Lack of impact moderating movement adaptation when soccer players perform game specific tasks on a third-generation artificial surface without a cushioning underlay

The objective of this study was to investigate how the inclusion of a cushioning underlay in a third-generation artificial turf (3G) affects player biomechanics during soccer-specific tasks. Twelve soccer players (9 males/3 females; 22.6 ± 2.3 y) participated in this study. Mechanical impact testing of each 3G surface; without (3G-NCU) and with cushioning underlay (3G-CU) were conducted. Impact force characteristics, joint kinematics and joint kinetics variables were calculated on each surface condition during a sprint 90° cut (90CUT), a sprint 180° cut (180CUT), a drop jump (DROP) and a sprint with quick deceleration (STOP). For all tasks, greater peak resultant force, peak knee extensor moment and peak ankle dorsi-flexion moment were found in 3G-NCU than 3G-CU (p < 0.05). During 90CUT and STOP, loading rates were higher in 3G-NCU than 3G-CU (p < 0.05). During 180CUT, higher hip, knee and ankle ranges of motion were found in 3G-NCU (p < 0.05). These findings showed that the inclusion of cushioning underlay in 3G reduces impact loading forces and lower limb joint loading in soccer players across game-specific tasks. Overall, players were not attempting to reduce higher lower limb impact loading associated with a lack of surface cushioning underlay

Phase transition and critical behaviour of the d=3 Gross-Neveu model

A second order phase transition for the three dimensional Gross-Neveu model is established for one fermion species N=1. This transition breaks a paritylike discrete symmetry. It constitutes its peculiar universality class with critical exponent \nu = 0.63 and scalar and fermionic anomalous dimension \eta_\sigma = 0.31 and \eta_\psi = 0.11, respectively. We also compute critical exponents for other N. Our results are based on exact renormalization group equations.Comment: 4 pages, 1 figure; v4 corresponds to the published articl

Is Playing Soccer More Osteogenic for Females Before the Pubertal Spurt?

The aims of this study were to assess bone mass in children and adolescent soccer players and to evaluate the influence of both gender and pubertal status on bone mass. A total of 110 soccer players (75 males / 35 females; 12.73 ± 0.65 / 12.76 ± 0.59 years) participated in this cross-sectional study. They were divided into two groups according to their pubertal status. Bone and lean masses were measured with Dual-energy X-ray Absorptiometry. An independent t-test and an adjusted by subtotal lean and training experience multivariate analysis of covariance were used to analyse the differences in bone mass values between genders and maturity status. Female soccer players presented higher bone mass values than their male counterparts in most of the measured weight-bearing sites. Moreover, when stratifying by pubertal status, peripubertal and postpubertal females had higher subtotal body and lumbar spine bone mass than males. Comparing between pubertal status groups before adjustment, both male and female postpubertal players showed higher bone mass than their pubertal counterparts. After adjusting, these differences disappeared and, in fact results were inverted as bone mass at the femoral neck was higher in both male and female peripubertal soccer players than in postpubertal players. Bone mass seems to be more intensely stimulated by playing soccer in female than male players, particularly in the lumbar spine. The results of peripubertal players showing higher bone mass at the femoral neck after adjusting suggest that playing soccer during the peripubertal stage could be an effective activity to achieve optimal bone mass values

Agreement of body composition methods in elite male football referees

Objective: The current literature about the body composition of elite football referees is scarce and almost non-existent. Therefore, and in order to establish the level of agreement between bioelectrical impedance analysis (BIA) and dual energy X-ray absorptiometry (DXA) in elite football referees, the aim of this study was to compare fat mass (FM) and fat-free mass (FFM) values measured with these two different methods. Method: A total of 30 male referees belonging to 1st, 2nd and 2ndB categories, and 36 assistant referees from 1st and 2nd categories in the Spanish national league participated in this study. Total and regional FM and FFM were assessed using a portable BIA analyser TANITA BC 418-MA (Tanita Corp., Tokyo, Japan) and DXA (Hologic Corp. Software version 12.4, Bedford, MA 01730). Agreement between methods was assessed by plotting the results in Bland-Altman graphs and the presence of heteroscedasticity was also examined. Differences between methods were analysed by two-paired samples t-test. Results: For the whole group, BIA underestimated body fat percentage in 3.87 points (CI 95%=3.22-4.52; p=&lt;0.01) and overestimated kg of total FFM in 3.56 points (CI 95%=3.08-4.05; p=&lt;0.01), however, no heteroscedasticity was shown in any case (all p&gt;0.05). Conclusions: The present study suggests that according to DXA, BIA values calculated with a non-specific equation are underestimating total FM and, consequently, overestimating total FFM in male elite football referees. Objetivo: La literatura científica existente sobre la composición corporal en árbitros de fútbol es todavía escasa. Por lo tanto y para establecer el nivel de concordancia entre el análisis de impedancia bioeléctrica y la absorciometría de rayos X de doble energía en árbitros de fútbol de elite, el objetivo de este estudio fue comparar los valores de masa grasa (MG) y la masa libre de grasa (MLG) medidos con ambos métodos. Método: Un total de 30 árbitros pertenecientes a las categorías de 1ª, 2ª y 2ª división B, y 36 asistentes de 1ª y 2ª división de la liga española participaron en este estudio. La MG y la MLG tanto a nivel total como regional se evaluó utilizando la impedancia bioeléctrica TANITA BC 418-MA (Tanita Corp., Tokyo, Japan) y absorciometría de rayos X de doble energía (Hologic Corp. Software versión 12.4, Bedford, MA 01730). La concordancia entre métodos se evaluó con gráficos de Bland-Altman y también se examinó la presencia de heterocedasticidad. Las diferencias entre métodos se analizaron con la prueba T de Student para muestras relacionadas. Resultados: Para el total de la muestra, la impedancia bioeléctrica infraestimó el porcentaje de MG en 3.87 puntos (IC 95%=3.22-4.52; p=0.05). Conclusión: El presente estudio sugiere que, tomando como referencia la absorciometría de rayos X de doble energía, la impedancia bioeléctrica calculada a partir de una ecuación no especifica para árbitros, infraestima la MG y consecuentemente, sobreestima la MLG en árbitros de fútbol de elite

Effects Of Playing Surfaces On Volumetric Bone Mineral Density In Adolescent Male Soccer Players

It has been well recognized that impact loading in sporting activity is highly associated with bone accretion. Recently, Carmona et al. showed that bone mass accretion was similar bone in prepubescent soccer players independently of the playing surface (artificial turf vs. non-grass ground surface). However, the osteogenic effects on volumetric bone mineral density (vBMD) generated by four different playing surfaces of the same sport are unknown. PURPOSE: to investigate the effects over a soccer season in vBMD of male soccer players by playing surface. METHODS: A total of 71 male soccer players (12.7±0.6 y) volunteered to participate in the study. 26 participants were training and playing on 2nd generation artificial turf, 16 on a 3rd generation artificial turf, 10 on a non-grass ground surface and 19 on natural grass (NG). vBMD, at 4 and 38% of the non-dominant tibia, was measured before and after season by peripheral quantitative computed tomography (Stratec XCT-2000 L pQCT scanner). Analysis of variance for repeated measures×2 (time) were performed to determine the effects of playing surface on vBMD controlling for pubertal status. Effect size were calculated according to the methods proposed by Cohen (small (f=0.1), medium (f=0.2), or large (f=0.4)). RESULTS: A group by time interaction was found for vBMD at 38% of the distal tibia (p=0.029 and f=0.38). When pairwise comparisons were carried out, NG showed group by time interactions compared to 2nd generation artificial turf (782 to 804 mg/cm3 vs. 790 to 798 mg/cm3; p=0.007 and f=0.50), and to 3rd generation artificial turf (782 to 804 mg/cm3 vs. 784 to 788 mg/cm3; p=0.027 and f=0.35). CONCLUSION: Soccer players training and playing in NG pitch showed better values in vBMD acquisition than those on 2nd and 3rd generation artificial turf. Despite previous studies presented no differences on bone mass accretion independently of the playing surface. Our results suggest that NG is the most recommended playing surface to improve vBMD in the non-dominant tibia

Comparison Of Body Composition Methods For The Assessment Of Body Fat In Adolescent Soccer Players

Anthropometry, dual energy x-ray absorptiometry (DXA) and air displacement plethysmography (ADP) are widely used for assessing body fat percentage (%BF). The accuracy among body composition methods in different kind of populations such as children, adults, obese persons, and athletes has been studied but there are some discrepancies between them. PURPOSE: To compare %BF assessed by DXA, ADP and anthropometry in adolescent soccer players. METHODS: %BF was assessed in ninety-two soccer players (64 males, 13.3 ± 0.5 y; 28 females, 13.3 ± 0.6 y) by anthropometry, DXA and ADP. Anthropometry measurements were registered following the recommendations of the ISAK. Anthropometry %BF was calculated using the equation proposed by Slaughter et al for adolescents. ADP %BF was calculated with 3 different formulas: (i) the general Siri equation (ADPSiri); (ii) the age- and sex-specific equation by Lohman (ADPLohman) and (iii) the age- and sex-specific equation by Silva (ADPSilva). Agreement and differences between methods were assessed by two-paired samples t tests and calculating the 95% limits of agreement. RESULTS: In the whole sample, ADPSiri ADPLohman ADPSilva and anthropometry underestimated %BF by 2.0, 6.9, 6.2, and 6.0% respectively compared to DXA (all p<0.05). The 95% limits of agreement ranged from ±5.91% to ±10.78%. Similar results dividing by sex were found. CONCLUSION: Although the 3 used methodologies have been several times described as valid for the assessment of %BF, based in our data it seems that ADP, anthropometry and DXA are not interchangeable for the assessment of %BF in adolescent soccer players

Longitudinal Effects Of Swimming On Bone Mass, Structure And Strength

PURPOSE: To investigate the changes over a swimming season in bone mineral density (BMD), bone mineral content (BMC), bone strength and bone structure in adolescent swimmers and compared them to normo-active controls (CG). METHODS: BMD and BMC were measured longitudinally (8 months) by Dual Energy X-ray Absorptiometry at the whole body, lumbar spine and non-dominant hip. Bone strength was measured at the midshaft radius and tibia with peripheral quantitative computed tomography (pQCT). Swimmers were divided into two groups; swimmers that swam and performed an extra-weight bearing sport (SWI-SPORT; n=11) and swimmers that only swam (SWI; n=23). Both groups were compared between them and to CG (n=28). ANCOVA for repeated measures x 2 (time) were performed between pre- and post-intervention to determine the effects of swimming on BMC and BMD values adjusting by change in height and subtotal lean, initial age and final Tanner stage and calcium intake for DXA values. For pQCT the same analyses were performed adjusting by change in object length, initial age and final Tanner stage. RESULTS: Eight months of swimming training had no effect on BMD or BMC, as no differences were found between SWI-PURE and CG acquisition. Nevertheless, practicing an extra-weight bearing sport in addition to swimming seemed to positively stimulate bone mass acquisition as SWI-SPORT was the only group that improved all measured skeletal sites and also a group by time interaction was found for the trochanter and total hip BMD when comparing SWI-SPORT to CG (p<0.05). Regarding pQCT measures, no group by time interactions were found for the radius. For the tibia, SWI-SPORT presented higher improvements in cortical thickness, resistance to fracture load (X-axis), and polar strain index than CG (all group by time interactions p<0.05). SWI-PURE also presented higher improvements in polar strain index when compared to CG (group by time interaction p<0.05). CONCLUSION: Swimming seems to be a neutral sport to practice regarding BMD and BMC acquisition. Nevertheless, it might entail some minor improvements in bone strength. Practicing a weight bearing sport in addition to swimming improves both bone mass acquisition and bone strength

The muscle-bone unit in adolescent swimmers

Most researchers adjust bone by lean mass when comparing swimmers with controls. This adjustment is done under the assumption that lean affects bone similarly in both groups. Nonetheless, we found that the muscle-bone association is uncoupled in swimmers, and consequently, researchers should avoid this adjustment when evaluating swimmers’ bone. Introduction: To examine the functional and structural muscle-bone unit in adolescent swimmers. Methods: Sixty-five swimmers (34 girls/31 boys) and 119 controls (51 girls/68 boys) participated in the study. Muscle cross-sectional area (MCSA), bone mineral content (BMC), and polar strength-strain index (SSIPOL) were measured in the non-dominant radius by peripheral quantitative computed tomography (pQCT). Subtotal BMC and lean mass were evaluated with dual-energy X-ray absorptiometry (DXA). Handgrip and isometric knee extension (IKE) tests were performed to determine muscle force. The effect of MCSA, lean and force on SSIPOL, and BMC were tested, and the functional and structural muscle-bone ratios of swimmers and controls were compared. Results: Both muscle size (MCSA and lean) and muscle force (handgrip and IKE) influenced BMC and SSIPOL in swimmers and controls similarly. Swimmers presented normal MCSA and lean values for their height, but when compared with controls, swimmers presented a higher amount of lean and MCSA for the same BMC or SSIPOL (structural muscle-bone unit). For the functional muscle-bone unit, different results were found for the lower and upper limbs, as no differences were found for the upper limbs, while for the lower limbs, swimmers presented higher muscle force for the same amount of BMC. Conclusions: The contradictory results regarding BMC in swimmers found in previous studies could partly be explained with the findings of the present study that reinforce the idea that swimming is not an effective sport to practice regarding bone mass and that the muscle-bone unit is different in swimmers than in controls