Med Sci Sports Exerc. 2015 Mar 25. [Epub ahead of print] Inhomogeneous Quadriceps Femoris Hypertrophy in Response to Strength and Power Training. Earp JE1, Newton RU, Cormie P, Blazevich AJ. Author information Abstract INTRODUCTION: Previous studies have reported inhomogeneous changes in quadriceps femoris (QF) cross-sectional area (CSA) in response to strength training. It is assumed that these differential changes in muscle shape influence the muscle's functional capacity during high-force and high-power movements. The purpose of the current study was to compare inter- and intra-muscular QF adaptations to high-load strength training and fast-speed power training. METHODS: 36 non-strength-trained men were randomly assigned to 4 groups and completed 8 weeks of parallel-depth heavy squat-lift training (HS-P), parallel-depth jump squat training (JS-P), volitional-depth jump squat training (JS-V) or no training (C). QF, vastus lateralis (VL), intermedius (VI), medialis (VM) and rectus femoris (RF) CSA were measured in distal-, mid- and proximal-thigh regions using extended field-of-view ultrasonography and compared using a 3×2 mixed-model MANOVA with Bonferroni post-hoc tests (p<0.05). RESULTS: HS-P and JS-P elicited similar changes in mid-CSAQF as well as summed-CSA of the QF, VL, VI and VM. CSAVL and CSAVI increased in both HS-P and JS-P at mid-thigh, but only JS-P significantly increased CSA proximally and only HS-P distally. CSAVM increased in HS-P and JS-P distally, but only HS-P at mid-thigh. No hypertrophy was observed in RF at any location and no significant differences were observed between JS-P and JS-V. HS-P elicited greater proximal hypertrophy in each of the vasti muscles while only JS-P elicited distal VL and VI hypertrophy. CONCLUSIONS: These observed inhomogeneous changes in CSA may alter the thigh's moment of inertia and moment arms of muscle 'compartments', and the influence of elastic component force transmission on the muscular force expression. Such selective hypertrophy is speculated to be biomechanically beneficial to high-force or high-power movements used in training.