Feasibility and safety of upper limb extremity ergometer exercise in the cardiac intensive care unit in critically ill patients with cardiac disease: a prospective observational study - Hirakawa, Kotaro; Nakayama, Atsuko; Arimitsu, Takeshi; Kon, Kazuki; Ueki, Hiromichi; Hori, Kentaro; Ishimoto, Yuki; Ogawa, Ayaka; Higuchi, Ryosuke; Hosoya, Yumiko; Nanasato, Mamoru; Isobe, Mitsuaki (Frontiers in Physiology, 2025)