Hopping on the treadmill (it is still a late in the season 90 degree muggy here) I cranked the treadmill up one full mile per hour faster than my norm. Sounds like a little until you try it. WOW!!!!
That didn't last long. Maybe a little under half a mile? I then compromised and finished out the rest of the full mile at .5 to .7 extra miles per hour faster. STILL a significant speed increase.
I cut two minutes off my normal treadmill mile!
My lungs were gasping for breath and my heart rate was through the roof. Yay! Mission accomplished. Yup. Lungs and heart definitely need more work.
Hindrances: Running so hard my lungs couldn't keep up (still need to work on breathing) and to remember to put my long hair in a pony tail first. Half way through my long hair began sticking to my back and shoulders. Funny what can annoy you when you are working out.