2016 book. Dr. Mercola suggests that we should exercise as fast as we can for 30 seconds and follow with about 90 seconds of recovery while exercising at a much slower rate - pretty much what one sees in good kata practice. It is suggested to continue this regimen for about 20 minutes. This form of exercise should focus on the super fast with muscle fibers. And, it is important to vary your forms so you should practice different kata.
For me, I typically train for about an hour in explosive karate and kobudo kata and finish my training regimen with weight and resistance exercises. I've done this for most of my life and even continued to so so when working as a geologist in the middle of no where in places like Donlin Creek, Alaska surrounded by three trillion, starving mosquitos, Ellendale, Australia surrounded by flies and crocks, and while searching for gold in Lewiston, Wyoming, where I was surrounded by coyotes. So, to keep healthy try learning 'TRADITIONAL' karate as opposed to Sport Karate and practice your kata.