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This study aimed to investigate the changes in blood viscosity, pulmonary hemodynamics, nitric oxide (NO) production, and maximal oxygen uptake ( $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ ) during a maximal incremental test conducted in normoxia and during exposure to moderate altitude (2,400 m) in athletes exhibiting exercise-induced hypoxemia at sea level (EIH). Nine endurance athletes with EIH and eight without EIH (NEIH) performed a maximal incremental test under three conditions: sea level, 1 day after arrival in hypoxia, and 5 days after arrival in hypoxia (H5) at 2,400 m. Gas exchange and oxygen peripheral saturation (SpO₂) were continuously monitored. Cardiac output, pulmonary arterial pressure, and total pulmonary vascular resistance were assessed by echocardiography. Venous blood was sampled before and 3 min after exercise cessation to analyze blood viscosity and NO end-products. At sea level, athletes with EIH exhibited an increase in blood viscosity and NO levels during exercise while NEIH athletes showed no change. Pulmonary hemodynamics and aerobic performance were not different between the two groups. No between-group differences in blood viscosity, pulmonary hemodynamics, and $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ were found at 1 day after arrival in hypoxia. At H5, lower total pulmonary vascular resistance and greater NO concentration were reported in response to exercise in EIH compared with NEIH athletes. EIH athletes had greater cardiac output and lower SpO₂ at maximal exercise in H5, but no between-group differences occurred regarding blood viscosity and $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ . The pulmonary vascular response observed at H5 in EIH athletes may be involved in the greater cardiac output of EIH group and counterbalanced the drop in SpO₂ in order to achieve similar $\dot{\mathrm{V}}{\mathrm{O}}_2\text{max}$ than NEIH athletes.

Previous studies have used supplements to increase dietary nitrate intake in clinical populations. Little is known about whether effects can also be induced through vegetable consumption. Therefore, the aim of this study was to assess the impact of dietary nitrate, through nitrate-rich vegetables (NRV) and beetroot juice (BRJ) supplementation, on plasma nitrate and nitrite concentrations, exercise tolerance, muscle oxygenation, and cardiovascular function in patients with peripheral arterial disease. In a randomized crossover design, 18 patients with peripheral arterial disease (age: 73 ± 8 years) followed a nitrate intake protocol (∼6.5 mmol) through the consumption of NRV, BRJ, and nitrate-depleted BRJ (placebo). Blood samples were taken, blood pressure and arterial stiffness were measured in fasted state and 150 min after intervention. Each intervention was followed by a maximal walking exercise test to determine claudication onset time and peak walking time. Gastrocnemius oxygenation was measured by near-infrared spectroscopy. Blood samples were taken and blood pressure was measured 10 min after exercise. Mean plasma nitrate and nitrite concentrations increased (nitrate; Time × Intervention interaction; p < .001), with the highest concentrations after BRJ (494 ± 110 μmol/L) compared with NRV (202 ± 89 μmol/L) and placebo (80 ± 19 μmol/L; p < .001). Mean claudication onset time and peak walking time did not differ between NRV (413 ± 187 s and 745 ± 220 s, respectively), BRJ (392 ± 154 s and 746 ± 176 s), and placebo (403 ± 176 s and 696 ± 222 s) (p = .762 and p = .165, respectively). Gastrocnemius oxygenation, blood pressure, and arterial stiffness were not affected by the intervention. NRV and BRJ intake markedly increase plasma nitrate and nitrite, but this does not translate to improved exercise tolerance, muscle oxygenation, and/or cardiovascular function.

Caffeine is commonly used to improve athletic performance across a variety of sports. Previously, the CYP1A2 gene has been shown to modify the effects of caffeine on endurance performance. The effect of caffeine on strength and power activities is unclear and may differ depending on an individual’s CYP1A2 genotype. A randomized controlled trial was used to determine whether caffeine impacts strength and power, determined by the handgrip and vertical jump tests, respectively, and whether CYP1A2 genotype modifies any effects. Competitive male athletes (age = 25 ± 4 years) completed vertical jump (n = 97), and handgrip tests (n = 102) under three conditions: 0 (placebo), 2, or 4 mg of caffeine per kilogram of body mass (in milligrams per kilogram). CYP1A2 (rs762551) genotype was determined from saliva samples. No differences between caffeine doses and placebo were observed for strength or power; however, significant Caffeine × Gene interactions were observed for all exercise tests. Individuals with the CC genotype experienced a 12.8% decrease in handgrip strength with 4 mg/kg of caffeine compared with placebo (53 ± 11 kg vs. 61 ± 17 kg, p = .02). No differences were observed in those with the AC or AA genotypes. Despite observing a significant Caffeine × Gene interaction for vertical jump performance, no differences were observed between caffeine doses and placebo for all genotypes. In summary, caffeine (4 mg/kg) worsened handgrip strength performance in those with the CC genotype, but no differences were observed in those with the AC or AA genotypes. Athletes may want to consider their CYP1A2 genotype prior to using caffeine to improve muscle strength.

The Low Energy Availability in Females Questionnaire (LEAF-Q) was validated to identify risk of the female athlete triad (triad) in female endurance athletes. This study explored the ability of the LEAF-Q to detect conditions related to low energy availability (LEA) in a mixed sport cohort of female athletes. Data included the LEAF-Q, SCOFF Questionnaire for disordered eating, dual-energy X-ray absorptiometry-derived body composition and bone mineral density, Mini International Neuropsychiatric Interview, blood pressure, and blood metabolic and reproductive hormones. Participants were grouped according to LEAF-Q score (≥8 or <8), and a comparison of means was undertaken. Sensitivity, specificity, and predictive values of the overall score and subscale scores were calculated in relation to the triad and biomarkers relevant to LEA. Fisher’s exact test explored differences in prevalence of these conditions between groups. Seventy-five athletes (18–32 years) participated. Mean LEAF-Q score was 8.0 ± 4.2 (55% scored ≥8). Injury and menstrual function subscale scores identified low bone mineral density (100% sensitivity, 95% confidence interval [15.8%, 100%]) and menstrual dysfunction (80.0% sensitivity, 95% confidence interval [28.4%, 99.5%]), respectively. The gastrointestinal subscale did not detect surrogate markers of LEA. LEAF-Q score cannot be used to classify athletes as “high risk” of conditions related to LEA, nor can it be used as a surrogate diagnostic tool for LEA given the low specificity identified. Our study supports its use as a screening tool to rule out risk of LEA-related conditions or to create selective low-risk groups that do not need management as there were generally high negative predictive values (range 76.5–100%) for conditions related to LEA.

This prospective study evaluated the 3-year change in menstrual function and bone mass among 40 female adolescent endurance runners (age 15.9 ± 1.0 years) according to baseline disordered eating status. Three years after initial data collection, runners underwent follow-up measures including the Eating Disorder Examination Questionnaire and a survey evaluating menstrual function, running training, injury history, and prior sports participation. Dual-energy X-ray absorptiometry was used to measure bone mineral density and body composition. Runners with a weight concern, shape concern, or global score ≥4.0 or reporting >1 pathologic behavior in the past 28 days were classified with disordered eating. Compared with runners with normal Eating Disorder Examination Questionnaire scores at baseline, runners with disordered eating at baseline reported fewer menstrual cycles/year (6.4 ± 4.5 vs. 10.5 ± 2.8, p = .005), more years of amenorrhea (1.6 ± 1.4 vs. 0.3 ± 0.5, p = .03), and a higher proportion of menstrual irregularity (75.0% vs. 31.3%, p = .02) and failed to increase lumbar spine or total hip bone mineral density at the 3-year follow-up. In a multivariate model including body mass index and menstrual cycles in the past year at baseline, baseline shape concern score (B = −0.57, p value = .001) was inversely related to the annual number of menstrual cycles between assessments. Weight concern score (B = −0.40, p value = .005) was inversely associated with lumbar spine bone mineral density Z-score change between assessments according to a multivariate model adjusting for age and body mass index. These finding support associations between disordered eating at baseline and future menstrual irregularities or reduced accrual of lumbar spine bone mass in female adolescent endurance runners.

Currently, little is known about the extent of interindividual variability in response to beta-alanine (BA) supplementation, nor what proportion of said variability can be attributed to external factors or to the intervention itself (intervention response). To investigate this, individual participant data on the effect of BA supplementation on a high-intensity cycling capacity test (CCT_110%) were meta-analyzed. Changes in time to exhaustion (TTE) and muscle carnosine were the primary and secondary outcomes. Multilevel distributional Bayesian models were used to estimate the mean and SD of BA and placebo group change scores. The relative sizes of group SDs were used to infer whether observed variation in change scores were due to intervention or non-intervention-related effects. Six eligible studies were identified, and individual data were obtained from four of these. Analyses showed a group effect of BA supplementation on TTE (7.7, 95% credible interval [CrI] [1.3, 14.3] s) and muscle carnosine (18.1, 95% CrI [14.5, 21.9] mmol/kg DM). A large intervention response variation was identified for muscle carnosine (σ_IR = 5.8, 95% CrI [4.2, 7.4] mmol/kg DM) while equivalent change score SDs were shown for TTE in both the placebo (16.1, 95% CrI [13.0, 21.3] s) and BA (15.9, 95% CrI [13.0, 20.0] s) conditions, with the probability that SD was greater in placebo being 0.64. In conclusion, the similarity in observed change score SDs between groups for TTE indicates the source of variation is common to both groups, and therefore unrelated to the supplement itself, likely originating instead from external factors such as nutritional intake, sleep patterns, or training status.

Along with digestion and absorption of nutrients, the gastrointestinal epithelium acts as a primary intestinal defense layer, preventing luminal pathogens from entering the circulation. During exercise in the heat, epithelial integrity can become compromised, allowing bacteria and bacterial endotoxins to translocate into circulation, triggering a systemic inflammatory response and exacerbating gastrointestinal damage. While this relationship seems clear in the general population in endurance/ultraendurance exercise, the aim of this systematic review was to evaluate the effect of exercise in the heat on blood markers of gastrointestinal epithelial disturbance in well-trained individuals. Following the 2009 Preferred Reporting Items for Systematic Reviewed and Meta-Analyses guidelines, five electronic databases were searched for appropriate research, and 1,885 studies were identified. Five studies met the inclusion criteria and were subject to full methodological appraisal by two reviewers. Critical appraisal of the studies was conducted using the McMasters Critical Review Form. The studies investigated changes in markers of gastrointestinal damage (intestinal fatty acid–binding protein, endotoxin, and/or lipopolysaccharide-binding protein) following acute exercise in warm to hot conditions (≥ 30 °C) and included trained or well-trained participants with direct comparisons to a control temperate condition (≤ 22 °C). The studies found that prolonged submaximal and strenuous exercise in hot environmental conditions can acutely increase epithelial disturbance compared with exercise in cooler conditions, with disturbances not being clinically relevant. However, trained and well-trained populations appear to tolerate exercise-induced gastrointestinal disturbance in the heat. Whether this is an acquired tolerance related to regular training remains to be investigated.