Almost always have a hot bath for low back pain.
A hot bath can really help an aching back.
A hot bath is not only a much better choice for most low back pain than icing — which can be harmful — but soaking in the bath may be one of the best therapies there is for low back pain, especially one of the cheapest. Some people actually avoid a hot bath when they have low back pain, because they think they are “inflamed” and the heat will make it worse. This is very rarely the case.
The great majority of low back pain is essentially muscular in nature, contrary to the popular and mistaken medical view that it’s usually caused by something “mechanical” like a intervertebral disc herniation.
Specifically, the cause of most back pain is myofascial trigger points (“knots” in your muscles), which can cause far more grief than most people realize — and yet they are
relatively treatable. A little reassurance, rubbing, and a hot bath go a surprisingly long way, even with the most horrendous case of low back pain. A hot bath is amazingly good therapy for back pain and the price is right! Trigger points are eased by heat, and usually irritated by cold.
With thanks to http://saveyourself.ca/articles/bathing.php