Yesterday my workout called for something hard- like 800 meter repeats, and I was disappointed to see the weather was not going to cooperate- windy, cold, and light rain.
Fortunately the Super Gym on Camp Humphreys includes a 10 lap per mile track - the tight turns are less than ideal however this was good enough for me to get in the quality I needed for 800s.
Warm up took longer than usual, and I was having trouble with my right knee, both the result of biking yesterday. And I was wearing Asics Gel 1140s for added protection (left foot has also been acting up). The first 3 with 60 seconds recovery were 3:08, 3:05, 3:04.
Feeling no foot pain I switched to the light-weight Brooks Launch and ran the last 3 in 2:59, 2:59. 2:57- not bad on this track (my guess is the turns cost me at least 1 sec per lap) but I was definitely done after 6. I felt immediately that I was more efficiently with the lighter shoes, landing more mid-foot than heel. My opinion is could increase risk for injury if you are not ready for it, which is why I prefer artificial turf for intervals these days.
Coincidently, check out this recent article in Runner's World- Barefoot vs Running Shoes: Which is More Efficient? Researchers found that adding 100 grams per shoe increased oxygen cost of treadmill running by 1%. They also noted that runners with shoes did better than without, however I would like to see that study repeated on a softer surface. From personal experience, my intervals on artificial turf are always a little faster without shoes.