Purpose: To analyze the influence of training status on the percentage of maximum oxygen consumption, heart rate and velocity (%VO_2max, %HR_max and %V_max) at which ventilatory threshold 1 and ventilatory threshold 2 occur (VT1 and VT2, respectively), in males and females separately considering age, during a ramp incremental treadmill test. Methods: 791 males (36.8 ± 9.9 years) and 301 females (33.9 ± 11.0 years) performed a ramp incremental exercise test until fatigue where VT1 and VT2 were determined. Participants were classified as low, medium or high training status combining the oxygen consumption at VT1, VT2 and VO_2max by clustering analysis. Results: VO_2max is poorly correlated with the %VO_2max, %HR_max and %V_max at which VT1 and VT2 occur (r < 0.3), in contrast, there is a positive correlation between oxygen consumption at VT1 and VT2 with the %VO_2max, %HR_max and %V_max at which VT1 and VT2, respectively, occur in males and females (r = 0.203–0.615). Furthermore, we observed the %VO_2max, %HR_max and %V_max at which thresholds occur were greater the higher the training status (all p < 0.003). Conclusion: The physiological determinants of the percentage of maximum at which VT1 and VT2 occur are more related to oxygen consumption at VT1 and VT2, respectively, than to VO_2max. Moreover, due to the higher percentage of maximum at which VT1 and VT2 occur in individuals with a higher training status, the common strategy consisting of establishing exercise intensity as a fixed percentage of maximum might not be effective to match intensity across individuals with different training status. Clinical trial registration: NCT06246760.

The first aim was to explore the difference in metabolic flexibility between sexes in response to changing exercise intensity under control conditions. The second aim was to evaluate metabolic flexibility between sexes in response to exercise intensity adding two different metabolically challenging stimuli (glycogen depletion and heat). Eleven males (22 ± 3 years, 176.2 ± 4 cm, 68.4 ± 4.9 kg, and 60.2 ± 4.1 mL/kg FFM/min) and nine females (22 ± 2 years, 166.7 ± 4.5 cm, 61.9 ± 2.9 kg, and 64.2 ± 5.6 mL/kg FFM/min) performed a maximal incremental exercise test (30 W every 3 min) on a cycle ergometer under three conditions: control (24 h high-carbohydrate diet followed by the incremental test), glycogen depletion (glycogen-depletion protocol followed by 24 h low-carbohydrate diet and then the incremental test), and heat (24 h high-carbohydrate diet followed by 30 min passive heating and then the incremental test in heat). In the last minute of each step, lactate was analysed, fat (FATox/FFM) and carbohydrate oxidation (CHox/FFM), and energy expenditure (EE/FFM) normalized to fat-free mass (FFM) was estimated by indirect calorimetry. Females presented a greater FATox/FFM as exercise intensity increases across conditions (control, glycogen depletion, and heat) ( p = 0.006). In contrast, CHox/FFM was not significantly different between sexes at any specific intensity across conditions ( p > 0.05). Consequently, EE/FFM was higher in females throughout the different intensities across conditions ( p = 0.002). Finally, lactate concentration was not different between sexes at the same intensities across conditions ( p = 0.87). In conclusion, females present a greater metabolic flexibility, due to the higher FATox/FFM throughout the different intensities, regardless of whether the test is performed in conditions emphasizing the oxidative pathway (glycogen depletion) or the glycolytic pathway (heat). Clinical trials: NCT05703100

The aim of the study was to analyze the influence of an aerobic fitness level on the percentage of maximum oxygen consumption, heart rate, and power output (%VO_2max, %HR_max, and %W_max) at which ventilatory thresholds 1 (VT1) and 2 (VT2) occur during a ramp incremental cycle‐ergometer test in males and females considering age. 1450 males and 241 females performed a ramp incremental exercise test until exhaustion to determine VT1, VT2, and VO_2max. Combining the oxygen consumption at VT1, VT2, and VO_2max by clustering analysis, males were classified as a low, medium, or high aerobic fitness level and females were classified as a low or high aerobic fitness level. Results showed VO_2max was very poorly correlated with the %VO_2max at which VT1 and VT2 occur (r ≤ 0.115), whereas oxygen consumption at VT1 and VT2 showed a stronger positive association with the %VO_2max at which VT1 and VT2 occur, respectively (r = 0.357–0.604). Furthermore, the %VO_2max at which VT1 and VT2 occur were greater the higher the aerobic fitness level (all p ≤ 0.002), observing a high heterogeneity in the %VO_2max at which VT1 and VT2 occur even stratifying the sample by sex and aerobic fitness levels. In conclusion, the percentage of maximum at which VT1 and VT2 occur are better related to oxygen consumption at VT1 and VT2, respectively, than to VO_2max. Moreover, the common strategy consisting of establishing exercise intensity as a fixed percentage of maximum might not be effective to match intensity across individuals even if sex and aerobic fitness levels is considered.Trial Registration: NCT06246760.

To explore how sex hormone fluctuations may affect bone metabolism, this study aimed to examine P1NP and β-CTX-1 concentrations across the menstrual and oral contraceptive (OC) cycle phases in response to running. 17β-oestradiol, progesterone, P1NP and β-CTX-1 were analysed pre- and post-exercise in eight eumenorrheic females in the early-follicular, late-follicular, and mid-luteal phases, while 8 OC users were evaluated during the withdrawal and active pill-taking phases. The running protocol consisted of 8 × 3min treadmill runs at 85% of maximal aerobic speed. 17β-oestradiol concentrations (pg·ml⁻¹) were lower in early-follicular (47.22 ± 39.75) compared to late-follicular (304.95 ± 235.85;p = < 0.001) and mid-luteal phase (165.56 ± 80.6;p = 0.003) and higher in withdrawal (46.51 ± 44.09) compared to active pill-taking phase (10.88 ± 11.24;p < 0.001). Progesterone (ng·ml⁻¹) was higher in mid-luteal (13.214 ± 4.926) compared to early-follicular (0.521 ± 0.365; p < 0.001) and late-follicular phase (1.677 ± 2.586;p < 0.001). In eumenorrheic females, P1NP concentrations (ng·ml⁻¹) were higher in late-follicular (69.97 ± 17.84) compared to early-follicular (60.96 ± 16.64;p = 0.006;) and mid-luteal phase (59.122 ± 11.77;p = 0.002). β-CTX-1 concentrations (ng·ml⁻¹) were lower in mid-luteal (0.376 ± 0.098) compared to late-follicular (0.496 ± 0.166; p = 0.001) and early-follicular phase (0.452 ± 0.148; p = 0.039). OC users showed higher post-exercise P1NP concentrations in withdrawal phase (61.75 ± 8.32) compared to post-exercise in active pill-taking phase (45.45 ± 6;p < 0.001). Comparing hormonal profiles, post-exercise P1NP concentrations were higher in early-follicular (66.91 ± 16.26;p < 0.001), late-follicular (80.66 ± 16.35;p < 0.001) and mid-luteal phases (64.57 ± 9.68;p = 0.002) to active pill-taking phase. These findings underscore the importance of studying exercising females with different ovarian hormone profiles, as changes in sex hormone concentrations affect bone metabolism in response to running, showing a higher post-exercise P1NP concentrations in all menstrual cycle phases compared with active pill-taking phase of the OC cycle.

Bone metabolism is a dynamic process regulated by systemic and local factors, including sex hormones. While in vitro studies suggest that hormonal fluctuations impact bone biomarkers, in vivo findings remain inconsistent. Therefore, this systematic review aimed to evaluate whether biochemical markers of bone resorption and bone formation fluctuate across different phases of the menstrual cycle in healthy regular menstruating females. Following PRISMA guidelines, a comprehensive search was conducted in PubMed and Web of Science (January 2025). A total of 18 studies were included and assessed for quality using the NHLBI Quality Assessment Tool. Considerable heterogeneity was found across studies in design, phase classification, and outcome reporting. While 5 out of 7 studies on β-CTX-I reported lower concentrations during the luteal phase, 6 out of 8 studies showed that osteocalcin concentrations did not vary across the MC. Findings concerning other biomarkers included in this review were limited and inconsistent, hindering the identification of a clear trend. Current evidence does not establish a consistent pattern in bone metabolism biomarker fluctuations across the MC. Variability in methodology, hormone verification, and participant characteristics may contribute to these inconsistencies. PROSPERO registration CRD42022375821.

The primary objective of this study was to examine the influence of hormonal ovarian profile and training characteristics on spine, pelvis, and total body bone mineral density (BMD) in a group of well‐trained females. Forty‐two eumenorrheic females, twenty‐eight monophasic oral contraceptive (OC) users and thirteen postmenopausal females participated in this study. Body composition was measured by total body dual‐energy X‐ray absorptiometry (DXA) to determine BMD of the areas of interest. Endurance‐trained premenopausal females showed lower spine BMD compared to resistance‐trained premenopausal females (1.03 ± 0.1 vs. 1.09 ± 0.09 g/cm²; p = 0.025). Postmenopausal females reported lower BMD level in comparison to eumenorrheic females in pelvis (1.079 ± 0.082 vs 1.19 ± 0.115 g/cm²; p = 0.005), spine (0.969 ± 0.097 vs 1.069 ± 0.109 g/cm²; p = 0.012) and total (1.122 ± 0.08 vs 1.193 ± 0.077 g/cm²; p = 0.018) and OC users whose duration of OC use was less than 5 years (OC < 5) in pelvis (1.235 ± 0.068 g/cm²; p < 0.001) and spine (1.062 ± 0.069 g/cm²; p = 0.018). In addition, lower BMD values were found in OC users who had been using OC for more than 5 years (OC ≥ 5) than eumenorrheic females in pelvis (1.078 ± 0.086 g/cm²; p = 0.029) and spine (0.966 ± 0.08 g/cm²; p = 0.05). Likewise, OC ≥ 5 showed lower values than and OC < 5 in pelvis (p = 0.004) and spine (p = 0.047). We observed a lower spine BMD value in premenopausal endurance‐trained females compared to premenopausal resistance‐trained females. Moreover, this research observed that prolonged use of OCs may reduce bone mass acquisition in the spine and pelvis, even in well‐trained females. Finally, postmenopausal showed lower BMD despite being exercising women.Trial registration: ClinicalTrials.gov identifier: NCT04458662.Highlights Ovarian hormonal profile should be considered when assessing BMD in female athletes. The duration of oral contraceptive use influences spine and pelvis regional BMD in exercising females. Postmenopausal women show lower BMD when compared to premenopausal females despite being exercising females.