I'm going to go ahead and say if your shoes aren't *the* problem, they certainly aren't helping matters.
Good running shoes are the single most important investment I made in tri's. They made all the difference. Go to a specialty running store and get them to evaluate your stride/walk and your foot. They'll put you in either a neutral shoe
(if you're part of that tiny percentage of the population who doesn't roll in when the walk
) or a support shoe
(if you're in the majority that needs some form of correction because of pronation
(rolling in
)
). Walmart shoes are fine for just kicking about the gym and doing circuits, but I doubt they've got the sort of cushioning and support needed to handle the 3x of your body weight that hits every stride when you run. Yeah, they're expensive, at least $65, although sometimes you can get them on sale when the styles are changing...the most expensive is about $115-125, but that's a top of the line, high support shoe, which might be more than you need
(Asics Kayano, Brooks Beast, etc
). Most people spend about $75-80, needing mid-range support shoes
(like Asics 2130, Brooks Adrenaline, etc
) or mid-range neutrals
(Asics Landreth etc
). A few need motion control shoes, but that's a tiny percentage of the population. Seriously, go to the running store. They'll treat your feet like a NASA exercise, it's great!
Again, it might not be *the* problem with your back right now
(because of course, I'm an art historian, not a doctor
), but the price of a pair of good running shoes negates the astronomical cost of physiotherapy later from knee injuries and the like.
Welcome to the sport!