Abstract
Background: Contractile quadriceps fatigue is associated with acute reductions in exercise capacity in COPD (Gagnon, 2009). We hypothesized patients with fatigable quadriceps would present with reduced physical activity (PA).
Aim: To compare PA between COPD patients who develop quadriceps fatigue (F) after exercise training and those who are less fatigable (NF).
Methods: 19 patients with COPD (65±8years; FEV1 51±17%pred) referred to pulmonary rehabilitation performed PA monitoring (McRoberts; NL) for 7 days before starting exercise training. Potentiated quadriceps twitch force (Twqpot) was measured via magnetic stimulation before and after 1 exercise session in the 2nd training week to determine muscle fatigability. A >15% decrease in Twqpot from initial value defined F. PA levels were compared between F and NF.
Results: Test-day training loads were similar for F and NF (64±9% vs 66±10%Wmax for cycling; 77±4% vs 79±7%6MWD speed for walking, p>0.05). F had on average 32% lower daily step count and spent 37% less energy during active time compared to NF, however these differences were not statistically significant (table 1).
Conclusion: These preliminary data suggest individuals who develop contractile quadriceps fatigue after an exercise session have lower PA levels. When confirmed in a larger sample, our data suggest quadriceps fatigability could be an (as yet) undiscovered mechanism explaining physical inactivity in COPD.
- Copyright ©ERS 2015
