DIVE BIOMECHANICS

In an article published together with Leandro Cortizo in the Revista de Entrenamiento Deportivo (Spain), we analyzed the biomechanics of diving.

We described the biomechanics of takeoff from the set position (Figure 1a), assuming that covering the distance to reach the ball requires only one step, the approach step, before taking off. The leg closest to the ball (the attack leg) is the one that provides the greatest thrust in moving the Goalkeeper towards the ball, raising the center of gravity.

In performing the approach step, the torso and the body’s center of gravity move down and laterally (Figure 1b), loading the weight of the body on the attack leg. The muscles and tendons of the leg (gastrocnemius, soleus, Achilles tendon, quadriceps and its tendon, patellar tendon, hamstrings and gluteus maximus) tense, storing elastic energy that is released on takeoff. By pointing the foot in the direction of the dive, both the traction produced by the contraction of the Achilles tendon muscle group (plantar flexion) and the leg extension produced by the quadriceps muscle are aligned in the vertical plane of the dive, avoiding the dissipation of energy in the force components that would occur if the foot pointed in another direction.

When the Goalkeeper accelerates vertically and laterally (Figure 1c), the three laws of Newton described in a previous note come into play. To break the inertia of the relatively static set position (Newton’s 1st Law) and initiate the dive, the foot of the attack leg exerts a force (F= m x a) on the ground, which pushes back with an equal force in the opposite direction (Newton’s 3rd Law), and the change in movement would be proportional to the force acting on the ground (Newton’s 2nd Law). As body mass is constant, the change of movement depends on the acceleration generated.

As we noted in a previous article, the Goalkeeper’s body acts as a kinematic chain, in which the accelerations in different joints of the body (ankle, knee, hip, back, shoulder and elbow) generate total momentum. Therefore, the actions of the muscles and tendons that extend the back and propel the hands and arms directly towards the ball are important in increasing the general thrust of the body and the distance traveled in the expected direction.

In future notes on biomechanics we will analyze other specific actions of the Goalkeeper.

Reference

Vizcaíno, S.F. & Cortizo, L.H. (2017). Análisis biomecánico cualitativo del vuelo del portero de fútbol. RED 37(2): 1-8