displayed better agility and endurance compared to the nonselected OFs (P < 0.05). Goalkeepers (GKs) were taller and heavier and had more body fat than OFs; also, they performed worse in the physical tests (P < 0.05). Finally, selected GKs were older and taller, had a higher predicted height and advanced maturity and performed better in the handgrip (dynamometry) and jump tests (P < 0.05). Thus, the technical staff selected OFs with a particular anthropometry and best performance, particularly agility and endurance, while GKs had a different profile. Moreover, chronological age had an important role in the whole selection process.

Sprint, agility, strength and endurance capacity in wheelchair basketball players.

The aims of the present study were, firstly, to determine the reliability and reproducibility of an agility T-test and Yo-Yo 10 m recovery test; and secondly, to analyse the physical characteristics measured by sprint, agility, strength and endurance field tests in wheelchair basketball (WB) players. 16 WB players (33.06 ± 7.36 years, 71.89 ± 21.71 kg and sitting body height 86.07 ± 6.82 cm) belonging to the national WB league participated in this study. Wheelchair sprint (5 and 20 m without ball, and 5 and 20 m with ball) agility (T-test and pick-up test) strength (handgrip and maximal pass) and endurance (Yo-Yo 10 m recovery test) were performed. T-test and Yo-Yo 10 m recovery test showed good reproducibility values (intraclass correlation coefficient, ICC = 0.74-0.94). The WB players’ results in 5 and 20 m sprints without a ball were 1.87 ± 0.21 s and 5.70 ± 0.43 s and with a ball 2.10 ± 0.30 s and 6.59 ± 0.61 s, being better than those reported in the literature. Regarding the pick-up test results (16.05 ± 0.52 s) and maximal pass (8.39 ± 1.77 m), players showed worse values than those obtained in elite players. The main contribution of the present study is the characterization of the physical performance profile of WB players using a field test battery. Furthermore, we demonstrated that the agility T-test and the aerobic Yo-Yo 10 m recovery test are reliable; consequently they may be appropriate instruments for measuring physical fitness in WB.

Differences in ground contact time explain the less efficient running economy in north african runners.

The purpose of this study was to investigate the relationship between biomechanical variables and running economy in North African and European runners. Eight North African and 13 European male runners of the same athletic level ran 4-minute stages on a treadmill at varying set velocities. During the test, biomechanical variables such as ground contact time, swing time, stride length, stride frequency, stride angle and the different sub-phases of ground contact were recorded using an optical measurement system. Additionally, oxygen uptake was measured to calculate running economy. The European runners were more economical than the North African runners at 19.5 km · h−1, presented lower ground contact time at 18 km · h−1 and 19.5 km · h−1 and experienced later propulsion sub-phase at 10.5 km · h−1,12 km · h−1, 15 km · h−1, 16.5 km · h−1 and 19.5 km · h−1 than the European runners (P < 0.05). Running economy at 19.5 km · h−1 was negatively correlated with swing time (r = -0.53) and stride angle (r = -0.52), whereas it was positively correlated with ground contact time (r = 0.53). Within the constraints of extrapolating these findings, the less efficient running economy in North African runners may imply that their outstanding performance at international athletic events appears not to be linked to running efficiency. Further, the differences in metabolic demand seem to be associated with differing biomechanical characteristics during ground contact, including longer contact times.

Stride Angle as a Novel Indicator of Running Economy in Well-Trained Runners

Abstract Santos-Concejero, J, Tam, N, Granados, C, Irazusta, J, Bidaurrazaga-Letona, I, Zabala-Lili, J, and Gil, SM. Stride angle as a novel indicator of running economy in well-trained runners. J Strength Cond Res 28(7): 1889–1895, 2014—The main purpose of this study was to investigate the relationship between a novel biomechanical variable, the stride angle, and running economy (RE) in a homogeneous group of long-distance athletes. Twenty-five well-trained male runners completed 4-minute running stages on a treadmill at different set velocities. During the test, biomechanical variables such as stride angle, swing time, ground contact time, stride length, stride frequency, and the different sub-phases of ground contact were recorded using an optical measurement system. V[Combining Dot Above]O2 values at velocities below the lactate threshold were measured to calculate RE. Stride angle was negatively correlated with RE at every speed (p < 0.001, large effect sizes). Running economy was also negatively correlated with swing phase and positively correlated with ground contact time and running performance according to the best 10-km race time (p ⩽ 0.05, moderate and large effect sizes). Last, stride angle was correlated with ground contact time at every speed (p < 0.001, large effect sizes). In conclusion, it seems that optimal execution of stride angle allows runners to minimize contact time during ground contact, whereby facilitating a better RE. Coaches and/or athletes may find stride angle a useful and easily obtainable measure to track and make alterations to running technique, because changes in stride angle may influence the energy cost of running and lead to improved performance.

Interaction effects of stride angle and strike pattern on running economy.

This study aimed to investigate the relationship between stride angle and running economy (RE) in athletes with different foot strike patterns. 30 male runners completed 4 min running stages on a treadmill at different velocities. During the test, biomechanical variables such as stride angle, swing time, contact time, stride length and frequency were recorded using an optical measurement system. Their foot strike pattern was determined, and VO2 at velocities below the lactate threshold were measured to calculate RE. Midfoot/forefoot strikers had better RE than rearfoot strikers (201.5±5.6 ml · kg(-1) · km(-1) vs. 213.5±4.2 ml · kg(-1) · km(-1)respectively; p=0.019). Additionally, midfoot/fore-foot strikers presented higher stride angles than rearfoot strikers (p=0.043). Linear modelling analysis showed that stride angle is closely related to RE (r=0.62, p<0.001) and that the effect of stride angle on RE was different in the 2 groups. From an arbitrary value of 4°, a rearfoot strike pattern is likely to be more economical, whereas at any lower degree, the midfoot/forefoot strike pattern appears to be more desirable. A biomechanical running technique characterised by high stride angles and a midfoot/forefoot strike pattern is advantageous for a better RE. Athletes may find stride angle useful for improving RE.

Anthropometry and Performance in Wheelchair Basketball

Abstract Granados, C, Yanci, J, Badiola, A, Iturricastillo, A, Otero, M, Olasagasti, J, Bidaurrazaga-Letona, I, and Gil, SM. Anthropometry and performance in wheelchair basketball. J Strength Cond Res 29(7): 1812–1820, 2015—This study investigated whether anthropometric characteristics, generic and specific sprinting, agility, strength, and endurance capacity could differentiate between First-Division and Third-Division wheelchair basketball (WB) players. A First-Division WB team (n = 8; age = 36.05 ± 8.25 years, sitting body height = 91.38 ± 4.24 cm, body mass = 79.80 ± 12.63 kg) and a Third-Division WB team (n = 11; age = 31.10 ± 6.37 years, sitting body height = 85.56 ± 6.48 cm, body mass = 71.18 ± 17.63 kg) participated in the study. Wheelchair sprint, agility, strength, and endurance tests were performed. The First-Division team was faster (8.7%) in 20 m without the ball, more agile (13–22%), stronger (18–33%), covered more distance (20%) in the endurance test, and presented higher values of rate of perceived exertion for the exercise load (48%) than the Third-Division team. Moreover, the individual 20-m sprint time values correlated inversely with the individual strength/power values (from r = −0.54 to −0.77, p ⩽ 0.05, n = 19). Wheelchair basketball coaches should structure strength and conditioning training to improve sprint and agility and evaluate players accordingly, so that they can receive appropriate training stimuli to match the physiological demands of their competitive level.

Physical growth and changes in intermittent endurance run performance in young male Basque soccer players.

The present 4-year longitudinal study examined physical growth and development of intermittent endurance run performance in young Basque soccer players aged 10–15 years applying multilevel regression modeling. Anthropometry, predicted adult stature and Yo-Yo Intermittent Recovery level 1 test (Yo-Yo IR1) of players from the under-11 teams from the Athletic Club of Bilbao were measured at pre- and end-season (two measurements per year of study, n = 33 considered for analysis). A non-linear effect of age on intermittent endurance run was observed, with significantly higher increases in Yo-Yo IR1 between 10–11 year-old and 14–15 year-old players. The development of Yo-Yo IR1 performance in all the years of the study was influenced positively by training exposure during the seasons (P < 0.01) and independent of maturity status and body size (P > 0.05). The steady development of intermittent endurance run performance during pubertal years in adolescent Basque soccer players is partially influenced by training exposure.

The Functional Classification and Field Test Performance in Wheelchair Basketball Players

Abstract Wheelchair basketball players are classified in four classes based on the International Wheelchair Basketball Federation (IWBF) system of competition. Thus, the aim of the study was to ascertain if the IWBF classification, the type of injury and the wheelchair experience were related to different performance field-based tests. Thirteen basketball players undertook anthropometric measurements and performance tests (hand dynamometry, 5 m and 20 m sprints, 5 m and 20 m sprints with a ball, a T-test, a Pick-up test, a modified 10 m Yo-Yo intermittent recovery test, a maximal pass and a medicine ball throw). The IWBF class was correlated (p<0.05) to the hand dynamometry (r= 0.84), the maximal pass (r=0.67) and the medicine ball throw (r= 0.67). Whereas the years of dependence on the wheelchair were correlated to the velocity (p<0.01): 5 m (r= −0.80) and 20 m (r= −0.77) and agility tests (r= −0.77, p<0.01). Also, the 20 m sprint with a ball (r= 0.68) and the T-test (r= −0.57) correlated (p<0.05) with the experience in playing wheelchair basketball. Therefore, in this team the correlations of the performance variables differed when they were related to the disability class, the years of dependence on the wheelchair and the experience in playing wheelchair basketball. These results should be taken into account by the technical staff and coaches of the teams when assessing performance of wheelchair basketball players.

Influence of regression model and initial intensity of an incremental test on the relationship between the lactate threshold estimated by the maximal-deviation method and running performance

Abstract This study investigated the influence of the regression model and initial intensity during an incremental test on the relationship between the lactate threshold estimated by the maximal-deviation method and performance in elite-standard runners. Twenty-three well-trained runners completed a discontinuous incremental running test on a treadmill. Speed started at 9 km · h−1 and increased by 1.5 km · h−1 every 4 min until exhaustion, with a minute of recovery for blood collection. Lactate–speed data were fitted by exponential and polynomial models. The lactate threshold was determined for both models, using all the co-ordinates, excluding the first and excluding the first and second points. The exponential lactate threshold was greater than the polynomial equivalent in any co-ordinate condition (P < 0.001). For both models, the lactate threshold was lower when all co-ordinates were used than when the first and the first and second points were excluded (P < 0.001). 10-km race pace was correlated with both the exponential and polynomial lactate thresholds for all the co-ordinate conditions (r ≥ 0.75, P < 0.001 and r ≥ 0.56, P < 0.05, respectively). The results suggest that the exponential lactate threshold should be used instead of the polynomial equivalent since it is more strongly associated with performance and is independent of the initial intensity of the test.