Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.
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Question: Context: Sit-to-stand tasks are commonly facilitated by modifying the initial position of the center of mass relative to the feet. It was hypothesized that modifications in the center of mass trajectory during sit-to-stand tasks altered the total body momentum at seat departure and redistributed the lower extremity net joint moments.', 'Between-task within-subject comparison was employed using a robust statistical method to accommodate for small sample size.', 'Six individuals performed four sit-to-stand tasks with systematic modifications in the initial center of mass position by varying the orientation of the lower extremity segments. The momentum of the center of mass and lower extremity net joint moments were quantified and compared.', 'Reducing the horizontal center of mass displacement significantly reduced horizontal total body momentum required at seat departure. Sit-to-stand tasks initiated with more horizontal shank and thigh positions required significantly greater knee and hip extensor net joint moments than those with more vertical shank and thigh positions. Sit-to-stand tasks initiated with vertical shank positions also required significantly greater hip extensor net joint moments as compared to those with more horizontal shank orientations.
Answer: When changes in initial center of mass position are made, alteration in center of mass horizontal momentum and the orientation of the lower extremity segments relative to the reaction force are observed. Consequently, mechanical demand imposed on the ankle, knee, and hip joint is redistributed. The magnitude of the net joint moments is dependent on the segment orientation, the reaction force, and the adjacent net joint moment.

Answer: Does modifying center of mass trajectory during sit-to-stand tasks redistribute the mechanical demand across the lower extremity joints?


Question: Context: Small studies suggest exogenous estrogen may improve vitamin D status, but the etiology is unclear because women who use hormones may make lifestyle choices that differentially affect vitamin D status.', 'Our objective was to investigate the association between use of hormonal contraception and 25-hydroxy-vitamin D (25(OH)D).', 'We used linear regression modeling of cross-sectional data to estimate percent change in season-adjusted serum 25(OH)D with estrogen use after adjustment for other factors.', 'At the enrollment clinic visit (2010-2012) into a cohort study of uterine fibroids, each subject provided a blood sample, had anthropomorphic variables and skin reflectance measured, and answered questionnaires on demographics, dietary and supplement intake, contraceptive use, reproductive and medical history, and behaviors.', 'A total of 1662 African American women, community volunteers, 23-34 years old, living in the Detroit, Michigan, area were included.', 'None.', 'Serum 25(OH)D was measured.', 'Serum 25(OH)D concentrations were low (70% <20 ng/ml). Current use of an estrogen-containing contraceptive was associated with a 20% (95% confidence interval: 14-27) increase in 25(OH)D after adjustment. There was no increase in 25(OH)D among participants who had used estrogen in the past, but were not current users, indicating that results were unlikely to be due to unmeasured confounding by factors related to contraceptive choice.
Answer: The increase in 25(OH)D with use of estrogen-containing contraceptives raise mechanistic questions regarding the biological pathways involved, and highlights the need for studies that examine possible endogenous estrogen effects on vitamin D.

Answer: Does use of Estrogen-Containing Contraception be Associated With Increased Concentrations of 25-Hydroxy Vitamin D?


Question: Context: We evaluated the prognostic value of mid-regional proadrenomedullin (MR-proADM) in atrial fibrillation (AF) patients undergoing radiofrequency ablation.', 'Plasma concentrations of MR-proADM were measured at baseline and after 12months in 87 AF patients in whom radiofrequency ablation was performed. The association between MR-proADM and AF recurrence was tested by univariable and multivariable Cox models.', 'In all 87 patients radiofrequency ablation was successfully performed. Of the total population 54% had paroxysmal AF. The mean left ventricular ejection fraction was 54% (minimum 25%). After 12months of follow-up, 71% of the patients were free of AF recurrence. At baseline, mean MR-proADM in the total population was 0.72nmol/l±0.22. Patients with AF recurrence had significantly higher baseline MR-proADM (0.89nmol/l±0.29) as compared with patients without AF recurrence (0.65nmol/l±0.14; p<0.001). After 12months, mean MR-proADM plasma concentration remained higher in patients with AF recurrence (0.81nmol/l±0.22 as compared with patients free of AF 0.54nmol/l±0.20; p<0.001). Receiver operating characteristic (ROC) curve analysis for MR-proADM yields a specificity of 98% and a sensitivity of 64% with an optimal cut-off value of 0.82nmol/l to predict recurrence of AF after catheter ablation. In the logistic regression analysis only MR-proADM remained independently predictive for AF recurrence.
Answer: This is the first study revealing the association between MR-proADM elevation before ablation and poor outcomes after ablation of AF. Larger studies are needed to validate these results.

Answer:
Do mid-regional proadrenomedullin levels predict recurrence of atrial fibrillation after catheter ablation?