Footwear: in 848 recreational runners, hard-midsole shoes raised injury risk (SHR 1.52)
But the protective effect of cushioning showed only in lighter runners; transitioning too fast is the other real risk
Participants
n=848 healthy recreational runners randomly received one of two shoe prototypes that differed only in cushioning (global stiffness 61.3 ± 2.7 vs 94.9 ± 5.9 N/mm, soft vs hard). Followed 6 months; injury = any physical complaint reducing or interrupting running for at least 7 days. Light/heavy split at the median body mass (78.2 kg men, 62.8 kg women).
Protocol
Randomized controlled trial (ClinicalTrials.gov NCT03115437): 848 healthy runners randomly received 1 of 2 shoe prototypes that differed only in cushioning, a soft and a hard version (from the abstract).
Runners were tracked for 6 months, logging their running and any injury; an injury was any physical complaint that cut back or stopped running for 7 days or more.
Analysis: time-to-event models with subhazard rate ratios (SHR, 95% CI); a stratified analysis of lighter vs heavier runners split at the median body mass.
Key Findings
Runners given the hard shoes carried a higher risk of injury: SHR 1.52 (95% CI 1.07–2.16). Body mass on its own showed no link with injury risk (SHR 1.00).
Split by body mass, hard shoes raised injury risk in the lighter runners (SHR 1.80, 95% CI 1.09–2.98) but not in the heavier ones (SHR 1.23, 95% CI 0.75–2.03) — so extra cushioning protected, relative to the hard shoe, only the lighter runners, the opposite of the common belief.
Not from this paper (related work; each summary checked against that paper's own abstract): Theisen 2013 (DOI 10.1136/bjsports-2013-092613), 247 leisure runners, 5 months — midsole hardness not associated with injury (HR 0.92, 95% CI 0.57–1.48); BMI, previous injury and mean session intensity were risk factors.Ridge 2013 (DOI 10.1249/mss.0b013e3182874769), 36 runners — after a 10-week gradual transition to minimalist shoes, 10 of 19 in the minimalist group showed increased foot bone-marrow oedema on MRI vs the control group (P = 0.009).Ryan 2013 (DOI 10.1136/bjsports-2012-092061), 103 runners over 12 weeks — the partial-minimalist shoe had the most injuries (12 vs 4 in the neutral shoe); full-minimalist runners reported more shin and calf pain.
Practical Application
In this 848-runner RCT the soft shoe carried lower injury risk overall (hard-shoe SHR 1.52), but only lighter runners benefited from the cushioning; heavier runners showed no difference. Do not tell heavier runners they need softer shoes — choose by comfort, fit and habituation; a softer shoe is a reasonable default for lighter runners.
Switching shoe category or making a big drop change: transition over many weeks, low volume first, and watch forefoot/metatarsal pain (bone-stress red flag, REF-622).
Limitations
Two prototypes of one model; 6-month window; the body-mass interaction is a stratified (subgroup) analysis; the minimalist-transition studies are small.
How this entry was checked and changed
Content correction 2026-09-27
"Heavier runners may benefit from softer cushioning" -> reversed: the abstract shows the protective effect of cushioning only in lighter runners (SHR 1.80 in hard shoes); heavier runners showed no significant difference (SHR 1.23).
Added the abstract's numbers (n=848, stiffness of the two shoes, SHRs, injury definition, median body-mass cut-offs).
Theisen, Ridge and Ryan summaries rewritten against their own abstracts (n, follow-up, effect sizes); "some progressing to stress reaction/fracture" removed (not in the Ridge abstract).
2026-09-28: added Protocol from the abstract (Europe PMC, DOI 10.1177/0363546519892578, PMID 31877062).