text: Xn(cid:5)1 
  h 
  Vm ¼  ðAmi þ Ami þ 1Þ 
  2 
  i¼1 
  
  where Am represents the muscle CSA calculated from each 
  image, i is the image number, n is the total number of 
  images, and h is the distance between images. The volume of 
  ﬁve functional muscle groups was calculated as the sum 
  of the following muscles: hip extensors (gluteus maxi- 
  mus, adductor magnus, BFlh, SM, and ST), hip ﬂexors 
  (iliopsoas, RF, sartorius, and tensor fasciae latae), knee 
  extensors (RF, VI, VM, and VL), knee ﬂexors (gracilis, 
  BFlh and BFsh, SM, ST, sartorius, popliteus, and medial 
  and lateral gastrocnemius), and plantarﬂexors (medial 
  and lateral gastrocnemius and soleus). The sum of all the 
  measured lower-body muscles was also quantiﬁed as the 
  volume of “all muscles.” 
  
  Once muscle MRI scanning had been completed, a ﬂex 
  coil (GE Medical) was used to acquire unilateral T1-weighted 
  axial (time of repetition/time to echo 650/9.476 ms, image 
  matrix 512 (cid:3) 512, ﬁeld of view 180 (cid:3) 180 mm, pixel size 
  0.3516 (cid:3) 0.3516 mm, slice thickness 2 mm, and interslice gap 
  0 mm) and sagittal images (time of repetition/time to echo 
  606/9.512 ms, image matrix 512 (cid:3) 512, ﬁeld of view 180 (cid:3) 180 
  mm, pixel size 0.3516 (cid:3) 0.3516 mm, slice thickness 2 mm, 
  and interslice gap ¼ 0 mm) from both knee joints. The axial 
  images were obtained perpendicular to the line of the tendon 
  from (cid:6)2 cm superior to the apex of the patella to (cid:6)2 cm 