shoes: trainers vs racers is there a difference?

I have several pairs of shoes; four are lightweight and I have another two pairs of trainers (until I retire them).

Two pairs of the lightweight shoes I use for racing only (Adidas Evo spikeless x-country flat and Adizero RC's) depending on the course conditions.  My other lightweight shoes (Adizero Breeze and Bostons) I rotate through as my everyday training shoe along with my regular trainers.  Once I retire these trainers, I am going to replace them with more lightweight shoes as I've found that I greatly prefer to run in a minimalist shoe.

Having said that, I would not recommend someone train full time in a lightweight shoe until they have gotten used to them; if all you've ever run in is a regular trainer, it will be a big difference to go to a lightweight shoe.

For an idea in the differences, my RC's are about 185g, Boston's about 270g and my regular trainers are about 350g.

Shane

Racing in a lighter shoe definitely makes a difference.  I used x-country racing flats/spikes in high school (probably more simplistic than the Zoot/Newton shoes you pointed out).  Training with heavy Sauconys all week long, then switching to the flats/spikes for race day made my legs a lot less tired during the race b/c there was a lot less weight for my feet to pick up stride after stride for 3.1 miles. 

However, at the time, I was pretty fast.  I wasn't winning the race, but I was placing for my team at 20 & high change to 22 & low change mins. 

Today, I don't think my 26 min 5k needs a racing flat...and a flat alone certainly isn't going to take me back to my high school times.  There are other things that will make a much bigger difference to take on first...like significant speed training...hills (lots of hills!)...mileage higher than my current 15/wk...the 10 lbs I carry now that I didn't at 16, etc. 

So, I think it is worth your while if you are really fast and close to placing...or if you are able to handle and prefer less of a shoe for regular everyday training.  For Joe-schmoe (or Jess-schmoe), I don't think special racing flats in addition to regular trainers are going to do much. 

Some popular press stuff:

Academic Studies

(There are hundreds of articles.  Here are just a few; the academic discussion goes back a long way, and specifically the thought that less cushioning may be better predates the current hype by decades -- see for example the first article.)

Tests a specific hypothesis about why foot injuries are less common in populations that do not wear shoes.  Interesting because the study purports to show that one can in fact gain the hypothesized physiological 'adaptation' (involving the flexibility of the medial longitudinal arch) simply by wearing shoes less frequently.

Argues that one aspect of the purported biomechanical differences induced by barefoot (versus shod) running is due to poor measurement procedure, and that upon correct measurement, there is no appreciable difference.  This is a rare skeptical voice -- most articles on this topic suggest a difference in form of some sort or another between shod and barefoot running.  Of course, the fact that most of these studies focus on a very specific aspect of form means that there is room for both views, wrt different aspects of form.

Supports and extends earlier research purported to show that barefoot running minimizes pronation.

Study suggests that shoes encouraged landing with a more dorsiflexed and stiffer ankle, as well as a more flexed knee.  The explanation is very interesting -- they suggest that the body naturally regulates the amount of stiffness in the entire system, and if there is some cushioning at one end (the shoe), then the body makes other things more stiff to 'compensate'.

Argues that prescriptions for standard running shoes do not meet the standards of evidence-based medicine.  (Note for BTers:  evidence-based medicine is very controversial, despite the name.  Lots of very reasonable things that doctors do might not meet this standard.)

Some web sites devoted to bare-footedness:

A book that is apparently causing some of the current hype:

And of course shoe companies are beginning to clamor over how to make money off of this hype (though in fairness to Nike, their Free shoes caused some of the hype).