title: Arm mechanical efficiency and arm exercise capacity are relatively preserved in chronic obstructive pulmonary disease.
abstract: OBJECTIVE
  Previous studies indicate that energy expenditure related to physical activity is enhanced and that mechanical efficiency of leg exercise is reduced in patients with chronic obstructive pulmonary disease (COPD). However, it is yet unclear whether an inefficient energy expenditure is also present during other activities in COPD. This study was carried out to examine arm efficiency and peak arm exercise performance relative to leg exercise in 33 (23 male) patients with COPD ((mean +/- SEM) age: 61 +/- 2 yr; FEV : 40 +/- 2% of predicted) and 20 sex- and age-matched healthy controls.
  
  
  METHODS
  Body composition, pulmonary function, resting energy expenditure (REE), and peak leg and arm exercise performance were determined. To calculate mechanical efficiency, subjects performed submaximal leg and arm ergometry at 50% of achieved peak loads. During exercise testing, metabolic and ventilatory parameters were measured.
  
  
  RESULTS
  In contrast to a reduced leg mechanical efficiency in patients compared with controls (15.6 +/- 0.6% and 22.5 +/- 0.6%, respectively; < 0.001), arm mechanical efficiency was comparable in both groups (COPD: 18.3 +/- 0.9%, controls: 21.0 +/- 1.2%; NS). Arm efficiency was not related to leg efficiency, pulmonary function, work of breathing, or REE. Also, arm exercise capacity was relatively preserved in patients with COPD (ratio arm peak work rate/leg peak work rate in patients: 89% vs 53% in controls; < 0.001).
  
  
  CONCLUSIONS
  Mechanical efficiency and exercise capacity of the upper and lower limbs are not homogeneously affected in COPD, with a relative preservation of the upper limbs. This may have implications for screening of exercise tolerance and prescription of training interventions in patients with COPD. Future studies need to elucidate the mechanism behind this observation.
authors.affiliation: Department of Pulmonology, University Hospital Maastricht, The Netherlands. f.franssen@pul.unimaas.nl
authors.forename: Frits M E
authors.initials: FM
authors.lastname: Franssen
authors.forename: Emiel F M
authors.initials: EF
authors.lastname: Wouters
authors.forename: Erica M
authors.initials: EM
authors.lastname: Baarends
authors.forename: Marco A
authors.initials: MA
authors.lastname: Akkermans
authors.forename: Annemie M W J
authors.initials: AM
authors.lastname: Schols
mesh_terms: D001132:Arm; D001696:Biomechanical Phenomena; D004734:Energy Metabolism; D005080:Exercise Test; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006801:Humans; D007866:Leg; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*