Up-Downs @ 34 = Bad Idear

The wife and I are exercising this morning, following some aerobic/cardio routine thing.  We get to this part that we do "fast feet"  This is bascially running in place real fast.  You move your feet as fast as you can.  This reminded me of the old high school football "exercise" called Up-Downs.  With up=downs, you move your feet as fast as you can until some signal from your coach tells you to drop (whistle, yell "DROP!", etc).  Then you have to get back up as fast as you can k  Part of the drop (at least how we did it) was to basically land on your chest and not really break your fall in anyway.  This goes on in football practice until the coach tires of what I assume is a pretty humorious scene.  So I put my hands up in like my old linebacker stance while I was doing this exercise today, goofing around.  The wife asks what am I doing and I explain this to her.  For some reason I ended up doing two up-downs in the basement.  Either she didn't understand the description and wanted to see what one looked like or she completely understood the description and wanted to see if I was dumb enough to do one.  Like I said, I did two.  Let me detail the problems with this. 

1. A basement concrete floor is much harder than the ground even if covered with carpeting and a pad
   
2. In football practice you have shoulder pads on
   
3. I have 25 more lbs than I did 16 years ago. more weight=more force when I hit the ground
   
4. I'm fricken 34 not 17!

Well on one of the up-downs that I did I hit my jaw a little bit on the floor, not bad or anything just enough to make it sore.  On the other one, or heck maybe the same one, I'm surprised I did not break my sternum or ribs.  It sure as heck didn't feel real good.  Next time I decide to do up-downs, I'm going to try and remember this....