...It comes naturally

Take a few minutes out to go play with the family dog. Or think back to a time the two of you spent together. How cute is he, every time Fido your fun loving four legged fluffy little friend, sets out for one of his runs? One of those not too fast, not too slow, just long and steady runs around the neighborhood. So adorable. Or for that matter, remember when that beastly strong little guy of yours went out and nose'd that huge rock in the garden back and forth ten times for three or four sets. The way he sat there until he was completely rested before he did it again. Just sat there, scratching his big floppy ears with his hind leg. Breaks your heart it's so cute.
What? No? You've never seen that? You mean to tell me that you've never actually seen the family pet head out for a good old fashioned cardio day?
Of course not. We both know that's farcical at best. What do Fido and Rover do when they get loose? Probably looks a little more like; RUN!! RUN!! RUN FAST!! STOP! GO OVER THERE! WAIT!! STOP!! RUN OVER THERE!!! RUN!! NOW OVER THERE!!. Tug on the chew tow. PULL!!PULL HARDER!!! Gimme Gimme GIMME! RUUUN!!!!
All of this to illustrate one point. The separation of what we traditionally think of as cardio (aerobic) work and strength (anaerobic) training is a completely synthetic, man made distinction. Those of you who know me know how big a fan I am of the Gym Jones video "One Piece." Now, while I don't agree with all their methodologies or the hype surrounding their unbelievably svelte Trojan warriors, the thesis in this video is an important one. The body is one piece. Train it that way. If you haven't seen the video, I've imbedded it below.
It's not just your muscles, your joints, or your cardiovascular system. It's your energy systems, your coordination and the amount of control you have over the whole thing. Why do you suppose there's so much overlap in conventional weight training? To get strong we do 3 to 5 sets of 8 to 12 reps. To train endurance we do 2 to 3 sets of 12 to 20 reps... They were never meant to be separated to begin with.
Challenge: Go pick up the heaviest thing you possibly can with a reasonable degree of safety. Do it again. Again. When you can't lift that anymore, pick up something that's almost as heavy. Keep going. Keep moving. Do the unthinkable. Keep moving that thing for 5 whole minutes. 10 minutes. How many times do you think you can move that thing in 20 minutes resting only just as long as it takes to pick it up again as you go?
How do you feel at the end of that 20 minutes? Starts to give you an idea of why Fido outlasts you in the park every weekend..and just how artificial and ineffective that 45 minutes on the treadmill in your 30% heart rate zone really is.