, 2005; Chiu et al., 2003). Tillin and Bishop (2009) suggested that PAP is able to potentially increase mechanical power as well as explosive activity and hence, performance and/or the training stimulus of that activity. To our knowledge, the effect of dynamic stretching on performance of a multiarticular sport skill, such as the soccer kick, has not been thoroughly Paclitaxel human endothelial cells investigated. The instep kick is one of the most characteristic skills of a soccer player (Amiri-Khorasani et al., 2011a,b, 2010a,b, 2009; Kellis and Katis, 2007; Kellis et al., 2006). Soccer kicks performed via a stretch-shortening cycle of the knee extensors display higher ball velocity compared to soccer kicks involving only concentric actions (Bober et al., 1987).

For this reason, research studies have focused on the role of stretch-shortening cycle of the knee extensors for a successful kick. Particularly, a soccer kick is accompanied by a stretch of the knee extensor musculature during backswing followed by instantaneous shortening during forward shank movement. Each phase, however, is accompanied by different behavior of the quadriceps components. During backswing, the thigh accelerates via a high activation of rectus femoris (Dorge et al., 1999; Sorensen et al., 1996). Forward swing is characterized by a high activation of vastus lateralis which then decreases when the shank starts to decelerate (Dorge et al., 1999; Sorensen et al., 1996). It seems, therefore, that evaluation of only one component of the quadriceps muscle cannot fully describe the role of the whole muscle group during the soccer kick.

In previous experiments, Amiri-Khorasani et al. (2010a) reported that maximum ball speed and vastus medialis electromyographic (EMG) activation during soccer instep kicking increased more after dynamic rather than static stretching. However, in this study the experimental groupconsisted only of six subjects and EMG activation of only vastus medialis was analyzed. It is not clear whether this reflects the whole quadriceps muscle or the effects of stretching are muscle-dependent. Since some of the quadriceps are mono-articular (vastii muscles) while others are bi-articular (rectus femoris) then it would be interesting to examine whether dynamic stretching affects activation of only some parts of the quadriceps and whether this differs from static stretching effects.

Therefore, the purpose of the present study was to investigate the acute effects of dynamic and static stretching on vastus medialis (VM), Carfilzomib vastus lateralis (VL) and rectus femoris (RF) activation during maximal instep soccer kicks. We hypothesized that dynamic stretching would cause a higher increase in quadriceps muscle activation compared to that observed after static stretching. Material and Methods Participants Twelve male college soccer players (mean �� SD: body height: 180.08 �� 4.16 cm; body mass: 78.16 �� 4.44 kg; age: 19.16 �� 0.