title: Hip but not thigh intramuscular adipose tissue is associated with poor balance and increased temporal gait variability in older adults.
abstract: BACKGROUND
  Intramuscular adipose tissue (IMAT) of the lower extremity is a strong negative predictor of mobility function. Variability in temporal gait factors is another important predictor of mobility function. The purpose of this study was to examine the relationships between IMAT in the hip and thigh muscles, balance, and temporal gait variability in older adults.
  
  
  METHODS
  Forty-eight healthy community dwelling older adults (74 +/- 1 year) underwent a CT scan to quantify IMAT in the gluteus maximus (Gmax), gluteus medius/minimus (Gmed/min), hamstrings, vastus lateralis, and adductor muscles. Temporal Gait measures were collected on a GAITRite walkway and gait variability was determined by calculating intraindividual standard deviations. Individuals were divided by tertiles of temporal gait variability into categories of high, medium, and low variability. Differences in the IMAT of the hip abductors were calculated for those with high and low gait variability and partial correlations for gait variability and all muscle composition measures were determined for all variables with normalized gait speed as a covariate.
  
  
  RESULTS
  Gmed/min IMAT was greater in those with higher gait variability compared to those with lower gait variability (p<0.05). Gmed/min IMAT was related to stride width variability (r=0.30, p<0.05). Gmax IMAT was also related to time variability of swing (r=0.42), stance (r=0.26), double limb support (r=0.43), double support loading (r=0.44), and double support unloading (r=0.50) (all p<0.05).
  
  
  CONCLUSIONS
  Increased IMAT in the proximal hip muscles, particularly the hip abductors, was associated with increased gait variability and poorer balance. These findings may have implications for the assessment and treatment of balance and falls such that interventions for enhancing balance and mobility among older individuals should take into account the importance of gluteal muscle composition.
authors.forename: Odessa
authors.initials: O
authors.lastname: Addison
authors.forename: Patricia
authors.initials: P
authors.lastname: Young
authors.forename: Mario
authors.initials: M
authors.lastname: Inacio
authors.forename: Woei-Nan
authors.initials: WN
authors.lastname: Bair
authors.forename: Michelle G
authors.initials: MG
authors.lastname: Prettyman
authors.forename: Brock A
authors.initials: BA
authors.lastname: Beamer
authors.forename: Alice S
authors.initials: AS
authors.lastname: Ryan
authors.affiliation: University of Maryland School of Medicine, Department of Physical Therapy and Rehabilitation Science, Allied Health Building, Room 115, 100 Penn Street, Baltimore, MD 21201-1082, USA. mrogers@som.umaryland.edu.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Rogers
mesh_terms: D050154:Adiposity; D000367:Age Factors; D000368:Aged; D000375:Aging; D005260:Female; D005684:Gait; D020233:Gait Disorders, Neurologic / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D006615:Hip; D006801:Humans; D057187:Independent Living; D008297:Male; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D004856:Postural Balance; D011237:Predictive Value of Tests; D016658:Psoas Muscles / Q000000981:diagnostic imaging / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging / Q000503:physiopathology; D012307:Risk Factors; D012678:Sensation Disorders / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D013848:Thigh; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography