As far as cardiopulmonary function is concerned, you should know that running is the most useful thing in the gym. If there is a cycling course, you can do it. Cardiopulmonary exercise is not as effective as running, but it is more interesting and useful for shaping thighs. If you want to exercise your heart and lungs, you don't have to run for long. You must master the method:

After the warm-up, walk on a high slope at a medium speed, keep your body as straight as possible, and use the forefoot to exert force 1~2 laps.

1 lap high speed+no slope, forefoot force;

1 lap low speed+gentle slope jogging, forefoot force;

Mainly the method of exchanging slope and speed, by adjusting breathing (breathing with chest, not abdominal breathing), the breathing frequency and heartbeat frequency are constantly changed.

The treadmill is ok, but it has a fatal shortcoming-insufficient pedaling force. After running for a long time, if you run on the highway again, you will find that your legs are raised very high, but you just don't go forward and you can't exert any strength, just like you are raising your legs in the same place. Therefore, it is best to start running with the forefoot and run casually when the hind legs are weak. After all, safety comes first.