(1) Background: The influence of the menstrual cycle on physical fitness in athletes is controversial in the scientific literature. There is a marked fluctuation of sex hormones at three key points of the menstrual cycle, where estrogen and progesterone vary significantly. Hormonal contraception induces hormonal levels different from the natural menstrual cycle, requiring specific study in relation to physical fitness. (2) Method: Women aged 18 to 40 years with regular natural menstrual cycles and women using hormonal contraception were recruited, creating two study groups. All participants needed to be athletes classified as level II-III according to the classification by McKay et al (2021), based on training volume/physical activity metrics, among other variables. To assess their physical fitness, Cardiorespiratory Fitness (measured by VO2max), high-speed strength, hand grip strength, and flexibility were evaluated. Blood samples were taken to determine the menstrual cycle phase through analysis of sex hormone levels. Additionally, urine tests for ovulation detection were performed for the natural menstrual cycle group. Neurosensory stimulation tests were incorporated to measure sensory threshold and pain threshold in each phase. Body composition in each phase and its relationship with the other variables were also taken into account. (3) Results: Athletes in the natural cycling group showed differences in VO2max (mL·kg-1·min-1) (phase I =41.75 vs phase II =43,85 and (p=0.004) and phase I vs phase III=43,25 mL·kg-1·min-1 (p =0.043)), as well as in body weight (phase I = 63.23 vs. phase III = 62.48 kg; p=0.006), first pain threshold (phase I = 1.34 vs. phase II = 1.69 (p=0.027) and phase III = 1.59 mA (p=0.011)), and sensitive threshold (phase I = 0.64 vs. phase II = 0.76 mA (p=0.017)). The pain threshold was found to be an important covariate in relation to VO2max, explaining 31.9% of the variance in phase I (p=0.006). These findings were not observed between the two phases of contraceptive cycling. (4) Conclusion: The natural menstrual cycle will cause significant changes in the physical fitness of athletes. The use of hormonal contraception is not innocuous. Women with natural cycles show a decrease in cardiorespiratory fitness in phases II and III, which is a factor to be considered in relation to training level and workload.

(1) Background: Ultra-endurance exercise involves a high physical impact, resulting in muscle damage, inflammatory response and production of free radicals that alter the body's oxidative state. Supplementation with antioxidants, such as beetroot, may improve recovery in ultra-endurance runners. The aim of this study was to determine whether there is a correlation between the beetroot intake and the recovery of serum oxidative status, inflammatory response and muscle damage parameters after an ultra-endurance race. (2) Methods: An observational and longitudinal study was conducted by means of surveys and blood samples collected from 32 runners during the IX Penyagolosa Trails CSP® race and the two following days. The variables C-reactive protein (CRP), lactate dehydrogenase (LDH), creatine kinase (CK), the activity of the antioxidant enzymes glutathione peroxidase (GPx) and glutathione reductase (GR), as well as the oxidative damage markers malondialdehyde (MDA), carbonyl groups (CG) and loss of muscle strength using the Squat Jump test (SJ) were analyzed to discriminate whether beetroot consumption can modulate the recovery of ultra-trail runners. (3) Results: Significant differences were observed between runners who ingested beetroot and those who did not, in terms of oxidative status, specifically in serum GPx activity at 24 and 48 hours, muscle damage variables CK and LDH and in SJ test at the finish line. Therefore, the intake of supplements containing beetroot positively influences the recovery of serum oxidative status and muscle damage after ultra-endurance running.

Background: Exercise is an accepted intervention to improve the quality of life (QoL) of breast cancer patients. Exercise programs have been developed and all have shown satisfactory results in improving QoL. There is a lack of research comparing different prescription modalities. The aim of this study is to evaluate the effectiveness of physical exercise (in-person, home-based, prescription) on QoL in breast cancer patients actively undergoing treatment; Methods Quasi-experimental study with randomized assignment to three groups (in-person: guided and supervised in-person exercise program; home-based exercise: guided and supervised exercise program with streaming monitoring; recommendation: exercise recommendation). Quality of life was measured using the QLQ-C30 questionnaire. Baseline and 24-week analysis. Results: The total sample analyzed was n=80. QoL improved significantly at 24 weeks in the face-to-face and home-based exercise groups, but not in the advice group. Exercise in all modalities improved fatigue, nausea, vomiting, appetite, and constipation. QoL at 24 weeks depended on active chemotherapy, tumor type, and assigned exercise group (r2 = 0.503; p < 0.001). Conclusions: QoL in breast cancer patients undergoing active treatment improves after a 24-week exercise program, especially in face-to-face and home-based exercise. Home-based exercise, streaming-based recommendation is a viable option for exercise recommendation.