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.

[Q]: Context: Old compared with young adults walk with reduced ankle and increased hip mechanical output. We examined the idea that age, leg strength, or both are related to the age-related changes in mechanical output during gait.', 'Healthy young (n = 32, age 21.5 years) and old adults (n = 32, age 76.8 years) participated in biomechanical gait analyses at 1.5 m/s and were also measured for maximal leg strength.', 'Analysis 1 confirmed previous data as old compared with young adults walked with 50 % more hip positive work and 18 % less ankle positive work. Analysis 2 showed that leg strength did not affect gait kinetics in groups of subjects with similar ages. In a weak young and a strong old group, Analysis 3 showed that old adults still walked with 23 % greater hip positive work. The group by joint interaction in Analysis 4 was suggestive of an even greater reliance on hip and less reliance on ankle work in weak compared with strong old adults.
Answer: Age and leg strength both contribute to the age-related changes in mechanical output during gait. Exercise prescription, normally targeting the knee extensors, should also involve ankle and hip muscles.
[A]: Do age and muscle strength mediate the age-related biomechanical plasticity of gait?


[Q]: Context: Corticosteroids are a critical component of therapy for acute lymphoblastic leukemia (ALL) but are associated with late effects, such as osteoporosis. Risk factors remain poorly defined. Because CRHR1 polymorphisms have been associated with other corticosteroid effects, our goal was to define whether CRHR1 polymorphisms predict which patients with ALL are likely to develop bone mineral deficits.', 'The mean bone mineral density z scores of 309 long-term survivors of ALL were determined by quantitative computed tomography of the trabecular lumbar spine. We analyzed whether CRHR1 genotypes, adjusted for sex, ALL treatment regimen, and weight, could predict bone density.', 'We found that three single nucleotide polymorphisms (SNPs), all in linkage disequilibrium, were associated with bone density in a sex-specific manner. Bone density was lower in males (P = .001), in nonblack patients (P < .08), in those who were not overweight (P < .001), and in those who received intensive antimetabolites and glucocorticoids (P < .001). After adjustment for these features, the G allele at the rs1876828 SNP was associated with lower z scores (P = .02) in males but tended to have the opposite association in females (P = .09).
Answer: CRHR1 polymorphisms may impact the risk of bone density deficits in patients treated with corticosteroids and antimetabolites in a sex-specific manner.
[A]: Do cRHR1 polymorphisms predict bone density in survivors of acute lymphoblastic leukemia?


[Q]: Context: Whether extremely low birth weight (ELBW) infants are at risk of cerebral hypoperfusion is uncertain because key issues concerning their cerebral blood flow (CBF) and mean arterial pressure (MAP) are unresolved: (1) whether CBF is pressure-passive or autoregulated; (2) the normal level of MAP; and (3) whether inotropic drugs used to increase MAP might inadvertently impair CBF. We addressed these issues in ELBW infants undergoing intensive care.', 'CBF (measured by near-infrared spectroscopy) and MAP were measured in 17 infants aged 1.5 to 40.5 hours.', 'Five infants remained normotensive (MAP 37 +/- 2 mm Hg, [mean +/- SEM]); twelve became hypotensive (MAP 25 +/- 1 mm Hg) and were treated with dopamine (10-30 mug x kg(-1) per min). CBF of hypotensive infants (14 +/- 1 mL x 100 g(-1) per min) was lower than the CBF of normotensive infants (19 +/- mL x 100 g(-1) per min). After commencement of dopamine in hypotensive infants, MAP increased (29 +/- 1 mm Hg) and CBF also increased (18 +/- 1 mL x 100g(-1) per min). CBF was correlated with MAP in hypotensive infants before (R = 0.62) and during (R = 0.67) dopamine, but not in normotensive infants. A breakpoint was identified in the CBF versus MAP autoregulation curve of untreated infants at MAP = 29 mm Hg; no breakpoint was evident in dopamine-treated infants.
Answer: In ELBW infants (1) cerebral autoregulation is functional in normotensive but not hypotensive infants; (2) a breakpoint exists at approximately 30 mm Hg in the CBF-MAP autoregulation curve; and (3) dopamine improves both MAP and CBF.
[A]:
Do hypotensive extremely low birth weight infants have reduced cerebral blood flow?