Inter-limb range of motion and jumping asymmetry linked to running performance in healthy adult recreational endurance runners: A cross-sectional study

Background Inter-limb asymmetry is often considered a limiting factor in athletic performance, yet evidence regarding its impact on endurance running remains limited. Therefore, this study aimed to quantify inter-limb asymmetry in ankle dorsiflexion range of motion (ROM) and repeated jump performance, to examine its association with running performance, and to compare running performance across asymmetry levels in healthy adult recreational endurance runners of varying training status. Methods Sixty runners (50% male) performed an ankle dorsiflexion ROM test and a 5 repeated horizontal/vertical jump test to quantify inter-limb asymmetry. Multiple linear regression was used to assess the predictive value of asymmetry metrics for running performance assessed by the Cooper test. Additionally, task- and metric-specific median-split analyses were performed to compare running performance between low- and high-asymmetry groups using independent-samples t tests. Results Mean ankle dorsiflexion ROM asymmetry was 3.30%, while jump-derived asymmetry ranged from 4.87% to 13.90%, with all asymmetry metrics exceeding their respective intra-limb variability. Inter-limb asymmetry did not significantly predict Cooper test performance (p = 0.073 to 0.947), and no significant differences in running performance were observed between low- and high-asymmetry groups for most metrics (p = 0.080 to 0.875). As an exception, the low-asymmetry group in terms of the reactive strength ratio (5 repeated horizontal jump test) demonstrated superior running performance, with a moderate effect size (p = 0.011). Conclusions Recreational endurance runners exhibit meaningful inter-limb asymmetries in ankle dorsiflexion ROM and 5 repeated jump performance. However, these asymmetries generally do not impair running performance. Reactive strength ratio asymmetry may be more sensitive to performance differences, highlighting the importance of a task- and metric-specific approach when interpreting asymmetry thresholds. Trial registration: ClinicalTrials.gov (NCT06808399). Registered on 02 April 2025.