1)Sway Back...

On a lateral view x-ray sway back presents as a lumbar spine that curves away from the sacrum (base of spine) at L5 (lowest lumbar vertebrae). The curve is not the normal reversed "C" shape. Normally L3 is above L5 if you dropped a plum line. This puts enormous weight bearing stresses on the facets (joints) where L5 articulates with the sacrum and L4...but especially the sacrum. You must be very careful with squats, having good technique and a core as tough as nails.

2) Hyper-Lordosis :

Here the curve is shaped like a reverse "C", but is increased in it's degree of lordosis. L3 is above L5. The increased weight bearing is the on the facets but more evenly spread out over the entire lumbar spine. Still, you are more susceptible to injury and Lumbago or low back pain. Core work is essential as is perfect form when squatting.

Squats are the best exercise for a total body workout. They will even increase a bench press. But they are tough on the back. Good form and a super core are a must... then the squats will actually enhance low back strength if you build gradually.

Core work for a strong low back! KEY!
I do core at least 2x a week. Everything is done slowly. 15 reps slowly is worth 50 reps snapped off with aggression. Less risk of injury also, and that's what this is all about.
I do:
Slant board sit-ups : 15-30. Legs at right angles, raise slowly, twist elbow to, opposite knee, lower slowly!

Low back extensions. Legs straight, heels locked in, bend at the waist to a right angle. Raise slowly to just past 180 degrees. (15-25 reps ...2 sets)

Superman's : On your stomach, raise up on your elbows and toes. Back straight or ever so slightly raised. Shoulders flat, no bowing. Elbows under your shoulders. Hold the position for 20 seconds, move your toes back 3 inches and continue to hold position, move toes back another 3 inches and hold 20 seconds. If you are not quivering yet, you are not doing thwem right ;-) Hands should be in front of you together or like praying.

Reverse supermans :
On your back... raise one leg and opposite arm for 15 seconds. Switch sides. repeat 6 times per side.

Side position : Lay on your side. Feet together, lean up on your elbow. Body straight. Raise body off the ground so that all weight is born on the elbow and one foot. Hold position for 10 seconds. Lower 5 seconds. Repeat 5 times per side.

Medicine Ball (large): Get on your knees with the ball in your hands, arms extended away from you. Rotate to right angles side to side. 40 turns. Can be kind of fast here.

Put the ball on the ground. Sit facing it. Lift your heels over the ball to the other side to the ground without touching the ground. You swing your entire lower body with they feet pivoting on your butt and hands. 2 sets, 20 reps.

Lay on your back. Feet on a wall at right angles. Do a crunch, come half way down and then re-cruch. A double crunch if you will. Hands on shoulders or alongside the head. Never behind or ahold of your head. 15 reps

Hanging leg raisers : either from shoulder straps on a pull up bar or a leg raiser stand where your feet hang down. Raise the knees toward the chest, lower slowly, then raise both legs out straight to a right angle. It is key to come down to straight very slowly here. Repeat 10 to 20 times. 2 sets.

Do these in different order. Mix 'em up and keep your mind fresh and the body guessing. Shock the system by doing them in different order or before arms or back if normally done after. Do them on an off day or alone so that you get a good quality 30 minutes in there. These will protect your back. Always stretch very well on a daily basis!