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Masafumi Terada, Megan Beard, Sara Carey, Kate Pfile, Brian Pietrosimone, Elizabeth Rullestad, Heather Whitaker, and Phillip Gribble

This study aimed to compare time-to-boundary and sample entropy during a single-leg balance task between individuals with chronic ankle instability (CAI), lateral ankle sprain copers, and healthy controls. Twenty-two participants with CAI, 20 lateral ankle sprain copers, and 24 healthy controls performed a single-leg balance task during an eyes-closed condition. Participants with CAI exhibited lower time-to-boundary values compared with lateral ankle sprain copers and healthy controls. However, we did not find differences in sample entropy variables between cohorts. A decrease in time-to-boundary values in participants with CAI indicated that CAI may constrain the ability of the sensorimotor system to maintain the center of pressure within the boundaries of the base of support. However, the regularity of the center of pressure velocity time series appears not to be altered in the CAI cohort in this study.

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Shelby Waldron, J.D. DeFreese, Brian Pietrosimone, Johna Register-Mihalik, and Nikki Barczak

Sport specialization has been linked to multiple negative health related outcomes including increased injury risk and sport attrition, yet a gap remains in our understanding of potential psychological outcomes of early specialization (≤ age 12). The current study evaluated the associations between retrospective athlete reports of sport specialization and both retroactive and current psychological health outcomes. Early specializers reported significantly higher levels of multiple maladaptive psychological outcomes (e.g., global athlete burnout, emotional and physical exhaustion, sport devaluation, amotivation). Overall, findings suggest that specialization environment factors, in addition to the age of specialization, are potentially critical factors in determining health and well-being outcomes. Findings support prominent position statements suggesting early specialization may be associated with increased health risks. Study findings may also inform the development of guidelines and recommendations to aid parents, coaches, and athletes in positively impacting athlete psychosocial outcomes.

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Amanda E. Munsch, Alyssa Evans-Pickett, Hope Davis-Wilson, Brian Pietrosimone, and Jason R. Franz

Insufficient quadriceps force production and altered knee joint biomechanics after anterior cruciate ligament reconstruction (ACLR) may contribute to a heightened risk of osteoarthritis. Quadriceps muscle lengthening dynamics affect force production and knee joint loading; however, no study to our knowledge has quantified in vivo quadriceps dynamics during walking in individuals with ACLR or examined correlations with joint biomechanics. Our purpose was to quantify bilateral vastus lateralis (VL) fascicle length change and the association thereof with gait biomechanics during weight acceptance in individuals with ACLR. The authors hypothesized that ACLR limbs would exhibit more fascicle lengthening than contralateral limbs. The authors also hypothesized that ACLR limbs would exhibit positive correlations between VL fascicle lengthening and knee joint biomechanics during weight acceptance in walking. The authors quantified VL contractile dynamics via cine B-mode ultrasound imaging in 18 individuals with ACLR walking on an instrumented treadmill. In partial support of our hypothesis, ACLR limb VL fascicles activated without length change on average during weight acceptance while fascicle length on the contralateral limb decreased on average. The authors found a positive association between fascicle lengthening and increase in knee extensor moments in both limbs. Our results suggest that examining quadriceps muscle dynamics may elucidate underlying mechanisms relevant to osteoarthritis.