BACKGROUND: Now that marathon racing is growing in popularity, many thousands of 
enthusiastic athletes are participating in various ultramarathons all over the 
world each year. However, it remains controversial whether such a sport 
contributes to the promotion of health. The occurrence of transient cardiac 
dysfunction and irreversible myocardial injury has been reported in association 
with such exercise in healthy individuals. Brain natriuretic peptide (BNP) is a 
cardiac hormone, as is atrial natriuretic peptide (ANP), and its measurement has 
been widely used for clinical evaluation of cardiac dysfunction. However, little 
is known about the response of plasma BNP to prolonged strenuous exercise. We 
hypothesized that confirmation of minimal cardiac dysfunction or myocardial 
injury may be made by measurements of plasma BNP.
METHODS: Levels of plasma ANP, BNP, catecholamines, blood lactate, and serum 
cardiac troponin T (cTnT) were determined before and after a 100-km 
ultramarathon in 10 healthy men to examine the effects of the exercise on levels 
of ANP and BNP and correlations between the natriuretic peptides and cTnT as a 
marker for myocardial damage.
RESULTS: Whereas all variables significantly increased after the race, increased 
levels of ANP and BNP were most strongly correlated with increases in cTnT 
levels. The cTnT level after the race was greater than the upper reference limit 
in 9 of 10 men.
CONCLUSIONS: Such exercise significantly increased ANP and BNP levels in healthy 
men, and the increases could be partially attributed to myocardial damage during 
the race.