Periodizing and programming strength and endurance training according to the phases of the menstrual cycle has been recommended in popular and social media. The approach is based on the idea that the nonreproductive actions of female sex hormones like estradiol and progesterone can be “taken advantage of” to enhance or optimize training. Female sex hormone concentrations, which fluctuate across the menstrual cycle, influence physiological processes acting on muscle, nervous, epithelial, and connective tissues, although sometimes being associated with adverse symptoms. These changes in sex hormone concentrations are suggested to influence strength and endurance training outcomes to some extent. However ...