the open window theory implies that there is altered immunity following an acute bout of exercise , which lasts from three to 72 hours after exercise depending on the parameter measured .
according to the theory , there is an increased risk of contracting infectious diseases after physical exercise .
the  j  means that individuals engaged in moderate physical activity are at lower risk compared with sedentary individuals . on the other side , excessive volumes of strenuous endurance exercise
it is evident that great numbers of molecules encompass the term  proinflammatory cytokines . 
these cytokines are produced very early in the response to multiple stresses and are important by being involved in both innate and acquired immunity .
cytokines are characterised as being inducible and belong to different families , including proinflammatory cytokines ( il-1 , il-2 , il-4 , il-6 , il-8 , and tnf ) , which are cytokines that promote systemic inflammation , and anti - inflammatory cytokines ( il-5 , il-6 , and il-10 ) , which refer to the property of a substance that reduces and protects against inflammation .
inflammation in excess is detrimental and excessive production and release of tnf and il-1 may lead to pathology .
vascular endothelial growth factor ( vegf ) is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis .
proinflammatory cytokines like il-1 , il-6 , il-8 , tgf- , and tnf- variably increase vegf expression , depending upon the dose , cell , or tissue type .
surgery , trauma , burn , and sepsis induce a pattern of hormonal and immunological responses with the same response profile as that of exercise . earlier studies regarding exercise and effects on immunological parameters indicate that the profiles of proinflammatory and anti - inflammatory cytokine levels are stimulated based on the intensity and duration of the physical exercise [ 8 , 9 ] .
long - distance runners , for example , marathon runners , have shown high postexercise levels of il-1 , il-6 , and il-8 after six hours ' endurance exercise [ 911 ] , while there were no changes observed in plasma cytokine levels after a 5-kilometre run . measurements from cycle
ergometer and treadmill running show no response of short - term exercise with high and moderate intensity , an increase in il-6 after one - hour cycling at 75% of maximal oxygen consumption ( vo2max ) and three - hours alternating cycling and treadmill running at 6065% of vo2max showed high postexercise values of il-6 , il-1 , and tnf [ 1315 ] .
other studies indicate that long - term sleep and energy deficiency lead to immune depression [ 16 , 17 ] .
microsphere - based multiplexing bioassay system has , during the last few years , become an important tool in cytokine detection .
the assay is performed with great speed and accuracy by making use of hundreds of specially prepared magnetic beads , or microspheres , and is reporting on the contents of the sample .
this is in contrast to the classical analysis of cytokine expression patterns , which has been performed by enzyme - linked immunosorbent assays ( elisa ) for each separate analysis .
very few studies within the field of exercise immunology have so far used the multiplex technology in cytokine detection in relation to exercise or physical activity executed by healthy people . according to prior reports
, we expect in our study that the marathon / half - marathon race and the ranger - training course will lead to immunological responses in the subjects as seen in surgery and sepsis patients . the aim of this study was to examine the secretion of the cytokines il-1 , il-2 , il-4 , il-5 , il-6 , il-8 , il-10 , il-12 , tnf , ifn , gm - csf , and vegf before and after three different trials of physical exercise : the oslo marathon / half - marathon and a military training course of eight days continuous exercise combined with sleep and energy deprivation . both the spontaneous secretion of the cytokines and the lipopolysaccharide- ( lps- ) induced whole blood stimulation of cytokines were examined .
fourteen men participating in oslo marathon race ( mean age 40 ; range 2956 ) , eight women ( mean age 36 ; range 2739 ) and eight men ( mean age 34 ; range 3045 ) participating in oslo half - marathon race , and ten physically well - trained male cadets from the norwegian military academy in the age between 21 and 28 years were recruited to this study .
the marathon runners were selected based on the previous year 's result list with the criterion that the expected running time should be 3  h 30  min ; the corresponding criterion for the half - marathon runners was 1  h 30  min for men and 1  h 45  min for women .
the ranger - training course took place in the eastern part of norway , in a forest area at 500  m altitude .
the temperature during the eight days of the course was between 18 and 30c during daytime and between 5 and 15c at night .
the cadets were provided nearly no food during the course and approximately 3 hours/8  d sleep was allowed . in the restitution period ( day 9 through day 11 ) , the cadets followed regular sleeping and eating habits as before the course .
the subjects were informed about the study and gave their written informed consent for participation .
for the marathon runners and the half - marathon runners , blood samples were collected shortly before the race and immediately after the race . for the military cadets ,
blood samples were collected at the start of the ranger - training course , after 2 , 4 , and 8 days ( end of the ranger - training course ) , and after one ( day 9 ) and three ( day 11 ) days ' recovery .
the blood samples from the cadets were taken between 6 and 8 a.m. for all groups , venous blood was sampled into either edta- , na - citrate- , or heparin - anticoagulated vacuum tubes ( becton dickinson , plymouth , uk ) . the blood samples from the ranger - training course were collected in the field , kept on ice , and transported within 60 minutes to the nearest military training camp , terningmoen , where a temporary laboratory was established .
the blood samples from the marathon and the half - marathon runners where collected in the start area of the race , kept on ice , and transported within 30 minutes to ullevl university hospital .
plasma was separated at 2500  g for 10 minutes and samples were stored at 80c until analysis . to compare the cytokine production capacities of leukocytes , one set of experiments
was performed with heparinized whole blood from the half - marathon runners and the ranger - training cadets .
the blood samples were stimulated ex vivo with the potent cytokine inducer lipopolysaccharide ( lps ) , 1  g / ml ( working solution ) ( from escherichia coli 026 : b6 , sigma st .
louis , mo , usa ) for 6  h at 37c , before storing plasma samples at 80c until analysis .
white blood cell ( wbc ) , platelet and erythrocyte counts , haemoglobin , and haematocrit were assessed in edta blood using the technicon h2 system ( bayer corporation , tarrytown , ny , usa ) at the department of medical biochemistry , oslo university hospital , ullevl .
plasma levels of individual cytokines ( il-1 , il-6 , il-8 , il-10 , and tnf ) were measured using the quantikine colorimetric sandwich enzyme - linked immunosorbent assays ( elisa ) from r&d , abingdon , uk , according to the manufacturer 's instructions .
we used the multiplex bead - based sandwich immunoassay technology ( luminex , austin , tx , usa ) and a human cytokine 12-plex kit ( r&d ) , strictly following the manufacturer 's instructions , to measure the concentration of the following cytokines before and after the marathon race : il-1 , il-2 , il-4 , il-5 , il-6 , il-8 , il-10 , il-12 , tnf , ifn , gm - csf , and vegf .
unfortunately , we only had the multiplex bead - based sandwich immunoassay technology ( luminex ) available for the study with the marathon runners .
the levels of cytokine release in the half - marathon runners and the cadets from the ranger - training course were therefore measured using the quantikine colorimetric sandwich enzyme - linked immunosorbent assays ( elisa ) .
results are given as means and standard errors of the mean ( mean , sem ) .
difference within groups ( marathon and half - marathon ) was analysed using two - tailed paired sample t - test .
independent sample t - test was used in order to compare men and women within the half - marathon group . since we did not observe any statistically significant differences between the women and men , we have chosen to present the results from the half - marathon runners as one group .
paired sample t - test was used to compare results from day 0 to results after 2 , 4 , and 8 days during the ranger - training course , and after day 1 and 3 days recovery . in the ranger - training course the repeated and longitudinal values obtained before , during , and after the period of exercise which made the subjects being their own controls .
the total leukocyte counts ( wbc ) ( 10/l ) increased by 3.2-fold ( values before : 5.1 , values after : 16.4 , p < 0.01 ) after the marathon race , 2.4-fold ( values before : 6.3 , values after : 15.2 , p < 0.01 ) after the half - marathon race , and 1.5-fold ( values before : 6.3 , values after : 9.5 , p < 0.01 ) at the end of the ranger - training course ( day 8) . after the ranger - training course , wbc were back to normal values after one - day ( day 9 ) recovery .
the increase in wbc was mainly due to a significant increase in neutrophils after both of the marathon races and after the ranger - training course , but monocyte counts were also consistently increased in all three experimental settings .
the platelet counts ( 10/l ) increased significantly after both the marathon race ( values before : 194 , values after : 243 , p < 0.01 ) and the half - marathon race ( values before : 255 , values after : 313 , p < 0.05 ) and after eight days at the ranger - training course ( values before : 214 , values after : 265 , p < 0.05 ) .
we observed no changes in haemoglobin values after the marathon and the half - marathon races .
a slight decrease in haemoglobin values was observed after eight days in the military training course ( p < 0.05 ) , maintained during the whole recovery period .
the haematocrit values remained unchanged after the running races , whereas the values were reduced during days 48 of the ranger - training course as well as during the recovery phase . 

we performed a plain analysis of plasma levels of 12 cytokines in 14 individuals before and after a marathon race .
three of these cytokines were heavily increased when comparing pre / post plasma levels : il-6 ( 26-fold increase , p
< 0.001 ) , il-10 ( 28-fold increase , p < 0.000 ) , and il-8 ( 11-fold increase , p < 0.001 ) .
the other measured cytokines , il-1 , il-2 , il-4 , il-5 , il-12 , tnf , ifn , gm - csf , and vegf , did not change significantly after the marathon race .  

half - marathon ( table 1 ) . in the half - marathon race we demonstrated
significantly increased plasma levels of il-6 ( 40-fold increase , p < 0.001 ) , il-10 ( 10-fold increase , p < 0.001 ) , and il-8 ( 14-fold increase , p < 0.001 ) , whereas il-1 and tnf were unchanged after the race . when examining lps - stimulated cytokine levels , il-6 , il-1 , and tnf were reduced after the race ( il-6 45% reduced , p < 0.001
; il-1 24% reduced , p < 0.05 ; and tnf 43% reduced , p < 0.001 ) . on the contrary , il-10 and il-8 were further increased when lps stimulation was superposed ; il-10 225% increased , p < 0.01 , and il-8 242% increased , p < 0.001 .  

ranger - training course ( tables 2 and 3 ) . the subjects of the ranger - training course showed smaller increase than in the half - marathon race with surprisingly highest levels in the postrace recovery period ( table 2 ) .
il-1 , il-6 , il-8 , il-10 , and tnf were all significantly increased at some stage during the course .
additional investigations including lps stimulation of whole blood showed reduced production capacity for il-1 , il-6 , and tnf , whereas the il-8 and il-10 levels were further increased in a similar manner as after the half - marathon ( table 3 ) .
several studies have observed leukocytosis after physical exercise [ 2 , 18 , 19 ] .
physical exercise leads to an excessive increase in total number of neutrophils immediately and is followed by a slightly smaller increase a few hours after the exercise . in our study , the blood samples were taken immediately after the exercise and only the initial increase in leukocytes was measured .
we observed a 3.2-fold and a 2.4-fold increase in leukocytes after the marathon race and the half - marathon race , respectively . at the end of the ranger - training course ( day 8) , the levels of leukocytes
had increased by 1.5-fold . in agreement with former studies we found that the increase in leukocyte counts is primarily due to increase in neutrophils , although monocytes and lymphocytes were increased as well .
the first increase in neutrophils is mainly due to release of marginated cells caused by mechanical shear stress and catecholamines .
the reason for the different levels of leukocytes in the three exercise trials is probably due to the type and the duration of the activity , and this corresponds to earlier studies [ 23 , 24 ] .
acute exercise in healthy individuals has an effect on cytokines and the inflammatory response as well .
the intensity , duration , and type of physical exercise can all influence proinflammatory and anti - inflammatory cytokines and thereby influence the susceptibility to inflammatory diseases .
[ 4 , 25 ] reported a 2-fold increase in tnf and il-1 after a marathon race , in addition to a nearly 100-fold increase in il-6 values .
exercise studies of three hours ' duration performed in laboratories have shown increase in the same parameters .
we observed after the marathon and the half - marathon races a 26-fold and a 40-fold increase in il-6 .
the magnitude of increase in il-6 is closely related to the duration of the activity , the age of the athlete , the body mass index ( bmi ) , and the physical condition of the person [ 13 , 14 ] .
the participants in our trials were moderate to well - trained individuals executing physical exercise of long duration .
the half - marathon runners were on average 5 years younger compared to the marathon runners , they run half the distance of a marathon race , and they probably ran the half - marathon race with higher heart rate compared to the level of intensity of the marathon runners .
our study did not separately measure the effect of running intensity and running duration on the plasma cytokine levels after marathon and half - marathon running .
for the marathon runners we observed 11-fold and 28-fold increase in il-8 and il-10 , respectively , but no change in tnf and il-1. in the half - marathon runners , we observed a 10-fold increase in il-10 and 14-fold increase in il-8 , but as for the marathon race , no changes in il-1 and tnf values were recorded .
it seems that tnf and il-1 do not increase exponentially during exercise , which is different when compared to infections .
it could be hypothesized that the high levels of the anti - inflammatory cytokines il-6 and il-10 in our study might prevent the production of tnf- and il-1 after the races .
il-6 is called an inflammatory responding cytokine described as a proinflammatory cytokine but can also stimulate anti - inflammatory cytokines .
il-6 is highly increased during strenuous physical exercise and thus takes part in the control of the inflammatory response to strenuous physical exercise [ 25 , 28 ] .
the proinflammatory tnf is known to be inhibited by il-10   and induced by different stressors [ 30 , 31 ] .
the values obtained after physical exercise are inconstant related to the variations in duration and intensity of the exercise tasks .
in the ranger - training course , there was no increase in il-6 or il-10 during the period of activity , but , surprisingly , a small increase in the recovery phase ( days 9 and 11 ) .
il-1 and il-8 showed a small increase during the course and in the recovery period .
the boosting of cytokine responses in peripheral blood leukocytes by lps in many ways mimics the initial innate immune response to bacterial infection , lps stimulation showed that the plasma levels of both il-6 , il-1 , and tnf were significantly reduced after the half - marathon race as well as during and after the ranger - training course .
who have observed reduced il-6 , il-1 , and tnf- levels in lps - stimulated samples 30  min and 3  h after exercise in half - marathon runners . the observed reduction after the half - marathon race and
the ranger - training course may be due to either actually reduced production capacity as a result of exercise or at least a temporary change in the regulatory pathways leading to altered cytokine synthesis and release .
in contrast , il-8 and il-10 were boosted both by the exercise itself and after additional lps stimulation .
it seems that the anti - inflammatory il-10 production is more triggered in the long - lasting marathon race ( 28-fold increase ) compared with the shorter workload of the half - marathon race ( 10-fold increase ) .
furthermore , the il-6 release was more pronounced in the more work - intensive half - marathon than the longer - lasting but less intensive marathon race ( 40-fold versus 26-fold increase ) , possibly being mainly due to a larger release from the muscle mass of the lower extremities .
although a similar cytokine profile was registered in the ranger - training course , the magnitude of cytokine increases was not as impressive as for the corresponding marathon races , again possible due to a lesser work load per time unit as well as the lower work intensity .
regardless , we have in all three experimental settings demonstrated an increase of proinflammatory and anti - inflammatory cytokines , which in many ways are similar to the cytokine profile , which characterises inflammatory and infectious diseases [ 8 , 27 ] .
the balance between proinflammatory and anti - inflammatory cytokines during exercise may lay the ground for potentiation of the inflammatory status by introducing additional coincidental pathogens of both gram - negative and gram - positive origin , which thereby can tilt the balance into overt disease . both lps of gram - negative bacteria and lipoteichoic acid ( lta ) , peptidoglycan , and purified protein derivative ( ppd ) of gram - positive bacteria all have a number of biological activities , including also being potent cytokine inducers [ 35 , 36 ] .
most of the studies do only look at the direct immunological responses occurring immediately after different types of physical activity .
the very new part in our study is the three days follow - up after the end of the ranger - training course .
it may , however , be noted that the training course was performed at a season of the year where the general burden of common cold or influenza - like disease is at a minimum .
in conclusion , our study of long - term physical exercise performed in three different trials showed a significant increase in plasma levels of the cytokines il-6 , il-8 , and il-10 , whereas tnf and il-1 levels were unchanged or reduced .
 open window  of altered immunity after long - term physical exercise and which lasts for at least 72 hours after the exercise .
the results support the j - curve theory ; athletes are more sensitive to pathogens in the immediate period after intensive physical exercise , probably due to the exercise - induced inflammatory state that can exaggerate the response to coincidentally occurring pathogens .
 the open window theory indicates altered immunity 3 to 72 hours after exercise . 
 the j - curve describes the risk of illness in response to exercise . the aim of this study was to examine the secretion of proinflammatory and anti - inflammatory cytokines before and after long - term strenuous exercise . 
 fourteen marathon and 16 half - marathon runners and 10 military cadets participating in a military ranger - training course were recruited to this study . within - subject 
 design was used measuring levels of plasma cytokines before , during , and after exercise . 
 plasma cytokines were measured using luminex multiplex technology and elisa . 
 comparing pre / post plasma levels both the marathon- and the half - marathon runners showed heavily increased levels of il-6 , il-10 , and il-8 ( p < 0.001 ) . 
 lps stimulation among the half - marathon runners decreased the postrace levels of il-6 , il-1b , and tnf by 45% , 24% , and 43% , respectively ( p < 0.01 ) . during the ranger training course the spontaneous and lps - stimulated levels of il-6 , il-8 , il-10 , il-1b , and tnf changed in a similar fashion as in the half - marathon runners although the fluctuations were smaller . 
 our study supports the open window and the j - curve theory ; the immune system is more activated and the subjects are more threatened to infectious pathogens after intensive physical activity and in the period after exercise . 
1. Introduction
2. Material and Methods
3. Results
4. Discussion
5. Conclusion