This post might speak to runners, rowers, and cyclists in particular who have tight hamstrings, and because of their sport, may also have tightness in the chest and shoulders.
Think of it like this. When your hamstrings are tight they scrunch the back of your leg and pull down on your low back. When your chest is tight, it rounds the spine causing a pull up on your low back. So your lower back lands in the middle of a very uncomfortable tug-of-war. It's being pulled taught, beyond what feels ok, yet it is actually being OVERstretched. Furthermore, because of the constant tugging from above and below, it is difficult to fully contract the lower back muscles (in other words, to extend the lumbar spine or reduce the overstretching), leaving them tight AND weak.
I teach Weight Training at Temple and a student whose back felt tight and achy asked me about stretches he could do to alleviate the discomfort. Rather than stretch your lower back, what you actually need to do in this instance is: open your chest, open your hamstrings, and strengthen your lower back.
Open Your Chest:
Stand facing a wall. Reach your right arm out to the side slightly higher than your shoulder. Fully straighten at the elbow. Open up your palm and press into it; don't allow your forearm to come onto the wall. Start to turn your feet to the left until you feel a stretch in the shoulder, chest, and even the biceps. Keep turning your torso until you reach an edge. Breathe there. Repeat for the left arm.
Open Your Hamstrings:
Lying Hamstring Stretch
Lie on your back. Loop a strap, belt, or towel around the arch of your left foot and extend that leg at the knee. Allow as much strap as you need to keep both shoulder blades grounded and the knee straight but not locked out. Once you have found a sensation of slight discomfort, breathe into the back of your leg. Repeat on the other side.
Strengthen Your Back:
Set up as shown lying on your belly, propped on the forearms. Line up your elbows underneath the shoulders. Starting from the feet: press down into the tops of the feet and reach back through the big toes; flex your quads gently and feel your kneecaps lift off the floor; press your pubic bone forward and down into the mat - you should feel your low back open from this action; draw in with your forearms and hands, hugging tightly onto the mat and lift your upper chest. Focus on feeling the entire back - lower, mid and upper - contracting strongly.