Foot core training to prevent running-related injuries. A survival analysis of a single-blind, randomized controlled trial

Key points

1. 01Control group runners were 2.42 times more likely to sustain a running-related injury than intervention group runners (hazard ratio 2.42, 95% CI 1.98-3.62, P = .035).
2. 02The injury rate was 32.8% in the control group versus 14.0% in the intervention group over 12 months.
3. 03Greater foot strength gain and higher Foot Posture Index scores each correlated with longer time to injury (r = 0.45, P = .044 and r = 0.41, P = .031 respectively).
4. 04Older age was the only independent risk factor identified, with each additional year associated with a 1.07-fold increase in injury risk (P = .014).
5. 05Adherence to the supervised 8-week program was 88%, and remote adherence averaged 90.4% in the first 8 weeks, declining to 48.9% by 12 months.

How it was conducted

Design

Single-blind, parallel, randomized controlled trial with 12-month follow-up (NCT02306148)

Participants

118 recreational long-distance runners aged 18-55 years running 20-100 km per week for at least 1 year, with no injury in the prior 2 months

Groups

Intervention group (n = 57): 8-week supervised foot-ankle strengthening program (12 progressive exercises, once weekly in-person plus 3 times weekly remote); Control group (n = 61): 5-minute placebo static stretching 3 times per week

Primary outcome

Running-related injury incidence over 12 months, assessed weekly by self-report and confirmed by physical therapist

Secondary outcomes

Time to injury, Foot Posture Index, foot strength gain, Arch Index assessed at baseline, 8 weeks, and 16 weeks

Analysis

Intention-to-treat; Kaplan-Meier survival analysis with log-rank test; Cox proportional hazards regression

What they found

• Running-related injury occurred in 28 of 118 runners (23.5%; 95% CI 16.1%-31.4%): 20 from the control group (16.9%; 95% CI 10.2%-23.7%) and 8 from the intervention group (6.7%; 95% CI 2.2%-11.3%).
• Cox proportional hazards ratio: 2.42 (P = .035; 95% CI, 1.98-3.62), meaning control group participants were 2.42 times more likely to experience a running-related injury.
• Kaplan-Meier log-rank test at 12 months: P = .027; significant differences between groups first appeared at 8 months (P = .015).
• Cumulative risk difference at 12 months was 18.39%; at 10 months it peaked at 20.32%.
• 12-month survival probability: control group 0.666, intervention group 0.850.
• Time to injury correlated with Foot Posture Index (r = 0.41; P = .031) and foot strength gain (r = 0.45; P = .044).
• Age was the only significant independent covariate: each additional year of age was associated with a 1.07-fold increase in injury risk (P = .014; 95% CI, 1.013-1.129).
• Mean time to injury in the first 25% of injured participants: 7.63 +/- 2.60 months in the control group vs 10.15 +/- 2.69 months in the intervention group.
• Previous running-related injury did not significantly affect injury risk in survival analysis (log-rank P = .540).

Limitations

• Injury classification was based primarily on participant self-report, which may introduce under-reporting or misclassification bias.
• The study did not differentiate between injury types or anatomical sites, so it is unclear which injuries the foot program is most effective at preventing.
• Possible nocebo or placebo effects from group exercise sessions and information exchange cannot be fully excluded as contributors to the result.
• Excluding runners injured in the 2 months before baseline may have introduced selection bias toward a healthier, lower-risk population.

Why it matters

For patients

Recreational long-distance runners who commit to a foot-strengthening routine for at least 4 to 8 months may substantially reduce their risk of being sidelined by injury.

For clinicians

A progressive foot core program can be offered as a practical injury-prevention intervention, with benefits emerging between 4 and 8 months and an 88% supervised adherence rate suggesting it is feasible.

For readers

This well-controlled RCT provides level 1 evidence that foot core training cuts running injury risk by more than half over a year, though the underlying biomechanical mechanisms still require investigation.