***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Exercise has shown little success in mitigating bone loss from long- duration spaceflight . The first crews of the International Space Station ( ISS ) used the " interim resistive exercise device " ( iRED ) , which allowed loads of up to 297 lb(f ) ( or 1337 N ) but provided little protection of bone or no greater protection than aerobic exercise . In 2008 , the Advanced Resistive Exercise Device ( ARED ) , which allowed absolute loads of up to 600 lb(f ) ( 1675 N ) , was launched to the ISS . We report dietary intake , bone densitometry , and biochemical markers in 13 crewmembers on ISS missions from 2006 to 2009 . Of these 13 , 8 had access to the iRED and 5 had access to the ARED .  In both groups , bone-specific alkaline phosphatase tended to increase during flight toward the end of the mission ( p = 0.06 ) and increased 30 days after l and ing ( p < 0.001 ) . Most markers of bone resorption were also increased in both groups during flight and 30 days after l and ing ( p < 0.05 ) . Bone densitometry revealed significant interactions ( time and exercise device ) for pelvis bone mineral density ( BMD ) and bone mineral content ( p < 0.01 ) , hip femoral neck BMD ( p < 0.05 ) , trochanter BMD ( p < 0.05 ) , and total hip BMD ( p < 0.05 ) . These variables were unchanged from preflight only for ARED crewmembers , who also returned from flight with higher percent lean mass and lower percent fat mass . Body mass was unchanged after flight in both groups . All crewmembers had nominal vitamin D status ( 75 ± 17 nmol/L ) before and during flight . These data document that resistance exercise , coupled with adequate energy intake ( shown by maintenance of body mass determined by dual-energy X-ray absorptiometry [ DXA ] ) and vitamin D , can maintain bone in most regions during 4- to 6-month missions in microgravity . This is the first evidence that improving nutrition and resistance exercise during spaceflight can attenuate the expected BMD deficits previously observed after prolonged missions Summary We report the results of alendronate ingestion plus exercise in preventing the declines in bone mass and strength and elevated levels of urinary calcium and bone resorption in astronauts during 5.5 months of spaceflight . Introduction This investigation was an international collaboration between NASA and the JAXA space agencies to investigate the potential value of antiresorptive agents to mitigate the well-established bone changes associated with long- duration spaceflight . Methods We report the results from seven International Space Station ( ISS ) astronauts who spent a mean of 5.5 months on the ISS and who took an oral dose of 70 mg of alendronate weekly starting 3 weeks before flight and continuing throughout the mission . All crewmembers had available for exercise a treadmill , cycle ergometer , and a resistance exercise device . Our assessment included densitometry of multiple bone regions using X-ray absorptiometry ( DXA ) and quantitative computed tomography ( QCT ) and assays of biomarkers of bone metabolism . Results In addition to pre- and post-flight measurements , we compared our results to 18 astronauts who flew ISS missions and who exercised using an early model resistance exercise device , called the interim resistance exercise device , and to 11 ISS astronauts who exercised using the newer advanced resistance exercise device ( ARED ) . Our findings indicate that the ARED provided significant attenuation of bone loss compared with the older device although post-flight decreases in the femur neck and hip remained . The combination of the ARED and bisphosphonate attenuated the expected decline in essentially all indices of altered bone physiology during spaceflight including : DXA-determined losses in bone mineral density of the spine , hip , and pelvis , QCT-determined compartmental losses in trabecular and cortical bone mass in the hip , calculated measures of fall and stance computed bone strength of the hip , elevated levels of bone resorption markers , and urinary excretion of calcium . Conclusions The combination of exercise plus an antiresoptive drug may be useful for protecting bone health during long- duration spaceflight 
    Output:
    
Microgravity-induced bone changes depend on the skeletal-site position relative to the gravitational vector .
Post-flight recovery depends on spaceflight duration and is limited to a short post-flight period during which bone formation exceeds resorption