Soccer

Rules of the Game

• Objective of the game: To win the game by outscoring your opponent, which is achieved by hitting the ball into the opponent’s goal

• Game lasts for 90 minutes; divided into two 45-minute halves

• Eleven players on the field—10 field players and one goalkeeper

• The ball cannot be played by the hands (except goalkeeper), but all other surfaces of the body can be used.

• Rules protect against rough play—there are direct and indirect fouls.

  • Direct fouls include kicking the opponent, tackling from behind, using hands, and pushing.

  • Indirect fouls include offside, obstruction, and certain unintentional fouls.

  • Offside rule: must have two players between an offensive player and the goal; this often includes the goalkeeper

• Required equipment: Ball, uniforms, and goalposts; most leagues require shin guards

• There are different methods of putting the ball back in play when it goes out of touch (out of bounds):

  • Throw in: when the ball goes out over the sideline

  • Goal kick: when the ball goes out over the endline, last touched by an offensive player; kicked in from the goal box by the defensive team

  • Corner kick: when the ball goes out over the endline, last touched by a defensive player; kicked in from the field corner by the offensive team

Sport-Specific Demands and Skills

• Physical demands: Players engage in discontinuous, high-output activity that involves aerobic and anaerobic metabolism.

  • At the elite level, players typically cover 8–10 km during a game, making soccer an endurance sport. Two-thirds of this distance is spent in low-intensity activity such as walking and jogging.

  • The aerobic system is heavily involved, with heart rates around 85% of the maximum rate and oxygen demand about 70% of maximum oxygen uptake ( $\dot{V}$ O ₂ max).

• Strength demands: High demand on trunk and lower extremities. Most skills require balancing on one leg, which emphasizes lower extremity strength and proprioception.

• Soccer-specific skills: Various surfaces of the lower extremity are used to strike or control the ball and tackle, thus putting various structures at risk.

  • Inside of foot pass/block tackle: Foot and hip externally rotated, knee flexed, foot “locked” in dorsiflexion ( Fig. 67.1 ). Results in significant valgus stress at the knee, which may be associated with traumatic injury such as a sprain of the medial collateral ligament (MCL).

    

  • Outside of foot pass/shot: Internal rotation of the leg, foot in inversion, plantarflexion. Results in increased risk of forceful inversion plantarflexion injuries, mid/forefoot injuries, ligament sprains, and peroneal tendon problems (see Fig. 67.1 ). In younger athletes, this may lead to apophysitis or avulsion fractures.

  • Instep of foot: Extreme plantarflexion in “locked” foot, hip flexors, quadriceps, rectus, and hamstrings (see Fig. 67.1 ); ball velocity at release is between 17 and 28 meters/second.

  • In the approach and ball strike phase of an instep kick, a varus torque of >200 newton meters (Nm) and extension torque of >280 Nm is generated on the proximal tibia.

  • A total of 2000 Nm is generated during a soccer kick. Only 15% is transferred to the ball; the remainder is absorbed by the eccentric contraction of the hamstrings.

  • Heading: Purposeful, forceful striking of the ball with a player’s head to control, clear, or redirect on goal; increases the risk of head and neck injuries because of player contact (head to head or other body part, or head to goal post or ground) that occurs while fighting for possession in the air (see Fig. 67.1 )

  • Appropriate technique is important in all skills to avoid and decrease injuries.

Factors Affecting Performance and Recovery