***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: Objective : To investigate the relationship between body mass index ( BMI ) , haemoglobin ( Hb ) concentration and work productivity in Indonesian female industrial workers engaged in cigarette rolling . Design : R and omized-stratified , cross-sectional study . Setting : A clove cigarette factory in Central Java Province , Indonesia . Subjects : Two-hundred and thirty female cigarette-rollers . Methods : Anthropometric variables ( height , weight , mid-upper arm circumference , BMI ) , body composition ( lean body mass and fat mass from skinfolds thicknesses  ) , Hb , work productivity ( cigarettes/hour ) were determined . Results : Of the 230 selected subjects 40.4 % were anaemic and 41.3 % had BMI < 18.5 . Average production was 620±86 cigarettes/h . Productivity was positively correlated with work experience ( r=0.214 , P<0.01 ) , lean body mass ( r=0.183 , P<0.01 ) , height ( r=0.150 , P<0.05 ) , Hb ( r=0.141 , P<0.05 ) , and arm muscle area ( r=0.120 , P<0.05 ) . Anaemic subjects produced 4.9 % less ( P<0.01 ) than the non-anaemic ones . No linear relationship existed between BMI and productivity , but subjects with a BMI < 18.5 , or < 17.0 , produced respectively 5.1 % ( P<0.05 ) and 6.8 % ( P<0.05 ) less than subjects with BMI between 18.5–22.5 . Conclusions : Work productivity of persons with low BMI and Hb may be reduced . However , BMI was not a good screening tool to detect low producers . When using BMI < 18.5 and a production < 550 cigarettes/h as cut-offs sensitivity ( 64.7 % ) and specificity ( 55.5 % ) were low . Sponsorship : Deutsche Gesellschaft für Technische Zusammenarbeit ( GTZ ) GmbH – SEAMEO TROPMED Jakarta Our objective was to investigate the effects of iron depletion on adaptation to aerobic exercise , assessed by time to complete a 15-km cycle ergometer test . Forty-two iron-depleted ( serum ferritin < 16 microg/l ) , nonanemic ( Hb > 12 g/dl ) women ( 18 - 33 yr old ) received 100 mg of ferrous sulfate ( S ) or placebo ( P ) per day for 6 wk in a r and omized , double-blind trial . Subjects trained for 30 min/day , 5 days/wk at 75 - 85 % of maximum heart rate for the final 4 wk of the study . There were no group differences in baseline iron status or in 15-km time . Iron supplementation increased serum ferritin and decreased transferrin receptors in the S compared with the P group . The S and P groups decreased 15-km time and respiratory exchange ratio and increased work rate during the 15-km time trial after training . The decrease in 15-km time was greater in the S than in the P group ( P = 0.04 ) and could be partially attributed to increases in serum ferritin and Hb . These results indicate that iron deficiency without anemia impairs favorable adaptation to aerobic exercise Eighty iron-deficient , nonpregnant female workers were r and omly assigned to ferrous sulphate ( 60 or 120 mg Fe/d ) or placebo treatment for 12 wk . Energy expenditure was estimated during 3 d by heart rate ( HR ) recording . Production efficiency ( PE ) was calculated as the ratio of productivity to energy expenditure . In the iron-treated group mean hemoglobin ( Hb ) increased from 114 to 127 g/L ( P < 0.001 ) , mean serum ferritin increased from 9.7 to 30.0 micrograms/L ( P < 0.001 ) , and mean free erythrocyte protoporphyrin decreased from 1.01 to 0.49 mumol/L ( P < 0.001 ) . Mean HR at work decreased from 95.5 to 91.1 beats/min ( P < 0.001 ) , which was inversely correlated with the change in Hb ( r = -0.60 , P < 0.001 ) . PE increased significantly in the iron-treated group ( P < 0.001 ) and its change paralleled the change in Hb ( r = 0.58 , P < 0.001 ) . The results show that iron supplementation enabled these women to do the same work at a lower energy cost Studies in laboratory animals found that iron deficiency without anemia decreased oxidative capacity and increased reliance on carbohydrate as the substrate for energy , thereby causing impaired endurance . The purpose of this cross-sectional study was to investigate the relation between iron deficiency without anemia and physical performance in healthy active women aged 19 - 36 y. Iron-status assessment included determination of hemoglobin , hematocrit , transferrin saturation , and serum ferritin values . Dietary iron intake was assessed by frequency question naires and physical activity level was estimated by frequency question naires and 2-wk records . Fifteen women with normal iron status and 15 women with iron depletion ( serum ferritin < 12 micrograms/L ) were chosen r and omly from a group of 69 nonanemic women and given physical-performance tests , including determinations of maximum oxygen consumption ( VO2max ) , ventilatory threshold , and delta-efficiency . There were no significant differences between the two groups in body size , body composition , physical activity level , dietary iron intake , delta-efficiency , or ventilatory threshold . Compared with the iron-depleted group , the iron-sufficient group had significantly higher hemoglobin , transferrin saturation , and serum ferritin values and a significantly greater tendency to use iron supplements . When physical activity level and fat-free mass were controlled for , the iron-depleted group had a significantly lower VO2max . The difference in VO2max was significantly associated with serum ferritin concentration ; hemoglobin value was not a significant confounder . Therefore , reduction of VO2max in nonanemic women with iron depletion was likely caused by factors related to reduced body iron storage but was unrelated to decreased oxygen-transport capacity of the blood In order to quantify the effects of anemia , a study was undertaken in which an attempt was made to correct this nutritional deficiency since it was found that the productivity of non-anemic laborers was approximately 20 % greater than the productivity of anemic laborers . Treatment was elemental iron for a period of 60 days ( at a cost of US$ .0013 per laborer per day ) this result ed in an increase in productivity of approximately 15 % for tappers and 20 % for weeders as compared to control groups . These findings are highly significant . The benefit cost ratio in terms of latex production alone , for example , of correcting this deficiency could be 260:1 . The high rate of anemia in the adult male population is almost doubled in the population of females and children . The effects of anemia on women and on the learning behavior patterns of school children is documented in other studies . In Indonesia it would cost approximately US$ 0.50 per year per person to cure the anemia and US$ 0.75 per year per person to reduce hookworm infestation in a given area , including distribution costs . The evidence suggests that an increase in the consumption of some local foods whose supply is plentiful , could lead to significant improvement in blood iron status Twenty-nine adult iron-deficient anemis subjects ( 13 men and 16 women ) with hemoglobin levels of 4.0 to 12.0 g/100 ml blood were divided into either an iron treatment or placebo group . Hematological , cardiorespiratory and performance data were collected before , during , and after treatment and compared with data from a control group of subjects ( 4 men and 6 women ) from the same socioeconomic population .  Hemoglobin levels for the iron treatment group improved from 7.7 to 12.4 g for the women and from 7.1 to 14.0 g for the men . Values for the control group were 13.9 g and 14.3 g for the women and men , respectively . The placebo group showed virtually no change over the 80-day period ( 8.1 - 8.4 g for women and 7.7 - 7.4 g for men ) . Peak exercise heart rates ( 5 min , 40-cm step test ) were significantly reduced after treatment from 155 to 113 for the iron treatment men and 152 to 123 for the women compared with the placebo group which showed no changes . Values for the control group were 119 and 142 for the men and women , respectively . In response to the exercise test , no difference in oxygen consumption was found between the iron treatment and placebo group although 15 % more O2 was delivered per pulse in the iron treatment group . Blood lactates were significantly highein the placebo than iron treatment group both at rest , 1.18 versus 0.64 mmole/liter , and 1 min after exercise , 5.30 versus 2.68 mmoles/liter . No changes in h and grip or shoulder adductor strength were observed following treatment . These results clearly support the concept that performance requiring high oxygen delivery is significantly affected by hemoglobin levels The effects of  iron-deficiency anaemia on  workers productivity  were studied in a tea plantation in Sri Lanka . The quantity of tea picked per day was studied before and after iron supplementation or placebo treatment . After one month 's treatment significantly more tea was picked when the haemoglobin ( Hb ) concentration was increased by iron supplementation than when it was not . The degree of improvement was greater in more-anaemic subjects ( those with concentrations of 6.0 - 9.0 g Hb/dl ) . The level of physical activity of anaemic subjects in their everyday environment was also recorded for four or 24 hours continuously both before and after treatment . After three weeks these levels was significantly greater in the iron-treated than matched placebo-treated subjects . The economic implication s of increased work productively with iron treatment are evident , particularly in developing countries . These results also provide strong evidence for the clinical impression that people with iron-deficiency anaemia suffer from tiredness and weakness The purpose of this investigation was to examine the effects of oral iron supplementation on endurance performance in initially iron-depleted , nonanemic female distance runners . Eighteen iron-depleted ( serum ferritin less than 20 ng.ml-1 , hemoglobin greater than or equal to 12 g.dl-1 ) women ( 22 - 39 yr ) performed a VO2max test and an endurance run to exhaustion . Subjects were pair-matched on the basis of endurance time and then r and omly assigned to an iron supplement or a placebo group . Following supplementation , the iron group had a significantly higher ( P = 0.03 ) mean serum ferritin concentration ( 23.4 vs 15.7 ng.ml-1 ) and lower ( P = 0.04 ) mean total iron-binding capacity than the placebo group . Both groups increased their time to exhaustion ( 25.5 % and 22.2 % for the iron and placebo groups , respectively ) but were not significantly different ( P = 0.72 ) from each other . There were also no differences ( P greater than 0.05 ) between the groups with respect to lactate concentrations and physiological measures taken during the two exercise tests . The results of this study suggest that 8 wk of oral iron supplementation improves iron status in iron-depleted female distance runners , but does not enhance endurance capacity The effect of an endurance training regimen on muscle oxidative enzymes and work performance was studied in iron-deficient and -sufficient rats . Three-week-old male Sprague-Dawley rats ( n = 40 ) were r and omly assigned to diets containing either 6 mg iron/kg ( iron deficient ) or 50 mg iron/kg ( iron sufficient ) . After 2 wk , each group of rats was further divided into untrained or endurance-trained subgroups . Training consisted of daily treadmill running of gradually increasing duration for a 1-mo period . After the training period , sedentary and endurance-trained iron-deficient rats were anemic ( Hgb approximately 8 g/dl compared with 16 g/dl in the 2 control groups ) and had significantly lower skeletal muscle cytochrome c concentration , cytochrome oxidase activity , and succinic oxidase activity compared with the iron-sufficient groups . In response to training iron-deficient rats also generally had a substantial increase in skeletal muscle oxidative enzymes ( P less than 0.05 ) , in contrast to iron-sufficient animals , in which there was little or no training effect . Work performance in response to training in the iron-deficient rats improved more than sixfold in an endurance type of exercise ( P less than 0.05 ) , but maximal oxygen consumption during a brief , intense type of exercise was not significantly affected . The results suggest that endurance training of iron-deficient rats results in a milder anemia and less drastic reduction of skeletal muscle oxidative enzymes which in turn allows better performance in an endurance type of exercise Serum transferrin receptor ( sTfR ) concentration has been recognized recently as a reliable indicator of functional iron deficiency , but its response to iron supplementation has not been investigated in marginally iron-deficient women . In this r and omized , double-blinded trial , 37 female subjects aged 19 - 35 y with iron depletion without anemia ( hemoglobin > 120 g/L and serum ferritin < 16 microg/L ) received an iron supplement or placebo for 8 wk . Iron status was measured before treatment 
    Output:
    
The presumed mechanism for this effect is the reduced oxygen transport associated with anemia ; tissue iron deficiency may also play a role through reduced cellular oxidative capacity .
Endurance capacity was also compromised in SIDA and MIDA , but the strong mediating effects of poor cellular oxidative capacity observed in animals have not been demonstrated in humans .
Energetic efficiency was affected at all levels of iron deficiency in humans , in the laboratory and the field .
The reduced work productivity observed in field studies is likely due to anemia and reduced oxygen transport .
The social and economic consequences of iron-deficiency anemia ( IDA ) and IDNA have yet to be eluci date d. The biological mechanisms for the effect of IDA on work capacity are sufficiently strong to justify interventions to improve iron status as a means of enhancing human capital .
This may also extend to the segment of the population experiencing IDNA in whom the effects on work capacity may be more subtle , but the number of individuals thus affected may be considerably more than those experiencing IDA