Background: The study’s purpose was to examine the effect of instrument assisted soft tissue mobilization (IASTM) on tissue mobility and functional movement patterns. Design: A crossover study design was used beginning with the experimental IASTM treatment. A convenience sample (N=70) of 40 males and 30 females aged 18 and 56 years of age were recruited. IASTM was applied to bilateral gastrocnemius/soleus complexes and Achilles tendons with HawkGrips versus walking. Measurements were taken before and again after treatment. Ankle and knee ROM was measured using a goniometer. Gait and center of pressure (COP) was measured using Noraxon MyoMuscle insoles and software. Length of treatment was kept consistent for both sessions. Results: MANOVA results (p <0.001) demonstrated significance for bilateral knee flexion and ankle ROM between pre-and-posttest IASTM treatment. A statistically significant effect in ankle dorsiflexion and seven gait and COP components were noted between pre-test IASTM and post-test walk. Statistically significant interaction effects were seen between post-test IASTM and post-test walk ankle in plantarflexion and seven gait and COP components. Conclusions: Our findings indicate that IASTM improves ROM and alters movement patterns. Changes observed support that IASTM is more effective when combined with a mobility program. The effects on COP and gait demonstrate altered movement patterns and a need for further examination. It shows support for further research using IASTM to treat other conditions with limited ROM and dysfunctional movement patterns.