X-Factor refers to the separation between the hips and shoulders during a rotational movement. X-Factor can refer to separation over the full swing movement, but often the most important portion is just prior to the rotation (also known as Peak X-Factor), since this is when the athlete creates separation to transfer motion from one segment to the next. Increasing Peak X-Factor provides more range to twist through, potentially allowing for higher rotational speeds.
Some of the factors that can influence a hitter’s X-Factor include:
Their kinematic sequencing. If the athlete does not rotate their hips before their shoulders, they will likely have less separation between these two segments relative to if they rotated their hips first.
Their relaxation during the mid-phase of a swing. If a batter is very “tense”, they are likely excessively co-contracting their trunk musculature. This co-contraction will make it difficult for the batter to create a larger X-Factor, and will negatively impact their swing or pitch sequencing and velocity.
Their strength and mobility. Some batters may need to address their strength or mobility in the gym in order to increase their X-Factor.
The solid line(s) on each graph represents the value of that metric (e.g. pelvis velocity or X-factor) across all swings in the report. The shaded band on each side of that line represents the standard deviation, which is a good indicator of variability between each swing. Click here to read more about movement variability in general, with more detailed examples.