Effects of inorganic nitrate supplementation on power, speed, and strength endurance throughout the menstrual cycle

Nitrate supplementation has been shown to enhance exercise performance and capacity, mainly in studies involving male participants. In contrast, its effects on resistance exercise are less well established, and the limited inclusion of women restricts the generalizability of existing evidence. Women are underrepresented in nitrate supplementation research, and many studies involving this population have failed to demonstrate positive effects. Nevertheless, some findings do suggest that nitrate supplementation may benefit performance in female athletes. The absence of favourable results may be related to methodological factors, such as the lack of control over i) menstrual cycle phase, ii) practices that affect oral microbiota, and iii) the use of supplementation and exercise protocols that are not optimal for observing a positive effect. Therefore, the aim of the present study is to investigate whether, under conditions conducive to observing an ergogenic effect, acute nitrate supplementation affects power, velocity, and muscular endurance in women at different phases of the menstrual cycle. To this end, 35 healthy women with regular resistance training and regular menstrual cycles will perform two exercise tests: 3 sets of 2 repetitions of back squats and, subsequently, 3 sets of 2 repetitions of bench press at 50% of 1RM, performed with maximum explosive intent, to assess power and speed using a linear position transducer. Thereafter, participants will perform 3 sets to muscle failure at 70% of 1RM, also performed in back squats and bench presses, with 2-minute rest intervals, to assess muscle endurance. The visits will be conducted in a counterbalanced, randomized crossover design, 2.5 hours after participants receive, in a double-blind manner, either 70 ml of concentrated beetroot juice containing 6.4 mmol of nitrate (BET) or 70 ml of nitrate-depleted concentrated beetroot juice (PLA). Assessments will be performed during the early follicular phase (low estrogen) and the late follicular phase (high estrogen) of the menstrual cycle, controlling for factors that affect oral microbiota and using supplementation and exercise protocols optimized to detect a positive effect of nitrate supplementation. The aim of this study is to investigate the efficacy of acute nitrate ingestion on muscle power, velocity, and strength endurance in physically active women during periods of low estrogen (early follicular phase) and high estrogen (late follicular phase) under conditions favorable for observing the ergogenic effect of this substance. This will be the first study to investigate the effects of nitrate supplementation on muscle power, velocity, and muscular endurance in women across different phases of the menstrual cycle. The results of this study will be highly relevant for understanding the interaction between nitrate supplementation and menstrual cycle phases and will significantly contribute to more effective strategies for optimizing female performance.