Its taken up a little bit too much space on this blog for the past 6 months.
The experiences of the past several months have shown me that the VFF is a great training shoe, and an excellent way to shift into a mid/forefoot strike running style. On the off-road Half Marathon, and the long training runs at the end of the training cycle (9-11 mile long runs in the city), both my legs and lungs felt less pulverized than they had ever been during my experiences running those same distances in motion control shoes.
But I DO NOT plan on using the VFF again for distances longer than 6-7 miles, or as my race day shoes.
For me the early problems I had with the VFF's, specifically calf pain, disappeared eventually. But my feet never got used to the impact -- especially as I got into the higher distances (9-11 mile training runs). What would happen on the longer runs is that I'd have plenty of energy left everywhere else, but my feet would be so sore from the constant pounding that couldn't put the hammer down.
This doesn't mean I'm going back to my ASICS Motion Controls -- anything but that. I have no desire at this point to going back to heel striking, and I'm not going to spend money on shoes that would bring me back to that form of running.
What this does mean is that I'll probably use the VFF's for shorter runs, intervals, hill workouts, stair climbing, etc. Doing these shorter runs that are built around drills & specific workout routines will help preserve the forefoot/mid-foot running style I've developed since January. I'll probably buy a more conventional running shoe, but with a flatter and thinner bottom than motion control shoes, maybe a pair of racing flats, for longer runs, or race days. The regular running shoes (hopefully) would shield my feet from the repeated pounding I got from the VFF's, but would still let me run with a fore/midfoot strike -- preserving my knees, hips, quads, and lungs.
In the end, its not running in bare feet (what the VFF tries to simulate) that is better for you, its running with a mid/forefoot strike. The VFF is a means to achieving that end -- not an end in and of itself.
UPDATE
When I checked my VFF's this morning, I finally saw the damage the last run did to them.
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Those yellow spots you see towards the edge of the soles are where the outermost layer of rubber has worn out. Before the trail run there was only one yellow spot. Afterwards there were two.
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This hole is where the rubber wore all the way through. It wasn't like this before the trail run.
LESSON: Never use the VFF Sprint on city streets, trail runs, or any substantial outdoor workout.