I monitor several online forums on the topic of running and more specifically shoes. I do it primarily to find trends, listen to various peoples opinions and learn or chime in with my knowledge. I have actually brought shoes into our inventory here at Kyle's that were highly regarded in some of these forums
Occasionally a forum topic will disturb me and I have seen this one (or a variation of it) several times. The question usually goes something like, "why do my feet go numb when I run or walk for several miles?" Seems like a simple enough question that typically results in an equally simple answer. What I have seen more than once, and is really disturbing, is a reply along these lines: the respondent will claim that the cause is probably "compartment syndrome" or poor circulation. One responder urged the person to suspend all exercising until they have seen a cardiologist... really? Can you say overkill to the extreme..
Just about everyone who comes into the shop for running shoes that have had a self-serve experience at a big box or department store buys the same size running shoes as their casual or dress shoes. What they do not take into consideration is the swelling that occurs during exercise. I typically put that person in shoes a full size (frequently even more) larger than they think they should wear. I hear "I've never worn size X in my life. That can't be right" just about every day.
Feet in shoes too small go numb because as the feet swell, the person subconsciously starts to curl their toes under. This is their toes "defense mechanism" to prevent bruising or loss of toenails. As the toes curl, muscles in the feet flex resulting in restricted blood flow. Unless you have a history of poor circulation there is no need to see a freaking cardiologist. Just try some bigger shoes.
Fact of the matter is that there is no adverse consequence to wearing running shoes that are "too big."* A thumbnail width of space between your longest toe and the front of the shoe is recommended. But that measurement needs to be done while you are standing up straight. It is very difficult to do by yourself unless you have abnormally long arms. One of the best reasons I can think of to come to Kyle's and not only get the right shoes, but the right size shoes. We'll make sure of that.
*See "Combat Running Blisters"
Bill-Guru of Shoe