Greater exercise tolerance in COPD during acute intermittent compared to continuous shuttle walking protocols: a proof-of-concept study

Objectives: Ground-based walking is a simple training modality which would suit pulmonary rehabilitation (PR) settings with limited access to specialist equipment. Patients with COPD are, however, unable to walk uninterruptedly at a relatively fast walking pace to optimise training benefits. We compared an intermittent (IntSW) to a continuous (CSW) shuttle walking protocol. Methods: In 14 COPD patients (mean ± SD. FEV ₁: 45 ± 21% predicted) we measured walking distance, cardiac output (CO), arterial oxygen saturation (SpO ₂), and symptoms during (a) an IntSW protocol, consisting of 1-min walking alternating with 1-min rest, and (b) a CSW protocol, both sustained at 85% of predicted VO ₂ peak to the limit of tolerance (Tlim). Results: Median (IQR) distance was greater (p = 0.001) during the IntSW protocol (735 (375–1107) m) than the CSW protocol (190 (117–360) m). At iso-distance (distance at Tlim during CSW) the IntSW compared to the CSW protocol was associated with lower CO (8.6 ± 2.6 vs 10.3 ± 3.7 L/min; p = 0.013), greater SpO ₂ (92 ± 6% versus 90 ± 7%; p = 0.002), and lower symptoms of dyspnoea (2.8 ± 1.3 vs 4.9 ± 1.4; p = 0.001) and leg discomfort (2.3 ± 1.7 vs 4.2 ± 2.2; p = 0.001). At Tlim symptoms of dyspnoea and leg discomfort did not differ between the IntSW (4.4 ± 1.9 and 3.6 ± 2.1, respectively) and the CSW protocol. Conclusions: The IntSW protocol may provide important clinical benefits during exercise training in the PR settings because it allows greater work outputs compared to the CSW.