title: Physiological responses during downhill walking: A new exercise modality for subjects with chronic obstructive pulmonary disease?
abstract: Skeletal muscle quadriceps low-frequency fatigue (LFF) during exercise promotes improvements in exercise capacity with exercise training. In healthy subjects, eccentric muscle work induced by downhill walking (DW) generates higher muscular stress, whilst metabolic cost is lower compared to level walking (LW). We investigated quadriceps LFF and metabolic cost of DW in patients with chronic obstructive pulmonary disease. Ten participants (67 ± 7 years, FEV1 51 ± 15% predicted) performed DW, DW carrying a load (DWL) of 10% body weight via vest and LW, in random order. Quadriceps potentiated twitch force (TWqpot) was assessed before and after each walk, and muscle damage was assessed before and 24 hours after each walk via serum creatine kinase (CK) levels. Ventilation (VE) and oxygen consumption (VO2) were measured via breath-by-breath analysis during each walk. DW and DWL resulted in a greater decrease in TWqpot (-30 ± 14 N in DW, p < 0.05; and -22 ± 16 N in DWL, p < 0.05) compared to LW (-3 ± 21 N, p > 0.05). CK levels only increased 24 hours following DW and DWL (p < 0.05). DW and DWL showed lower VE and VO2 than LW (p < 0.05). DW is associated with enhanced quadriceps LFF and lower cardiorespiratory costs than LW. The addition of a chest load to DW does not seem to enhance these effects.
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium.
authors.forename: Carlos Augusto
authors.initials: CA
authors.lastname: Camillo
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium Hasselt University, Rehabilitation Research Centre, Biomedical Research Institute, Faculty of Medicine and Life Sciences, Diepenbeek, Belgium.
authors.forename: Chris
authors.initials: C
authors.lastname: Burtin
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium.
authors.forename: Miek
authors.initials: M
authors.lastname: Hornikx
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium.
authors.forename: Heleen
authors.initials: H
authors.lastname: Demeyer
authors.affiliation: University Hospital Leuven, Respiratory Division and Rehabilitation, Leuven, Belgium.
authors.forename: Kristien
authors.initials: K
authors.lastname: De Bent
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium.
authors.forename: Hans
authors.initials: H
authors.lastname: van Remoortel
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium Monash University, Department of Physiotherapy, Victoria, Australia Institute for Breathing and Sleep, Victoria, Australia.
authors.forename: Christian R
authors.initials: CR
authors.lastname: Osadnik
authors.affiliation: University Hospital Leuven, Respiratory Division and Rehabilitation, Leuven, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: Janssens
authors.affiliation: KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium University Hospital Leuven, Respiratory Division and Rehabilitation, Leuven, Belgium thierry.troosters@med.kuleuven.be.
authors.forename: Thierry
authors.initials: T
authors.lastname: Troosters
mesh_terms: D000368:Aged; D004417:Dyspnea / Q000209:etiology; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue; D010101:Oxygen Consumption; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology / Q000534:rehabilitation*; D052097:Quadriceps Muscle / Q000502:physiology; D016896:Treatment Outcome; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing
keywords: Pulmonary disease; cardiorespiratory costs; chronic obstructive; downhill walking; exercise; fatigue