Fig. 1

Representative magnetic resonance imaging scans for measuring cross-sectional areas of trunk and lower limb muscles. The cross-sectional areas (CSA; CSAs) of the rectus abdominis (RA), lateral abdominal wall (LAW), elector spinae (ES), and psoas major (PM) were obtained at the mid-level of the L4–L5. a The CSA of the gluteus major (GM) was obtained at the level of the greater trochanter. b The CSA of the adductors (ADD) was obtained at the proximal 30% of the thigh length. c The CSA of the quadriceps femoris (QF) was obtained at 50% of the thigh length. d The CSA of the hamstrings (HAM) was obtained at 70% of the thigh length. e The CSAs of the dorsiflexors (DF) and plantar flexors (PF) were obtained at the proximal 30% of the lower leg length (e)