Glute Bridge
What it strengthens: 
Glutes, hamstrings, lower back (the “posterior chain”)

Cassandra's Note: 
This is another one of those exercises that you can modify endlessly to accommodate everyone's needs. I love this exercise for anyone, but especially those with lower back or knee problems. I do a glute bridge variation in every one of my workouts. 

Lie on your back with your knees bent and your feet flat on the floor about hip width apart. Place your hands on the floor by your sides and away from your body a bit to give some side to side support. Press into your heels and squeeze your butt to lift your hips off the floor and into a straight line from your shoulders to your knees. Your head stays down and relaxed as the weight of your torso moves to your upper back, not your neck. Squeeze what your mama gave you (your butt) then slowly lower back down to start. 

To make harder: 
Hold at the top of the movement for longer and/or do more repetitions and/or try to get your hips as high as you can each time.