There is a major focus on glute and hip strength, core strength, and single leg stability.
In the Rut training plan you have, you will see on either Tuesdays, Wednesdays or Thursdays (depending on the week), that there's recommendations for supplemental core/hip/glute stability work. This is the day of the week to do one of the workouts in this plan.
This plan is a supplemental strength plan only.