The relationship between hemoglobin and [Formula: see text]: A systematic review and meta-analysis

Carbon monoxide supplementation: evaluating its potential to enhance altitude training effects and cycling performance in elite athletes

Altitude training is a cornerstone for endurance athletes for improving blood variables and performance, with optimal effects observed at ∼2,300-2,500 meters above sea level (m.a.s.l.). However, elite cyclists face challenges such as limited access to such altitudes, inadequate training facilities, and high expenses. To address these issues, a novel method involving daily exposure to carbon monoxide (CO) has been proposed to amplify altitude training adaptations at suboptimal altitudes. Thirty-one male cyclists were assigned to three groups: Live-High Train-High with CO inhalation (LHTHCO), Live-High Train-High (LHTH), and Live-Low Train-Low (LLTL). The LHTHCO group underwent CO inhalation twice daily in the afternoon/evening to elevate carboxyhemoglobin concentration to ∼10%. Hematological variables, in vivo muscle oxidative capacity, and physiological indicators of cycling performance were assessed before and after a 3-week altitude training camp at 2,100 m.a.s.l. LHTHCO demonstrated a larger increase in hemoglobin mass (Hbmass) compared to both LHTH and LLTL. Although there were no statistical differences between LHTHCO and LHTH in submaximal and maximal performance measures, LHTHCO displayed greater improvements in 1-min maximal power output during incremental testing (Wmax), power output at lactate threshold, and maximal oxygen consumption (V̇o2max) compared to LLTL. LHTH demonstrated a larger improvement than LLTL in Wmax and V̇o2max, with no group differences in Hbmass or submaximal measures. Muscle oxidative capacity did not differ between groups. These findings suggest that combining moderate-altitude training with daily CO inhalation promotes hematological adaptations more effectively than moderate altitude alone and enhances cycling performance metrics in cyclists more than sea-level training.NEW & NOTEWORTHY Three weeks of training at moderate altitude with exposure to low doses of CO can significantly enhance hematological adaptations in elite cyclists compared to moderate-altitude training alone. Cycling performance determinants improved more with CO inhalation at moderate altitude compared to sea-level training, whereas there were no differences in submaximal and maximal performance measures compared to moderate-altitude training alone. This study highlights the potential of CO supplementation as an effective adjunct to altitude training regimens.

The Relationship between Inflammatory Factors, Hemoglobin, and VO2 Max in Male Amateur Long-Distance Cross-Country Skiers in the Preparation Period

Background: Identifying factors affecting heart health in amateur athletes can significantly impact their health and help them achieve high performance. The current knowledge of these predictors is insufficient. The purpose of this study was to identify the biochemical determinants of maximal oxygen uptake (VO2 max) in male amateur long-distance cross-country skiers (37.9 ± 6.58 years, 51.08 ± 4.61 VO2 max ml/kg/min) in the preparation period. Methods: In this cross-sectional study, a time trial test was used to determine VO2 max and venous blood via biochemical markers. Descriptive statistics and Pearson correlation were used to analyze the data. The regression model determined the predictors. Results: VO2 max was significantly correlated with nine moderate or weak variables. Two regression models (R2 = 0.94 and R2 = 0.9) each identified two determinants of VO2 max, hemoglobin (p < 0.001) and C-reactive protein (p < 0.001), as well as erythrocyte sedimentation (p < 0.001) and platelets (p = 0.03). Only hemoglobin positive affected VO2 max. Conclusions: The results may indicate, in addition to results regarding hemoglobin concentration and its changes, the necessity to monitor the immune system, which may affect the capacity for amateur exercise. Biochemical monitoring is an essential tool for evaluating the individual adaptation to exercise and developing an effective training plan. The application of this knowledge can facilitate the achievement of optimal individual performance capabilities among cross-country skiing amateurs.

Cardiorespiratory fitness, body composition, diabetes, and longevity: a two-sample Mendelian randomization study

CONTEXT

Cardiorespiratory fitness, commonly assessed as maximal volume of oxygen consumption (VO2max), has emerged as an important predictor of morbidity and mortality.

OBJECTIVE

We investigated the causality and directionality of the associations of VO2max with body composition, physical activity, diabetes, performance enhancers, and longevity.

METHODS

Using publicly available summary statistics from the largest genome-wide association studies publicly available, we conducted a bidirectional two-sample Mendelian randomization (MR) study. Bidirectional MR tested directionality, and estimated the total causal effects, whereas multivariable MR (MVMR) estimated independent causal effects. Cardiorespiratory fitness (VO2max) was estimated from a submaximal cycle ramp test (N≈90,000) and scaled to total body weight, and in additional analyses to fat-free mass (mL/min/kg).

RESULTS

Genetically predicted higher (per one standard deviation increase) body fat percentage was associated with lower VO2max (β=-0.36 [95% CI: -0.40, -0.32], p=6E-77). Meanwhile, genetically predicted higher appendicular lean mass (0.10 [0.08,0.13] p=3E-16), physical activity (0.29 [0.07,0.52]), and performance enhancers (fasting insulin, hematocrit, and free testosterone in men) were all positively associated with VO2max (p<0.01). Genetic predisposition to diabetes had no effect on VO2max. MVMR showed independent causal effects of body fat percentage, appendicular lean mass, physical activity, and hematocrit on VO2max, as well as of body fat percentage and type 2 diabetes (T2D) on longevity. Genetically predicted VO2max showed no associations.

CONCLUSION

Cardiorespiratory fitness can be improved by favorable body composition, physical activity, and performance enhancers. Despite being a strong predictor of mortality, VO2max is not causally associated with T2D or longevity.

Hemodynamic, ventilatory and gas exchange responses to exercise using a cycle ergometer and the incremental shuttle walk test in pregnant women

BACKGROUND

Cardiovascular disease, including hypertension, in pregnant women is a leading cause of morbidity and mortality globally. The development of reference intervals for cardiovascular responses using exercising testing to measure oxygen utilisation (V̇O2) with cardiopulmonary exercise testing (CPET), and distances walked using the incremental shuttle walk test (ISWT), may be promising methods to assess and stratify pregnant women regarding their risk of adverse pregnancy outcomes, to encourage exercise during pregnancy, and to improve exercise prescriptions during pregnancy. We aimed to determine the reference intervals for V̇O2 at rest, anaerobic threshold (AT), and submaximal exercise using CPET, and the reference interval for the ISWT, to develop a correlation equitation that predicts submaximal V̇O2 from the distance walked in the ISWT, and to explore the relationship between hemoglobin (Hb) and ferritin concentration and V̇O2 at AT in women in second trimester.

METHODS

After prospective IRB approval (HREC 15/23) and clinical trials registration (ANZCTR ACTRN12615000964516), and informed written consent, we conducted CPET and the ISWT according to international guidelines in a university associated tertiary referral obstetric and adult medicine hospital, in healthy pregnant women in second trimester (14 to 27 gestational weeks). Hemoglobin and ferritin concentrations were recorded from pathology results in the participants' medical records at the time of exercise testing. Adverse events were recorded.

RESULTS

About 90 participants undertook CPET, 28 of which also completed the ISWT. The mean ± SD age and body mass index (BMI) were 32 ± 3.2 years, and 25 ± 2.7 kg/m2. Median (IQR) gestation was 23 (22-24) weeks. One in 4 women were 24 weeks or greater gestation. The reference intervals for V̇O2 at rest, AT, and submaximal exercise were 2.9 to 5.3, 8.1 to 20.7, and 14.1 to 30.5 mL/kg/min respectively. The reference interval for the ISWT was 218 to 1058 meters. The correlation equation to predict submaximal V̇O2 from the distance walked in the ISWT was submaximal V̇O2 (mL/kg/min) = 0.012*distance walked in ISWT (m) + 14.7 (95%CI slope 0.005-0.070, Pearson r = 0.5426 95%CI 0.2126-0.7615, P = .0029). Hemoglobin concentration was positively correlated with V̇O2 at AT (AT V̇O2 (mL/kg/min) = 0.08*Hb (g/L) + 4.9 (95%CI slope 0.0791-0.143, Pearson r = 0.2538 95%CI 0.049-0.438, P = .016). There was no linear association between ferritin and submaximal V̇O2 (Pearson r = 0.431 P = .697). There were no maternal or fetal complications.

CONCLUSIONS

CPET and ISWT are safe and feasible in women in second trimester including those at or beyond 24 weeks gestation. We have established the reference interval for V̇O2 at rest, AT, and submaximal exercise by CPET, the reference interval for the distance walked for the ISWT, and a correlation equation to predict submaximal V̇O2 for use in clinical practice and research. Hemoglobin rather than ferritin is likely correlated with exercise capacity in pregnancy suggesting vigilance to correct lower hemoglobin levels may positively impact maternal health.

CLINICAL TRIALS REGISTRY

The study was prospectively registered with the Australian and New Zealand Clinical Date of registration - 15/9/2015; Date of initial participant enrolment - 4/11/2015; Clinical trial identification number; ACTRN12615000964516; URL of the registration site - https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=369216.