BACKGROUND: An improved muscle strength are of great importance in many sports, hence an increased understanding on how to generate optimal strength training programs in women without negative side effects that may lead to the female athlete triad are essential. The purpose of this study was to investigate potential negative effects of high frequency periodized menstrual/oral contraceptives (OC) cycle based leg resistance training on components in the female athlete triad. METHODS: Fifty-nine women, with experience of resistance training and with regular menstrual/OC cycles were included in the analyses. The participants were randomly assigned a training program consisted of high frequency leg resistance training, periodized to the first two weeks (group 1) or the last two weeks (group 2) of each cycle, or to a control group performing regular training, during four consecutive menstrual/ OC cycles. The main analysis was the pre-to-post change of sex and growth hormones, cortisol, total body fat mass, bone mineral density in the spine. We further examined the participants' own experience of the training programs. RESULTS: No significant negative impact on sex and growth hormones, cortisol, total body fat mass and bone mineral density in the spine, was detected in any of the groups. Moreover, the women in group 1 experienced their training program as positive. CONCLUSIONS: The high frequency periodized leg resistance training was not associated with exercise-related negative consequences on components in the female athlete triad. Moreover, the training was well accepted when performed during the first two weeks of each cycle.