Definitions of terms that you will find in the Blog Post below

External rotation: Lateral rotation Biomechanics The act of turning about an axis passing through the center of the leg; ER of the leg occurs with closed chain supination; the talus acts as an extension of the leg in frontal and transverse planes.
Rotation: The process of turning around an axis. In obstetrics, the turning of the fetal head (or presenting part) for proper orientation to the pelvic axis.
Bat Lag:
Flexion: The bending of a joint between two skeletal members to decrease the angle between the members; opposite of extension.
Extension: The movement of a limb to increase the angle of the joint. Some joints (at the wrist, in the neck) are able to hyperextend.
Force: The energy or power; that which originates or arrests motion.
Ground Reaction Force: Refers generically to any force exerted by the ground on a body in contact with it.
Center of Pressure: Is the point on a body where the total sum of a pressure field acts, causing a force and no momentum about that point.
Center of Mass: Is the mean location of all the mass in a system. In the case of a rigid body, the position of the center of mass is fixed in relation to the body.
Momentum: Is the product of the mass and velocity of an object (p = mv).
Dynamic Balance: The ability to maintain and distribute balance evenly (refers to your stance).
Absorption of Force: The ability to absorb that force in a short amount of time (or impulse) is important in being elastic and loading the tendon for increase power output. If the athlete does not possess the strength to absorb the force in a short impulse time then they may have to flex deeper into the movement, thus increasing the risk of poor compensation patterns and injury.
Axis of Trunk: Sagittal motion.
Sagittal Plane: Is a vertical plane which passes from front to rear dividing the body into right and left sections.
Median Plane or Mid-Sagittal Plane: Sometimes used to describe the sagittal plane running through the midline. This plane cuts the body into halves (assuming bilateral symmetry),[1] passing through midline structures such as the navel and spine. It is one of the lines defining the right upper quadrant of the human abdomen.
Exertion: Is a concept describing the use of physical or perceived energy. It normally connotates a strenuous or costly effort related to physical, muscular, philosophical actions and work.