Many of you will be familiar with this classic home exercise.

Have a sore knee? Do it.

Have a bad back? Do it.

Have a sprained ankle? Do it.

Reasons why it’s so good:

Minimal equipment required - a rubber band
MInimal space required - you need maybe 3 x 3 feet area
Weight-bearing, closed kinetic chain, for stability / balance
Resisted, open kinetic chain, for hip / spinal dissociation
Posterior chain, anterior chain. lateral chain, spiral chain muscle groups - true core (abs, but also the muscles that anchor the abs)

Instructions:

Anchor the theraband from a low point, perhaps wrapping it around a table leg. The other end will be looped around your ankle. You can also use a pulley machine with an ankle strap at the gym.
There will be 4 standing body orientations - “4 points of a compass” - facing the anchor (North); 90 degrees clockwise (East); facing away from anchor (South); add another 90 degree turn (West).
Your challenge is to maintain balance while standing upright, without arching or flattening your spine, and not rotating through your pelvis, while pushing against the resistance of the band.

x3 - 4 sets for each Left and Right (so x6 - 8 sets total)

10 - 20 repetitions each direction (N-E-S-W)

10 - 20 second break between positions

20 - 60 second break between left and right positions

NORTH

EAST

Now, the problem with using the N-E-S-W system is that this exercise is done on Right AND Left leg. Our subject in the photos (Mr. Christian Kubas deserves praise for volunteering to model, thank you very much) has switched his standing leg, so beware the legs are switched in the photo. Below is a description to keep with the compass theme, NOT to match the photos.
So, for this tutorial, we will imagine you are standing on your Left leg, and the Right ankle has a theraband around it. When you switch the side of the theraband, obviously you will be working different muscle groups even though you are standing in the exact same orientation.
So, the theraband is anchored to the right and around the Right ankle. Push the Right leg away (band in front of or behind your left leg, feel free to mix it up), using your outer hip, and return to outer position.
AVOID: leaning upper body towards the anchor

SOUTH

Facing away from the anchor, use your quadriceps and hip flexors to straighten the leg in front of you
AVOID: do not lean forwards or backwards

WEST

Continuing with the example of standing on your Left and band attached on your Right, the theraband will now be anchored to the right . Using your inner thigh, pull the right leg inwards (in front of, or behind your standing leg - mix it up!), and slowly return to start position.
AVOID: leaning sideways; don’t drop one side of your pelvis, stay strong on your standing leg

PROGRESSIONS:

This exercise is also great because it is simple to add challenges:

Hips Don't Lie - They Like to Work It