The resistance band single leg high knee is a good exercise to strengthen the legs and glutes. This exercise improves hip mobility and helps with posture and balance. Learn more about properly executing this exercise with the video above.
Regression
To make this movement easier, have your client move closer to their anchor to reduce tension or by using a lighter resistance Slastix.
Progression
Increase the intensity of this movement by having your client move further away from their anchor, placing more tension on the Slastix.