E-17 Free Communication/Slide - Running Mechanics: JUNE 1, 2007 8:00 AM - 10:00 AM ROOM: 263
Heel contact during locomotion produces an impact acceleration that propagates up the musculoskeletal system. Impacts sustained during running may contribute to bone health as well as overuse injury. Greater peak tibial accelerations (TA) at impact have been associated with stress fracture. Knowledge of strategies we use to alter impacts may prove useful for prevention and treatment of running injuries and prescribing exercises to optimize bone health.
PURPOSE: The purpose of the study was to determine kinematic parameters associated with changes in impact acceleration during normal and soft running.
METHODS: Nine runners (5 male, 4 female, 73.6±12.7 kg, 178.4 ±10.5 cm) participated in this study. Retro-reflective markers were placed on the trunk and lower extremity for 2D motion analysis (120 Hz). Auniaxial piezoelectric accelerometer was mounted to the distal anterior medial tibia to quantify impacts (3600 Hz). Participants were asked to run under normal (N) and soft (S) conditions on a treadmill at their preferred speed (2.72±.48 m/sec). After warm up, subjects ran approximately 2 minutes in each condition. Motion capture and accelerometer data were collected concurrently for ten strides at the end of each running condition. Data were exported and analyzed in MatLab. Statistical analysis was performed in SAS.
RESUITS: Participants were able to decrease impacts, as measured by TA, during the soft condition (N: 4.58±1.69 g, S: 3.15±1.30 g, p<.0001). Univariate analysis revealed heel velocity at contact (HVEL) had the strongest association with TA (r=.67). A geometric model using HVEL and hip, knee, and ankle angles at contact was compared to an excursion model using HVEL and hip, knee and ankle joint excursions (from initial contact to TA). The geometric and excursion models had similar associations with TA (R=.817 and R=.784 respectively). Within the geometric model, backward elimination procedures determined that ankle angle at contact did not contribute greatly to the prediction of TA. The final model included HVEL and hip and knee angles at contact (R=.807).
CONCLUSIONS: HVEL and hip and knee angles at contact have a strong positive correlation with TA. Attempts to alter impact accelerations should consider these variables.