Soccer has in its composition many movements that end up imposing a power asymmetry between the lower limbs (mmii), may be kicking, passing, movement, etc. (MAGALHÃES et al., 2004). Athletes always opt for a leg to get this overhead (FOUSEKIS et al., 2010).
Efficient practices for cardiorespiratory fitness, motor coordination, and improvement of physical abilities such as speed, muscle strength, power. However, soccer in his practice professionally, due to repetitive movements daily, can cause increased risk of injuries caused influenced by asymmetry (GRACE et al., 1984).
Based on what was mentioned above, some authors aimed to evaluate the possibility of muscle asymmetry and there is disagreement on this issue. Forsekis et al. (2010), Rahnama et al. (2005) and Capranica et al. (1992) found asymmetry, while Magalhães et al. (2004), Mognoni et al. (1994) and Bennell et al. (1998) found no significant differences between the lower limbs.
Thus, what may indicate the reason for the existence or not of muscular asymmetry in soccer are the actions imposed by the athlete’s position in the field (WEBER et al., 2010).
Carmo et al. (2013) evaluated 164 professional soccer players in preseason evaluating the strength and fatigue index of knee extensor and flexor separated by position. The authors found no significant differences comparing the positions in any of the variables, suggesting not affect the athlete’s action at stake if the training is similar. Magalhães et al. (2010) and Goulart et al. (2007) obtained similar results before.
Another important result from this study was that the athletes had a lower imbalance to 10%, suggesting a lower risk of muscle injury (Read about the muscle imbalance assessment methods and understand).
Tourny-Chollet et al. (2000), comparing the bilateral deficit between positions, found major differences between midfielders and attackers compared to the defenders. The study included only 21 athletes and were divided into defenders, midfielders and attackers which may have influenced the results.
Knee flexors typically have higher fatigue indices compared to knee extensors (CARMO et al., 2013). The factor that can explain this is the highest proportion of type II fibers in the knee flexors, which are less resistant, while the quadriceps is predominantly the existence of type I fibers, characterized by having greater resistance (GARRET, 1984).
The high hamstring index can explain the higher incidence of lesions in this region in the second half of departure, while the incidence is much lower than in the quadriceps (EKSTRAND et al., 2011; FOUSEKIS et al., 2011).
Apparently the training routine has greater influence on the asymmetry in the power of soccer players than the function that the athlete has in matches.