Reference Biomechanical Parameters and Natural Asymmetry Among Runners Across the Age Spectrum Without History of Running-Related Injury

Heather Ketelaar Vincent^*Reed PoppOrlando CicilioniKevin Robert VincentLydia PezzulloMatthew MartensonRyan M Nixon, PhD

• University of Florida, Gainesville, Florida, United States

Running biomechanics and expected mechanical asymmetries among runners with no history of running injury have not been established across the age continuum. Therefore, the purposes of this study were to: 1) provide age specific biomechanical gait parameters in runners aged 15-75 years with no history of running injuries, and 2) determine whether age influenced gait parameter asymmetry. This cross-sectional study included 250 runners with no history of running-related injury (15-75 yr; 22.8±3.3 kg/m 2 ; 45.2% female). Participants were grouped by age into four brackets (in years): ≤18, 19-35, 36-55 and ≥55. All runners completed comprehensive running intake forms and performed a 3-dimensional gait analysis. Kinematic data were collected using a motion capture system and normalized to a gait cycle, while participants ran on a level grade at self-selected speed on an instrumented treadmill. Current running volume, temporal-spatial, kinetic and kinematic parameters were compared between groups. Univariate analyses of variance with covariates (sex, running velocity) were used to test age effects on biomechanical variables and asymmetry outcomes. Effect sizes of age bracket were determined for runner characteristics and biomechanical variables. Runners ≥55 years had the slowest velocity and 1.7%-4% slower cadence compared to the younger age brackets, with 0.1%-0.7% and 0.8%-3.7% less right-to-left interlimb asymmetry in step length and pelvic drop, respectively (all p<.05). Runners 36-55 years produced 0.1%-0.5% and 5.8%-10% less right-to-left interlimb asymmetry in stance times and ankle flexion moments, respectively, and 7.9%-8.2% lower vertical average loading rates (VALR) than other age brackets (all p<.05). Overall, the highest right-to-left interlimb asymmetries expressed in percent, occurred in ankle flexion moments, ankle and knee frontal excursions and peak VALR (ranging 12.1%-33.8% different between right and left limbs). Given that we did not find consistent effects of age across the biomechanical variables, the asymmetries found here may be related to other factors than age. Natural interlimb mechanical asymmetry can be very high in healthy non-injured runners especially among kinetic parameters. These data can help inform reference ranges of normative biomechanical metrics, and guide clinicians in gait retraining and performance targets across the age spectrum.