The Ability of Sagittal Plane Kinematic Variables to Predict Loading in Different Populations of Runners

Abstract

It is known that sagittal plane kinematics are able to predict loading in runners. This may be of use to clinicians who don’t have access to force measurement devices. However, running biomechanics differ between genders and age groups. Thus it may be that models used to predict loading in demographically distinct groups of runners need to be specific to age and gender. PURPOSE: To determine if kinematic predictors of kinetic variables during running apply across genders and age groups. METHODS: Sagittal plane kinematics and kinetics were assessed in young male (YM: n=13, age=23.1 ± 2.3 yrs, mass=77.0 ± 12.1 kg, height=1.79 ± 0.08 m, velocity=3.32 ± 0.48 m/s) and middle-aged female runners (MF: n=28, age=47.3 ± 7.0 yrs, mass=63.7 ± 7.8 kg, height=1.66 ± .07 m, velocity=2.55 ± 0.37 m/s) using a 5 camera motion analysis system (Qualysis, Goteborg, Sweden) running on an instrumented treadmill (Treadmetrix, Park City, Utah) at their preferred running pace. Kinematics (knee flexion at initial contact, foot angle at initial contact, step position, peak knee flexion and COM excursion) were the independent variables; kinetics (average vertical loading rate, braking impulse, knee power absorption and peak knee extension moment and peak vertical ground reaction force) were the dependent variables. Linear regression models were developed to predict loading in both groups (α=0.05). RESULTS: In both YM and MF, sagittal plane kinematics were useful in predicting peak knee moment (YM: R2=0.56, p=.002; MF: R2=0.47,p=.0002), knee power absorption (YM: R2=0.78, p=.0002; MF: R2=0.55, p<.0001), braking impulse (YM: R2=0.66, p=0.01; MF: R2=0.67, p<.0001), and peak vertical ground reaction force (YM: R2=0.31, p=0.03; MF: R2=0.23, p=0.02). Peak knee flexion appeared in the most models (peak knee moment, knee power absorption and braking impulse for both men and women), and thus may be the most useful single kinematic variable to assess loading across age groups and genders. In all models, greater knee flexion was associated with increased magnitude of loading. Average vertical loading rate could not be predicted using the chosen kinematics in either group. CONCLUSIONS: When equipment for kinetic assessment is not available, sagittal plane gait analysis may be a useful tool for clinicians to estimate loading in runners.