Velocity-based training (VBT) is a unique resistance-training technique used by athletes, which utilizes velocity rather than load to dictate progressions. No study has examined the impact of VBT on muscle morphology or lower-limb power. PURPOSE: This study examined correlations between ultrasound-derived muscle morphology and lower-body power in Parkinson’s disease (PD) patients before and after a 10-week VBT program. METHODS: Participants’ data included leg press 1-repetition-maximum (1RM) and peak power (PP) at 40 - 80%1RM and muscle thickness (MT), echo intensity (EI), and fascicle angle (FA) of the left and right rectus femoris (RF) and vastus lateralis (VL) taken via B-mode ultrasound. RESULTS: At pretest, data from 17 subjects showed significant correlations between MT and PP at 40-80%1RM in all muscles (all p<.05, r >.54) except at 70-80%1RM for the right RF. FA was correlated to PP at 40-80%1RM in the right VL (p<.05, r>.51), and EI in the right RF at 60%1RM (p<.05, r=-.503). At post-testing, MT and PP at 40-80% 1RM were correlated in the right and left VL and left RF (p<.05, r>.56), and between FA and 40-80%1RM power in both VL (p<.02, r>.56). Significant correlations were observed between EI and PP muscles at 40-80%1RM in both VL (p<.05, r>.54), excluding 50%1RM in the left VL. No significant correlations were found between RF FA and EI and lower body power. CONCLUSION: Improvements in lower PP before and after VBT may be influenced by different morphological variables indicating changes in specific structure-function relationships of PD patients following VBT training.