During landing, the human body is required to absorb impact forces throughout its tissues. Muscle and connective tissue is able to dissipate much of this force, however, a portion of the impact is delivered to the bones. Forces acting on the human skeleton can cause microscopic fractures which may lead to stress fracture. The present study seeks to calculate changes in the magnitude of strain using noninvasive methods. A musculoskeletal model representing a healthy male subject (22 years, 78.6 kg, 1.85 m) was created. A flexible tibia, created from a computed tomography scan of the subject’s right tibia, was included in the model. Motion capture data were collected while the subject performed drop landings from three separate heights (26, 39, and 52 cm) and used to compute simulations in LifeMOD. Surface electromyography and joint angle data were compared to their simulated counterparts using a cross correlation. Maximum magnitudes of principal and maximum shear strain were computed. The model had reasonable agreement between joint angle curves. A large Cohen’s d effect size showed that our subject had increased tibial strain and strain rate as the drop height increased. This study demonstrates a valid method of simulating tibial strain during landing movements. Future studies should focus on recruiting a larger sample and applying this method. / School of Physical Education, Sport, and Exercise Science

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

In gymnastics, females are often afflicted with lower extremity injuries during the landing phase of a backward rotating skill. The purpose of this study was to assess the efficacy of using a drop landing and backward somersault landing to compare and contrast the kinetic and kinematic differences between the two tasks in order to determine if a drop landing is a suitable representative task to analyze when examining landing injury mechanisms. Eleven female NCAA Division I gymnasts (age 19.3 ± 0.9 yrs; body height 1.66 ± 0.05 m; body mass 61.36 ± 6.02 kg) were recruited to perform drop landings and backward somersaults. Two force plates along with a 3D movement analysis system were used to collect kinetic and kinematic data. A repeated measures ANOVA was used to examine the differences in the variables with the significance level set at 0.05. There were mechanical differences and significance found between the peak vertical ground reaction forces, loading rate, kinetic and kinematic variables in the sagittal and frontal planes during the two tasks. It is evident that results may underestimate the effect of gymnastics landing impacts on risk of lower extremity injury because of the mechanical differences and significance found between the two tasks. / Access to thesis permanently restricted to Ball State community only.