Effects of Patterns of Pressure Application on Resting Electromyography During Massage

Abstract

Background: To increase the understanding of the physiological mechanisms by which massage therapy produces health benefits such as pain relief and anxiety reduction, the relationship between specific elements of massage and physiological outcomes must be addressed. Purpose: The effects on resting muscular activity of applying varying levels of pressure during massage were investigated. Methods: In this clinical crossover study, conducted in a simulated clinical setting, human subjects (n = 25; mean age: 34.1 years) received 3 different levels of massage pressure to the legs. A licensed therapist applied pressure to the rectus femoris in a distal-to-proximal direction. Each volunteer received the 3 levels of pressure in 2 different orders increasing (IP) and decreasing pressures (DP)—separated by at least 4 weeks. Surface electromyography (EMG) was used to measure muscle activity levels at baseline and after each pressure level. Results: During the trials of IP, EMG did not vary significantly [Greenhouse–Geisser corrected analysis of variance F(1.71 df) = 0.30, p = 0.71]. During the trials of DP, EMG varied significantly [Greenhouse–Geisser corrected analysis of variance F(1.58 df) = 4.49, p = 0.03], with the largest variation, an increase of 235%, noted between baseline activity and activity after deep pressure. After application of light pressure, activity returned to baseline levels. Interestingly, the overall levels of force required to achieve subjective pressure levels as reported by the client were higher in the DP protocol than in the IP protocol (p < 0.02). Conclusions: These results suggest that the physiological response of the muscle depends on the pattern of applied pressure during massage. That finding is consistent with a mechanism by which light- or moderate-pressure massage (or a combination) may reduce the gain of spinal nociceptive reflexes. As those reflexes are elevated in chronic pain syndromes, pressure variation provides a possible mechanism for the relief of chronic pain by massage therapy.