There are 4 basic dimensions of fitness.
1. Moving where you are out of breath
2. Low intensity but longer duration movement
3. Lifting heavy things
You can assess most exercise regimens against these 4 dimensions.
Walking of course, would fall into the second dimension. Yoga, depending on the type could fall into all categories as sometimes lifting yourself is lifting something heavy. Qigong could also fit into all 4 depending on the type. Martial arts would be 1, 3, and 4 but could be all 4.
On top of these criteria is the time duration. For 1 – most recent research says that things like marathons actually cause some actual heart damage. It is not recommended, it is extreme from a biological perspective. Safe upper limit on time duration is probably no more than 20 min. For 2 – the minimum I would say is 30 min, a goal of getting to one hour of walking is advisable. For dimension 3 – bodyweight exercises and calisthenics count and are a great way to start For 4 – this is often neglected, but there are many resources online to enhance your flexibility, its advisable to see if you can incorporate with the other dimensions in some way.
Ideally, you would get in all of the above dimensions in some way during one week Dimension 1 is not for everyone however and I recommend if starting out, you just focus on dimension 2 and work up to being able to walk for one hour at a time. . If you can do that, you could try to ramp up the incline for example on the treadmill. Take it easy – your body appreciates any movement. Of course, get your doctors advice if you have any heart issues
Flexibility does not mean you need to be a yogi and pull your legs over your head 🙂 it can just be working on full range of motion in the daily range of movement. This is another reason I like QiGong as a recommendation and practice. There are lots of resources online.
And with all that which one is the most important? By far it is walking! If you don’t have time or feel like you have the energy. Go take a walk for 30 minutes, that is the best thing you could ever do for yourself.
Some of the ideas above adapted from the writings of Mark Sisson.