Journal
CHRONIC RESPIRATORY DISEASE
Volume 12, Issue 2, Pages 155-164Publisher
SAGE PUBLICATIONS LTD
DOI: 10.1177/1479972315575717
Keywords
Pulmonary disease; chronic obstructive; downhill walking; exercise; fatigue; cardiorespiratory costs
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Funding
- Flemish Research Foundation [G.0871.13]
- PROactive IMI-JU [115011]
- National Council for Scientific and Technological Development (CNPq), Brazil [202425/2011-8]
- European Respiratory Society Fellowship [LTRF 2014 - 3132]
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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.
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