Muscle can spasm (tighten involuntary) to protect an area of the body such as the back when it is inappropriately loaded. Once in spasm the back can be completely immobilized and very very painful. Rest can help reduce the spasm however it has been shown that getting moving as soon as possible is the best long term solution. Whilst in spasm the nerves are over reactive and can cause re-spasming at any time. Longer term issues from untreated spasm can include the formation of trigger points and fascial adhesions causing longer term repetitive dysfunction or weakness.