I am an unabashed fan of the late Dr. Len Schwartz and his work, see this post. I just saw a comment on that post from John, mentioning his new youtube channel with some videos with Dr. Schwartz: Panaerobic Longstrength . The link should work, or if not just go to youtube and search for “Panaerobic Longstrength”.
There is a lot of insight about aerobic conditioning and whole body development when Dr. Schwartz is talking during these demonstrations.
I was also interested to see him explain and demonstrate his “isotonometrics”. This uses your own muscles as resistance against each other. For example, here he has his hands clasped, and as he twists to the right, his right arm is resisting his left:
You can make this as hard as you want by how hard you resist. There is also a video where he demonstrates this to an exercise class for seniors. Bear in mind that Dr. Schwartz is in his 70s in these videos. I think his ideas have stood the test of time and I’m glad John is keeping his work alive.