Heat/Cold Modalities and Local Circulation
Both modalities act primarily to affect local circulation in the tissues. The application of a hot pack or heating pad, causes the blood vessels in the skin to dilate or “open-up”. This allows blood to flow more freely and acts to rapidly distribute the heat being applied throughout the body. The end result of this process is that very little heat penetrates to the muscles lying underneath the skin.
The application of cold packs to the body surface does just the opposite; it causes the local blood vessels to constrict, drastically reducing the amount of blood circulating in the region. With circulation impaired, cold can penetrate much deeper into the body tissue, easily chilling the underlying muscles.
When To Use Heat Packs
While it is doubtful that the application of a heat pack has any theoretical effect on the muscle harboring the trigger point(s), clinical experience has demonstrated that clients receive some benefit from it, especially if they have more established or chronic complaints. I typically advise patients to apply heat to the muscles I have treated after their appointment with me. The use of a heating pad for a 20 minutes on-20 minutes off-20 minutes on regimen can help to flush metabolic wastes that have accumulated from trigger point activity. Dr. Travell also advocated the use of a heating pad on a client’s abdominal region, prior to treatment, to promote blood circulation throughout the body and relax the client.
When To Use Cold Packs
The application of cold is useful in cases of acute injury where tissue swelling is likely to occur. It is also useful in deadening neurogenic types of pain; such as the physical compression of a nerve from a herniated spinal disc. As I rarely see patients immediately after an injury, or refer them immediately in cases of neurogenic pain, I rarely use or advise the use of cold packs in my practice. More often I advise against the use of cold packs because they can chill a muscle and aggravate latent or active trigger points within the muscle.