The Effect of the Menstrual Cycle on Immune Cell Activity and Recovery After Resistance Exercise

Inclusion Criteria: * Women between the ages of 18 and 40. * Must weigh at least 110 pounds. * Healthy as determined by medical history, physical activity readiness, and menstrual cycle questionnaires. * Actively resistance training for at least 6 months (minimum of 3 resistance training sessions per week, with at least one lower body session). * Pre-menopausal and have a regular menstrual cycle (eumenorrheic), with a clear start of menses (early follicular phase). * Not currently pregnant or planning to become pregnant during the study. * Have not used hormonal birth control or intrauterine devices in the past 3 months (or three full menstrual cycles). * Able to recall approximate start dates of their last 6 menstrual cycles. * Willing to follow study instructions, including avoiding exercise, alcohol, and caffeine before testing visits. * Free from previous or current lower body injuries that could limit performance. * Not regularly taking any medications that could interfere with the study. * Determined to have a high likelihood of successful blood draws by a certified phlebotomist. Exclusion Criteria: * Do not give consent to participate. * Have been determined unfit to participate based on medical or activity history (using health questionnaires). * Currently take prescription or over-the-counter medication that could affect the study results. * Have a chronic illness requiring medical care. * Not currently resistance-trained (don't meet the exercise requirement). * Pregnant or planning to become pregnant during the study. * Do not have regular periods or have been diagnosed as amenorrhoeic (absence of menstruation). * Currently taking any performance-enhancing drugs. * Currently using hormonal birth control or intrauterine devices (IUDs), or have used them in the past three months (or three full menstrual cycles). * Determined unlikely to have a successful blood draw by a trained phlebotomist. * Weigh less than 110 pounds.