The role of aerobic fitness on session rating of perceived exertion in futsal players

Purpose: The aim of this study was to verify the influence of aerobic fitness (VO(2)max) on internal training loads, as measured by the session rating of perceived exertion (session-RPE) method. Methods: Nine male professional outfield futsal players were monitored for 4 wk of the in-season period with regards to the weekly accumulated session-RPE, while participating in the same training sessions. Single-session-RPE was obtained from the product of a 10-point RPE scale and the duration of exercise. Maximal oxygen consumption was determined during an incremental treadmill test. Results: The average training load throughout the 4 wk period varied between 2,876 and 5,035 arbitrary units. Technical-tactical sessions were the predominant source of loading. There was a significant correlation between VO(2)max (59.6 +/- 2.5 mL.kg(-1).min(-1)) and overall training load accumulated over the total period (r = -0.75). Conclusions: The VO(2)max plays a key role in determining the magnitude of an individual's perceived exertion during futsal training sessions.

Leg preference and interlateral asymmetry of balance stability in soccer players

To examine the effect of long lasting practice on pedal behavior in sport, we compared experienced adult soccer players and nonsoccer players on leg preference in motor tasks requiring general mobilization, soccer related mobilization, and body balance stabilization. We also evaluated performance asymmetry between the right and left legs in static and dynamic unipedal body balance based on center of pressure displacement, and correlated that with kg preference in balance stabilization tasks. Results revealed (a) a distinct leg preference between mobilization and stabilization tasks, which were significantly different between Mayers and nonplayers, (b) similar balance stability between the right and left legs, (c) greater stability of experienced players compared with nonplayers in static and dynamic balance, and (d) absence of a significant kg preference correlation with interlateral balance asymmetry. These results suggest an effect of extensive soccer skill practice on establishing leg preference for specific mobilization tasks and overall balance control.

Salivary immunoglobulin a responses in professional top-level futsal players

Moreira, A, Arsati, F, de Oliveira Lima-Arsati, YB, de Freitas, CG, and de Araujo, VC. Salivary immunoglobulin a responses in professional top-level futsal players. J Strength Cond Res 25(7): 1932-1936, 2011-The purpose of this study was to investigate the responses of salivary immunoglobulin A (SIgA) in 10 professional top-level Brazilian futsal players after 2 highly competitive games separated by 7 days. Unstimulated saliva was collected over a 5-minute period at PRE- and POST-match. The SIgA was measured by an enzyme-linked immunosorbent assay and expressed as the absolute concentration (SIgAabs) and secretion rate of IgA (SIgArate). Rate of perceived exertion and heart rate were used to monitor the exercise intensity. A 2-way analysis of variance with repeated measures showed nonsignificant differences between matches to SIgAabs, SIgArate, and saliva flow rate (p > 0.05). However, significant time differences were observed for all these parameters. In summary, we showed that a competitive training match induced a decrease in SIgA levels in top-level futsal players, which suggests an increment of the vulnerability to infections meditated by the training stimulus. This decrease suggests that the athletes were at an increased risk of developing an upper respiratory tract infection, and therefore, it could be necessary to take protective actions to minimize contact with cold viruses or even reduce the training load for athletes.

Hematological parameters and anaerobic threshold in Brazilian soccer players throughout a training program

We assessed the responses of hematological parameters and their relationship to the anaerobic threshold of Brazilian soccer players during a training program. Twelve athletes were evaluated at the beginning (week 0, T1), in the middle (week 6, T2), and at the end (week 12, T3) of the soccer training program. On the first day at 7:30 AM, before collecting the blood sample at rest for the determination of the hematological parameters, the athletes were conducted to the anthropometric evaluation. On the second day at 8:30 AM, the athletes had their anaerobic threshold measured. Analysis of variance with Newman-Keuls`post hoc was used for statistical comparisons between the parameters measured during the soccer training program. Correlations between the parameters analyzed were determined using the Pearson`s correlation coefficient. Erythrocytes concentration, hemoglobin, and hematocrit were significantly increased from T1 to T2. The specific soccer training program led to a rise in erythrocytes, hemoglobin, and hematocrit from T1 to T2. We assumed that these results occurred due to the plasma volume reduction and may be explained by the soccer training program characteristics. Furthermore, we did not observe any correlation between the anaerobic threshold and the hematological parameters.

Mild head injury and speed of information processing: A prospective study of professional rugby league players

The sensitivity of several short tests of speed of information processing to the effects of mild head injury in rugby league football was investigated. The measures used were the Symbol Digit Modalities Test, the Digit Symbol Substitution Test, and the Speed of Comprehension Test. Two studies were conducted, the first to examine the effect of practice, the second to determine sensitivity to cognitive impairment immediately following injury. The first study established alternate form equivalence and demonstrated that performance on the Speed of Comprehension and Digit Symbol Substitution tests improved with practice, whereas the Symbol Digit Modalities test remained stable. A second study of 10 players who subsequently sustained mild head injuries showed that measures of speed of information processing were sensitive to impairment in the postacute phase, whereas an untimed task of word recognition (Spot-the-Word) was not. Speed of Comprehension was more sensitive to postinjury impairment than either the Digit Symbol Substitution or Symbol Digit Modalities tests. A repeated baseline assessment before injury using the higher score to reflect a player's potential, allowed measurement of impaired performance on sensitive tests.

Dynamic peripheral visual performance relates to alpha activity in soccer players

Many studies have demonstrated the relationship between the alpha activity and the central visual ability, in which the visual ability is usually assessed through static stimuli. Besides static circumstance, however in the real environment there are often dynamic changes and the peripheral visual ability in a dynamic environment (i.e., dynamic peripheral visual ability) is important for all people. So far, no work has reported whether there is a relationship between the dynamic peripheral visual ability and the alpha activity. Thus, the objective of this study was to investigate their relationship. Sixty-two soccer players performed a newly designed peripheral vision task in which the visual stimuli were dynamic, while their EEG signals were recorded from Cz, O1, and O2 locations. The relationship between the dynamic peripheral visual performance and the alpha activity was examined by the percentage-bend correlation test. The results indicated no significant correlation between the dynamic peripheral visual performance and the alpha amplitudes in the eyes-open and eyes-closed resting condition. However, it was not the case for the alpha activity during the peripheral vision task: the dynamic peripheral visual performance showed significant positive inter-individual correlations with the amplitudes in the alpha band (8-12 Hz) and the individual alpha band (IAB) during the peripheral vision task. A potential application of this finding is to improve the dynamic peripheral visual performance by up-regulating alpha activity using neuromodulation techniques.

Risk of hepatitis C among brazilian ex-soccer players

In order to evaluate the significance of injecting vitamins complexes and stimulants minutes before soccer games and its role in spread of hepatitis C virus (HCV) we interviewed and tested 40 ex-soccer players, who played professionally in Mato Grosso, Brazil, between 1970 and 1989. Five players were found anti-HCV positive with enzyme-immunoassay. When re-tested by imunoblot (RIBA), three of these five were confirmed to be positive reacting. The anti-HCV positivity (7.5%) was higher than usually found among blood donors (0.9%) in this region (p < 0.01). None of the players had had prior history of any risk factor that might indicate HCV exposure. We suggest that the common practice of soccer players in the inner part of Brazil in the 70's and 80's, to receive fortifying injections, often with shared syringes, may place ex-soccer players in a potencial risk group for HCV infection and warrants further investigation and attention by public health workers.

Repeated sprinting on natural grass impairs vertical stiffness but does not alter plantar loading in soccer players.

This study aimed to determine changes in spring-mass model (SMM) characteristics, plantar pressures, and muscle activity induced by the repetition of sprints in soccer-specific conditions; i.e., on natural grass with soccer shoes. Thirteen soccer players performed 6 × 20 m sprints interspersed with 20 s of passive recovery. Plantar pressure distribution was recorded via an insole pressure recorder device divided into nine areas for analysis. Stride temporal parameters allowed to estimate SMM characteristics. Surface electromyographic activity was monitored for vastus lateralis, rectus femoris, and biceps femoris muscles. Sprint time, contact time, and total stride duration lengthened from the first to the last repetition (+6.7, +12.9, and +9.3%; all P < 0.05), while flight time, swing time, and stride length remained constant. Stride frequency decrease across repetitions approached significance (-6.8%; P = 0.07). No main effect of the sprint number or any significant interaction between sprint number and foot region was found for maximal force, mean force, peak pressure and mean pressure (all P > 0.05). Center of mass vertical displacement increased (P < 0.01) with time, together with unchanged (both P > 0.05) peak vertical force and leg compression. Vertical stiffness decreased (-15.9%; P < 0.05) across trials, whereas leg stiffness changes were not significant (-5.9%; P > 0.05). Changes in root mean square activity of the three tested muscles over sprint repetitions were not significant. Although repeated sprinting on natural grass with players wearing soccer boots impairs their leg-spring behavior (vertical stiffness), there is no substantial concomitant alterations in muscle activation levels or plantar pressure patterns.

Neuro-mechanical and metabolic adjustments to the repeated anaerobic sprint test in professional football players.

PURPOSE: This study aimed to determine the neuro-mechanical and metabolic adjustments in the lower limbs induced by the running anaerobic sprint test (the so-called RAST). METHODS: Eight professional football players performed 6 × 35 m sprints interspersed with 10 s of active recovery on artificial turf with their football shoes. Sprinting mechanics (plantar pressure insoles), root mean square activity of the vastus lateralis (VL), rectus femoris (RF), and biceps femoris (BF) muscles (surface electromyography, EMG) and VL muscle oxygenation (near-infrared spectroscopy) were monitored continuously. RESULTS: Sprint time, contact time and total stride duration increased from the first to the last repetition (+17.4, +20.0 and +16.6 %; all P < 0.05), while flight time and stride length remained constant. Stride frequency (-13.9 %; P < 0.001) and vertical stiffness decreased (-27.2 %; P < 0.001) across trials. Root mean square EMG activities of RF and BF (-18.7 and -18.1 %; P < 0.01 and 0.001, respectively), but not VL (-1.2 %; P > 0.05), decreased over sprint repetitions and were correlated with the increase in running time (r = -0.82 and -0.90; both P < 0.05). Together with a better maintenance of RF and BF muscles activation levels over sprint repetitions, players with a better repeated-sprint performance (lower cumulated times) also displayed faster muscle de- (during sprints) and re-oxygenation (during recovery) rates (r = -0.74 and -0.84; P < 0.05 and 0.01, respectively). CONCLUSION: The repeated anaerobic sprint test leads to substantial alterations in stride mechanics and leg-spring behaviour. Our results also strengthen the link between repeated-sprint ability and the change in neuromuscular activation as well as in muscle de- and re-oxygenation rates.

Dynamic Criteria: a Longitudinal Analysis of Professional Basketball Players" Outcomes

This paper describes the fluctuations of temporal criteria dynamics in the context of professional sport. Specifically, we try to verify the underlying deterministic patterns in the outcomes of professional basketball players. We use a longitudinal approach based on the analysis of the outcomes of 94 basketball players over ten years, covering practically players" entire career development. Time series were analyzed with techniques derived from nonlinear dynamical systems theory. These techniques analyze the underlying patterns in outcomes without previous shape assumptions (linear or nonlinear). These techniques are capable of detecting an intermediate situation between randomness and determinism, called chaos. So they are very useful for the study of dynamic criteria in organizations. We have found most players (88.30%) have a deterministic pattern in their outcomes, and most cases are chaotic (81.92%). Players with chaotic patterns have higher outcomes than players with linear patterns. Moreover, players with power forward and center positions achieve better results than other players. The high number of chaotic patterns found suggests caution when appraising individual outcomes, when coaches try to find the appropriate combination of players to design a competitive team, and other personnel decisions. Management efforts must be made to assume this uncertainty.

A comparison of injuries among children and adult football (soccer) players

Football is a universal and an affordable game but we need to minimize the incidence of accidents among the increasing number of young football players. Our 11 year retrospective epidemiological study (1990-2000) of football injuries in children (N= 1000) was compared with those of adult players in the 2006 European Championship. This comparative study confirmed that the anatomical, biomechanical and biological conditions differ between adults and children and that they warrant particular attention to protect the latter vulnerable group against bone avulsions, overuse pathologies and fatigue-fractures. Injuries were shown to increase significantly with age up to 16 years (P=0.005). Children suffer mainly from contusions, fractures and sprain injuries. Head injuries were more common in boys (P=0.070), while girls were more prone to sprains. The types of injuries differ between adults and children (sprain versus fractures), the anatomical location of injuries is different (lower limbs in adults, lower and upper limbs in children), the circumstances of the injuries are different (contact in adults versus non-contact in children), and teenage girls have different types of injuries than teenage boys. An increased incidence of injuries is due to changes in the position of the center of gravity and in the morphotype during rapid growth. For these reasons it is mandatory to adapt the training to the age and sex of the players. It is unsafe to train children the same way as adults. The height, the weight and the speed of growth must be taken into account by the multidisciplinary team when organising the training programmes. -- Le football fait partie des sports les plus pratiqués au monde en raison de sa popularité et de son accessibilité économ ique. L'incidence des blessures liées à cette pratique doit être diminuée surtout chez les jeunes joueurs en raison de la croissance exponentielle du nombre de joueurs féminins et masculins. Une étude épidémiologique rétrospective sur 11 ans (1990-2000) a été réalisée chez les enfants victimes de blessures liées au football (N==1000), puis a été comparée aux données recueillies de l'UEFA lors d'un Championnat Européen en 2006 sur les lésions des joueurs adultes. Cette étude comparative confirme que les structures anatomiques, biologiques et les tensions biomécaniques chez l'enfant diffèrent de celles de l'adulte. Les enfants ont un risque plus élevé de souffrir d'avulsion osseuse et de fractures de fatigue que les adultes. Les blessures augmentent significativement avec l'âge jusqu'à 16 ans (P==0,005). Les traumatismes crâniens sont plus fréquents chez les garçons tandis que les entorses sont plus à risque chez les filles. Les adultes font plus souvent des entorses tandis que les enfants font plus de fractures. La localisation anatomique diffère également entre ces deux groupes (les membres inférieurs chez l'adulte et les membres inférieurs et supérieurs chez l'enfant). La circonstance des blessures diffère également (choc avec un autre joueur chez l'adulte et des blessures sans contact chez l'enfant). Chez les adolescents, les blessures des filles diffèrent de celles des garçons. L'augmentation chez les enfants de cette incidence est liée au déplacement lors de la croissance du centre de gravité, avec une maladresse accrue lors des phases de croissance. Pour toutes ces raisons, il est justifié d'adapter les entraînements de football en fonction de l'âge, du sexe et du morphotype. L'entrainement des enfants doit être différent de celui des adultes. Le poids, la taille et la vitesse de croissance doit être prise en compte dans des structures multidisciplinaires afin de permettre une meilleure longévité sportive des jeunes joueurs de football.

Effects of Plyometric and Resistance Training on Muscle Strength and Neuromuscular Function in Young Adolescent Soccer Players

This study examined the effect of 8-weeks of resistance (RT) and plyometric (PLYO) training on maximal strength, power and jump performance compared with no added training (CON), in young male soccer players. Forty-one 11-13 year-old soccer players were divided into three groups (RT, PLYO, CON). All participants completed 5 isometric knee extensions at 90° and 5 isokinetic knee extensions at 240°/s pre- and post-training. Peak torque (PT), peak rate of torque development (pRTD), electromechanical-day (EMD), rate of muscle activation (Q30), muscle cross-sectional area (mCSA) and jump performance were examined. Both RT and PLYO resulted in significant (p < 0.05) increases in PT, pRTD and jump performance. RT resulted in significantly greater increases in both isometric and isokinetic PT, while PLYO resulted in significantly greater increases in isometric pRTD and jump performance compared with CON (p < 0.05). Q30 increased to a greater extent in PLYO (20%) compared with RT (5%) and CON (-5%) (p = 0.1). In conclusion, 8-weeks of RT and PLYO resulted in significant improvements in muscle strength and jump performance. RT appears to be more effective at eliciting increases in maximal strength while PLYO appears to enhance explosive strength, mediated by possible increases in the rate of muscle activation.

Adaptation and validation in Spanish of the Group Environment Questionnaire (GEQ) with professional football players

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How soccer players head the ball: a test of optic acceleration cancellation theory with virtual reality

We measured the movements of soccer players heading a football in a fully immersive virtual reality environment. In mid-flight the ball’s trajectory was altered from its normal quasi-parabolic path to a linear one, producing a jump in the rate of change of the angle of elevation of gaze (α) from player to ball. One reaction time later the players adjusted their speed so that the rate of change of α increased when it had been reduced and reduced it when it had been increased. Since the result of the player’s movement was to regain a value of the rate of change close to that before the disturbance, the data suggest that the players have an expectation of, and memory for, the pattern that the rate of change of α will follow during the flight. The results support the general claim that players intercepting balls use servo control strategies and are consistent with the particular claim of Optic Acceleration Cancellation theory that the servo strategy is to allow α to increase at a steadily decreasing rate.