Acute Effects of Instrument-Assisted Soft Tissue Mobilization Using Lower-Cost and Higher-Cost Tools Lower-Leg Tissue Stiffness and Ankle Dorsiflexion Range of Motion in Healthy Adults: A Randomized Controlled Trial

Healthy adults aged 18 to 30 years will be randomly allocated to one of three parallel groups: higher-cost IASTM, lower-cost IASTM, or passive control. Only one lower limb will be assessed in each participant; the contralateral limb will not serve as a control.

Before and immediately after the intervention or control period, tissue stiffness will be assessed using MyotonPRO (Myoton AS, Tallinn, Estonia) at four predefined locations: the medial gastrocnemius, lateral gastrocnemius, soleus, and Achilles tendon. Gastrocnemius measurement locations will be identified at one-third of the respective anatomical reference distances described in the protocol. The soleus measurement will be performed medially at one-third of the distance from the medial malleolus toward the medial femoral condyle. The Achilles tendon will be assessed 2 cm proximal to the calcaneus. Two consecutive measurements will be obtained at each site at each assessment, and their mean will be used for analysis.

Ankle dorsiflexion range of motion will be assessed using a digital inclinometer positioned on the lateral aspect of the lower leg during a weight-bearing lunge performed while maintaining the assessed knee extended and the heel in contact with the floor.

Participants in either IASTM group will receive a six-minute standardized treatment of the posterior lower-leg region. The first minute will consist of familiarization with the instrument, desensitization, and application of IASTM cream. This will be followed by five minutes of treatment using long gliding strokes along the direction of the muscle fibers, with the instrument held at approximately a 45-degree angle. Treatment intensity will be adjusted to produce slight pain or moderate discomfort. The treatment protocol will be identical between IASTM groups except for the tool used.

Participants allocated to the control group will rest passively for an equivalent six-minute period without receiving IASTM. Participants receiving IASTM will rate intervention pleasantness and perceived relaxation immediately after treatment using 0-to-10 numerical rating scales.