Smaller Compressive and Anteroposterior Joint Reaction Forces in Older Compared to Young Runners

Abstract

Age-related changes in bone structure and mechanics may increase the risk of injury when performing exercise such as running. Joint-related injury such as osteoarthritis is a primary concern for older runners. A contributing factor to bony injury is joint loading. However, it is not known whether increased loading exists in older runners. PURPOSE: To compare anteroposterior and compressive joint reaction forces (JRFs) in the lower extremities during running in healthy young and older runners. METHODS: Nine healthy young runners (YA) and 10 healthy older adult runners (OA) performed fifteen over ground running trials at a fixed velocity (3.35 m/s). Running velocity was maintained (+ 5%) using an infrared timing gate. Three-dimensional kinematics and ground reaction forces were recorded simultaneously using an 8-camera motion capture system (240 Hz, Qualisys, Inc.) and force platform (960 Hz, AMTI, Inc.), respectively. Visual 3D was used to calculate ankle, knee and hip JRFs (compressive and anterior/posterior) during the stance phase of the gait cycle. Independent samples t-tests were used to compare mean JRFs in both directions. RESULTS: YA exhibited significantly larger mean JRFs at the ankle (p=0.04; YA: -13.2±1.0 BW; OA: -12.6±0.7 BW) and knee (p=0.04; YA: -13.0±0.9 BW; OA: -12.3±0.9 BW) while no differences were observed at the hip (p=0.08; YA: -12.0±1.0 BW; OA: -11.1±1.4 BW). In the anterior/posterior direction, older adults had significantly smaller ankle JRFs compared to young adults (p=0.01; YA: 5.1±0.7 BW; OA: 4.5±0.4 BW) while no differences were observed at the knee (p=0.20; YA: -3.0±1.2 BW; OA: -2.7±0.8 BW) or hip (p=0.37; YA: 2.4±2.0 BW; OA: 2.2±1.9 BW). CONCLUSIONS: These data demonstrate that OA have smaller compressive JRFs and anteroposterior shear forces than YA. Therefore, it can be suggested that the greater incidence of bony and cartilage injuries experienced by older runners is not due to greater forces applied to the lower extremity joints during running.