maximal oxygen consumption ( vo2 max ) is the amount of oxygen the human body can utilize in muscles and/or tissues . vo2
low aerobic fitness is associated with congestive heart failure , anemia , and obstructive pulmonary disease .
vo2 max is determined by both the capacity of oxygen delivery to the blood stream and the capacity of oxygen extraction from blood .
botanical supplements have been studied for decades , some of which have been associated with health or performance benefits .
echinacea is an herbal supplement that is derived from the north american purple coneflower plant and has shown some potential mechanisms that , with supplementation , could augment oxygen transport .
echinacea supplementation was found to increase vo2 max likely through an increase in the number and size of red blood cells , hemoglobin , and hematocrit associated with increases in serum erythropoietin .
recent research suggests echinacea induced erythrocythemia and vo2 max results in an increase in serum erythropoietin ( epo ) [ 1 , 5 ] .
this glycoprotein hormone , primarily produced in the kidneys , regulates red blood cell production .
epo improves exercise performance by increasing oxygen blood transport , which results in a greater vo2 max .
the increase in red blood cell mass is proceeded by a decrease in plasma volume to control hemoconcentration .
the regulation of epo production is based upon oxygen concentration in the blood and is increased by any condition that results in a decrease in the quantity of oxygen that is transported in the blood to the tissues [ 1 , 8 ] . running economy ( re )
is the energy cost reduction of submaximal running evaluated through the measurement of oxygen consumption during steady state exercise [ 8 , 9 ] .
potential mechanisms for improved submaximal re ensuing from erythrocythemia include an increase in the amount of adenosine triphosphate ( atp ) produced per mole of oxygen consumed , a decrease in the amount of atp necessary for running at a given speed , or a combination of both mechanisms [ 1 , 8 , 9 ] .
another adaptation resulting from erythrocythemia is a reduction in the heart rate [ 8 , 9 ] .
based upon the literature , it is reasonable to assume that echinacea will increase epo and , in turn , affect erythrocyte production . however , oxygen availability is generally not a limiting factor for exercise in normobaric environments .
therefore , an increase in epo alone may not be sufficient to increase exercise performance or maximum aerobic capacity , where both delivery and extraction of oxygen by tissue are necessary to increase vo2 max .
recent studies have shown an increase in supplementation usage , which may be related to the growing competitiveness in sports on both the collegiate and professional level [ 1416 ] . in a study of male and female elite figure skaters ,
supplement use was reported to prevent illness and disease , to increase energy , and to enhance performance .
given the available information regarding echinacea , it is important to evaluate whether or not supplementation is effective at increasing maximum aerobic capacity in the absence of an increased volume of physical activity and exercise . the purpose of this study was to determine the effects of oral echinacea supplementation on vo2 max and economy during submaximal treadmill walking and running in human participants .
it was hypothesized that echinacea supplementation might augment running performance in humans based upon previous evidence of changes in epo hormones levels demonstrated in previous research [ 1 , 5 ] .
the local institutional review board approved the study for the use of human subjects . all subjects provided informed written consent prior to beginning the study and were aware of their right to withdraw at any time .
participants were tested for maximum aerobic capacity , provided with a 30-day supply of supplements , and were asked to stringently adhere to their typical routine and levels of physical activity and exercise . following the completion of the 30-day supplementation period , each participant
was again tested for maximum aerobic capacity . all subjects reported consumption of all doses of the required supplement .
participant information can be seen in table 1 . the botanical supplement ( vo2- advantage , second wind llc , highland park , il , usa ) contained only substances that are generally regarded as safe by the united states food and drug administration .
the product contains a concentrated dose of echinacea purpurea ( 8  grams    day ) , as well as rhodiola rosea , cordyceps sinesis , quercetin , beta alanine , catechins , vitamin c , vitamin b-3 , vitamin b-12 , iron , folic acid , inositol , and alpha - lipoic acid .
the subjects were provided with a 30-day supply of the supplement , and all subjects were compliant in consuming the required doses .
the graded exercise test format included the use of the same equipment during both pre- and posttesting sessions .
the subjects ran on a track master tmx 425 treadmill ( full vision inc . , newton , ks . ) during the assessment .
participant 's expired air was sampled and analyzed with a parvomedic trueone 2400 metabolic measurement system ( parvomedics , sandy , ut ) .
the system utilized a mixing chamber and was set to report data every 10 seconds .
listed accuracy for the gas sensors in the unit are paramagnetic o2 analyzer 0.1% , infrared co2 analyzer 0.1% , and pneumotach 2% .
the test was concluded when the oxygen consumption was determined to have reached a plateau , or the participant volitionally ceased exercise .
participants were determined to have reached vo2 max if they demonstrated a plateau in oxygen consumption ( < 100  ml o2 change with increasing workload ) or achieved an rer value of greater than 1.15 .
heart rate during the test was determined through a polar wear link heart rate sensor ( polar electro inc . ,
lake success , ny ) that was linked to a receptor on the metabolic measurement system .
the lpa is a short self - report instrument designed to assess college student 's sedentary / nonsedentary activity , class rank , gender , and grade point average .
demographic variables are recorded as follows : class rank as freshman , sophomore , junior , or senior , gender as female or male , and grade point average between 0.0 and 4.0 .
types of sedentary activity include time spent in typing / schoolwork , web surfing / entertainment , and video gaming .
each sedentary / nonsedentary activity type classification has further descriptors for clarification : web surfing / entertainment included ( television , facebook , myspace , etc . ) and
these activities were assessed for frequency ( 02 days , 35 days , and 6 - 7days ) per week as well as duration per bout ( 015  min , 1630  min , and greater than 30  min ) .
each frequency and duration was assigned a score of 1 to 3  pts for each of the possible responses .
grade point average was assessed via predetermined ranges of answers ( 00.99 , 11.99 , 22.99 , 33.99 , 4.0 , or above ) .
aerobic exercise ( running , walking , biking , aerobics classes , etc . ) and weightlifting ( machine , free weight , etc . ) were assessed in a similar fashion for frequency and duration .
total scores for each item assessed were computed as the sum of the frequency and duration scores . the instrument has demonstrated test - retest reliability and criterion referenced validity . in order to determine
if an increase in physical activity and exercise duration was present , participants were assessed at the beginning and at the end of the supplementation period through the use of the lpa survey ( table 2 ) .
prior to analysis , all continuous variables were checked for normality using shapiro - wilks analysis . paired samples t - test
wilcoxon signed ranks tests were used to compare activity levels reported on the lpa survey from the start of the study to the conclusion of the study .
a repeated measures anova ( pre - post supplementation    stage of graded exercise test ) was used to evaluate changes in economy of movement during the assessment of maximum aerobic capacity .
all analyses were performed with the use of a modern statistics software package ( spss ver 21.0 , ibm , new york , usa ) .
the data collected for the survey was ordinal in nature ; therefore nonparametric procedures were employed for analysis .
the results of the wilcoxon signed ranks test suggest that there were no significant changes in aerobic activity level , z(12 ) = 1.577 , p = .115 nor were there significant changes in weight lifting activity , z(12 ) = 1.826 , p = .068 . based upon the lack of significant change in reported activity , maximum aerobic capacity before and after was analyzed independent of self - reported activity levels .
data collected from graded exercise tests to determine maximum aerobic capacity were found to be normally distributed via shapiro - wilks analysis ( p > .45 ) .
paired samples t - test analysis did not reveal a significant difference in maximum aerobic capacity , t(12 ) = 0.67 , p = .516 .
presupplementation maximum aerobic capacity ( m = 51.0 ,  sd = 6.8 ) was similar to postsupplementation values ( m = 51.8 ,  sd = 6.5 ) .  
the 3 minutes of absolute oxygen consumption ( l o2/min ) was averaged for the comparison .
the repeated measures anova did not reveal a main effect for changes in economy pre to post , f(1,11 ) = 0.067 , p = .800 , nor an interaction effect for time ( pre , post ) by stage ( 14 ) , f(3,33 ) = 0.669 , p = .577 .  
based upon the present investigation , a botanical supplement with a concentrated dose of echinacea is not sufficient to increase maximum aerobic capacity .
this finding is in contrast to previous reports in the literature that reported increases in vo2 max with echinacea supplementation . in that study ,
a similar dose of 8 grams per day of echinacea was administered for 28 days ( the present study used 30 days ) , and significant increases in vo2 max in the supplement group were noted .
however , the increase in maximum aerobic capacity in the supplement group was very small , indicated by an increase of only 1.5% .
this result is likely to be statistically significant but the practical significance is questionable given the very small effect of the supplement .
a more recent study   is in agreement with the present study which found that an 8 gram per day dose of echinacea was not found to increase the maximum aerobic capacity of trained distance runners .
it may be important to note that all three studies utilized a similar does of echinacea purpurea , which allows for comparison of the effects . in the present investigation and the baumann et al .  
study , there was almost no change in the mean aerobic capacity of the participants who received the supplement . in the whitehead et al .  
however , the longest use of the supplementations resulted in no difference in vo2 max . in regard to economy , the present investigation did not reveal any changes in walking or running economy during the first 4 stages of the graded exercise test .
this is , again , in contrast to the changes reported by whitehead et al .  
this study reported significant , but very minimal , changes in walking / running economy during the first 2 stages of a graded exercise test ( stage 1 : 1.5% increase in economy ; stage 2 : 1.67% increase in economy ) . based upon the available evidence
, it seems unlikely that echinacea supplementation has a meaningful impact on exercise economy during walking and running .
the limitations of the present study involved the use of self - reported compliance for adherence to the supplementation regime , the use of a self - reported instrument ( lpa survey ) to examine potential changes in physical activity and exercise behavior , and the use of supplement that had components other than echinacea .
though these limitations are necessary to disclose , the nature of the study was likely similar to the use of the supplement in a real - world setting .
therefore , the results are applicable to those who have an interest in exercise or sport nutrition .
based upon the present study , the use of a botanical supplement with a concentrated dose of echinacea purpurea can not be recommended to increase aerobic capacity or economy during exercise in healthy , recreationally active adults .
given the information regarding the ability of echinacea to augment epo levels , these supplements should be evaluated for use in populations where oxygen delivery limits functional capacity , such as those individuals with disease states or those persons who will transition to living at altitude .
 the present investigation evaluated the efficacy of a botanical supplement that delivered a concentrated dose of echinacea purpurea ( 8 grams day1 ) . 
 the participants were 13 apparently healthy , recreationally active college students ( vo2 max : 51  ml o2/kgmin ) . 
 the participants were provided with a 30-day supplementation regime . 
 data regarding maximum aerobic capacity was collected through pre- and posttesting surrounding the 30-day supplementation regime . 
 the participants were instructed to maintain normal levels of physical activity and exercise during the experimental period . 
 the levels of physical activity and exercise were monitored via the leisure and physical activity survey . 
 the participants did not report any significant increases in aerobic physical activity or exercise during the supplementation period . 
 paired samples t - test analysis did not reveal a significant difference in maximum aerobic capacity , t(12 ) = 0.67 , p = .516 . 
 presupplementation maximum aerobic capacity ( m = 51.0 , sd = 6.8 ) was similar to postsupplementation values ( m = 51.8 , sd = 6.5 ) . 
 this study suggests that botanical supplements containing a concentrated dose of echinacea purpurea is not an effective intervention to increase aerobic capacity of recreationally active individuals . 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion
5. Conclusions