Ground contact results in the generation of a heel-strike transient that propagates through the musculoskeletal system. The inability to attenuate the heel-strike-induced shock wave is a possible factor in the development of various gait pathologies and overuse-type injuries, such as knee osteoarthrosis, stress fractures, and low back pain. It is hypothesized that prolonged running will result in increased shock transmission at the tibia and sacroiliac joint during conditions of controlled velocity/stride mechanics. Subjects performed an extended running trial for 25-minutes at 75% HRReserve. EMG data of the vastus medialis, vastus lateralis, and tibialis anterior and accelerometer data from the tibial tuberosity and sacrum were recorded at one-minute intervals. Accelerometer data at the tibial tuberosity did show a significant increase during the run protocol. Linear regression of EMG frequency and tibial shock also demonstrated a significant relationship. An extended running protocol will lead to increases in tibia shock acceleration independent of stride mechanics. / School of Physical Education