One of the oldest forms of healing,1--2 massage is undergoing a much-needed evolution. Over the past decade, the modern practice of medical massage has gained popularity on account of its scientific methodology. Medical massage begins with a clear-cut diagnosis and ends with a readily identifiable outcome. Understanding its biologic mechanism of action allows practitioners to make meaningful interventions that specifically target a patient’s myofascial or neurophysiologic pathophysiology. Thanks to the rapidly expanding paradigm of autonomic neuromodulation and the desire by medical massage therapists to explain how their treatments work, a unifying theory has emerged. That is, neurophysiology explains how and why soft tissue therapy improves bodily processes including, but not limited to, digestion, emotional states, sleep, weight regulation, pain control and immune function.3--4 The recognition that moderate pressure massage gave patients slower heart rates, lower blood pressure and reduced cortisol levels pointed to changes within the autonomic nervous system.5 Eventually, investigations led to the vagal nerve network as the final common pathway. This 10th cranial nerve and associated brainstem nuclei affect nearly every bodily function, serving as a neural expressway mediating the tightly orchestrated, restorative, parasympathetic nervous system. Effect on Babies Some of the most compelling research on massage and the vagus nerve involves term and pre-term infants. For example, massage allows preterm infants to better autoregulate their body temperature.6 Properly massaged infants show less physiologic stress and reactivity,7 higher vagal tone and significantly less fussing, crying and stress behavior such as hiccups. Though medical acupuncturists have recognized for years that somatic afferent stimulation from needling and electroacupuncture alters autonomic function, it is now evident that somatic input from moderate pressure massage (as opposed to light stroking) can cause changes in autonomic tone as well.8 Vagal afferent fibers on the body wall innervate pressure-sensitive mechanoreceptors; massage applied to the skin, subcutaneous tissue and underlying myofascia activates these nerve endings. Signals then travel to brainstem nuclei and cerebral centers that coordinate autonomic nervous system (ANS) homeostasis by means of moment-to-moment alterations in parasympathetic and sympathetic output. The main ANS regulatory center associated with the vagal nucleus is the nucleus tractus solitarius (NTS). The NTS receives convergent afferent input from both somatic and visceral sources. After it collects and processes this information, the NTS adjusts its output to the nucleus ambiguus and dorsal motor nucleus of the vagus (DMNV); i.e., vagal efferent pathways. Vagal output impacts nearly all organs, including the heart, respiratory system and digestive tract.9 Thus, somatovisceral reflexes from massage form the anatomic substrate through which massage affects autonomic neurophysiology. Vagal Stimulation Ordinarily, animals suffering from acute and chronic illness experience heightened sympathetic tone that can cause maladative changes. The complementary, dualistic reciprocity encoded within the ANS dictates that as parasympathetic tone increases, sympathetic (fight or flight) activity calms down.10 Consequently, reducing sympathetic hyperactivity through massage can benefit patients by countering peripheral vasoconstriction, inflammation, muscle tension, spinal cord windup and pain.11-12 Vagal stimulation from moderate pressure massage also improves gastric motility and weight gain in premature infants.13 Parasympathetic stimulation prevents increases in permeability across the gut lumen.14 Higher vagal tone translates to elevated availability of ingested nutrients and better digestion.15 When more nutrients enter the bloodstream, insulin and insulin-like growth factor-1 (IGF-1) levels rise. IGF-1 regulates growth in preterm infants, and evidence indicates that massage therapy raises both insulin and IGF-1 levels in premies.16 Alternatively, vagal nerve stimulation from massage may reduce insulin levels and elevate blood glucose.17 Since the NTS and similar autonomic centers determine what adjustments need to be made within the neuroendocrine system to move the organism toward homeostasis, the baseline function of an individual influences the response of the NTS. Translating these findings to veterinary medicine, it seems reasonable to assume that massage would help prevent unnecessary deaths in “faders,” i.e., puppies and kittens who fail to thrive, as it has in human infants.18 For older veterinary patients suffering from postoperative ileus, megaesophagus and inflammatory bowel disease, regulation of digestive function through massage may provide much-needed parasympathetic, digestive, support.19-20 Controlling Cravings When considering massage for obese patients, one can consider evidence indicating that long-term vagal stimulation in rats suffering from diet-induced obesity led them to reduce their food intake. This suggests that vagal pathways send satiety signals to the brain, effectively modifying the individual’s appetite and body fat content.21 Regular massage may thus diminish food cravings while simultaneously elevating a cat’s or dog’s desire to exercise on account of improved body comfort.22 The relaxing benefits of medical massage would assist veterinary patients in counteracting stress during minimally painful procedures, though it should never be relied upon to replace conventional anesthesia and analgesia for more painful events. Facial massage calms by activating trigeminovagal reflexes.23 Veterinary technicians can include certain techniques while assisting with gentle restraint; slow, up-and-down moderate pressure massage along the midline between the nose and forehead can sometimes induce a quasi-hypnotic state in patients.24 Don’t believe it? Try it on yourself! Narda Robinson, DVM, DO, Dipl. ABMA, FAAMA, offers an evidential and scientific perspective on the latest trends in complementary and alternative veterinary medicine. She oversees complementary veterinary education at Colorado State. 1. Calvert RN. The History of Massage. Rochester, Vermont: Healing Arts Press, 2002, p. 27. 2. Mainous RO. Infant massage as a component of developmental care: past, present, and future. Holist Nurs Pract. 2002;17(1):1-7. 3. Diego MA and Field T. Moderate pressure massage elicits a parasympathetic nervous system response. International Journal of Neuroscience. 2009;119:630-638. 4. Touch Research Institute. Massage Therapy Research. Touchpoints. 2010;17(3):1. Accessed at http://www6.miami.edu/touch-research/Touchpoints%20Summer%202010.pdf on 07-20-10. 5. Diego MA and Field T. Moderate pressure massage elicits a parasympathetic nervous system response. International Journal of Neuroscience. 2009;119:630-638. 6. Diego MA, Field T, and Hernandez-Reif M. Temperature increases in preterm infants during massage therapy. Infant Behav Dev. 2008;31(1):149-152. 7. Feldman R, Singer M, and Zagoory O. Touch attenuates infants’ physiological reactivity to stress. Developmental Science. 2010;13(2):271-278. 8. Diego MA and Field T. Moderate pressure massage elicits a parasympathetic nervous system response. International Journal of Neuroscience. 2009;119:630-638. 9. Lutz W and Sulkowski WJ. Vagus nerve participates in regulation of the airways: inflammatory response and hyperreactivity induced by occupational asthmogens. International J Occupational Medicine and Environmental Health. 2004;17(4):417-431. 10. Gellhorn E. Principles of Autonomic-somatic Integrations: Physiologic Basis and Psychological and Clinical Implications. Minneapolis, MN: University of Minnesota press, 1967, pp 52-163. Cited in: Cottingham JT, Porges SW, and Lyon T. Effects of soft tissue mobilization (Rolfing pelvic lift) on parasympathetic tone in two age groups. Physical Therapy. 1988;68(3):352-356. 11. Huang SY, Di Santo M, Wadden KP, et al. Short-duration massage at the hamstrings musculotendinous junction induces greater range of motion. J Strength and Conditioning Research. 2010; epub ahead of print. 12. Huang J, Wang Y, Jiang D, et al. The sympathetic-vagal balance against endotoxemia. J Neural Transm. 2010;117:729-735. 13. Field T, Diego MA, Hernandez-Reif M, et al. Moderate versus light pressure massage therapy leads to greater weight gain in preterm infants. Infant Behav Dev. 2006;29(4):574-578. 14. Bansal V, Costantini T, Ryu SY, et al. Stimulating the central nervous system to prevent intestinal dysfunction after traumatic brain injury. J Trauma 2010;68:1059-1064. 15. Chang HY, Mashimo H, and Goyal RK. Musings on the wanderer: What’s new in our understanding of vago-vagal reflex? IV. Current concepts of vagal efferent projections to the gut. Am J Phys Gastrointestinal and Liver Physiology. 2003;284:G357-G366. Cited in: Field T, Diego M, and Hernandez-Reif M. Preterm infant massage therapy research: A review. Infant Behavior & Development. 2010;33:115-124. 16. Field T, Diego M, Hernandez-Reif M, et al. Insulin and insulin-like growth factor 1 (IGF-1) increase in preterm infants following massage therapy. Developmental and Behavioral Pediatrics. 2008;29:463-466. 17. Holst S, Lund I, Petersson M, et al. Massage-like stroking influences plasma levels of gastrointestinal hormones, including insulin, and increases weight gain in male rats. Autonomic Neuroscience: Basic and Clinical. 2005;120:73-79. 18. Blunden T. Diagnosis and treatment of common disorders of newborn puppies. In Practice. 1988; 10(5):175-184. 19. Gao Z, Muller MH, Karpitschka M, et al. Role of the vagus nerve on the development of postoperative ileus. Langenbecks Arch Surg. 2010;395:407-411 20. Lubbers T, Buurman W, and Luyer M. Controlling postoperative ileus by vagal activation. World J Gastroenterol. 2010;16(14):1683-1687. 21. Gil K, Bugajski A, Kurnik M, et al. Physiological and morphological effects of long-term vagal stimulation in diet induced obesity in rats. J Phys Pharm. 2009;60 (Supp 3):61-66. 22. Kibcolt JK. Stress, food, and inflammation: Psychoneuroimmunology and nutrition at the cutting edge. Psychosomatic Medicine. 2010;72:365-369 23. Hatayama T, Kitamura S, Tamura C, et al. The facial massage reduced anxiety and negative mood status, and increased sympathetic nervous activity. Biomedical Research. 2008;29(6):317-320. 24. Personal experience of the author.
