Energy balance during an ironman triathlon in male and female triathletes

Energy balance of 10 male and 8 female triathletes participating in an Ironman event (3.8-km swim, 180-km cycle, 42.2-km run) was investigated. Energy intake (El) was monitored at 7 designated points by dietary recall of food and fluid consumption. Energy expenditure (EE) during cycling and running was calculated using heart rate-(V)over dotO(2) regression equations and during swimming by the multiple regression equation: Y= 3.65upsilon+0.02W-2.545 where Y is (V)over dotO(2) in L.min(-1), upsilon is the velocity in m.s(-1), W is the body weight in kilograms. Total EE (10,036+/-931 and 8570+/-1014 kcal) was significantly greater than total EI (3940+/-868 and 3115+/-914 kcal, p<.001) for males and females, respectively, although energy balance was not different between genders. Finishing time was inversely related to carbohydrate (CHO) intake (g.kg(-1).h(-1)) during the marathon run for males (r=-.75,p<.05), and not females, suggesting that increasing CHO ingestion during the run may have been a useful strategy for improving Ironman performance in male triathletes.