"Recovery time" is the time it takes for your heart rate to return to normal after exercise. Recovery time is much longer if you're not super fit, and that creates an opportunity. As your heart rate slowly returns to normal, you "ride" at least some aerobic benefit all the way down. You may get an extra four or five minutes of benefit, absolutely free (though, obviously, you won't get full benefit near the tail end of recovery).
Say you can manage a 15 minute aerobic workout. And say your recovery time is six minutes. That's 19 or 20 minutes of de facto workout. But here's the trick: play with that a bit. After your workout, you will be unable to jog (or cycle, etc) with much intensity, but you can surely walk swiftly on the treadmill, perhaps even at an incline. Ten minutes of this will delay your recovery, making light exercise yield a greatly magnified benefit.
You will find, in other words, that a brisk treadmill walk which normally would bring your heart rate only to, say, 90 bps may, after an intense workout, keep your rate at, say, 110 or 120 bps. While this non-peak heart rate won't yield maximum benefit, it's still within
And "minimal discomfort" is essential, because for this to work, you must first push hard in your regular workout (i.e. maintaining 140, 160, 180 bps, depending on your age). Don't skimp on that! And don't take any break afterwards (you don't want to allow yourself to recover). Just immediately switch to walking, cycling, etc., near the top end of your easy comfort range, for as much time as is available. Sort of like a warm-down, only a little more vigorous and for a lot more time.
This wouldn't work for a an elite athlete, whose pulse quickly slows to a crawl in the absence of heavy exertion. It's a free ride exclusively for the rest of us!
Another tip: it's been shown that we continue to burn fat for some time after a workout. It's a good idea to wait 30-60 minutes before eating anything, because eating is thought to suspend this after-burn.
By combining these two tips, you can magnify a fairly short aerobic workout into a much more extended fat burning session with little additional discomfort.
Pass it on!