Note, I'm not selling anything in this post. I am going to recommend a book at the end, but the advice on taking care of your lower back will cost you nothing unless you don't own a tennis ball. In that case, I am going to suggest you buy one somewhere. If you have lower back pain or sciatica and have never tried the two stretches recommended here, there's a halfway decent chance you'll find significant relief today!
I've done a lot of research on this because both my parents had bad backs, and I've had problems since I was in my 20's. Worse, My wife had two years worth of sciatica. We tried everything. We bought back programs, and we saw two different chiropractors and two different muscle therapists. We paid for treatments from a really impressive machine that gave my wife the equivalent of traction.
Most of the things we tried helped some. The problem was that she had a ruptured disk that was directly on one of the nerves that becomes part of the sciatic nerve. She ended up needing surgery to remove the debris from the blown disk. (We were thrilled to get Dr. Kevin Foley and his "minimally invasive" surgery. It seemed miraculous.)
Despite the fact that she needed surgery, we learned a lot along the way. I also took up long distance running as a 40-year-old so that I had my own sciatica and knee issues. The stretches I'm recommending here have a long history of being effective not just on me but on friends.
The Iliopsoas Muscle and the Psoas Major
Almost unbelievably, we have a muscle that anchors on the bottom six vertebrae of our spine. Yeah, really! Here's a picture of it!
From Wikimedia Commons, public domain
That's the psoas major. It is one head of the iliopsoas muscle. The other head attaches to the inside of the pelvis, which isn't so bad.
The psoas major is the reason you've been told not to do situps with your legs straight. In fact, nowadays most trainers don't recommend situps at all, just crunches. When you do a crunch, you lift just your shoulders off the ground and tighten your ab muscles. As soon as you lift your lower back off the ground, you engage the psoas major and yank right on the bottom of your spinal column!
That's not too bad with your legs bent, as the angle is better. With your legs straight, however, you have terrible leverage and your psoas major is mostly just compressing your disks, not lifting.
The other problem with the psoas major affects office workers or those who drive a lot. You can probably tell from the picture that if you sit down you are going to greatly shorten the muscle. That's not a problem until you stand back up. If you sit most of the time, when you stand back up the psoas major is going to be tight and feel like it's being stretched. As a result, it will squeeze those six vertebrae together, compressing the disks between them. That can lead to both a sore lower back and to nerve pain.
So here's how you stretch the psoas major:
The piriformis muscle helps rotate your leg. It runs from your tailbone to your femur at the hip. It is buried under your gluteus maximus, so it is very difficult to "palpate" (i.e., touch). In other words, you can't massage it. You can't really massage the psoas major, mentioned above, either. That's part of the reason they give so many problems.
I am going to tell you how to get a little bit of massage on the piriformis below, though.
The problem with the piriformis is that it sits directly on the sciatic nerve. If it gets tight and sore, it can press on the nerve and give you sciatica, which is shooting pains down your leg and sometimes numbness. In some people the sciatic nerve even goes right through the piriformis. (And some people don't have one!!!)
The piriformis can get irritated in anyone. Runners typically have problems with it. I'd imagine bike riders do, too.
I'm going to show you how to stretch it, and then how to massage it.
First, the stretch:
The stretch is simple enough, but I had somewhat minor sciatic pain from my piriformis for years in my late 30's. When someone showed me this stretch it was such a relief I almost cried for joy.
You can also massage the piriformis by sitting on a tennis ball on the floor. Massage therapists say that the piriformis basically runs right where the middle of your back pocket would fall when you're wearing jeans (assuming you're not "sagging").
You don't need to move around a lot. Find the sore spots and just put as much pressure as you can COMFORTABLY stand. Don't make it horribly painful. It's amazing how such "acupressure" relaxes the muscle.
You may find there's a lot of sore spots around your bottom and hips that are helped by such pressure.
WARNING: Just be very careful to sit where muscle is on the ball, not bone. It's really just your tailbone, the top of your femur (your hip joint), and the bottom of your pelvis that you need to avoid. Those are not hard to find.
Ok, I hope that helps.
Oh, wait. I promised to recommend a book. Instead, let me recommend a web site, where I think the best and cheapest amount of information on taking care of muscles and joints are. I've been using this site to help others for about 12 years, with immense success. The book I would recommend from that site is any of the "Pain-Free" series. "Pain-Free Living" is the most comprehensive, but it's also the most expensive. You'll find the other books, even though they're specialized for runners and triathletes, espouse the same principles and will apply to you, and they're cheaper.
The website is julstro.com. I get a commission if you buy anything from her site. I never feel better than when I'm recommending a julstro product.
Of course, try out what I wrote above and what's in the videos above. I'll bet 30% of the people who read this, assuming you're over 30, will find significant benefit from the stretches. Others will have friends who would benefit.
I've got a number of stories about people who've been helped by this advice that you can read at my Christian history site. I don't want to write a bunch of stories here and make this page longer.