ENERGY-BALANCE IN CROSS-COUNTRY SKIERS - A STUDY USING DOUBLY LABELEDWATER

Energy intake covering energy expenditure is essential for performance as well as for health aspects in endurance athletes. This study was p erformed to determine the energy needs for elite cross country skiers during a week of training and to demonstrate whether energy balance co uld be maintained. Energy intake was calculated from weighed dietary r ecords and doubly labeled water was used to simultaneously measure ene rgy turnover. Average daily energy intake ranged from 15.7 to 20.4 MJ. d(-1) in the females and from 25.7 to 36.0 MJ.d(-1) in the males. This correlated well with the data for average daily energy turnover (r = 0.96; P = 0.0001) that ranged from 15.1 to 20.2 MJ.d(-1) and from 25.4 to 34.9 MJ.d(-1), in females and males, respectively. The mean differ ence being 0.1 (+/-1.9) MJ.d(-1). The close match between energy intak e and energy expenditure has not previously been shown in athletes at these high levels of energy turnover. However, if energy intake over s eparate 24-h periods was compared with corresponding data for training , no significant relationship was found. This indicates that the athle tes were not in energy balance during shorter periods. Furthermore, th e validity of theoretical calculations of energy turnover, in highly t rained subjects, derived from multiples of estimated BMR, is questione d.