Stand up straight with a towel or band around your lower back.
Position the band around your affected area and hold the ends in each hand.
To improve your extension, pull diagonally forwards and up with both of your hands, placing some tension through the band.
Simultaneously lean your lower body backwards over the band.
Oscillate the movement, pulling with the band as you lean back, and easing gently off the band as you straighten back up a little.
Repeat this movement rhythmically.