Type of Thesis
Purpose: Many individuals exhibit biomechanical asymmetries during running. Yet, despite the prevalence, it is unknown how these biomechanical asymmetries affect metabolic cost. Altering biomechanical variables such as peak and stance average vertical ground reaction force (GRF) production, contact time, stride frequency, leg stiffness, and peak horizontal GRF production, all influence muscular demands that can change the metabolic cost of running and affect distance-running performance. Therefore, we investigated how step frequency asymmetries affected these biomechanical variables and the metabolic cost of running.
Methods: 10 healthy runners ran on a force measuring treadmill at 2.8 m/s while matching their steps to an audible metronome that beat at different randomly selected asymmetric step frequencies (0, 7, 14, and 21%). We measured metabolic rates (i.e. net metabolic power), GRFs, and stride kinematics throughout each trial.
Results: For every 10% increase in step frequency and stance average vertical GRF asymmetry, net metabolic power increased 3.5% (p<0.001), and for every 10% increase in contact time asymmetry, net metabolic power increased 7.5% (p=0.038). Furthermore, for a 10% increase in peak braking and propulsive GRF asymmetry, net metabolic power increased 1.3 and 2.0%, respectively (p<0.001). Net metabolic power was independent of peak vertical ground reaction force (p=0.422), and leg stiffness (p=0.054) asymmetry.
Conclusion: Increases in step frequency, stance average vertical GRF, ground contact time, and peak braking and propulsive GRF asymmetries result in an increased metabolic cost of running. However, healthy runners manipulate these biomechanical variables differently and thus have variability in the metabolic demand of asymmetrical running.
Azua, Eric N., "Asymmetric Step Frequencies Increase the Metabolic Cost of Running" (2017). Undergraduate Honors Theses. 1281.