To reinforceThe Conditioning aspect.

I am really glad to see this post from Sensei/Sifu as I have always been a great believer and practitioner of cross training and what might be considered traditional fitness as a critical adjunct to anyone's martial arts, be it external or internal. I think the MMA craze (or degenerate fighting as Bruce Lee student Jerry Poteet calls it) has turned off some traditional minded martial arts people as much of the success in MMA comes from stamina, conditioning, and strength rather than from good technique. We should not let our opinions about the role of traditional fitness in a "style" we may not like keep us from benefiting from these methods of training ourselves.
I did a lot of traveling earlier in my martial arts training and trained at a number of schools for a week or two at a time all across the US and Canada and one of my pet peeves was a school where the head instructor was too out of shape to lead class and instead stood in front with his arms crossed on top of his belly shouting commands. You know the look, the belt knot has two little one inch tips peeking out from the knot because the belt is a size 5 and the belly is a size 15. I guess I was spoiled (and still am) by the example set by my teacher. There was an extended period of time, when we were on Wells Street when Sensei and I would run, lift weights, and do kata or work on SD or sparring drills 3 - 4 days a week. This was on top of his teaching and my attending a full schedule of classes.
Now I grant you that we were both a bit younger back then (I think this was just after the Civil War), but this type of mixing it up really set the tone for my training even to this day. The internal training has allowed me to continue to train at a very robust and vigorous level and the external, fitness type activities allow me to still have a pretty good degree of credibility training with some strong and fast college kids, some of whom want to see what the old man has got.
I still find that I can challenge myself in many ways physically, mentally, emotionally, and spiritually by blending the traditional with the non-traditional. My cardio is mainly teaching Aerobic Kickboxing classes. A good CV workout, absolutely, but it also lets me throw upwards of 300-500 basic punches and kicks every week as well as incorporating bag work and some bokken cutting drills and ab work in the mix. I have a super strong 63 year old training partner who has gotten me up to a bench of 275 lbs. (not bad for 57 y.o.) which along with making me feel good (yes, and looking pretty good, I'm vain, so sue me) is critical for maintaining bone density, muscle strength, and RBC production in the marrow.
The nicest thing is that I rarely feel that my training is stale, because I do so many different things. Even adding recreational fitness activities (I also bike and kayak) will help everything else. There is not one thing in your life that will not be positively affected by adding fitness related activity. This is especially true of your martial arts. The best of any art means that it is a living, organic, changing process so don't be averse to trying something new. You won't regret it and you just might find new vigor in the rest of you endeavors.
Thanks Sensei.