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IntroductionNocturnal heart rate variability (HRV) reflects cardiac autonomic regulation during the night and may index menstrual-cycle and premenstrual-symptom change. Most prior studies covered a single cycle and used group-average analyses, leaving unclear whether day-level nocturnal HRV is associated with symptoms within individuals.MethodsIn this intensive longitudinal wearable study, 20 women aged 18–20 years (59 complete cycles; 1,561 cycle-phase-assigned person-days) wore a textile chest-lead electrocardiogram (ECG) sensor and completed twice-daily self-report diaries. The root mean square of successive differences (RMSSD), the standard deviation of normal-to-normal intervals (SDNN), and mean heart rate (MeanHR) were derived from 5-min epochs of nocturnal beat-to-beat (RR) intervals. Cycle phases were estimated from recorded menstrual onsets without hormonal confirmation. Intraclass correlations for the HRV indices ranged from 0.40 to 0.54. Linear mixed-effects models estimated cycle-phase effects and within-subject HRV–symptom associations; participant-level cluster-robust analyses served as sensitivity checks.ResultsRelative to the follicular phase, the late-luteal phase (the final five days of the cycle) showed higher nocturnal MeanHR (+4.66 bpm, 95% CI [3.77, 5.55]) and lower RMSSD and SDNN (approximately 16% and 11%; all Holm-adjusted p < 0.0001); these contrasts were robust to participant-level inference and to alternative phase and sample definitions, and MeanHR was higher in 18 of 20 participants. Nocturnal HRV in the menstrual phase did not differ significantly from that in the follicular phase. Within individuals, after adjustment for cycle phase, lower RMSSD and SDNN and higher MeanHR were associated with worse self-rated morning physical condition and morning fatigue (16–18 of 19 participants in the expected direction), but statistical support after multiplicity correction depended on the inferential method; no association was detected for mental condition. Evidence that the strength of this association differs between women was inconclusive, and a larger late-luteal change among participants who recalled greater premenstrual worsening at baseline was not supported by participant-level tests.DiscussionThese findings indicate that nocturnal HRV and heart rate capture menstrual-cycle-related change and covary contemporaneously with day-to-day physical symptoms within individuals; no predictive or diagnostic-accuracy analysis was performed, and confirmation in larger cohorts with prospective symptom assessment and hormonal verification of cycle phase is needed.
Low energy availability is a core feature of Relative Energy Deficiency in Sport that impairs skeletal and hematologic health. However, the contributions of short-term energy restriction and exercise as well as their potential interactive effects remain unclear. This study aimed to clarify the effects of short-term food restriction on exercise-induced bone mass acquisition and its simultaneous impact on iron metabolism in young female rats. Female Sprague-Dawley rats (5 wk old) underwent environmental acclimation and treadmill running exercise training for 1 wk each and randomly grouped into seven groups. The groups included a sedentary and ad libitum feeding group, along with groups fed 90%, 70%, or 50% of the average ad-lib intake under sedentary or running exercise conditions for 15 d. The results showed low tibial bone mineral density (BMD) and ferritin levels and high serum iron levels due to a significant main effect of food restriction. Hematocrit-adjusted erythrocyte counts were unchanged, indicating an iron metabolic disturbance characterized by depleted stores despite high circulating iron. Exercise significantly increased tibial BMD, but the 50% food restriction groups (sedentary and exercise) showed significantly lower values than the exercise 90% group. Serum iron levels showed significant differences even in the 70% food restriction group compared with the 90% group. Tibial BMD and serum iron levels were weakly negatively correlated. This study revealed that, in young female rats, short-term 50% food restriction resulted in decreased BMD while short-term 70% and 50% food restriction resulted in iron metabolic disturbances under both sedentary and exercise conditions.
[Purpose] This study aimed to determine the time course of changes in bone mass and bone strength induced by the combination of voluntary running exercise and food restriction in young female rats.[Methods] Female Sprague-Dawley rats (aged 7 weeks) were randomly divided into the following three experimental groups after a 1-week acclimatization period: sedentary and ad libitum feeding (SED), voluntary wheel running exercise and ad libitum feeding (EX), and voluntary wheel running and food restriction (EX-FR). Dissections were performed at 2, 4, 8, and 12 weeks. The strength of the femoral mid-shaft was assessed using the three-point bending test. The bone mineral density (BMD) of the tibia was measured using a dual-energy X-ray absorptiometry machine.[Results] At 2 weeks, the body weight, abdominal fat weight, and bone weight of the femur in the EX-FR group were significantly lower than those in the SED and EX groups. The BMD of the tibia in the EX-FR group was significantly lower than that in the EX group. At 4 weeks, the bone strength of the femur in the EX-FR group was significantly lower than that in the EX group. At 8 weeks, the bone strength of the femur in the EX-FR group was significantly lower than that in the SED group.[Conclusion] These findings demonstrate that bone mass is affected earlier than bone strength under energy-deficient exercise conditions, providing important insights into the temporal progression of bone impairment associated with relative energy deficiency
PURPOSE:Appropriate dietary intake across different training phases is crucial for improving the performance of track and field jumpers. However, few studies have investigated dietary intake based on the training phase and competitive level. The purpose of this study was to evaluate dietary intake in track and field jumpers across different training phases and competitive levels. METHODS:A total of 28 male collegiate jumpers participated. A food frequency questionnaire assessing 1-month dietary intake was administered four times: transition phase (TP), preparatory phase (PP), early competitive phase (ECP), and late competitive phase (LCP). Participants were divided into the Exceeded Group (EG) and the Nonexceeded Group (NEG) based on competition standards. RESULTS:Of the 28 participants, 20 were included in the final analysis. Energy, protein, fat, vitamin B1, and vitamin B6 intake decreased during the ECP and LCP compared with intake during the TP. Intake of these nutrients was higher in the EG than in the NEG, with the EG significantly showing higher intake during the TP. However, these group differences were not observed during the LCP. CONCLUSION:These results indicate the necessity of appropriate dietary strategies for each training phase.
When using allergenic food powders, unintentional cross-contact of food powders potentially occurs due to their dispersibility. This study compared the dispersibility of five food powders-skim milk, infant formula, wheat flour, buckwheat flour, and soybean flour-to identify the parameters for improving the hygienic control of cross-contact. In a drop-dispersal experiment, 50 g of each food powder was dropped from a height of 1.2 m and allowed to settle for 5 min. Using immunochromatography and enzyme-linked immunosorbent assay, each dispersed food powder was detected in order of higher distance from dropping point: skim milk and buckwheat flour, infant formula, wheat flour, and soybean flour. To clarify the cause of the differences, the dispersed food particles were visualized using laser irradiation in the drop-dispersal experiment. The powder properties were also analyzed. The results showed that skim milk, buckwheat flour, infant formula, and wheat flour rose due to redispersion until reaching near the starting position of the fall. Subsequently, they became a cloud of particles on the experimental table and diffused into the surrounding area. Contrarily, for soybean flour, no rise due to redispersion after dropping and no diffusion to the surrounding area could be confirmed. Thus, food powders should be added from as low a position as possible to control redispersion. Among the properties, dispersibility can be a useful tool for simulating the dispersal distance and hygienic control of food powders. This could help reduce the risk of cross-contact due to unintentionally dispersed food allergens.
