Running footwear has been sold on injury prevention for decades, using a framework that research has substantially failed to support.
This is a summary of where the evidence sits rather than advice. Anybody with a running injury should be seeing a professional rather than reading about shoes.
The pronation framework
The dominant model for a long period.
The claim was that foot roll during landing could be classified into categories, that mismatched footwear caused injury, and that prescribing shoes by foot type would reduce it.
This produced the shop fitting process familiar to most runners — gait analysis on a treadmill, categorisation, and a corresponding shoe.
Trials testing whether assignment by foot type reduces injury have generally not found the predicted effect. Several large studies assigning participants to matched or unmatched footwear found no significant difference in injury rates, and in some cases the matched group did no better.
The framework has been substantially questioned within sports medicine, while remaining the basis of retail practice.
The cushioning question
Similarly unsettled.
More cushioning has been assumed to reduce impact and therefore injury.
Research on impact forces has complicated this considerably. Runners adjust their landing in response to underfoot feel, which means a softer shoe can be met with a harder landing, and the force reaching the body does not scale as simply as expected.
Studies comparing injury rates across cushioning levels have produced mixed results without a clear pattern.
The minimalist episode
Worth recounting because it illustrates the pattern.
A period of enthusiasm for very minimal footwear, based on arguments about natural running form, produced a substantial market shift.
Subsequent research and clinical experience found elevated rates of certain injuries among people transitioning quickly, particularly bone stress injuries in the foot.
The considered conclusion was that abrupt changes in footwear are the risk rather than any particular category, and that adaptation takes considerably longer than enthusiasts assumed.
The market moved on to maximal cushioning shortly afterwards, which is a reasonable illustration of how these cycles work.
What the evidence does support
A shorter list, and it is useful.
Comfort. Studies have found that self-selected comfortable footwear is associated with better outcomes than footwear assigned by any classification system. Comfort appears to be a reasonable proxy for a good individual match.
Gradual change. Sudden increases in training load are the most consistently identified injury risk factor, considerably more than footwear, and sudden changes in footwear compound it.
Rotation between pairs, which has some supporting evidence and a plausible mechanism in varying the loading pattern.
And replacing worn shoes, though the commonly quoted mileage figures are not well founded and vary enormously by runner and surface.
The carbon plate development
The one area where the performance claims have held up.
Footwear incorporating stiff plates and particular foam compounds has been shown in laboratory testing to improve running economy measurably.
The effect on race times has been visible enough that governing bodies introduced regulations on shoe construction.
That is a performance claim rather than an injury claim, it is supported, and it applies to a specific category of competitive footwear rather than to running shoes generally.
What retail practice does anyway
Worth noting the gap.
Gait analysis and category-based fitting remain standard in specialist retail, despite the weak support.
Some retailers have moved toward comfort-based fitting, which aligns better with the evidence.
The persistence is understandable. A structured process that produces a confident recommendation is commercially useful and reassuring to a customer, and telling somebody to choose whatever feels best is a harder sale.
What I would do
Try several, run in them if the shop allows, and choose what feels best rather than what a category suggests.
Change gradually, keeping the old pair for a transition period.
Rotate between two pairs if running frequently.
Increase training load slowly, which matters far more than any footwear decision.
And treat confident claims about injury prevention with scepticism, since the evidence for them has been examined repeatedly and has not held up.
When to replace them
Since the standard advice is not well founded.
Commonly quoted mileage figures do not appear to derive from strong evidence and vary enormously with runner weight, surface and gait.
What is more useful is the state of the midsole, which is where the cushioning is and which compresses permanently. Visible creasing and a loss of resilience when pressed indicate it has gone.
Outsole wear is visible and is generally not the limiting factor.
And a return of aches that resolve with a new pair is informative in retrospect, which is unsatisfying and is what most runners actually go by.
Surface and terrain
The variable that does have a straightforward answer.
Trail shoes offer grip on loose and uneven ground, and road shoes do not. That difference is functional and immediately apparent.
Beyond grip, the distinctions are smaller than marketed. Rock plates and reinforced uppers address specific conditions and add weight and stiffness.
For anybody running mostly on roads and paths, ordinary road shoes are appropriate and the terrain-specific categories are answering a question they do not have.