I can plod it out, but it's little more than a half-hearted jog - no sense of achievement, no sense of effort. I feel like I might as well be walking.
After all the distance running I've done, my legs are fairly well toughened up to the point where they'll stand up to any distance - only starting to hurt when the sheer repetitive plodding of the distance have inflamed the joints. I only seem to need sporadic long distance runs - say once a week - to maintain this ability.
Over the holidays, I took a break. My cardio fitness has dropped off in that short time, and I'm finding myself slow and my chest tight. It's not good for me to run with a tight chest - if I force the air in and out of my lungs, I run the risk of popping one. (Everyone runs that risk, but asthma makes it worse.)
Also, the bane of lactic acid is inversely connected to the efficiency of your oxygen intake and circulation. If you can't get the oxygen into your muscles quickly, anaerobic action takes over and makes lactic acid. (As I've commented before, fuel is important too.) A good circulation also helps to take away the waste lactic acid.
So, my new regime for the time being - plenty of high intensity training, to get my heart and lungs back into shape.
The HIT that I've prescribed myself is 3 sets of 20 second blasts, either on the static bike, or boxing. I warm up with a minute of easy activity - slowly pedalling the bike, or slow punches on the heavy bag - then 20 seconds of the fastest action I can manage. On the bike, I stand up for that fast action, too (strengthening my knees in the process). Then a slow couple of minutes, before another 20 second bust, and again for the 3rd burst.
The whole HIT process takes just about ten minutes, and one hardly breaks a sweat in the cold.