title: Preliminary evidence that low ankle-brachial index is associated with reduced bilateral hip extensor strength and functional mobility in peripheral arterial disease.
abstract: OBJECTIVE
  Peripheral arterial disease (PAD) has been associated with skeletal muscle pathology, including atrophy of the affected muscles. In addition, oxidative metabolism is impaired, muscle function is reduced, and gait and mobility are restricted. We hypothesized that greater severity of symptomatic PAD would be associated with lower levels of muscle mass, strength, and endurance, and that these musculoskeletal abnormalities in turn would impair functional performance and walking ability in patients with PAD.
  
  
  METHODS
  We assessed 22 persons with intermittent claudication from PAD in this cross-sectional pilot study. Outcome assessments included initial claudication distance and absolute claudication distance via treadmill protocols and outcomes from the 6-minute walk (6MW). Secondary outcomes included one repetition maximum strength/endurance testing of hip extensors, hip abductors, quadriceps, hamstrings, plantar flexors, pectoral, and upper back muscle groups, as well as performance-based tests of function. Univariate and stepwise multiple regression models were constructed to evaluate relationships and are presented.
  
  
  RESULTS
  Twenty-two participants (63.6% male; mean [standard deviation] age, 73.6 [8.2] years; range, 55-85 years) were studied. Mean (standard deviation) resting ankle-brachial index (ABI) was 0.54 ([0.13]; range, 0.28-0.82), and participants ranged from having mild claudication to rest pain. Lower resting ABI was significantly associated with reduced bilateral hip extensor strength (r = 0.54; P = .007) and reduced whole body strength (r = 0.32; P = .05). In addition, lower ABI was associated with a shorter distance to first stop during the 6MW (r = 0.38; P = .05) and poorer single leg balance (r = 0.44; P = .03). Reduced bilateral hip extensor strength was also significantly associated with functional outcomes, including reduced 6MW distance to first stop (r = 0.74; P = .001), reduced 6MW distance (r = 0.75; P < .001), and reduced total short physical performance battery score (worse function; r = 0.75; P = .003).
  
  
  CONCLUSIONS
  Our results suggest the existence of a causal pathway from a reduction in ABI to muscle atrophy and weakness, to whole body disability represented by claudication outcomes and performance-based tests of functional mobility in an older cohort with symptomatic PAD. Longitudinal outcomes from this study and future trials are required to investigate the effects of an anabolic intervention targeting the muscles involved in mobility and activities of daily living and whether an increase in muscle strength will improve symptoms of claudication and lead to improvements in other functional outcomes in patients with PAD.
authors.affiliation: Exercise, Health and Performance Faculty Research Group, Faculty of Health Sciences, University of Sydney, Sydney, Australia. b.parmenter@unsw.edu.au
authors.forename: Belinda J
authors.initials: BJ
authors.lastname: Parmenter
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Raymond
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Dinnen
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Lusby
authors.forename: Maria A
authors.initials: MA
authors.lastname: Fiatarone Singh
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D055109:Ankle Brachial Index; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006621:Hip Joint / Q000503:physiopathology*; D006801:Humans; D007383:Intermittent Claudication / Q000209:etiology / Q000503:physiopathology; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000503:physiopathology*; D009133:Muscular Atrophy / Q000209:etiology / Q000503:physiopathology; D009517:New South Wales; D058729:Peripheral Arterial Disease / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D010865:Pilot Projects; D011237:Predictive Value of Tests; D012307:Risk Factors; D012720:Severity of Illness Index; D016138:Walking