When dealing with rotational power in baseball, there are two common movements that come to mind: throwing + hitting. Both movements require a great deal of lower body drive and power in order to transition force through the core and ultimately out of the arms/hands. Without a completely integrated, whole body effort, the output will lead to a suboptimal result and possibly injury in a high volume setting.
Rotational Power- Hitting
During the swing, there are three planes of motion that movement is taking place: rotation (transverse), abduction (frontal), and extension (sagittal). At the start of the swing, the torso moves in a clockwise direction creating stored energy (elastic energy) to ultimately bring the bat to the ball during the swing. Also, the trail leg is placing force into the ground moving in a lateral direction (abduction). Additionally, the stored energy will allow the batter to bring the barrel to the ideal location at the right angle and amount of time (longer the better). Once the movement from the trail leg has ended, the force will then be transferred forward. In order for the kinetic energy to continue, the front leg has to has come into contact with the ground to create a blocking effect. During this time, the hip extensors and external rotators manage the violent forces acting on the front leg. It’s important to understand that without adequate mobility in the hips and T-spine and ideal stability in the core to prevent a decrease in transferrable forces to the extremities, you will not have good swing mechanics. Being stable rather than mobile in the core (lumbo-pelvic region) is important due to the fact that a lot of younger athletes look to generate motion and force from the wrong places - most commonly the lower back. Unfortunately, tightness and pain are a result and even a stress fracture if the athlete continues without and structural changes.
Rotational Power - Pitching
Similar to hitting, pitching takes place in all three planes of motion. The initial phase (wind-up) is setting the stage for the force to start in the ground and begin transferring through the body (kinetic chain) and ending out of the hand. This lateral force is occuring in the frontal plane which is then transitioned to the rotational or transverse plane once the lead leg comes into contact with the ground. This transition either allows or disallows for adequate hip and shoulder separation. For younger athletes, mobility is more than likely not an issue but core stability and strength commonly is. The separation necessary to minimize forces on the arm and shoulder can only be prevented with a stable lumbar spine. Younger athletes tend to use the lumbar spine to produce more motion or force which brings the rib cage into a flared position leading to faulty mechanics of the glenohumeral joint as we mentioned in the arm care section. Once the athlete has built the ideal amount of elastic energy, he will then transition from rotational (transverse) to linear (sagittal) motion towards home plate. The front leg (as long as its stable) allows for the force that began in the wind-up phase to end out of the hands. As one can see, there is a lot going on during the pitching motion. Some of the common differences from youth to professional level players are very evident. Research suggests that these faults include:
Stride length – Youth baseball pitchers had a shorter stride length than elite pitchers
Open landing – Youth baseball pitchers landed in a more open position than elite pitchers
Land with too much Shoulder ER – Youth baseball pitchers shoulder was too far into layback early in their delivery when foot plant occurred than elite pitchers
Trunk separation – Youth baseball has less separation of their hip and shoulder than elite pitchers
Medicine ball rotation training
Rear to front leg hip shift during rotational throws:
The top photos show a correct shift of weight from the back hip to the front hip. After loading the back hip, the elastic energy produced will need to be shifted to the front hip in order to provide optimal transfer to the medball.
The bottom left photo is an example of never shifting weight to the front hip. The transfer or shift to the front leg allows for extension which generally leads to more torque and stability created from the pelvis. We often see this issue with baseball players and golfers.
The bottom right is an example of an undesired shift from the back hip to the front hip. The weight is transferred out front during the shift from the back hip to the front hip which leads to a less balanced rotation. Being that force is produced best with a strong and balanced stance, this type of hip shift will lead to less force during the swing.