This can’t be correct (and isn’t correct). There are two things you need to do for exercise to help your body:
- Get the blood flowing and the air moving. That means walking (or swimming or elliptical or whatever you like) fast enough for long enough. 30 minutes a session, 5 days a week is usually sufficient. After that is diminishing returns.
- Resistance exercise. You need to get your muscles contracting and relaxing a few times to keep them strong enough to maintain your strength and to protect your bones. This can be lifting weights, push ups, sit ups, pull ups, whatever forms you like that will target the major muscle groups in your body. But don’t overdo it because you will surely get injured as you age, and once injured, you are only able to do a lot less, so it isn’t worth it.