RESUMEN
INTRODUCTION: This study aimed to determine whether massage pressure on the target muscles (biceps brachii muscle [BB] and the medial head of the gastrocnemius muscle [MG]) is related to the massage effect (reducing muscle stiffness). METHOD: Nine healthy participants participated in this study. A physiotherapist massaged the upper arms and lower legs of participants on a rigid desk in a laboratory. Massage was delivered for 10 min with a 3-min rest. The shear modulus (i.e., the muscle stiffness), assessed by shear wave elastography, was measured at various time points (before [PRE], immediately after [POST], and 5 [POST-5], 10, 15, and 20 min after the massage). The massage pressure data (N) were obtained only during massage by force plate sensors. RESULTS: The BB shear modulus was significantly reduced POST massage. The MG shear modulus significantly reduced POST massage and remained clearly reduced until POST-5. There was a negative correlation between the total massage pressure and the % change in the shear modulus in both muscles. DISCUSSION: Since the spindle (BB) and pennate (MG) muscles have structural differences, our results suggest that these differences may affect the pattern of changes in the shear modulus in response to massage. CONCLUSION: Massage pressure is related to the massage effect (reducing muscle stiffness), and its relationships to POST are not related to the differences in the morphologies of the spindle (BB) and pennate muscles (MG). However, differences in the morphologies of the spindle and pennate muscles may cause differences in the duration of the massage effects.