At night. The morning air, after a night's breathing by trees, has the highest concentration of carbon dioxide in the morning air, which is difficult to exercise and is not conducive to lung health. When the oxygen concentration reaches the highest at night, exercise will be fine, and you can take a shower after exercise. How cool! At home, I usually do crouching tiger, sit-ups, dumbbells, squats and leapfrog. You can exercise all parts.