Baseball Biomechanics

As most sports that involve a racquet/bat a baseball batter’s objective is to deliver the maximum amount of energy possible at impact. This energy is then transferred to the ball, accelerating it to a high velocity (Adair, 2002). A batted ball with high velocity can result in one of at least two successful outcomes, depending on the ball's trajectory. With a lower trajectory, the result is a hard ground ball or line drive, these types of hits can more easily pass by the infielders or at least significally decrease the chance of them being successfully fielded (Adair, 2002). If the trajectory of the ball is higher, the ball can land deep in the outfield for an extra base hit or possibly go over the fence for a home run (Adair, 2002). All of these results are quite favourable for the batter.

 

The best way to hit a homerun in baseball is to hit the ball the furthest possible. There are two considerations to look out for when doing this and this is the impact of the ball and the flight of the ball. The objective for coaches and batters is to maximise the range of variables and time for which the batter has control of (Sawicki et al., 2003). This will allow for a more accuracy result and will minimise any errors.

The Importance of the Kinetic Chain in Baseball

DeRenne (1993) states that, energy is created by the batter through his utilisation of the kinetic chain (DeRenne, 1993). Linear and angular momentum are transferred from the ground up through the lower limbs, trunk, and upper limbs body (Blazevich, 2010). Each proximal segment passes momentum to the connecting distal segment, such as the upper arm to forearm to hand (Blazevich, 2010). DeRenne (1993) further states that to increase the resultant momentum, the muscles of the proximal segment provide an additional unique momentum before passing it to the next segment (DeRenne, 1993). Blazevich (2010) illustrates that in batting, the bat is gripped firmly at the hands, and the bat, in essence, becomes the final link of the kinectic chain. While the ultimate goal remains to maximise the linear and angular bat velocity, the kinetic chain theory clearly shows that each segment must do its part to contribute to the resultant bat velocity (Blazevich, 2010).

 

An important factor of the kinetic chain is the coordination, or timing pattern, of each of the links of the chain (Fortenbaugh, 2011). Maximising the velocity of each of the body segments is critical, but the transfer of momentum and energy can only be optimised if it is passed along at the right time (Fortenbaugh, 2011). Fortenbaugh (2011) states that, by transferring the energy too early or too late, the proximal segment is not travelling at its maximum velocity, reducing the total energy available to impart on the ball at contact. Further complicating the task for hitters is that incoming pitches are thrown by the pitcher with varying arm angles and speeds, creating a multitude of different potential planes of movement (Fortenbaugh, 2011).

 

Adair (2002) states that the pelvis and upper trunk motions clearly show a significant role in batting biomechanics. Fortenbaugh (2011) proposes in a study that the pelvis rotated significantly faster and had a more open angle at bat collision on inside pitches than outside pitches. A larger open pelvis rotation angle at bat collision was also associated with increased bat end velocity, illustrating its importance.

 

The arms play an important role in the kinetic chain which focuses on the actions of the lead shoulder and the trail elbow. Since both of the arms are gripping the bat, the swing is a closed chain movement. This means that both arms have to work together to move the hands along an efficient path (Blazevich, 2010).

 

The final link in the kinetic chain of batting is, of course, the bat itself. The motion of swinging the bat can be described by an axis of rotation, its rotational speed and location in space (Smith, 2001). According to Estivalet and Brisson, range is an increasing function of bat velocity, the faster a bat is swung, the greater the batted ball velocity and the farther the ball will travel (Estivalet & Brisson, 2009).

 

Fortenbaugh (2011) describes optimum bat angle in a study that the bat elevation angle at bat collision was significantly greater on high pitches than low pitches (Fortenbaugh, 2011). It is important to make solid contact with the ball to maximise ball exit velocity (Adair, 2002). When the ball is coming to contact with the bat it is important for the batter to adjust the bat’s orientation to optimise contact. This can be done by rotating their head according to track the ball. This shows that batters are focused and keep their eye on the ball and they can turn less to hit high pitches and more to hit low pitches (Fortenbaugh, 2011).

Figure 1. This diagram indicates the swing process of the batter who makes four separate perceptual/cognitive judgements about the trajectory of the pitch (Gray,2009).