585 MEP147 – Increasing step frequency reduces cumulated patellofemoral joint stress more at slow running speed

AbstractBackground Patellofemoral pain syndrome is a highly prevalent running-related injury. Alterations in running speed and step frequency are typical preventative measures to reduce patellofemoral joint stress (PFJS). Remarkably, the combined effect of these interventions on PFJS load parameters has not yet been investigated.Objective To investigate whether step frequency alterations were equally effective across running speeds for key PFJS load parameters.Design Cross-sectional study Setting Laboratory-based testParticipants Twelve healthy recreational runners: 6 men and 6 women aged 22±3 years, with a body mass of 68.5±6.7kg, and height of 1.77±0.10m. Assessment of Risk Factors The participants performed an incremental speed protocol on an instrumented treadmill at habitual, 10% increased and 10% decreased step frequency. The protocol started at 8km/h and increased by 2km/h until 16km/h was reached. Kinematic data of the lower limbs and trunk and ground reaction forces were measured. PFJS load parameters were calculated using OpenSim musculoskeletal modelling. Main Outcome Measurements Peak PFJS per step and cumulated PFJS (impulse per km). Results For peak PFJS, significant main effects were confirmed for running speed (p<0.001) and step frequency (p<0.001), but there was no significant interaction effect (p=0.338). Faster running speeds resulted in higher peak PFJS over all step frequencies and increased step frequencies resulted in lower peak PFJS over all running speeds. For the cumulated PFJS, significant main effects for running speed (p<0.001) and step frequency (p<0.001) as well as a significant interaction effect (p<0.001) were found. Step frequency alterations affected the cumulated PFJS more at slow running speeds. Conclusion Whilst step frequency alterations are equally effective at slow and fast running speeds to change peak PFJS, the effectiveness on cumulated PFJS is higher at slow running speeds. This changes our view on how to optimise load management strategies for the prevention of patellofemoral pain syndrome in runners.Download figure Open in new tab Download powerpoint Abstract 585 Figure 1 Mean values for peak PFJS and cumulated PFJS across the measured running speeds for each step frequency condition