TNF and major depressive disorder: Our study showed that exercise training is a practical, feasible, and safe way to improve physical function, dyspnoea, pulmonary function, QOL, peripheral muscle performance of lower limbs, anxiety, depression, physical activity intensity level, muscle strength, oxygen saturation, fatigue, CRP, IL-6, TNF-α, lymphocytes, leukocytes, and D-dimer in COVID-19 patients.