Strengthergo 8

The patients performed the test in the upright position on an electronically braked ergometer (Strength Ergo 8; Mitsubishi Electric Engineering Company, Tokyo, Japan). At first, the patients rested for 2 min on the ergometer until their heart rate (HR) and respiratory condition slowed down. Following a 2-min rest (rest phase), the patients performed a 2-min warm-up pedaling at 0 W (warm-up phase). The intensity was increased with a RAMP protocol ergometer (10–15 W/min), depending on the exercise capacities of each patient (exercise phase). The patients exercised with a progressive intensity until they could no longer maintain the pedaling rate (volitional exhaustion). After the exercise tests were terminated, the patients were instructed to stop pedaling and to stay on the ergometer for 3 min (recovery phase). The blood pressure was measured every minute with an indirect automatic manometer. Single-lead and 12-lead electrocardiograms were continuously recorded during whole test from the beginning of the rest phase to the end of the recovery phase.

We included 534 patients with stable heart disease or patients who underwent simultaneous CPET and spirometry testing (age: 67.0 ± 12.9 years [95% confidence interval (CI): 65.9–68.1], height:161.9 ± 9.2 cm [95% CI: 161.2–162.7], body weight:62.5 ± 14.6 kg [95% CI: 61.3–63.7], Body mass index (BMI): 23.7 ± 4.4 kg/m² [95% CI: 23.3–24.1]) to scrutinize physical functions.
The CPET was conducted following guideline-based methods [38 (link)], using a stationary bicycle (StrengthErgo 8; Mitsubishi Electric Engineering, Tokyo, COMBI 75XL3; Konami Sports Co., Ltd., Tokyo) and a breath-by-breath analysis with a gas analyzer (AE-300 S or AE-310 S; Minato Medical Science Co., Ltd., Tokyo). The maximal symptomatic exercise was performed using the ramp protocol. The exercise protocol consisted of 2–3 min of rest and 2–3 min of warm-up. The ramp protocol was adjusted to 10–20 W/min, assuming the individual exercise tolerance level. The rating of perceived exertion (RPE) at the end of the exercise was assessed using the Borg scale.
Furthermore, a breath-by-breath gas analyzer (AE-300 S or AE-310 S; Minato Medical Science Co., Ltd., Tokyo) was used to measure the ventilatory volume of each breath using a hot-wire flowmeter [39 (link)]. Before each exercise testing, we calibrated it according to standard protocols.

A symptom-limited cycle ergometer (Strength Ergo 8, Mitsubishi Electric Engineering, Japan) was used for CPET. Each patient wore a mask, and breath was analyzed using a gas analyzer (Cpex-1, Inter Reha; Japan); ${\dot{\text{V}}\text{O}}_2$ , expiratory tidal volume (V_T), minute ventilation (V_E), ventilatory equivalent for carbon dioxide ( $\dot{\text{V}}$ _E/ $\dot{\text{V}}$ _CO2), dead space to tidal volume ratio (V_D/V_T), and breathing frequency at rest and at peak exercise were evaluated. Oxygen saturation, blood pressure, and the electrocardiogram were measured during the test. In the exercise protocol, pre-exercise resting measurements were obtained within the steady state period for more than 3 min. Incremental testing was then started by increasing the load by 10 W per minute with a ramp-exercise protocol. The examination was continued until exhaustion or the predicted maximum heart rate or blood pressure was surpassed, and showing electrocardiographic changes such as ST segment depression of greater than 2 mm and a short run of premature ventricular contractions. Dyspnea intensity was evaluated by a 10-point modified Borg category-ratio scale at rest and every 1 min after initiation of the incremental load test. The data generated were measured breath-by-breath and as 30-s averages at rest and during exercise.

Cardiopulmonary exercise testing was performed using a stationary bicycle (StrengthErgo 8; Mitsubishi Electric Engineering, Tokyo, Japan) and a breath-by-breath gas analyzer (AE-300S; Minato Ikagaku Co., Tokyo, Japan). Symptomatic maximal exercise was performed using a ramp protocol of 5–30 watts (W)/min according to age and condition after 2–3 min rest and warm-up of 0–10 W lasting 2–3 min. Rating of perceived exertion (RPE) at the end of the exercise was assessed using the Borg scale (Beaver et al., 1986a (link); Takano, 2000 (link); Dekerle et al., 2003 (link); Balady et al., 2010 (link); Lenti et al., 2011 (link); Wasserman et al., 2012 ; Yen et al., 2015 , 2018 (link); Nishijima et al., 2017 (link), 2019 (link); Keir et al., 2018 (link); Korkmaz Eryılmaz et al., 2018 (link); Carriere et al., 2019 (link); Iannetta et al., 2019 (link); Nakade et al., 2019 (link)).