If you’ve wondered what the cause of your low back pain is, a physical therapist is your best bet. This article, however, summarizes findings from recent scientific studies about how tight hamstrings can affect the muscles in your lower back. Namely, tight or short hamstrings cause a posterior tilt (or cat tilt) of your pelvis, bringing more stress to your lower back muscles during a forward fold.
Loosening up the hamstrings gradually with dynamic stretching can help decrease the tension in the low back. In fact, dynamic stretching is the best way to warm up your body for a workout, yoga or otherwise.
A great way to start is with a forward fold with bent knees. Clasp opposite elbows and gently sway left and right. Then play with the bend in your knees, finding just the right amount of stretch: you will feel opening, but not pain.
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