Minimalist running shoes are simply shoes designed to provide the closest experience to barefoot running possible while still protecting the feet from rocks, broken glass, and other hazards that make barefoot running dangerous.
Generally, this is done by eliminating the thick padding typically seen in running shoes and trading the solid sole for a thinner, more flexible sole that lends a more "barefoot" feel. Many minimalist runners enjoy the feel of the pavement beneath their feet and relish the freedom of being able to run nearly barefoot, while others prefer a little more protection from sharp objects and hot pavement. Whatever your preference, you will be able to find minimalist running shoes that suit your needs.
If you are like most runners, you will likely need to adjust your running stride when using your new minimalist shoes. Traditional running shoes have thick padding in the heel to cushion the foot as it hits the ground. This cushioning tends to allow most runners to comfortably lengthen their stride and strike the ground with the heel first. Actually, one of the main reasons some runners choose to use minimalist shoes is because this heel strike causes the knee to absorb too much of the force from each stride instead of allowing the ankle and calf muscles to absorb some of the shock, leading to knee pain and injuries in some frequent runners.
In minimalist shoes, there is little to no padding in the sole, making the heel strike very uncomfortable to maintain for long periods of time. Most minimalist runners compensate for this by shortening their stride and landing on the middle of the foot or even the ball of the foot, and then using the calf and ankle muscles to absorb the shock and gently spring forward into the next step. Minimalist runners who transitioned from regular running shoes are often amazed at how this "springy" stride allows them to run further and faster than they are accustomed to doing. This, however, can create the temptation to go too far too fast when just starting out with minimalist shoes.
If you have been using traditional running shoes with thick padding, making the transition to a minimalist shoe can be somewhat awkward. Other runners who have switched to minimalist shoes recommend using them in small bursts at first and gradually increasing your mileage in them instead of tossing out your old shoes entirely and making the switch all at once. This will give your muscles the chance to adjust to your new stride, which often forces the muscles of the calves and ankles to work harder than with regular running shoes that do the work for you. Running too far too soon in minimalist shoes can cause calf and ankle muscle soreness, which may put some people off from trying them again.
In addition to the lack of cushioning, minimalist shoes often provide little to no arch support, in an attempt to make the runner feel as close to barefoot as possible. Starting out at a smaller portion of your usual distance will allow your feet to slowly get used to absorbing the pressure in the arch and using the foot's natural spring to propel your body forward. If you are used to wearing traditional running shoes, your arches are likely weaker than they would naturally be because they are used to letting the shoes provide the support. You will need to slowly build up your arch strength to avoid foot pain and possible injuries. Starting out by running on grass or other soft surfaces can help your feet build up strength before you move to running on streets or sidewalks.
If a runner has problems transitioning to minimalist shoes, it will likely be because of the lack of arch support. Many people are too impatient to start out with lower mileage than usual and end up pushing too hard and being in pain the next day. While most people should not have a problem with minimalist shoes if care is taken to transition slowly, some runners never seem to get used to the unsupportive minimalist shoes and eventually return to using traditional padded running shoes.
Many runners for whom minimalist running has had a dramatic positive influence recommend at least trying minimalist shoes if you are at all interested. For some runners, they mean the difference between being able to run longer distances or sprint faster without the pain that comes from an unnatural stride facilitated by thick cushions and artificial foot support. Just remember to take it slowly at first and do not be afraid to return to your regular shoes if you find that they suit your running style better. Minimalist shoes, after all, are primarily a way of returning to the body's natural barefoot state in an attempt to reduce pain and injuries caused by running in an unnatural way. If running nearly barefoot seems even more unnatural to you than running with cushioned shoes, then by all means work with whatever makes your body most comfortable.