Thanks for posting. Minutes in zones 3+ are still really limited though. Yes stimulates the cv system but sounds to me like we agree that it isn't cardio.
Not really agreeing. There's several layers of cardio utility. Just like there are different benefits of various degrees of resistance training.
With the CV stimulation of weight lifting, you are still stressing the heart, lung and blood vessels and they will respond in a positive way improving their overall health, performance and durability. You are also predominantly working in a purely aerobic zone and using your own body fat for energy during the routine. Pushing harder and you start eating up glucose stores which is counter productive to weight loss. Once you go into the upper end of aerobic and into threshold zones/anaerobic zones you are working on overall speed and ability to perform at threshold levels. The CV benefit dwindles. A lot of people train too hard and actually lose CV benefits by running too fast (I'm as guilty as anyone).
Lifting has similar layers to it. The *important* parts of lifting are resistance training and the positive stress response that it puts on the body. It increases muscle and joint health. It makes the bones firmer. It makes posture and the core stronger for injury prevention. You'll gain those with relatively light weights. You don't have to go in and do some ridiculous ratios to your body weight. Just the simple use of your own body weight in things like pushups and pullups is enough to elicit that response. Muscles suffer microtears from the process, and they repair stronger than they previously were. Rinse and repeat.
It's not just about intensity.