lactate concentration in blood is one of the most frequent parameters utilized during exercise testing for endurance athletes ( 12 ) .
the reasons for this are : because blood lactate ( bl ) is a key marker for measuring the extent of anaerobic metabolisms , sampling is innocuous for the subject ; only a few drops of blood are required ; and the reliability and validity of testing bl has increased with new technologies ( 12 , 19 ) . most of the adenosine triphosphate ( atp ) needed for muscular contraction during the initial phases of incremental exercise comes from aerobic sources ( 22 ) , however , as the intensity of exercise increases , bl levels begin to rise in an exponential manner ( 13 ) .
it is accepted that the sudden rise in bl throughout incremental exercise is due to an increasing dependence on anaerobic metabolism , particularly , glycolysis ( 5 ) .
studies have established that bl measurements used in amalgamation with other physiological measurements are a valuable interpreter of success in distance running ( 10 , 23 ) . additionally , possessing
a sound understanding of bl may serve as a parameter in planning intensities needed to optimize training results ( 28 ) .
since 1968 , altitude training has been utilized by both athletes and coaches in their training methodologies , with the aim of augmenting performance ( 2 , 31 , 35 ) .
the belief is that by living and training at altitude , athletes will enhance performance through various physiological parameters ( 26 ) .
however , one parameter that remains perplexing for researchers is the bl response during and immediately following altitude exposure ( 26 , 37 , 38 ) .
reeves et al . , ( 1992 ) , described the lactate paradox as a  physiological response in which bl concentration during submaximal and maximal exercise is increased upon acute exposure but decreased with altitude acclimatization . 
simply stated , the paradox defines the finding of lower than expected concentrations during maximal exercise at altitude ( 25 ) . there is little explanation as to what causes the lactate paradox ( 6 , 7 , 24 , 36 , 37 , 38 ) .
though much research has been conducted on bl levels while subjects are at altitude ( 24 , 36 , 37 , 38 ) , to the best of our knowledge no study has examined lactate levels following acute exposure to a moderate altitude ( 1828 m ) .
therefore , the primary purpose of this study was to examine the difference between bl levels pre- and -post a 10-day moderate altitude training camp ( 1828 meters ) in varsity cross - country runners .
following approval from the lakehead university research ethics board , eight healthy participants aged 1822 years were recruited using purposive sampling .
each participant was a member of either a university or a high school varsity track and field and/or cross - country team . in total , there were five male and three female participants .
participants were included in the study if they were healthy ( i.e. , with no injuries ) and competitive runners who had trained and competed for a varsity team . following an explanation of the purpose and method of the study , consent to participate
participants were asked to : not eat a substantial meal within 3 hours before the test ; abstain from alcohol 24 hours prior to the test ; abstain from coffee , tea , or other caffeine sources at least 1 hour before the test ; and abstain from vigorous training or high intensity physical work for 24 hours prior to the test a physical activity readiness questionnaire ( par - q ) ( 1 ) and a lab specific maximal testing pre - participation screening questionnaire were completed to ensure participants were physically able to participate in the study . upon completion of the required questionnaires , each participant had anthropometric measures ( height , weight ) taken .
measurements were recorded using a my weigh md 500 digital scale and a tanita hr100 stadiometer ( tanita corporation ; japan ) . following these measures , participants had their resting hr ( after 5 minutes in a supine position ) , resting blood pressure , and a resting bl measured and recorded .
bl was measured using a capillary fingertip blood sample and a calibrated lactate pro portable analyzer ( kdk , corporation , kyoto , japan , arkray factory inc .
, kdk corporation shiga japan ) by the same clinician , using the same technique for each participant .
( 9.65 k.p.h . ) and completed 5 minutes of dynamic warm - up that focused on major muscle groups predominantly used during running . following the complete warm - up , participants bl values were obtained and recorded .
kempele , finland ) was fixed on the participant , as well as a nonin go2 achieve fingertip pulse oximeter ( nonin medical inc .
shawnee mission , ks , usa ) , connected to the ad instruments model ml206 gas analyzer metabolic cart ( ad instruments pty ltd , castle hill , australia ) , and placed on the woodway inc .
an incremental treadmill protocol was then started , which consisted of two stages . in stage one
, male and female participants underwent 33 minute treadmill increments . following completion of the 3 minute increments
this protocol was chosen , as stage one , allowed participants to achieve a steady - state , and stage two , allowed the speed at exhaustion to be determined .
three male participants , started at 9.3 m.p.h ( 14.96 kph ) and two male participants started at 9.9 m.p.h .
researchers observed and recorded heart rate ( hr ) and oxygen saturation ( spo2 ) every 30 seconds during the incremental treadmill test ( itt ) until exhaustion .
expired gases were collected using the metabolic cart and recorded in real time using power lab 26 t ( ad instruments pty ltd , castle hill , australia ) , and were analyzed using the software lab chart version 7 ( ad instruments pty ltd , castle hill , australia ) . immediately after exhaustion , subjects had their bl and rate of perceived exertion taken and recorded using a 620 borg rate of perceived exertion scale ( 3 ) .
participants began running their cool down , both men and women ran at 6 m.p.h . and had bl values obtained and recorded immediately post - exercise and at minutes 2 , 4 , 6 , and 8 post - exhaustion .
the subjects were tested in thunder bay , ontario , canada ( elevation 183 meters or 600 feet ) within 10-days prior to attending a 10-day altitude training camp ( located at teary peak , near the town of lead , in the black hills of south dakota , usa ) , at an elevation of approximately 1828 meters ( 6000 feet ) . at altitude ,
the training matched their absolute sea - level intensities and subjects recorded their training sessions in a daily log . upon conclusion of the altitude training camp , subjects were re - tested within 3-days of returning to thunder bay , ontario , canada ( 183meters or 600 feet ) , using the same equipment and procedure as pre - altitude testing .
room temperature ( degrees celsius ) and barometric pressure ( mmhg ) were recorded prior to every testing session .
usa ) was used to analyze the data . one categorical independent variable ( pre - altitude exposure and post - altitude exposure ) , and twelve continuous dependent variables ( average lactate , resting lactate , post - warmup lactate , lactate 0 minutes post - exercise , 2 minutes post - exercise , 4 minutes post - exercise , 6 minutes post - exercise , 8 minutes post - exercise , oxygen saturation , heart rate , time to exhaustion , and perceived exertion ) were examined .
the data were analyzed using paired samples t - tests to examine the effect of a 10-day altitude training camp intervention on the dependent variable for intervals of rest , post - warm - up , immediately after all out incremental exercise , 2,4,6 , and 8 minutes post - exhaustive exercise .
following approval from the lakehead university research ethics board , eight healthy participants aged 1822 years were recruited using purposive sampling .
each participant was a member of either a university or a high school varsity track and field and/or cross - country team . in total , there were five male and three female participants .
participants were included in the study if they were healthy ( i.e. , with no injuries ) and competitive runners who had trained and competed for a varsity team .
following an explanation of the purpose and method of the study , consent to participate was obtained from each participant .
participants were asked to : not eat a substantial meal within 3 hours before the test ; abstain from alcohol 24 hours prior to the test ; abstain from coffee , tea , or other caffeine sources at least 1 hour before the test ; and abstain from vigorous training or high intensity physical work for 24 hours prior to the test a physical activity readiness questionnaire ( par - q ) ( 1 ) and a lab specific maximal testing pre - participation screening questionnaire were completed to ensure participants were physically able to participate in the study . upon completion of the required questionnaires , each participant had anthropometric measures ( height , weight ) taken .
measurements were recorded using a my weigh md 500 digital scale and a tanita hr100 stadiometer ( tanita corporation ; japan ) . following these measures , participants had their resting hr ( after 5 minutes in a supine position ) , resting blood pressure , and a resting bl measured and recorded .
bl was measured using a capillary fingertip blood sample and a calibrated lactate pro portable analyzer ( kdk , corporation , kyoto , japan , arkray factory inc .
, kdk corporation shiga japan ) by the same clinician , using the same technique for each participant .
( 9.65 k.p.h . ) and completed 5 minutes of dynamic warm - up that focused on major muscle groups predominantly used during running . following the complete warm - up , participants bl values were obtained and recorded .
kempele , finland ) was fixed on the participant , as well as a nonin go2 achieve fingertip pulse oximeter ( nonin medical inc .
shawnee mission , ks , usa ) , connected to the ad instruments model ml206 gas analyzer metabolic cart ( ad instruments pty ltd , castle hill , australia ) , and placed on the woodway inc .
model elg treadmill ( woodway inc . , waukesha , wi , usa ) set at an incline of 0% grade . an incremental treadmill protocol
male and female participants underwent 33 minute treadmill increments . following completion of the 3 minute increments , participants entered stage two , which consisted of 1 minute increments until exhaustion .
this protocol was chosen , as stage one , allowed participants to achieve a steady - state , and stage two , allowed the speed at exhaustion to be determined .
three male participants , started at 9.3 m.p.h ( 14.96 kph ) and two male participants started at 9.9 m.p.h .
researchers observed and recorded heart rate ( hr ) and oxygen saturation ( spo2 ) every 30 seconds during the incremental treadmill test ( itt ) until exhaustion .
expired gases were collected using the metabolic cart and recorded in real time using power lab 26 t ( ad instruments pty ltd , castle hill , australia ) , and were analyzed using the software lab chart version 7 ( ad instruments pty ltd , castle hill , australia ) . immediately after exhaustion , subjects had their bl and rate of perceived exertion taken and recorded using a 620 borg rate of perceived exertion scale ( 3 ) .
participants began running their cool down , both men and women ran at 6 m.p.h . and had bl values obtained and recorded immediately post - exercise and at minutes 2 , 4 , 6 , and 8 post - exhaustion .
the subjects were tested in thunder bay , ontario , canada ( elevation 183 meters or 600 feet ) within 10-days prior to attending a 10-day altitude training camp ( located at teary peak , near the town of lead , in the black hills of south dakota , usa ) , at an elevation of approximately 1828 meters ( 6000 feet ) . at altitude ,
the training matched their absolute sea - level intensities and subjects recorded their training sessions in a daily log . upon conclusion of the altitude training camp , subjects were re - tested within 3-days of returning to thunder bay , ontario , canada ( 183meters or 600 feet ) , using the same equipment and procedure as pre - altitude testing .
room temperature ( degrees celsius ) and barometric pressure ( mmhg ) were recorded prior to every testing session .
usa ) was used to analyze the data . one categorical independent variable ( pre - altitude exposure and post - altitude exposure ) , and twelve continuous dependent variables ( average lactate , resting lactate , post - warmup lactate , lactate 0 minutes post - exercise , 2 minutes post - exercise , 4 minutes post - exercise , 6 minutes post - exercise , 8 minutes post - exercise , oxygen saturation , heart rate , time to exhaustion , and perceived exertion ) were examined .
the data were analyzed using paired samples t - tests to examine the effect of a 10-day altitude training camp intervention on the dependent variable for intervals of rest , post - warm - up , immediately after all out incremental exercise , 2,4,6 , and 8 minutes post - exhaustive exercise .
the average of all blood lactate ( bl ) values were higher post - altitude intervention ( 8.8  4.6 mmol / l ) compared to lactate values pre - altitude ( 7.4  3.3
bl was slightly lower at rest and post warm - up following a 10-day altitude intervention .
the resting bl before 10-day altitude intervention was ( 2.1  .5 mmol / l ) , compared to post - altitude ( 1.8  .7 ) , however , the difference between the means was not statistically significant t(7 ) = 1.30 , p = 0.22 .
mmol / l ) following the altitude intervention , compared to the lactate pre - altitude intervention ( 4.2  3.7
mmol / l ) , however , the difference did not reveal any statistical significance t(7 ) = .279 , p = 0.39 .
bl immediately post - itt following 10-days of altitude intervention was higher ( 13.6  3.6
mmol / l ) , as opposed to the bl immediately post - exercise in the pre - altitude trial ( 9.7  3.8 ) .
bl was also taken and recorded at 2 , 4 , 6 , and 8 minute s post - itt .
on average , bl was higher following the 10-day altitude intervention ( figure 1 ) , however , these differences were not statistically significant .
spo2 levels on average were higher during the itt following the 10-day altitude intervention ( 94.6  .932 % o2 ) , compared to the average spo2 levels before altitude intervention ( 92.2  1.23 % o2 ) .
the average hr during the itt was lower following the altitude intervention ( 176  11 bpm ) , when compared to the average hr values prior to the altitude intervention ( 187  9 bpm ) .
the average peak hr was lower post - altitude intervention ( 193.5  6.23 bpm ) compared to ( 197.90  6.90 bpm ) .
however , this was not statistically significant t(7 ) = 1.63 , p = 0.07 .
time to exhaustion ( seconds ) increased in 5 out of 8 participants post - altitude . on average , time to exhaustion for all participants post - altitude was ( 815.6  50.26 ) , compared to pre - altitude ( 784.5  95.24 ) .
the difference was not statistically significant t(7)= 1.21 , p = 0.13 . additionally , the rate of perceived exertion post - altitude was lower ( 17.37  1.50 ) compared to ( 17.87  .991 ) pre - altitude intervention , and was not statistically significant t(7 ) = 1.87 p = 0.51 .
the study examined the effect of a 10-day altitude training camp at approximately 1828 meters on the parameters of bl , spo2 , hr , time to exhaustion , and rate of perceived exertion following an incremental treadmill test .
the results show that the average of all bl levels immediately following itt , post - altitude intervention , are significantly increased .
there was no significant difference on bl levels at rest , post - warm up , or at intervals 2 , 4 , 6 , and 8 minutes post - itt following altitude , however , most of these values were higher on average .
these results were in contrast to previously reported findings ( 6 , 7 , 15 , 16 ) , that established a decrease , or no change in peak bl values post - altitude intervention .
this contrast may be attributed to a difference in altitudes investigated and the participants studied .
the itt was chosen as it is most often studied during exercise testing ( 12 ) .
this particular itt was chosen , as stage one , allowed participants to achieve a steady - state , and stage two , allowed the speed at exhaustion to be determined the average peak bl value both pre ( 9.68 mmol / l ) , and post -altitude intervention of 13.6 mmol / l , are similar to previous findings in the literature ( 12 ) . withers and colleagues ( 1991 )
study on human subjects at sea - level identified bl values following a normal incremental exercise test to be between 925 mmol / l after exercise and lasting into the first few minutes , post - exercise ( 39 ) .
the cause of the higher bl levels may be attributed to the fact that 5 out of 8 participants started an additional workload post - altitude .
although , there was no statistical difference in time to exhaustion , when comparing the pre- and post - altitude values , the slight increase in time to exhaustion can provide practical significance .
the average time to exhaustion increased , and although it was not statistically significant , the results imply that 5 out of 8 participants experienced favorable gains . for many athletes or coaches , this would be worth exploring .
in addition to the aforementioned reasons , it is possible that the lower hr levels in combination with the higher spo2 levels allowed the participants to last slightly longer during the itt ( 20 ) . the impact from both of these parameters will be discussed below .
it is possible that the average lower heart rates observed post - altitude intervention is due to a larger stroke volume .
this would be consistent with sime and colleagues ( 33 ) findings . in highly trained endurance athletes who possess a much higher cardiac output , pulmonary diffusion
a high cardiac output shortens the time during which the blood can pick up oxygen in the lungs , which may lead to lower blood spo2 ( 8 , 30 ) .
in contrast to these potential explanations , our results indicate a decrease in heart rate , accompanied by an increase in oxyhemoglobin saturation .
additionally , on average , participants were able to perform the test for slightly longer durations post - altitude .
the mechanism that mediates the test performance at longer duration could possibly be due to an increased release of erythropoietin ( epo ) following altitude intervention ( 11 ) .
an increased release of epo would cause a transient increase in red blood cell mass , thus , allowing more o2 transport ( 11 , 32 ) .
previous research indicates that these processes could take longer than 2-weeks , hence , this may only partially explain our results ( 33 ) .
some authors ( 17 , 27 ) suggest that due to the respiratory alkalosis that occurs with hyperventilation at altitude , the kidneys react to this by excreting more bicarbonate in an attempt to reinstate normal ph .
as bicarbonate is an important buffer of h+ , this adaptation has a negative impact on anaerobic capacity .
fortunately , as adaptation occurs , the hyperventilation response becomes blunted , causing resting and exercise ventilatory volumes to diminish towards , but never achieve those at sea - level . as a result ,
the kidneys excrete less bicarbonate and slowly return blood bicarbonate levels towards those of sea - level ( 17 , 27 ) .
this physiological mechanism may lead to higher lactate tolerance , which may explain our results , however , this notion should be further explored .
these changes were statistically significant , and the impact of this application in sport training is high .
previous research has presented positive physiological variations in regards to hr and spo2 ( 14 , 21 ) .
however , these studies differ as they were all 1424 days long , and at altitude equal to or greater than 2100 meters ( 6890 feet ) . additionally , these studies used different altitude training techniques ; chiefly live - high , train low . based on our results , we posit that cardiovascular changes such as , hr and oxyhemoglobin saturation , can be obtained at altitudes as low as 1828 meters and intervention duration as short as 10-days
. additionally , training at altitudes as low as 1828 meters may provide advantages of altitude training without some of the potential disadvantages , including : decrease in absolute training intensity ( 34 ) . a significant decrease in plasma volume ( 40 ) , and increased respiratory muscle work upon return to sea - level ( 18 ) .
significant limitations of the study include : the small number of participants ( n=8 ) , and a lack of measurement of related indices ( i.e. lactate threshold , hematocrit , and bicarbonate ) .
a one - group pre - test post - test design was used and future studies may consider including a control group .
the study is delimited to a small age range ( 1822 ) , that participants were all varsity level runners , and that the altitude was approximately 1828 meters .
the monitor did not capture one participant s hr accurately during the post - altitude test .
as a result , some of the hr readings from this test had to be omitted .
further , the pulse oximeter did not remain on one participant s finger near the end of the incremental test . as a result ,
the spo2 data obtained during this test was also omitted when analyzing the results . in conclusion
although altitude training has been extensively researched , controversy exists over the best techniques to use , the potential physiological benefits , the exact timeline that physiological changes occur , and its overall effectiveness for endurance athletes ( 40 ) .
the findings of this study have shown that blood lactate ( bl ) levels following a 10-day altitude intervention at approximately 1828 meters are higher on average , and are statistically significant immediately after maximal exercise .
the fact that 5 out of 8 participants increased their time to exhaustion following the altitude intervention , yet the average rate of perceived exertion was lower , may have some practical significance for training and competition .
additionally , the study suggests , that 10-days of altitude training at approximately 1828 meters , may be enough to alter physiological parameters such as , lower heart rate , higher spo2 , and enhanced coping to higher levels of blood lactate , thus , leading to a potential advantage in training and competition alike .
 altitude training has been shown to alter blood lactate ( bl ) levels due to alterations resulting from acclimatization . 
 this study aims to estimate the impact of altitude training on bl changes immediately following an incremental treadmill test and during recovery before and after 10-day altitude training at approximately 1828 meters . 
 eight varsity cross - country runners performed an incremental treadmill test ( itt ) , pre and post - altitude training . resting and post - warm - up bl values were recorded . during itt , 
 heart rate ( hr ) , oxygen saturation ( spo2 ) , and time to exhaustion were monitored . 
 bl was also measured post - itt at 0 , 2 , 4 , 6 , and 8 minutes . 
 the average of all bl values was higher following altitude intervention ( 8.8  4.6 mmol / l ) compared to pre - intervention ( 7.4  3.3 
 mmol / l ) . 
 these differences were statistically significant ( t(6 ) = 2.40 , p = .026 ) . 
 bl immediately ( 0 minutes ) after the itt was higher following the altitude intervention ( 13.6  3.6 
 mmol / l ) compared to pre - intervention ( 9.7  3.8 mmol / l ) and was statistically significant ( t(7 ) = 3.30 , p = .006 ) . 
 average hr during the itt was lower following the altitude intervention ( 176.9  11.1 bpm ) compared to pre ( 187  9.5 bpm ) , these differences were statistically significant ( t(28)= 18.07 , p= < .001 . 
 time to exhaustion was longer after the intervention , however was not statistically significant p = 0.13 . 
 these findings indicate that a 10 - day altitude intervention at 1828 meters may benefit varsity cross - country runners . 
 the higher post - exercise bl may be attributed to more anaerobic contributions . 
 lower hr may suggest a larger stroke volume and/or more efficient o2 carrying capacity . 
INTRODUCTION
METHODS
Participants
Protocol
Statistical Analysis
RESULTS
DISCUSSION