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Objectives: To compare muscle power between youth who acquired HIV perinatally and HIV unexposed uninfected (HUU) youth., Methods: We assessed muscle power (relative to body mass, P max /mass), muscle force normalized to body weight (F max /BW), force efficiency, jump height (H max ) and velocity (V max ) during a single two-legged jump with hands on waist on a force platform (Leonardo) in HIV+ youth (n=35, 9-21 y). Thirty-three and 22 participants returned at 12- and 24-months, respectively. We compared age- and sex-specific z-scores in the HIV+ youth to those in HUU controls (n=716, 9-21 y) adjusting for height and muscle cross-sectional area (MCSA, by pQCT)., Results: At baseline, z-scores for Pmax/mass, F max /BW and V max were less than 1 standard deviation lower than HUU after adjusting for height and MCSA (p⟨0.05). P max /mass z-score was negatively associated with level of immunosuppression (p=0.013), but this relationship was not significant after adjusting for height and MCSA (p=0.07). Z-scores for all mechanography outcomes remained stable over time in HIV+ youth., Conclusion: Small deficits in muscle power were apparent in children and youth who acquired HIV perinatally, and the trajectory of muscle power did not change over two years. Further study is needed to identify effective strategies to improve dynamic muscle function in this population.

Objectives: To determine if bone health is compromised in perinatally HIV-infected youth., Methods: We assessed BMC at the proximal femur, lumbar spine and total body using DXA in perinatally HIV-infected youth (n=31; 9-18y). Using pQCT, we assessed muscle CSA, total and cortical bone area, cortical BMD and thickness and strength strain index at the tibial shaft. Thirty and 18 participants returned at 12- and 24-months, respectively. We calculated age- and sex-specific z-scores for the HIV-infected youth using data from a healthy cohort (n=883; 9-18y)., Results: At baseline, height and MCSA were reduced in HIV-infected youth (-0.79 to -0.23, p<0.05). BMC z-scores adjusted for height and lean mass were lower than controls at all sites except the lumbar spine (-0.57 to -0.27, p<0.05). Bone area and strength z-scores were not different from zero after adjusting for tibial length and MCSA. In contrast, cortical BMD z-scores were greater in HIV-infected youth (0.46, p=0.011). Z-scores for all bone outcomes showed positive trends over time in HIV-infected youth., Conclusion: Although HIV infection may be associated with bone mass deficits during growth, bone geometry and strength appear adapted to muscle force. Further, deficits in bone mass may dissipate over time in this population.