This may be the most common question that comes up during a new patient visit. So doc, should I use ice or heat on my back when it hurts? My answer, with consideration of the literature that has been published over the last few decades, my clinical experience and the understanding of patient preferences is to use heat for diffuse muscular stiffness and ice for sharp localized pain.
How does heat help
Heat is a natural by-product of muscle activity and the support systems for that muscle (blood/oxygen supply, nerves, lubricants, hormones) act differently to help as the heat rises. Heat opens blood vessels which means more blood carrying oxygen and nutrients to fuel and rebuild injured muscle as well as take away toxins and damaged tissue. A warmed muscle is more able to slide along muscles/bones/tissues in the area giving you decreased resistance or stiffness. Much like a warm up for sport heat can help bring muscles to a point where the muscle contraction and release is more efficient, bringing relief to that sense of stiffness.
How does ice help
Ice is very effective as a numbing agent to reduce localized pain, especially near the skins surface. Rather than popping pain killers and waiting, ice can often provide immediate pain relief to superficial regions like your tail bone. Opposite to heat, ice encourages blood vessels to constrict and reduce blood flow which can be valuable if swelling or bruising is an issue.
Your body is excellent at regulating its temperature. So that hot water bottle may bring your skin temperature up but an inch below the surface that extra heat is dissipating quick. The same idea applies for ice. If your target is superficial an ice or heat pack will work well with continuous heat for up to 30 minutes or ice applied in intervals of 10 minutes on, 10 minutes off. If the target is deeper or thicker tissue you may want to drive up your whole body temperature with a hot shower.
Heat works well for diffuse muscle stiffness when used for up to 30 minutes continuously.
Use heat packs for smaller superficial areas and a hot shower for deeper/thicker muscles.
Ice works well for superficial sharp localized pain.
Use ice packs in intervals of 10 mins on, 10 mins off for pain relief and to reduce swelling/bruising.
Always be cautious applying extreme temperatures directly on your skin.