Do injury-resistant runners have distinct differences in clinical measures compared to recently injured runners?

Key points

1. 01Recently injured and acquired re-injury resistance runners had greater plantar flexion strength than never-injured runners, likely due to rehabilitation participation
2. 02Recently injured runners had greater hip abduction strength than never-injured runners, possibly reflecting targeted rehabilitation or compensatory adaptation
3. 03Joint motion measures (dorsiflexion, hip extension, hip rotation) showed no significant differences between injury groups
4. 04Foot alignment (navicular drop, Foot Posture Index) was largely similar across groups, except females with acquired re-injury resistance had a more neutral FPI than recently injured females
5. 05Limb symmetry measures showed no significant differences between injury groups, suggesting some asymmetry is normal regardless of injury history

How it was conducted

Design

Cross-sectional comparative study with three injury-status groups

Participants

223 recreational runners (116 recently injured, 61 acquired re-injury resistance, 46 never injured); 274 enrolled, 51 excluded for injury 1-2 years prior

Groups

Recently injured (3-12 months prior), acquired re-injury resistance (uninjured >2 years), and never-injured runners

Measures

Isometric hip abduction, hip extension, knee flexion, knee extension, plantar flexion strength; ankle dorsiflexion, hip extension, hip internal and external rotation motion; navicular drop; Foot Posture Index; bilateral symmetry angles

Analysis

Two-way ANOVAs (group x sex) with post-hoc Gabriel's Test; Kruskal-Wallace for non-normal data; chi-square for categorical measures

Setting

Dublin, Ireland; single baseline testing session, January-August 2018

What they found

• Plantar flexion strength was greater in recently injured runners compared to never-injured runners (P = .001) and in acquired re-injury resistance runners compared to never-injured runners (P = .001); overall group effect P = .002, partial eta squared = .057 (small effect size)
• Hip abduction strength was greater in recently injured runners compared to never-injured runners (P = .019, partial eta squared = .038, small effect size); trend toward significance vs. acquired re-injury resistance group (P = .067)
• No significant differences in knee flexion, knee extension, or hip extension strength between injury groups
• No significant differences in ankle dorsiflexion, hip extension, hip internal rotation, or hip external rotation motion between injury groups
• FPI interaction effect between sex and injury status (P = .023, partial eta squared = .036, small effect size); females with acquired re-injury resistance had significantly lower FPI (median +4, IQR +1 to +6) compared to recently injured females (median +7, IQR +4 to +8; P = .007)
• No significant association between navicular drop >10 mm and injury status: chi-square X2 (2, N = 209) = 1.644, P = .440
• No significant association between FPI classification and injury status: chi-square X2 (8, N = 212) = 3.363, P = .910
• No significant differences in symmetry angles for any measure between injury groups
• Males had significantly greater strength for all muscle groups except plantar flexion (P < .05), greater navicular drop (P = .000, partial eta squared = .062, moderate effect size), greater ankle dorsiflexion motion (P = .019, partial eta squared = .027, small effect size), and lower hip internal rotation motion (P = .038, partial eta squared = .02, small effect size) compared to females

Limitations

• Retrospective design prevents determining whether group differences are caused by injury or are pre-existing risk factors
• Isometric strength testing in a fixed position does not capture the concentric and eccentric demands of running, limiting ecological validity
• Grouping injuries together and averaging bilateral values limits injury-specific and side-specific comparisons
• Recall bias in self-reported injury history, and rehabilitation details were not collected for the acquired re-injury resistance group

Why it matters

For patients

Runners who have never been injured do not appear to have clearly superior strength, mobility, or foot alignment, so these tests alone cannot reliably predict who will stay injury-free.

For clinicians

Standard clinical tests of isometric strength, joint motion, and static foot alignment have limited discriminative value for identifying injury resistance in recreational runners, though they remain relevant within rehabilitation to track recovery and address specific deficits.

For readers

High rehabilitation participation among recently injured runners may mask or even reverse expected differences, meaning counterintuitive findings (higher strength in injured groups) likely reflect post-injury training adaptations rather than true risk factors.