Coordination and coordination variability during running with respect to internal loading and age

Abstract

Running is a largely popular and widely accessible form of exercise. However, running may pose risks to individuals due to its associations with high rates of injuries. Coordination between lower extremity joints and segments as well as coordination variability have linked to these running injuries. While mechanisms of injury are multifactorial, one theory suggests that reduced coordination variability may cause injury by increasing cumulative loading of soft tissue structures. This relationship may be important when assessing age, as prevalence of injuries differ between adolescents and adults. Therefore, this thesis aimed to 1) assess the relationship between coordination variability and loads in the Achilles tendon and patellofemoral joint during running 2) and evaluate differences in segmental coordination and variability between adolescent and collegiate runners. In Study 1, 64 healthy, adult runners ran on an instrumented treadmill while kinematics and kinetics were recorded. Coordination variability for knee-shank, knee-rearfoot, and shank-rearfoot couplings were calculated using vector coding. Achilles tendon and patellofemoral kinetics were calculated with musculoskeletal models. Surrogate variables were created for Achilles tendon and patellofemoral metrics using principal component analyses, and regressions were used to determine whether variability metrics predicted loading surrogates. One surrogate variable was created for Achilles loading, and lower knee-rearfoot variability predicted greater Achilles loading. Two surrogate variables were created for patellofemoral loading. Lower knee-rearfoot and knee-shank variability predicted greater peak patellofemoral loading, but no variability predicted cumulative patellofemoral loading. This suggests that a combination of low variability and large loads may be important for injury risk rather than cumulative loading. Study 2 assessed 21 competitive adolescent and 21 collegiate runners. Coordination variability was calculated using vector coding for various thigh, shank, and rearfoot couplings. Coordination patterns were analyzed using a binning frequency analysis. Adolescent and collegiate runners displayed different coordination patterns while running that primarily emerged from the transverse plane. Adolescent runners displayed greater coordination variability on average than collegiate runners. Combined with previous literature, this suggests a downward trend in coordination variability starting in adolescence and continuing through adulthood. In conclusion, coordination and its variability may be consequential in terms of injury mechanisms and different age populations.