Breaking down the biomechanics of the baseball swing, we must first begin in the neutral stance, just a baseball player awaits the pitch. A player’s lower torso is positioned so that the knees are slightly in a flexed position(~45 degrees), which would occur in the sagittal plane in an isometric muscle contraction. To help provide stability in the player’s stance, his/her legs would be slightly abducted just beyond shoulder width apart. This stance would put the players body in the frontal plane of motion. Due to his/her knees being in a flexed position, the players’ ankles would be in a dorsiflexed position which occurs in the sagittal plane of motion. During this phase of the batters stance, all the above mentioned muscles would be in an isometric contraction(no movement of the muscle fiber) waiting for the proper pitch to then swing.
Once the desired pitch is seen by the batter, the batter makes his/her approach to strike the ball. The power that is required to generate the most force will occur within the first movement of the frontal plane. The players legs will abduct slightly to transition the weight that was placed on the foot distal to the pitcher; this allows the player to begin to shift his/her weight so it is in a stable center of gravity. To provide this transition, the muscles of the gluteus medius (anterior and posterior) will abduct the femur(thigh bone) while simultaneously the gluteus maximus’ role is to extend the hip that is distal(far point) to the pitcher. At the same time, the knee is extending from the contraction of the quadriceps muscle. The leg promixal(closest) to the pitcher will put the quadriceps in a position that must become more flexed and decelerate the force of that leg. During this transition, the body will enter a rotational movement and the action of the torso will begin its’ transverse plane of motion.
The second power phase of the swing will occur in the transverse plane of motion as the lumbar spine enters a rotational movement powered by the muscles of the external and internal obliques. As the external is pulling from one side, the internal oblique is pulling from the opposite side. Simultaneously, as the torso is rotating, the baseball bat which was positioned behind the ear, distal to the pitcher, must make its way around. This movement, which is also occurring in the transverse plane, is powered by the posterior deltoid and latissimus dorsi. The shoulder joint that is proximal to the pitcher at this time is moving in a horizontal abducted motion and is in the transverse plane. As the baseball bat enters the midline of the body, the elbows that were in a flexed position(~90 degrees) begin to extend as the muscles of the triceps power this motion.
Putting the baseball swing into one fluid motion is a major key to a successful plate appearance. As you see, the baseball swing occurs in each of the three major planes of motion. The importance of muscle recruitment, that allows maximum power with precise accuracy, displays the difficulty of the art of hitting a baseball well.