Iwatsuki, H., Ikuta, Y., & Shinoda, K. (2001). Deep friction massage on the
masticatory muscles in stroke patients increases biting force. Journal of Physical
Therapy Science, 13(1), 17-20.

BACKGROUND

Patients who have suffered a cerebrovascular accident (CVA), also known as a stroke, will frequently have a disturbance of movement and/or feeling in the muscles of the face. Muscles affected will include those of mastication (the ones used for chewing). Because adequate rehabilitation from a stroke includes being able to chew properly, the strength of the muscles producing the bite is of prime importance. Inadequate strength in these muscles is one factor that often leads to long-term impairment following a CVA. For many patients it is particularly difficult because the mandible is one of the few bones that has attachments on both sides of the body. Since the effects of a CVA are often unilateral, there are significant biomechanical problems with muscle weakness on one side of the mandible that is different than the other.

In this study the investigators divided the subjects into three groups. There was a group of patients that were healthy young persons (average age about 20), a group that were healthy elderly persons (average age about 65), and a group of ten CVA patients with an average age of 66. Each of the three groups had the strength of their bite tested prior to any treatment being offered. The strength of the bite was then tested multiple times after the administration of a treatment of deep friction massage. The deep friction massage consisted of 10 minutes of friction massage applied to the masseter muscles. All massage treatments were performed by the same practitioner. At the conclusion of the massage treatments, the bite force was measured three times on both the left and right sides for both the healthy and affected subjects.

RESULTS AND DISCUSSION

In both the young and elderly healthy groups there was an approximate 5% increase in bite strength post treatment. In the CVA group the bite force increased by approximately 10 – 15% following the massage treatment. It is particularly interesting to note that there was an increase in bite force measured in the healthy subjects as well as in the CVA group. The CVA group had a greater percentage gain in bite strength and several explanations have been suggested as to why this occurred.

The authors state that disuse atrophy of the masseter muscles was presumed to be the primary cause of the decreased biting force. It is not entirely clear how the friction massage helps to address this disuse atrophy, but it is certainly a fascinating concept that should be investigated further. It was suggested that some of the strength gains might be related to increased circulation or reduction of adhesion of subcutaneous tissues that occur from the disuse. It is also likely that there is some other neuromuscular component happening here as well.

While we must avoid the temptation to over-generalize the results from this study, it is highly encouraging to see the implication that massage has significant benefits in restoring muscle tone following a neurological impairment like this. Further research efforts should be engaged to see if there are other situations where massage can be of benefit in restoring muscle tonus following neurological disorders.

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