Rotating between multiple shoe pairs is associated with meaningfully lower injury risk, and shoe cushioning measurably degrades well before most runners replace their shoes
Interpretation
Malisoux et al.'s observational study of 264 runners found rotating shoes was associated with a lower injury hazard ratio (0.614) than running in one pair — a real association, though not from a trial that randomised rotation itself. A separate RCT in 848 runners found cushioning's effect on injury depends on body mass: heavier runners in harder shoes had nearly double the injury rate of heavier runners in softer shoes. Cook et al.'s older mechanical testing found shoe shock absorption falls to around 75% by 50 miles and under 60% by 250-500 miles, regardless of price or brand — meaning the cushioning most runners rely on has already degraded substantially well before a typical 300-500 mile replacement point.
Practical implication
Recommend shoe rotation as a reasonable, evidence-associated injury-risk reducer, and pair that with mileage-based (not just visual) shoe replacement — the degradation happens before it's visible or felt. For heavier runners specifically, flag that softer cushioning has a stronger evidence base.
Sources
3 sources, independently verified.
Runners who rotated between multiple shoe pairs had a significantly lower injury hazard ratio (0.614, 95% CI 0.389-0.969) than those using one pair, after adjusting for previous injury (HR 1.722, a stronger risk factor) and other-sport participation (protective, HR 0.848 per hour/week). The main evidence behind the rotation recommendation, though this is an observational association, not a trial that randomised runners to rotate or not.
An RCT comparing softer vs harder midsole cushioning found no overall injury difference (shoe hazard ratio 1.00), but a significant body-mass interaction: heavier runners in harder shoes had almost double the injury rate of heavier runners in softer shoes (SHR 1.80, 95% CI 1.09-2.98), while the effect in lighter runners was not significant. Cushioning preference isn't one-size-fits-all — body mass changes which cushioning level is protective.
Mechanical testing found shoe cushioning retained roughly 75% of its original shock absorption at 50 miles, ~67% at 100-150 miles, and under 60% by 250-500 miles — with runner-worn shoes showing a similar ~70% retention at 500 miles. Price and brand had no measurable effect on this decay. An old study, but the only one in this batch that directly quantifies how fast shoe cushioning degrades with mileage, independent of any injury outcome.