Physiological responses to matched ramp-incremental exercise on recumbent cycle ergometer and treadmill in patients...

Exercise intolerance is a cardinal symptom in patients with heart failure (HF), and cardiopulmonary exercise testing (CPET) is the gold standard method for its assessment. The treadmill and cycle ergometers (upright and recumbent) are used in clinical practice for tracking disease progression and risk stratification, therefore, understanding the physiological differences related to ergometer is important. The aim of this study was to compare the physiological responses to exercise on treadmill and recumbent cycle ergometer in patients with HF with reduced ejection fraction (HFrEF) using a linear ramp protocol matched with controlled work rate (WR) profiles. Thirteen patients with HFrEF (left ventricular ejection fraction: 34.5% [28.7-47%]) were included. They performed two randomized ramp-incremental CPETs, on recumbent cycle and treadmill, both with incrementation rates of 10 watts per minute (W/min). The cardiorespiratory data obtained in both tests were WR-aligned and iso-WR responses were compared. Patients reached similar WR peak on both exercise modalities (84 ± 23 vs 91 ± 26 watts, P = 0.133, for recumbent cycle and treadmill, respectively) with no differences in ventilatory efficiency ( ${\dot{V}}_{\text{E}}$ / $\dot{V}$ CO₂ slope) (30.8 ± 4.7 vs 30.9 ± 7.3, P = 0.981). However, exercising on recumbent cycle resulted in lower peak oxygen uptake ( $\dot{V}$ O₂) (13.4 [11.3-15.9] vs 15.8 [14.7-18.4] mL/kg/min, p = 0.002) and higher Weber HF severity classification (p = 0.034). Considering the higher $\dot{V}$ O₂ peak reached and its role in clinical decision-making-despite similar ${\dot{V}}_{\text{E}}$ / $\dot{V}$ CO₂ slope between ergometers-treadmill should be considered the optimal ergometer for exercise intolerance and risk stratification assessment in patients with HFrEF, since it reflects a more accurate exercise capacity and disease severity.