The importance of measuring body composition in professional football players: A commentary

Professional football players are not considered to be excessively fat, but there is continuous pressure made by managers, coaches and physiotherapists to monitor player’s body composition to help reach optimal performance potential. Consequently, it is not uncommon for sport scientists to assume responsibility for monitoring and managing their players’ body composition over the playing season. As body fat is one of the main factors affecting body composition, the knowledge and understanding of whole body density and how it inluences the body could be useful to quantify the effectiveness of a prescribed training programme and/ or optimal performance potential

Varijacije tijekom sezone u izokinetičkom vršnom momentu sile kod mladih nogometaša

The aim of the study was to investigate the seasonal variation in the strength of the knee flexors and extensors in highly trained youth soccer players. The players (n=16; age 16.7±0.7) were measured at the end of the competitive season, at the beginning of the off-season and during the sixth week of a new competitive season. Isokinetic concentric peak torque was measured at 60°•s-1, 180°•s-1, 360°•s-1 in a sitting position. The testing range of motion was set from 10–90° of knee flexion. Players performed a set of six maximal repetitions for both dominant and non-dominant limb. Average values of peak torque significantly changed during the observed periods. Significant differences (p<.05) between the three measurement sessions were noted with respect to the knee flexors at all angular velocities. A post-hoc test confirmed a significant increase between the first and the second measurement for flexion in both dominant (180°•s-1; p=.033) and non-dominant legs (360°•s-1; p=.004). A significant increase was also found between the first and the third session for both limbs during knee flexion at all angular velocities. The results indicate that peak torque values of knee flexors and extensors varied differently in trained youth soccer players depending on muscle group and movement velocity with statistically significant changes in knee flexors only.Cilj je ovog istraživanja bio utvrditi varijacije tijekom sezone u snazi pregibača i opružača potkoljenice vrhunskih treniranih mladih nogometaša. Igrači (n=16; dob 16,7±0,7) su testirani na kraju natjecateljske sezone, na početku prijelaznog perioda te tijekom šestog tjedna nove natjecateljske sezone. Izokinetički koncentrični vršni moment sile mjerio se pri brzinama od 60°/s, 180°/s i 360°/s u sjedećem položaju ispitanika. Opseg pokreta se tijekom testiranja kretao od 10 do 90° fleksije koljena. Igrači su izveli seriju od šest maksimalnih ponavljanja prvo dominantnom, a onda i nedominantnom nogom. Prosječne vrijednosti vršnog momenta sile značajno su se mijenjale tijekom promatranih perioda. Značajne razlike (p<0,05) u snazi pregibača potkoljenice zabilježene su između sva tri mjerenja pri sve tri brzine izveđonja. Post hoc test je također potvrdio značajno povećanje snage pregibača potkoljenice između prvoga i drugog mjerenja za dominantnu (180°/s; p=0,033) i nedominantnu (360°/s; p=0,004) nogu. Značajno povećanje vršnog momenta sile pregibača potkoljenice obje noge pri svim brzinama također je zabilježeno između drugoga i trećeg mjerenja. Rezultati pokazuju da vršni moment sile pregibača i opružača potkoljenice različito varira kod treniranih mladih nogometaša ovisno o mišićnoj grupi i brzini pokreta, sa statističkom značajnošću promjena samo za pregibače potkoljenice

Validesa i fiabilitat de les ràtios de força isocinètica per estimar

Han estat a bastament emprats diversos índexs de força isocinètica (bilateral i unilateral) del genoll per a) identificar possibles factors de risc de lesió del lligament encreuat anterior (LEA) del genoll i/o esquinços de la musculatura isquiosural; b) monitorar l’eficàcia de programes de rehabilitació, i c) determinar si un esportista pot tornar a l’entrenament i/o competició de forma segura després d’haver superat un procés de rehabilitació. Tanmateix, la precisió d’aquests índexs isocinètics per avaluar desequilibris musculars ha estat acceptada en base a coneixements teòrics i empírics i, en menor mesura, a l’evidència científica respecte al grau de validesa i fiabilitat. Per això, els objectius d’aquesta revisió bibliogràfica foren: 1) analitzar i comparar la validesa i la fiabilitat dels índexs de força bilateral i unilateral del genoll per estimar i monitorar possibles desequilibris musculars, i 2) aportar valors de referència per categoritzar la funció muscular com a normal o amb risc significatiu de lesió. Un total de 13 articles científics compliren els criteris d’inclusió i exclusió establerts inicialment. Després d’haver analitzat els estudis es pot concloure que: a) són molt escassos els treballs científics que analitzen la validesa i la fiabilitat dels índexs de força bilateral i unilateral (convencional i funcional) per identificar desequilibris musculars; b) un desequilibri bilateral menor del 10-15% i un desequilibri unilateral menor del 45-60% podrien ser un bon llindar de seguretat per reduir la probabilitat de sofrir una lesió de la musculatura isquiosural i del LEA; c) sembla que els índexs de força del genoll presenten valors moderats de fiabilitat absoluta (error estàndard de la mesura < 15%), i d) calen més estudis que abordin la determinació de la fiabilitat i la validesa dels índexs de força en diferents modalitats esportives

Training effects of the FIFA 11+ and Harmoknee on several neuromuscular parameters of physical performance measures

The main purpose of this study was to analyse the training effects of the FIFA 11+ and Harmoknee on several parameters of physical performance measures in youth amateur football players. Forty-one adolescent players were randomised within each team into two groups (team 1: control vs. FIFA 11+; team 2: control vs. Harmoknee). The FIFA 11+ and Harmoknee groups performed the program 3 times a week for 4 weeks; the control groups completed their usual warm-up routines. Thirteen physical performance measures (joint range of motion, dynamic postural control, single legged hop limb symmetry, sprint time, jumping height and agility) were assessed. All physical performance parameters were compared via a magnitude-based inference analysis. Significant between-group differences (in favour of the FIFA 11+ players) were found for dynamic postural control (anterior [2.5%] and posteromedial [7.2%] distances), single legged hop limb symmetry (side-to-side symmetry during a triple hop test [8.3%]), 10 (8.4%) and 20 (1.8%) m sprint times and jumping height (9.1%) neuromuscular outcomes. For the Harmoknee, significant differences (in comparison to its paired control group) were found only for 10 (2.7%) and 20 (2.9%) m sprint times and jumping height (9.7%). Therefore, the main findings of this study suggest exchanging traditional warm-up programmes for the FIFA 11+ in male youth soccer players based on its superior effects on some neuromuscular parameters (sprinting, jumping and stability) of physical performance

Fiabilidad absoluta de los índices convencional y funcional y momento máximo de fuerza isocinética de la flexión y extensión de rodilla

Introducción Las pruebas de valoración de fuerza isocinética son probablemente las herramientas de estimación de la función muscular más utilizadas en el ámbito físico-deportivo. Sin embargo, existe una limitada evidencia científica que justifique su uso como herramientas de precisión. Por ello, el objetivo principal de este estudio fue examinar la fiabilidad absoluta de los índices de fuerza convencional y funcional, así como de los picos o momentos máximos de fuerza (PFM) concéntricos y excéntricos de la flexión y extensión de rodilla en adultos jóvenes físicamente activos. Material y métodos Cincuenta y dos participantes completaron 3 sesiones de evaluación de los índices de fuerza convencional y funcional y PFM concéntricos y excéntricos de la flexión y extensión de rodilla, con un intervalo de 72-96h entre sesiones consecutivas. La fiabilidad absoluta intersesión fue examinada mediante el cálculo de los estadísticos cambio en la media entre sesiones de valoración expresado en términos porcentuales (CM), porcentaje del error típico (expresado como coeficiente de variación [CVET]) e índice de correlación intraclase (ICC). Resultado Pobres valores de fiabilidad absoluta se encontraron para los índices convencional (CM=0,2-0,4%; CVTE=16-18%; ICC=0,6-0,7) y funcional (CM=–2,1-0,2%; CVTE=18-20%; ICC=0,3-0,7) de la rodilla. Igualmente, moderados valores de fiabilidad absoluta (CM=–3,0-1,5%; CVTE=9-16%; ICC=0,7-0,9) fueron observados para la variable PFM independientemente del movimiento articular de la rodilla (flexión y extensión), tipo de activación muscular (concéntrica y excéntrica) y velocidad angular (60°/s y 180°/s) empleada. Conclusiones Una modificación mayor de ≈12 y de ≈17% en los valores iníciales de la variable PFM (independientemente del tipo de contracción y movimiento articular) e índices isocinéticos (convencional y funcional), respectivamente, podrían ser considerados como reales y no simplemente debidos al error de la medida. Estos valores de fiabilidad absoluta podrían ser lo suficientemente sensibles como para detectar cambios de gran magnitud, como los acontecidos tras la aplicación de programas de rehabilitación en personas lesionadas

Seasonal variation in isokinetic peak torque in youth soccer players

The aim of the study was to investigate the seasonal variation in the strength of the knee flexors and\ud extensors in highly trained youth soccer players. The players (n=16; age 16.7±0.7) were measured at the end\ud of the competitive season, at the beginning of the off-season and during the sixth week of a new competitive\ud season. Isokinetic concentric peak torque was measured at 60°·s-1, 180°·s-1, 360°·s-1 in a sitting position. The\ud testing range of motion was set from 10–90° of knee flexion. Players performed a set of six maximal repetitions\ud for both the dominant and non-dominant limb. Average values of peak torque significantly changed during\ud the observed periods. Significant differences (p<.05) between the three measurement sessions were noted\ud with respect to the knee flexors at all angular velocities. A post-hoc test confirmed a significant increase\ud between the first and the second measurement for flexion in both the dominant (180°·s-1; p=.033) and nondominant\ud legs (360°·s-1; p=.004). A significant increase was also found between the first and the third session\ud for both limbs during the knee flexion at all angular velocities. The results indicate that peak torque values\ud of knee flexors and extensors varied differently in trained youth soccer players depending on muscle group and movement velocity with statistically significant changes in knee flexors only

Active Stretching and Eccentric Length-Tension Relationship of Hamstring Muscles

The purpose of this study was to investigate the acute effect of an active lower limb stretching routine with a sports-related training load on the hamstring eccentric length-tension relationship. 49 recreational sportsmen completed three assessment sessions, an initial familiarization session and two experimental sessions (control and stretching in random order). Immediately after the interventions (stretching or control), eccentric isokinetic peak torque, maximum force angle and total work were measured in prone position. If the alteration of the eccentric length-tension relationship could be used as a primary risk factor of hamstring muscle strains, the findings of the present study tentatively suggest that static stretching would not be able to alter the relative risk of hamstring muscles

Active Stretching and Eccentric Length-Tension Relationship of Hamstring Muscles

The purpose of this study was to investigate the acute effect of an active lower limb stretching routine with a sports-related training load on the hamstring eccentric length-tension relationship. 49 recreational sportsmen completed three assessment sessions, an initial familiarization session and two experimental sessions (control and stretching in random order). Immediately after the interventions (stretching or control), eccentric isokinetic peak torque, maximum force angle and total work were measured in prone position. If the alteration of the eccentric length-tension relationship could be used as a primary risk factor of hamstring muscle strains, the findings of the present study tentatively suggest that static stretching would not be able to alter the relative risk of hamstring muscles

Efecto agudo del estiramiento activo sobre la fuerza y potencia de la flexión y extensión de rodilla Acute effect of active stretching on knee flexion and extension strength and power output

Aim To analyze the acute effect of a short duration active-static stretching protocol on maximal isokinetic strength and power output during concentric and eccentric flexion and extension knee movements in recreational athletes. Method A total of 27 males and 25 females completed three measurement sessions, an initial session of familiarization and two experimental session (control and active stretching in randomized order) with 72–96 hours interval among consecutive sessions. The active stretching protocol consisted in 5 different unilateral exercises designed to stretch the major lower limb muscle groups. Each stretching exercise was performed twice, holding the position during 30s (2 × 30s), with a rest-interval among series, contra-lateral leg and /or exercises of 20s. In the control session no stretching exercises were performed. Immediately after performed both treatments (control and stretching), the isokinetic indexes of peak torque (PT) and average power (AP) were tested during concentric and eccentric flexion and extension knee movements. Results The ANOVA analysis carried out revealed no significant interaction effect between testing sessions (control and stretching) for knee flexion and knee extension peak torque and mean power in both concentric and eccentric muscle contractions. Conclusions Short (2 × 30s per muscle group) pre-exercise active-static lower-limb stretching routine did not elicit stretching-induce reductions in knee flexor and knee extensor isokinetic concentric and eccentric strength