VANHEEST, JL, CD RODGERS, CE MAHONEY, and MJ DE SOUZA. Ovarian Suppression Impairs Sport Performance in Junior Elite Female Swimmers. Med. Sci. Sports Exerc., Vol. 46, No. 1, pp. 156–166, 2014. Competitive female athletes restrict energy intake and increase exercise energy expenditure frequently resulting in ovarian suppression. The purpose of this study was to determine the impact of ovarian suppression and energy deficit on swimming performance (400-m swim velocity). Menstrual status was determined by circulating estradiol (E2) and progesterone (P4) in ten junior elite female swimmers (15–17 yr). The athletes were categorized as cyclic (CYC) or ovarian-suppressed (OVS). They were evaluated every 2 wk for metabolic hormones, bioenergetic parameters, and sport performance during the 12-wk season. CYC and OVS athletes were similar (P 9 0.05) in age