Mechanism of IASTM

Soft tissue injuries can occur from excessive tension or overuse. After an injury, inflammation and proliferation of new cells occur, during which fibrosis and formation of scar tissue in the injured soft tissue may occur. These changes reduce tissue elasticity and cause adhesion, which can lead to diminished soft tissue function and pain. In particular, scar tissue limits perfusion to the injured soft tissue, restricting the supply of oxygen and nutrients, and interferes with collagen synthesis and regeneration of tissues, which may then cause incomplete functional recovery. These alterations also increase the risk of reinjury.

The biggest goal of IASTM is to remove scar tissues and promote a return to normal function following soft tissue regeneration. When the scar tissue is removed by IASTM, functional normalization around the soft tissue can be achieved. Microvascular and capillary hemorrhage, along with localized inflammation, can occur as a result of using IASTM to apply appropriate pressure and shear force to the soft tissue. Such inflammation restarts the healing process by removing the scar tissue and releasing adhesions, while also increasing blood and nutrient supply to the injured area and migration of fibroblasts. Ultimately, new collagen is synthesized and realigned, which enables the turnover and regeneration of the injured tissue.

This hypothesis has been supported by some animal and human studies. Davidson et al. (1997) applied IASTM to the Achilles tendon in a rat model with enzyme-induced injury and found that earlier recovery of limb function was facilitated by a significant increase in the recruitment and activation of fibroblasts. Moreover, Gehlsen et al. (1999) also reported that when IASTM was applied to rats with enzyme-induced injury of the Achilles tendon, a significantly increased number of fibroblasts were observed in the tissue samples under electron microscopy. In other words, because IASTM affects fibroblasts, it was able to accelerate the healing of injured tendons. Fibroblasts are associated with collagen synthesis. Tropocollagen produced by fibroblasts acts as a precursor to collagen. Collagen deformation in soft tissues is one of the causes of delayed healing, while IASTM has a positive impact on the resynthesis and organization of collagen.

Such changes to collagen require fibronectin, the levels of which are increased by IASTM. Fibronectin is a noncollagenous glycoprotein that moves like adhesion molecules that connect collagen and cells, is synthesized by fibroblasts and epithelial cells, and is essential for tissue formation and repair. According to one study, applying IASTM to the tendons of injured rats showed increased fibronectin staining. In contrast, not applying any treatment after an injury can result in disorganized collagen alignment in the soft tissue and formation of scar tissue. Loghmani and Warden (2009) reported that applying IASTM to rats with an injury to the medial collateral ligament (MCL) of the knee resulted in quicker healing than that in the untreated ligament, with the ligament in the untreated leg showing poor collagen alignment and a greater degree of scar tissue formation.

IASTM has also been reported to cause changes in the vascular response in injured soft tissues. Loghmani and Warden (2013) applied IASTM to the injured MCL of the knee in rats and found that the leg that had IASTM applied showed a significant increase in perfusion, along with the proportion of arteriole-sized blood vessels in the tibial third of the ligament, as compared with the untreated leg. Recently, Loghmani et al. (2016) reported that applying IASTM resulted in a threefold increase in the number of tissue-resident mesenchymal stem cells that exist in arterial adventitia and microvessels. The fact that fibroblasts originate from mesenchymal stem cells (Mills et al., 2013), IASTM can be considered to be closely associated with fibroblast activity. Moreover, these changes serve as evidence that IASTM can increase the blood supply to injured soft tissues by exerting a positive effect on the repair of nearby microvascular morphology. Portillo-Soto et al. (2014) indicated that applying IASTM to the human calf increased the blood flow in the area where IASTM was applied, as observed by the increase in skin temperature (from 25.83°C±0.30°C to 31.831°C±0.205°C).

Meanwhile, some studies have mentioned that the mechanism of action of IASTM involves restarting the healing process by causing localized inflammation in the soft tissue. Poor vascularity in soft tissues due to injury acts as a factor that restricts the inflammatory response. Restriction of the inflammatory response causes disorganization or weakening of the soft tissue structure. On the other hand, an adequate amount of inflammation in the injured tissue can induce secretion of growth factors, which can facilitate healing by promoting stimulation of fibroblasts and collagen synthesis. Moreover, based on the results from studies of the association between inflammation and fibroblasts, as well as claims that IASTM can improve poor vascularity and significantly increase the number of fibroblasts, the inflammation hypothesis may seem plausible. However, a recent study by Vardiman et al. (2014) reported that no significant results were found when changes in the level of cytokines involved in inflammation, such as interleukin-6 and tumor necrosis factor-α, were observed after applying IASTM. They also found no effect on some indicators of musculoskeletal function (passive ROM, passive resistive torque, and maximum voluntary contraction peak torque). However, Vardiman et al. (2014) conducted their study in healthy males with no injuries. Unlike patients with sports injury, healthy individuals do not have inflammation. As a result, IASTM may not show any effect. To our knowledge, the study performed by Vardiman et al. (2014) is the only one that has examined changes in inflammation following IASTM. Therefore, the inflammation hypothesis of IASTM needs to be verified further through well-designed experimental studies in patients with sports injuries.


This is a small excerpt of Jooyoung Kim, Dong Jun Sung and Joohyung Lee study “Therapeutic effectiveness of instrument-assisted soft tissue mobilization for soft tissue injury: mechanisms and practical application.”, you can find the full text by clicking on the link:,et%20al.%2C%202007