If you really want to improve lung function and increase your stamina and endurance, you need to walk as hard as you can for at least 30 minutes non-stop. Warming up and cooling down are always appropriate. If you can't walk for 30 minutes non-stop, start where you are and work your way to the point where you can walk for 30 minutes non-stop. Then you can add time, distance or speed. Continuously pushing yourself little by little will keep your progress going. Assuming that you can walk 30 minutes non-stop, the faster and longer you can walk, the more you will increase your endurance and stamina.

Jean my pulmonary rehab emphasized 30 minutes also….4 or 5 times a week. I cannot walk more than about 5-10 minutes even on 3L continuous oxygen. At that point my oxygen sat drops considerably. So the therapist suggested a recumbant bike or sitting elliptical. Wirks much better for me and others may find it better as well.

Perhaps a combination of both? Warm up by own pace and power up then cool down by slower pace. Intentional walking is so different than just counting steps, I find it meditative. My dog taught me this!! LOL