Does a Competitive Season Alter Elastic Bounce Mechanics in University Distance Runners?

Does a Competitive Season Alter Elastic Bounce Mechanics in University Distance Runners?

Alvin Sherman Library

The spring-mass model (SMM) describes the body's center of mass oscillation during running as a bouncing system, where energy is absorbed and released, producing two asymmetries that represent muscle-tendon elastic function: (1) landing-takeoff (LTO; % relative difference propulsion to braking time), and (2) rebound (REB; % relative difference effective aerial to contact time). Additional SMM-derived variables, such as vertical stiffness(kvert) and step frequency (SF) may provide insight into the influence of a competitive season on running elastic bounce mechanics in university distance runners. The purpose of this study was to examine the impact of a competitive cross-country season on SMM-derived variables in this population. Twelve NCAA Division II cross-country runners (4 men, 8 women; age, 19.7±1.9 yrs; height, 1.72±0.06 m; mass, 62.0±7.8 kg) performed a six-minute run at a self-selected speed (3.5±0.5 m/s) on an instrumented treadmill synchronized with a 10-camera motion capture system pre and post a seven-week competitive season. Bilateral kinematics and kinetics were collected using Vicon Nexus software. Paired t-tests showed no significant changes in SF (left: t(11)=-0.85, p=0.42, d=0.23; right: t(11)=-0.87, p=0.40, d=0.25), kvert (left: t(10)=0.93, p=0.37, d=0.28; right: t(11)=0.52, p=0.61, d=0.16), LTO (left: t(11)=1.91, p=0.08, d=0.55; right: t(11) = 0.29, p = 0.779, d=0.08), and REB (left: t(11)=0.12, p=0.90, d=0.04; right: t(11)=0.17, p=0.87, d=0.05) indicating that elastic bounce mechanics remain stable across a competitive season. Effect sizes were trivial to medium. These findings suggest preservation of tissue-based elastic properties despite increased mechanical training load increases.