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 (EI) 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-VO, regression equations and during swimming by the multiple regression equation: Y = 3.65v+ 0.02W- 2.545 where Yis VO,in L x min(-1), v is the velocity in m s(-1), Wis the body weight in kilograms. Total EE (10,036 +/- 931 and 8,570 +/- 1,014 kcal) was significantly greater than total EI (3,940 +/- 868 and 3,115 +/- 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 x kg(-1) x 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.