Loss of CO from the intravascular bed and its impact on the optimised CO-rebreathing method

Additive Effect of EPO and Altitude on Hemoglobin Mass But Not Peak Oxygen Uptake

PURPOSE

This study evaluated whether recombinant human erythropoietin (rhEpo) treatment combined with hypoxia provided an additive effect on hemoglobin mass (Hb mass ) and peak oxygen uptake (V̇O 2peak ) compared with altitude or rhEpo alone.

METHODS

Thirty-nine participants underwent two interventions, each containing 4-wk baseline (PRE 1-4), 4-wk exposure at sea level or 2320 m of altitude (INT 1-4), and 4-wk follow-up (POST 1-4). Participants were randomly assigned to 20 IU·kg -1 rhEpo or placebo injections every second day for 3 wk during the exposure period at sea level (SL-EPO, n = 25; SL-PLA, n = 9) or at altitude (ALT-EPO, n = 12; ALT-PLA, n = 27).

RESULTS

Hb mass displayed a significant time-treatment effect ( P < 0.001) when comparing ALT-EPO and ALT-PLA. Specifically, the increase in Hb mass was higher ( P < 0.05 to P < 0.001) for ALT-EPO from INT 2 to POST 3 except for POST 2. Similarly, a significant time-treatment effect ( P < 0.001) existed for changes in Hb mass when comparing ALT-EPO with SL-EPO, with the increase in Hb mass being higher ( P < 0.01 to P < 0.001) for ALT-EPO from INT 2 to POST 4. A significant time-treatment effect was present when SL-PLA was compared with ALT-PLA ( P < 0.05) and SL-EPO ( P < 0.05). For V̇O 2peak , the time-treatment interaction was not significant when comparing ALT-EPO to ALT-PLA. However, when ALT-EPO was compared with SL-EPO, a significant time-treatment interaction existed ( P < 0.001) due to a decrease in V̇O 2peak during altitude.

CONCLUSIONS

The combined treatment of microdoses of rhEpo and altitude exposure results in an additive increase in Hb mass but does not significantly enhance V̇O 2peak compared with each treatment alone.

Metabolic insights into hypoxia adaptation in adolescent athletes at different altitudes: a cross-sectional study

Athletes use hypoxic training methods to enhance their performance under altitude conditions. Comparative studies involving populations from low (500-2,000 m) and moderate (2,000-3,000 m) altitudes offer an opportunity to understand the mechanisms behind adaptations to hypoxia. The present study combined data from metabolomics analysis based on gas- and liquid-chromatography mass spectrometry (GC-MS and LC-MS) to compare plasma profiles from 80 adolescent athletes at moderate- or low altitudes. 161 metabolites were identified, including 84 elevated and 77 decreased in moderate-altitude adolescents compared to their low-altitude counterparts. Pathway analysis revealed that metabolites related to carbohydrates, amino acids, and lipid metabolism differed between groups. Lipid metabolism was significantly altered in moderate-altitude athletes, including pathways such as linolenic and linoleic acid, sphingolipid, and arachidonic acid, as well as processes involving the transfer of acetyl groups into mitochondria and fatty acid biosynthesis. Biomarker analysis looking for signatures of chronic adaptation to moderate altitude identified glycerol and 5-oxoproline metabolites amongst the variables with the strongest sensitivity and specificity. This study demonstrates differences in metabolic profiles between moderate- and low-altitude populations and highlights the potential of these differential metabolites and associated metabolic pathways to provide new insights into the mechanisms of adaptation to moderate altitude.

Hemoglobin mass is accurately predicted in endurance athletes

Hemoglobin mass (Hbmass) prediction enhance the accessibility and practicality of athletes' hemoglobin status monitoring, facilitating better performance. Therefore, we aimed to create prediction equations for Hbmass in well-trained endurance athletes (EA), based on easily obtained measures. The population of 220 well-trained EA (40% females, maximal oxygen uptake = 63.4 ± 8.00 mL·kg·min-1) was randomly split for the models' derivation and validation in 2:1 ratio. Equations to predict total Hbmass (tHbmass) and Hbmass adjusted to fat-free mass (rHbmass) were developed with multivariable linear regression. The models were stratified for five complexity levels with the inclusion of anthropometric, biochemical, and fitness indices. Models for tHbmass (R2 = 0.87-0.92; root-mean-square error [RMSE] = 60.6-76.5 g) outperform the models for rHbmass (R2 = 0.28-0.58; RMSE = 1.00-1.26 g·kg-1). During internal validation, 9 of 10 of equations accurately predicted tHbmass (0.11 ± 54.7-54.8 ± 45.5 g; p = 0.18-0.99) and only 1 model differed significantly (p = 0.03). There were also no significant differences between observed and predicted values in 8 of 10 of equations for rHbmass (0.1 ± 1.4-1.0 ± 0.1 g·kg-1; p = 0.07-0.65) and 2 models showed significant differences (p = 0.01-0.04). Models present moderate-to-high accuracy. Equations are precise enough to provide complementary data in the epidemiology of diseases with abnormal hemoglobin values, antidoping policy or talent identification. However, they should not substitute direct testing of Hbmass in EA.

Effects of the Birthplace Altitude and Training Volume on Hematological Characteristics in Youth and Junior Male Colombian Cyclists

PURPOSE

The long-term development of talent in endurance sports is a topic of interest. Among various factors, the importance of total hemoglobin mass (tHbmass) and the potential benefits of being an altitude-native athlete remain unclear, particularly in young categories. This study aimed to investigate the impact of altitude and training content on hematological characteristics by comparing young male cyclists age 15-16 and 17-18 years who were born and trained at a moderate altitude (ie, greater than or equal to 2500 m; MA) and cyclists who were born and trained at low altitude (below 1000 m; LA).

METHODS

tHbmass (in grams and grams per kilogram), measured by using the optimized carbon monoxide rebreathing method during an incremental test on a cycle ergometer; hematocrit percentage, hemoglobin concentration; and erythrocyte, blood, and plasma volume were measured in youth male cyclists age 15-16 years and junior cyclists age 17-18 years who were born and trained at MA versus LA. All variables were analyzed with a 2-way (age [youth cyclist vs junior cyclist] × altitude level [MA vs LA]) analysis of variance with subsequent Tuckey post hoc test.

RESULTS AND CONCLUSION

Some altitude-induced benefits were reported in cyclists at age 15-16 years in the MA group with higher values in hematocrit percentage, hemoglobin concentration, and tHbmass (grams per kilogram) (P < .05) than their LA counterparts. This was also observed at age 17-18 years (P < .001), except for tHbmass, wherein no significant difference was found between MA and LA groups. In contrast, plasma volume was lower in MA than LA junior cyclists.

NEW FINDINGS

(1) The altitude of birth and residence could generate an advantage in tHbmass in young male cyclists age 15-16 and 17-18 years who train at MA compared with cyclists who are born and train at LA. (2) Altitude-induced benefits in physiological variables (hematocrit percentage, hemoglobin concentration, tHbmass in g·kg-1) were reported in cyclists at age 15-16 years and partially at age 17-18 years. In contrast, plasma volume was lower in MA than in LA junior cyclists. This may impact the strategies for identifying and developing talent in cycling.

Evidence of Left Ventricular Cardiac Remodeling After 6 Weeks of Sprint Interval Training

Sprint interval training (SIT) leads to similar improvements in maximal oxygen uptake (V̇O2max) and maximal cardiac output as previously reported for traditional endurance training, but the exercise-induced effects on cardiac remodeling are still largely unknown. The aim of the current study was therefore to explore the effects of SIT on cardiac structure and function assessed by echocardiography in relation to, and controlling for, changes in both blood volume (BV) and heart rate (HR). Healthy men and women (n = 28) performed 6 weeks of SIT. V̇O2max and total BV were measured, and echocardiography was performed before and after the intervention. There was a robust increase in BV (+7.1%; p < 0.001) and V̇O2max (+10.1%; p < 0.001) and a decrease in resting HR (-3.9%; p = 0.013) following the SIT intervention. Machine-learning-based feature selection and univariate analysis indicated that several measures of left ventricular dimension (+14.3% LVEDV, p = 0.013; +17.4% LVESV, p = 0.018; +12.3% LVSV, p = 0.031), left ventricular diastolic function (MVA, MVD-slope, MVDT), and left ventricular stroke volume (LVOT VTI) were altered by 6 weeks of SIT. When controlling for the exercise-induced changes in BV and HR, left ventricular dimensions remained significantly changed. Our data indicate that several measures of cardiac function are likely only indirectly affected by SIT, driven by increased BV. However, the disproportionate increase in left ventricular size exceeds what can be explained by changes in BV and HR alone, indicating volume-independent structural cardiac remodeling.

Strenuous training combined with erythropoietin induces red cell volume expansion-mediated hypervolemia and alters systemic and skeletal muscle iron homeostasis

Strenuous physical training increases total blood volume (BV) through expansion of plasma volume (PV) and red cell volume (RCV). In contrast, exogenous erythropoietin (EPO) treatment increases RCV but decreases PV, rendering BV stable or slightly decreased. This study aimed to determine the combined effects of strenuous training and EPO treatment on BV and markers of systemic and muscle iron homeostasis. In this longitudinal study, eight healthy nonanemic males were treated with EPO (50 IU/kg body mass, three times per week, sc) across 28 days of strenuous training (4 days/wk, exercise energy expenditures of 1,334 ± 24 kcal/day) while consuming a controlled, energy-balanced diet providing 39 ± 4 mg/day iron. Before (PRE) and after (POST) intervention, BV compartments were measured using carbon monoxide rebreathing, and markers of iron homeostasis were assessed in blood and skeletal muscle (vastus lateralis). Training + EPO increased (P < 0.01) RCV (13 ± 6%) and BV (5 ± 4%), whereas PV remained unchanged (P = 0.86). The expansion of RCV was accompanied by a large decrease in whole body iron stores, as indicated by decreased (P < 0.01) ferritin (-77 ± 10%) and hepcidin (-49 ± 23%) concentrations in plasma. Training + EPO decreased (P < 0.01) muscle protein abundance of ferritin (-25 ± 20%) and increased (P < 0.05) transferrin receptor (47 ± 56%). These novel findings illustrate that strenuous training combined with EPO results in both increased total oxygen-carrying capacity and hypervolemia in young healthy males. The decrease in plasma and muscle ferritin suggests that the marked upregulation of erythropoiesis alters systemic and tissue iron homeostasis, resulting in a decline in whole body and skeletal muscle iron stores.NEW & NOTEWORTHY Strenuous exercise training combined with erythropoietin (EPO) treatment increases blood volume, driven exclusively by red cell volume expansion. This hematological adaptation results in increased total oxygen-carrying capacity and hypervolemia. The marked upregulation of erythropoiesis with training + EPO reduces whole body iron stores and circulating hepcidin concentrations. The finding that the abundance of ferritin in muscle decreased after training + EPO suggests that muscle may release iron to support red blood cell production.

Haemoglobin mass responses and performance outcomes among high-performance swimmers following a 3-week live-high, train-high camp at 2320 m

AIM

Greater quantification and characterisation of training load (TL) throughout Live-high, train-high (LHTH) altitude (ALT) training is required to identify periodisation strategies that may lead to physiological and performance improvements in swimmers.

PURPOSE

This study aimed to examine the physiological responses and performance outcomes of 14 high-performance swimmers (FINA points: 836.0 ± 35.1) following 3 weeks of LHTH at 2320 m, while characterising the training load periodisation strategy adopted during the intervention.

METHODS

Haemoglobin (Hb) mass was measured pre-, 7 and 14 days post-ALT via CO rebreathing. Performance in each athlete's primary event at national standard meets were converted to FINA points and compared from pre-to-post-ALT. TL was quantified at sea level (SL) and ALT through session rating of perceived exertion (RPE), where duration of each session was multiplied by its RPE for each athlete, with all sessions totalled to give a weekly TL. Pre-to-post-ALT changes were evaluated using repeated-measures ANOVA.

RESULTS

Hb mass increased significantly from 798 ± 182 g pre-ALT to 828 ± 187 g at 7 days post (p = 0.013) and 833 ± 205 g 14 days post-ALT (p = 0.026). Weekly TL increased from SL (3179 ± 638 au) during week one (4797 ± 1349 au, p < 0.001) and week two (4373 ± 967 au, p < 0.001), but not week three (3511 ± 730 au, p = 0.149). No evidence of improved SL swimming performance was identified.

CONCLUSION

A periodisation strategy characterised by a sharp spike in TL followed by a slight de-load towards the end of a LHTH intervention led to improved physiological characteristics but no change in the competitive performance of high-performance swimmers.

Impact of a single blood donation on hemoglobin mass, iron stores, and maximum oxygen uptake in pre-menopausal women-A pilot study

BACKGROUND

During whole blood donation (BD), 500 mL of blood is drawn. The time interval between two BDs is at least 8-12 weeks. This period might be insufficient for restoring hemoglobin mass (Hbmass) and iron especially in women, who generally have lower Hbmass and iron availability. Since both variables influence physical performance, this pilot study aimed to monitor Hbmass, iron status, and maximum oxygen uptake (V̇O2max) recovery in women after a single BD.

STUDY DESIGN AND METHODS

In 10 women (24.7 ± 1.7 years), Hbmass, hemoglobin concentration [Hb], iron status, and V̇O2max were assessed before and up to 12 weeks after a single BD.

RESULTS

BD reduced Hbmass from 562 ± 70 g to 499 ± 64 g (p < .001). Although after 8 weeks no significant mean difference was detected, 7 women had not returned to baseline after 12 weeks. [Hb] did not return to initial values (13.4 ± 0.7 g/dL) after 12 weeks (12.9 ± 0.7 g/dL, p < .01). Ferritin decreased from baseline until week 6 (40.9 ± 34.2 ng/mL vs. 12.1 ± 6.9 ng/mL, p < .05) and was not restored after 12 weeks (18.4 ± 12.7 ng/mL, p < .05), with 6 out of 10 women exhibiting iron deficiency (ferritin <15 ng/mL). V̇O2max was reduced by 213 ± 47 mL/min (7.2 ± 1.2%; p < .001) and remained below baseline after 12 weeks (3.2 ± 1.4%, p < .01).

DISCUSSION

For most pre-menopausal women, 12 weeks were not sufficient to recover from BD and achieve baseline Hbmass and iron stores resulting in prolonged reduction of aerobic capacity. A subsequent BD might lead to a severe anemia.

The influence of sex, hemoglobin mass, and skeletal muscle characteristics on cycling critical power

Critical power (CP) represents an important threshold for exercise performance and fatiguability. We sought to determine the extent to which sex, hemoglobin mass (Hbmass), and skeletal muscle characteristics influence CP. Before CP determination (i.e., 3-5 constant work rate trials to task failure), Hbmass and skeletal muscle oxidative capacity (τ) were measured and vastus lateralis (VL) muscle biopsy samples were collected from 12 females and 12 males matched for aerobic fitness relative to fat-free mass (FFM) [means (SD); V̇o2max: 59.2 (7.7) vs. 59.5 (7.1) mL·kg·FFM-1·min-1, respectively]. Males had a significantly greater CP than females in absolute units [225 (28) vs. 170 (43) W; P = 0.001] but not relative to body mass [3.0 (0.6) vs. 2.7 (0.6) W·kg·BM-1; P = 0.267] or FFM [3.6 (0.7) vs. 3.7 (0.8) W·kg·FFM-1; P = 0.622]. Males had significantly greater W' (P ≤ 0.030) and greater Hbmass (P ≤ 0.016) than females, regardless of the normalization approach; however, there were no differences in mitochondrial protein content (P = 0.375), τ (P = 0.603), or MHC I proportionality (P = 0.574) between males and females. Whether it was expressed in absolute or relative units, CP was positively correlated with Hbmass (0.444 ≤ r ≤ 0.695; P < 0.05), mitochondrial protein content (0.413 ≤ r ≤ 0.708; P < 0.05), and MHC I proportionality (0.506 ≤ r ≤ 0.585; P < 0.05), and negatively correlated with τ when expressed in relative units only (-0.588 ≤ r ≤ -0.527; P < 0.05). Overall, CP was independent of sex, but variability in CP was related to Hbmass and skeletal muscle characteristics. The extent to which manipulations in these physiological parameters influence CP warrants further investigation to better understand the factors underpinning CP.NEW & NOTEWORTHY In males and females matched for aerobic fitness [maximal oxygen uptake normalized to fat-free mass (FFM)], absolute critical power (CP) was greater in males, but relative CP (per kilogram body mass or FFM) was similar between sexes. CP correlated with hemoglobin mass, mitochondrial protein content, myosin heavy chain type I proportion, and skeletal muscle oxidative capacity. These findings demonstrate the importance of matching sexes for aerobic fitness, but further experiments are needed to determine causality.

Effect of Fluid Intake on Acute Changes in Plasma Volume: A Randomized Controlled Crossover Pilot Trial

Plasma volume (PV) undergoes constant and dynamic changes, leading to a large intra-day variability in healthy individuals. Hydration is known to induce PV changes; however, the response to the intake of osmotically different fluids is still not fully understood. In a randomized controlled crossover trial, 18 healthy individuals (10 females) orally received an individual amount of an isotonic sodium-chloride (ISO), Ringer (RIN), or glucose (GLU) solution. Hemoglobin mass (Hbmass) was determined with the optimized carbon monoxide re-breathing method. Fluid-induced changes in PV were subsequently calculated based on capillary hemoglobin concentration ([Hb]) and hematocrit (Hct) before and then every 10 minutes until 120 min (t0-120) after the fluid intake and compared to a control trial arm (CON), where no fluid was administered. Within GLU and CON trial arms, no statistically significant differences from baseline until t120 were found (p > 0.05). In the ISO trial arm, PV was significantly increased at t70 (+138 mL, p = 0.01), t80 (+191 mL, p < 0.01), and t110 (+182 mL, p = 0.01) when compared to t0. Moreover, PV in the ISO trial arm was significantly higher at t70 (p = 0.02), t110 (p = 0.04), and t120 (p = 0.01) when compared to the same time points in the CON trial arm. Within the RIN trial arm, PV was significantly higher between t70 and t90 (+183 mL, p = 0.01) and between t110 (+194 mL, p = 0.03) and t120 (+186 mL, p < 0.01) when compared to t0. These results demonstrated that fluids with a higher content of osmotically active particles lead to acute hemodilution, which is associated with a decrease in [Hb] and Hct. These findings underpin the importance of the hydration state on PV and especially on PV constituent levels in healthy individuals.

Thermal and cardiovascular heat adaptations in active adolescents following summer

This study aimed to investigate seasonal heat acclimatization in active adolescents following summer. Fifteen (5 females) active adolescents (14.6 ± 1.0 y) completed a 45-min heat response test (HRT) walking at 60% V ˙ O2peak in 40°C and 30% relative humidity before and after summer (i.e. November 2022 and March 2023). During the HRT, gastro-intestinal temperature (Tgi), skin temperature (Tsk), heart rate, local sweat rate (LSR) and whole-body sweat loss (WBSL) were recorded. Carbon monoxide rebreathing and dual-energy X-ray absorptiometry scans determined resting hematological measures and body composition. Participants completed physical activity (PA) diaries and wore an accelerometer for two one-week periods (pre- and post-summer). Daytime wet-bulb globe temperature (WBGT) was calculated for each summer day. Data are presented as posterior mean and 90% credible intervals. Participants reported 7 ± 4 h·wk-1 of outdoor PA, and daytime WBGT was 21.2 ± 4.6°C. Following summer, resting Tgi and heart rate were reduced by 0.2°C [-0.3, -0.1; probability of direction = 99%] and 7 beats·min-1 [-10, -3; 100%], respectively. During the HRT, there was an earlier onset of sweating (-0.2°C [-0.3, -0.0; 98%]), an attenuated rise of Tgi (0.2°C [-0.5, 0.0; 92%]) and mean Tsk changed by -0.2°C [-0.5, 0.1; 86%]. There was minimal evidence for heat adaptations in LSR or WBSL, hematological parameters or perceptual measures. This is the first study to demonstrate seasonal heat adaptations in active adolescents. Reductions in resting Tgi and exercising Tsk and a lower Tgi at the onset of sweating were associated with a smaller rise in Tgi during the HRT following summer.

Duplicate measures of hemoglobin mass within an hour: feasibility, reliability, and comparison of three devices in supine position

Duplicate measure of hemoglobin mass by carbon monoxide (CO)-rebreathing is a logistical challenge as recommendations prompt several hours between measures to minimize CO-accumulation. This study investigated the feasibility and reliability of performing duplicate CO-rebreathing procedures immediately following one another. Additionally, it was evaluated whether the obtained hemoglobin mass from three different CO-rebreathing devices is comparable. Fifty-five healthy participants (22 males, 23 females) performed 222 duplicate CO-rebreathing procedures in total. Additionally, in a randomized cross-over design 10 participants completed three experimental trials, each including three CO-rebreathing procedures, with the first and second separated by 24 h and the second and third separated by 5-10 min. Each trial was separated by >48 h and conducted using either a glass-spirometer, a semi-automated electromechanical device, or a standard three-way plastic valve designed for pulmonary measurements. Hemoglobin mass was 3 ± 22 g lower (p < 0.05) at the second measure when performed immediately after the first with a typical error of 1.1%. Carboxyhemoglobin levels reached 10.9 ± 1.3%. In the randomized trial, hemoglobin mass was similar between the glass-spirometer and three-way valve, but ∼6% (∼50 g) higher for the semi-automated device. Notably, differences in hemoglobin mass were up to ∼13% (∼100 g) when device-specific recommendations for correction of CO loss to myoglobin and exhalation was followed. In conclusion, it is feasible and reliable to perform two immediate CO-rebreathing procedures. Hemoglobin mass is comparable between the glass-spirometer and the three-way plastic valve, but higher for the semi-automated device. The differences are amplified if the device-specific recommendations of CO-loss corrections are followed.

The effect of posture and exercise on blood CO kinetics during the optimized carbon monoxide rebreathing procedure

An indispensable precondition for the determination of hemoglobin mass (Hbmass) and blood volume by CO rebreathing is complete mixing of CO in the blood. The aim of this study was to demonstrate the kinetics of CO in capillary and venous blood in different body positions and during moderate exercise. Six young subjects (4 male, 2 female) performed three 2-min CO rebreathing tests in seated (SEA) & supine (SUP) positions as well as during moderate exercise (EX) on a bicycle ergometer. Before, during, and until 15 min after CO rebreathing cubital venous and capillary blood samples were collected simultaneously and COHb% was determined. COHb% kinetics were significantly slower in SEA than in SUP or EX. Identical COHb% in capillary and venous blood were reached in SEA after 5.0 ± 2.3 min, in SUP after 3.2 ± 1.3 min and in EX after 1.9 ± 1.2 min (EX vs. SEA p < .01, SUP vs. SEA p < .05). After 7th min, Hbmass did not differ between the resting positions (capillary: SEA 766 ± 217 g, SUP 761 ± 227 g; venous: SEA 759 ± 224 g, SUP 744 ± 207 g). Under exercise, however, a higher Hbmass (p < .05) was determined (capillary: 823 ± 221 g, venous: 804 ± 226 g). In blood, the CO mixing time in the supine position is significantly shorter than in the seated position. By the 6th minute complete mixing is achieved in either position giving similar Hbmass determinations. CO-rebreathing under exercise conditions, however, leads to ∼7% higher Hbmass values.

Relationship between Blood Volume, Blood Lactate Quantity, and Lactate Concentrations during Exercise

We wanted to determine the influence of total blood volume (BV) and blood lactate quantity on lactate concentrations during incremental exercise. Twenty-six healthy, nonsmoking, heterogeneously trained females (27.5 ± 5.9 ys) performed an incremental cardiopulmonary exercise test on a cycle ergometer during which maximum oxygen uptake (V·O_2max), lactate concentrations ([La^-]) and hemoglobin concentrations ([Hb]) were determined. Hemoglobin mass and blood volume (BV) were determined using an optimised carbon monoxide-rebreathing method. V·O_2max and maximum power (P_max) ranged between 32 and 62 mL·min^-1·kg^-1 and 2.3 and 5.5 W·kg^-1, respectively. BV ranged between 81 and 121 mL·kg^-1 of lean body mass and decreased by 280 ± 115 mL (5.7%, p = 0.001) until P_max. At P_max, the [La^-] was significantly correlated to the systemic lactate quantity (La^-, r = 0.84, p < 0.0001) but also significantly negatively correlated to the BV (r = -0.44, p < 0.05). We calculated that the exercise-induced BV shifts significantly reduced the lactate transport capacity by 10.8% (p < 0.0001). Our results demonstrate that both the total BV and La^- have a major influence on the resulting [La^-] during dynamic exercise. Moreover, the blood La^- transport capacity might be significantly reduced by the shift in plasma volume. We conclude, that the total BV might be another relevant factor in the interpretation of [La^-] during a cardio-pulmonary exercise test.

Microdoses of Recombinant Human Erythropoietin Enhance Time Trial Performance in Trained Males and Females

PURPOSE

We investigated the effects of recombinant human erythropoietin (rHuEPO) administration on exercise endurance, maximal aerobic performance, and total hemoglobin mass (tHb). We hypothesized that frequent, small intravenous injections of epoetin β would increase time trial performance, peak oxygen uptake (V̇O 2peak ), and tHb in both males and females.

METHODS

We included 48 healthy, recreational to trained males ( n = 24, mean ± SD V̇O 2peak = 55 ± 5 mL O 2 ·kg -1 ⋅min -1 ) and females ( n = 24; V̇O 2peak of 46 ± 4 mL O 2 ·kg -1 ⋅min -1 ) in a counterbalanced, double-blind, randomized, placebo-controlled study design stratified by sex. Time trial performance, V̇O 2peak , and tHb were determined before and after intravenous injections of either rHuEPO (9 IU·kg bw -1 epoetin β) or saline (0.9% NaCl) three times weekly for 4 wk.

RESULTS

A time-treatment effect ( P < 0.05) existed for time trial performance. Within the rHuEPO group, mean power output increased by 4.1% ± 4.2% ( P < 0.001). Likewise, a time-treatment effect ( P < 0.001) existed for V̇O 2peak , where the rHuEPO group improved V̇O 2peak and peak aerobic power by 4.2% ± 6.1% ( P < 0.001) and 2.9% ± 4.0% ( P < 0.01), respectively. A time-treatment effect ( P < 0.001) existed for tHb, where the rHuEPO group increased tHb by 6.7% ± 3.4% ( P < 0.001). A main effect of "sex" alone was also evident ( P < 0.001), but no sex-specific interactions were found. No changes were observed in the placebo group for mean power output, V̇O 2peak , peak aerobic power, or tHb.

CONCLUSIONS

Microdoses with intravenous rHuEPO provide a sufficient erythropoietic stimuli to augment tHb and enhance aerobic-dominated performance in both trained males and females.

Validity and reliability of capillary vs. Venous blood for the assessment of haemoglobin mass and intravascular volumes

Objectives: Haemoglobin mass (Hbmass) assessment with the carbon monoxide rebreathing method is a more accurate estimate than other measures of oxygen-carrying capacity. Blood may be collected by several means and differences in the measured variables may exist as a result. The present study assessed the validity and reliability of calculated Hbmass and intravascular volumes obtained from capillary blood (CAP) when compared to venous blood (VEN) draws. Methods: Twenty-two adults performed a carbon monoxide rebreathing procedure with paired VEN and CAP draws at baseline, pre-rebreathing and post-rebreathing (POST). Thirteen of these participants performed this protocol on two occasions to assess the data reliability from both blood sampling sites. In a second experiment, 14 adults performed a 20-min seated and a 20-min supine rest to assess for the effect of posture on haematological parameters. Results: Haemoglobin mass (CAP = 948.8 ± 156.8 g; VEN = 943.4 ± 157.3 g, p = 0.108) and intravascular volume (CAP = 6.5 ± 1 L; VEN = 6.5 ± 0.9 L, p = 0.752) were statistically indifferent, had low bias (Hbmass bias = 14.45 ± 40.42 g, LoA -64.78 g-93.67 g) and were highly correlated between sampling techniques. Reliability analysis demonstrated no difference in the mean change in variables calculated from both sampling sites and good to excellent intraclass correlation coefficients (>0.700), however, typical measurement error was larger in variables measured using CAP (VEN Hbmass TE% = 2.1%, CAP Hbmass TE% = 5.5%). The results indicate that a supine rest prior to the rebreathing protocol would have a significant effect on haemoglobin concentration and haematocrit values compared to a seated rest, with no effect on carboxyhaemoglobin %. Conclusion: The present study demonstrates that CAP and VEN were comparable for the calculation of Hbmass and intravascular volumes in terms of accuracy. However, reduced reliability and increased error in the CAP variables indicates that there are methodological considerations to address when deciding which blood drawing technique to utilise. To reduce this CAP error, increased replicate analyses are required.

Effect of hypobaric hypoxia on hematological parameters related to oxygen transport, blood volume and oxygen consumption in adolescent endurance-training athletes

Objective

To analyze the effect of altitude on hematological and cardiorespiratory variables in adolescent athletes participating in aerobic disciplines.

Methods

21 females and 89 males participated in the study. All were adolescent elite athletes engaged in endurance sports (skating, running and cycling) belonging to two groups: permanent residents in either low altitude (LA, 966 m) or moderate altitude (MA, 2640 m). Hematocrit (Hct), hemoglobin concentration ([Hb]), total hemoglobin mass (Hbt), blood, plasma and erythrocyte volumes (BV, PV and EV), VO₂peak and other cardiorespiratory parameters were evaluated.

Results

Sex differences were evident both in LA and HA skating practitioners, the males having higher significant values than the females in oxygen transport-related hematological parameters and VO₂peak. The effect of altitude residence was also observed in Hct, [Hb], Hbt and EV with increased (14%–18%) values in the hematological parameters and higher EV (5%–24%). These results matched the significantly higher values of VO₂peak measured in MA residents. However, BV and PV did not show differences between LA and MA residents in any case. Sports discipline influenced neither the hematological variables nor most of the cardiorespiratory parameters.

Conclusions

LA and MA adolescent skaters showed sex differences in hematological variables. Endurance-trained male adolescent residents at MA had an increased erythropoietic response and a higher VO₂peak compared to their counterparts residing and training at LA. These responses are similar in the three aerobic sports studied, indicating that the variables described are highly sensitive to hypoxia irrespective of the sports discipline.

Cardiac stroke volume in females and its correlation to blood volume and cardiac dimensions

We aimed to continuously determine the stroke volume (SV) and blood volume (BV) during incremental exercise to evaluate the individual SV course and to correlate both variables across different exercise intensities. Twenty-six females with heterogeneous endurance capacities performed an incremental cycle ergometer test to continuously determine the oxygen uptake (V̇O2), cardiac output (Q̇) and changes in BV. Q̇ was determined by impedance cardiography and resting cardiac dimensions by 2D echocardiography. Hemoglobin mass and BV were determined using a carbon monoxide-rebreathing method. V̇O2max ranged from 32 to 62 mL·kg-1·min-1. Q̇max and SVmax ranged from 16.4 to 31.6 L·min-1 and 90-170 mL, respectively. The SV significantly increased from rest to 40% and from 40% to 80% V̇O2max. Changes in SV from rest to 40% V̇O2max were negatively (r = -0.40, p = 0.05), between 40% and 80% positively correlated with BV (r = 0.45, p < 0.05). At each exercise intensity, the SV was significantly correlated with the BV and the cardiac dimensions, i.e., left ventricular muscle mass (LVMM) and end-diastolic diameter (LVEDD). The BV decreased by 280 ± 115 mL (5.7%, p = 0.001) until maximum exercise. We found no correlation between the changes in BV and the changes in SV between each exercise intensity. The hemoglobin concentration [Hb] increased by 0.8 ± 0.3 g·dL-1, the capillary oxygen saturation (ScO2) decreased by 4.0% (p < 0.001). As a result, the calculated arterial oxygen content significantly increased (18.5 ± 1.0 vs. 18.9 ± 1.0 mL·dL-1, p = 0.001). A 1 L higher BV at V̇O2max was associated with a higher SVmax of 16.2 mL (r = 0.63, p < 0.001) and Q̇max of 2.5 L·min-1 (r = 0.56, p < 0.01). In conclusion, the SV strongly correlates with the cardiac dimensions, which might be the result of adaptations to an increased volume load. The positive effect of a high BV on SV is particularly noticeable at high and severe intensity exercise. The theoretically expected reduction in V̇O2max due to lower SV as a consequence of reduced BV is apparently compensated by the increased arterial oxygen content due to a higher [Hb].

Comparison of the automatised and the optimised carbon monoxide rebreathing methods

Recently, a new automated carbon monoxide (CO) rebreathing method (aCO) to estimate haemoglobin mass (Hb_mass) was introduced. The aCO method uses the same CO dilution principle as the widely used optimised CO rebreathing method (oCO). The two methods differ in terms of CO administration, body position, and rebreathing time. Whereas with aCO, CO is administered automatically by the system in a supine position of the subject, with oCO, CO is administered manually by an experienced operator with the subject sitting. Therefore, the aim of this study was to quantify possible differences in Hb_mass estimated with the two methods. Hb_mass was estimated in 18 subjects (9 females, 9 males) with oCO using capillary blood samples (oCOc) and aCO taking simultaneously venous blood samples (aCOv) and capillary blood samples (aCOc). Overall, Hb_mass was different between the three measurement procedures (F = 57.55, p < .001). Hb_mass was lower (p < .001) for oCOc (737 g ± 179 g) than for both aCOv (825 g ± 189 g, -9.3%) and aCOc (835 g ± 189 g, -10.6%). There was no difference in Hb_mass estimated with aCOv and aCOc procedures (p = .12). Three factors can likely explain the 10% difference in Hb_mass: differences in calculations (including a factor for myoglobin flux), body position (distribution of CO in blood circulation) during rebreathing, and time of blood sampling. Moreover, the determination of Hb_mass with aCO is possible with capillary blood sampling instead of venous blood sampling.

JA, Duque L, Chaves-Gomez S, Cristancho-Mejía E, Schmidt WFJ. Hemoglobin Mass, Blood Volume and VO2max of Trained and Untrained Children and Adolescents Living at Different Altitudes

Introduction: To a considerable extent, the magnitude of blood volume (BV) and hemoglobin mass (Hbmass) contribute to the maximum O2-uptake (VO2max), especially in endurance-trained athletes. However, the development of Hbmass and BV and their relationships with VO2max during childhood are unknown. The aim of the present cross-sectional study was to investigate Hbmass and BV and their relationships with VO2max in children and adolescents. In addition, the possible influence of endurance training and chronic hypoxia was evaluated.

Methods: A total of 475 differently trained children and adolescents (girls n = 217, boys n = 258; untrained n = 171, endurance trained n = 304) living at two different altitudes (∼1,000 m, n = 204, ∼2,600 m, n = 271) and 9–18 years old participated in the study. The stage of puberty was determined according to Tanner; Hbmass and BV were determined by CO rebreathing; and VO2max was determined by cycle ergometry and for runners on the treadmill.

Results: Before puberty, there was no association between training status and Hbmass or BV. During and after puberty, we found 7–10% higher values in the trained groups. Living at a moderate altitude had a uniformly positive effect of ∼7% on Hbmass in all groups and no effect on BV. The VO2max before, during and after puberty was strongly associated with training (pre/early puberty: boys +27%, girls +26%; mid puberty: +42% and +45%; late puberty: +43% and +47%) but not with altitude. The associated effects of training in the pre/early pubertal groups were independent of Hbmass and BV, while in the mid- and late pubertal groups, 25% of the training effect could be attributed to the elevated Hbmass.

Conclusions: The associated effects of training on Hbmass and BV, resulting in increased VO2max, can only be observed after the onset of puberty.

Improvements in Maximal Oxygen Uptake After Sprint-Interval Training Coincide with Increases in Central Hemodynamic Factors

INTRODUCTION

Sprint-interval training has been shown to improve maximal oxygen uptake, in part through peripheral muscle adaptations that increase oxygen utilization. In contrast, the adaptations of central hemodynamic factors in this context remain unexplored.

PURPOSE

The aim of the current study was to explore the effects of sprint-interval training on maximal oxygen uptake and central hemodynamic factors.

METHODS

Healthy men and women (n = 29; mean age, 27 ± 5 yr; height, 175 ± 8 cm; body mass, 72.5 ± 12.0 kg) performed 6 wk of sprint-interval training consisting of three weekly sessions of 10-min low-intensity cycling interspersed with 3 × 30-s all-out sprints. Maximal oxygen uptake, total blood volume, and maximal cardiac output were measured before and after the intervention.

RESULTS

Maximal oxygen uptake increased by 10.3% (P < 0.001). Simultaneously, plasma volume, blood volume, total hemoglobin mass, and cardiac output increased by 8.1% (276 ± 234 mL; P < 0.001), 6.8% (382 ± 325 mL; P < 0.001), 5.7% (42 ± 41 g; P < 0.001), and 8.5% (1.0 ± 0.9 L·min-1; P < 0.001), respectively. Increased total hemoglobin mass along with measures of body surface area had a significant impact on the improvements in maximal oxygen uptake.

CONCLUSIONS

Six weeks of sprint-interval training results in significant increases in hemoglobin mass, blood volume, and cardiac output. Because these changes were associated with marked improvements in maximal oxygen uptake, we conclude that central hemodynamic adaptations contribute to the improvement in maximal oxygen uptake during sprint-interval training.

Hemoglobin Mass and Blood Volume in Patients With Altitude-Related Polycythemia

Patients with chronic mountain sickness (CMS) have a high hemoglobin concentration [Hb] due to increased hemoglobin mass (Hbmass) and possibly reduced plasma volume (PV). The values of Hbmass, PV and blood volume (BV) have been described differently, and the relationships between [Hb] and Hbmass or PV are poorly understood. This study obtained representative Hbmass, PV and BV data from healthy, high-altitude residents and CMS patients and quantified the dependency of [Hb] on Hbmass and PV.

METHODS

Eighty-seven subjects born at high altitude (∼3,900 m) were enrolled. Thirty-four had CMS (CMS), 11 had polycythemia without CMS (intermediate, IM), 20 were healthy highlanders (HH), and 22 living near sea level (SL, 420 m) served as the sea level (SL) control group. Hbmass, PV and BV were determined using a CO-rebreathing method modified for assessing polycythemia patients. Furthermore, [Hb], hematocrit (Hct), plasma erythropoietin concentration [EPO] and blood gas and acid-base status were determined.

RESULTS

In the HH group, Hbmass was 27% higher (940 ± 105 g) than in the SL group (740 ± 112 g) and 72% (1,617 ± 265 g) lower than in the CMS group. The PV in the HH group was similar to that in the SL group (-6%) and 15% higher than that in the CMS group (p < 0.001). In the HH group, the BV (5,936 ± 673 ml) did not differ from that in the SL group and was 28% lower than in the CMS group (7,606 ± 1075 ml, p < 0.001). Log [EPO] was slightly increased in the CMS group relative to the HH group (p < 0.01). All values in the IM group were between those in the HH and CMS groups. Hbmass and BV were positively correlated, and PV was negatively correlated with peripheral O₂ saturation. Increased Hbmass and decreased PV contributed approximately 65 and 35%, respectively, to the difference in [Hb] between the HH (17.1 ± 0.8 g/dl) and CMS (22.1 ± 1.0 g/dl) groups.

CONCLUSIONS

In CMS patients, the decrease in PV only partially compensated for the substantial increase in Hbmass, but it did not prevent an increase in BV; the decrease in PV contributed to an excessively high [Hb].

Six weeks of static apnea training does not affect Hbmass and exercise performance

PURPOSE

Acute apnea is known to induce decreases in oxyhemoglobin desaturation (SpO₂) and increases in erythropoietin concentration ([EPO]). This study examined the potential of an apnea training program to induce erythropoiesis and increase hematological parameters and exercise performance.

METHODS

Twenty-two male subjects were randomly divided into an apnea and control group. The apnea group performed a 6-week apnea training program consisting of a daily series of 5 maximal static apneas. Before and after training, subjects visited the lab on three test days to perform 1) a ramp incremental test measuring V̇O_2peak, 2) CO-rebreathing for Hb mass determination and a 3-km time trial and 3) an apnea test protocol with continuous finger SpO₂ registration. Venous blood samples were drawn before and 180 minutes after the apnea test for analysis of [EPO].

RESULTS

Minimal SpO₂ reached during the apnea test protocol was 91 ±7% pre and 82 ±7% post apnea training. The apnea test protocol did not elicit an acute increase in [EPO] (p=0.685) before nor after the training program. Consequently, resting [EPO] (p=0.170), Hbmass (p=0.134), V̇O_2peak (p=0.796) and 3-km cycling time trial performance (p=0.509) were not affected either.

CONCLUSION

The apnea test and training protocol, consisting of 5 maximal static apneas, did not induce a sufficiently strong hypoxic stimulus to cause erythropoiesis and therefore did not result in an increase in resting [EPO], Hbmass, V̇O_2peak or time trial performance. Longer and/or more intense training sessions inducing a stronger hypoxic stimulus are probably needed to obtain changes in hematological and exercise parameters.

The influence of maturation on exercise-induced cardiac remodelling and haematological adaptation

KEY POINTS

It has long been hypothesised that cardiovascular adaptation to endurance training is augmented following puberty. We investigated whether differences in cardiac and haematological variables exist, and to what extent, between endurance-trained vs. untrained, pre- and post-peak height velocity (PHV) children, and how these central factors relate to maximal oxygen consumption. Using echocardiography to quantify left ventricular (LV) morphology and carbon monoxide rebreathing to determine blood volume and haemoglobin mass, we identified that training-related differences in LV morphology are evident in pre-PHV children, with haematological differences also observed between pre-PHV girls. However, the breadth and magnitude of cardiovascular remodelling was more pronounced post-PHV. Cardiac and haematological measures provide significant predictive models for maximal oxygen consumption in children that are much stronger post-PHV, suggesting that other important determinants within the oxygen transport chain could account for the majority of variance in before puberty.

ABSTRACT

Cardiovascular and haematological adaptations to endurance training facilitate greater maximal oxygen consumption, and such adaptations maybe augmented following puberty. Therefore, we compared left ventricular (LV) morphology (echocardiography), blood volume, haemoglobin (Hb) mass (CO-rebreathe) and in endurance-trained and untrained boys (n = 42, age = 9.0-17.1 years, = 61.6±7.2 mL∙kg∙min, and n = 31, age = 8.0-17.7 years, O_2max = 46.5±6.1 mL∙kg∙min, respectively) and girls (n = 45, age = 8.2-17.0 years, O_2max = 51.4±5.7 mL∙kg∙min and n = 36, age = 8.0-17.6 years, O_2max = 39.8±5.7 mL∙kg∙min, respectively). Pubertal stage was estimated via maturity offset, with participants classified as pre- or post-peak height velocity (PHV). Pre-PHV, only a larger LV end-diastolic volume/lean body mass (EDV/LBM) for trained boys (+0.28 mL∙kg^LBM , P = 0.007) and a higher Hb mass/LBM for trained girls (+1.65 g∙kg^LBM , P = 0.007) were evident compared to untrained controls. Post-PHV, LV mass/LBM (boys:+0.50 g∙kg^LBM , P = 0.0003; girls:+0.35 g∙kg^LBM , P = 0.003), EDV/LBM (boys:+0.35 mL∙kg^LBM , P<0.0001; girls:+0.31 mL∙kgLBM, P = 0.0004), blood volume/LBM (boys:+12.47 mL∙kg^LBM , P = 0.004; girls:+13.48 mL∙kg^LBM , P = 0.0002.) and Hb mass/LBM (boys:+1.29 g∙kg^LBM , P = 0.015; girls:+1.47 g∙kg^LBM , P = 0.002) were all greater in trained vs. untrained groups. Pre-PHV, EDV (R² _adj = 0.224, P = 0.001) in boys, and Hb mass and interventricular septal thickness (R² _adj = 0.317, P = 0.002) in girls partially accounted for the variance in O_2max . Post-PHV, stronger predictive models were evident via the inclusion of LV wall thickness and EDV in boys (R² _adj = 0.608, P<0.0001), and posterior wall thickness and Hb mass in girls (R² _adj = 0.490, P<0.0001). In conclusion, cardiovascular adaptation to exercise training is more pronounced post-PHV, with evidence for a greater role of central components for oxygen delivery. Abstract figure legend: Schematic diagram depicting cardiac structural and haematological differences between trained and untrained boys and girls, pre-peak height velocity (PHV) and post-PHV alongside cardiac and haematological variables contributions to the variance in O_2max . Cardiac and haematological variables are greater in trained vs. untrained pre-pubertal children, and a greater number and magnitude of differences are observed at post-PHV. These variables provide significant predictive models for maximal oxygen consumption in children and are much stronger post-PHV, suggesting that other important determinants within the oxygen transport chain could account for the majority of variance in O_2max before puberty. This article is protected by copyright. All rights reserved.

Effects of 150- and 450-mL Acute Blood Losses on Maximal Oxygen Uptake and Exercise Capacity

PURPOSE

This study investigated whether maximal oxygen uptake (V˙O2max) and exercise capacity are affected by small acute blood loss (150 mL) and elucidated compensatory mechanisms.

METHODS

Thirteen male subjects (V˙O2max, 63 ± 9 mL·kg-1·min-1; mean ± SD) performed incremental exercise to exhaustion on a cycle ergometer in three experimental conditions: in euvolemia (control; blood volume [BV], 6.0 ± 0.7 L) and immediately after acute BV reductions of 150 mL (BVR150mL) and 450 mL (BVR450mL). Changes in plasma volume (PV) and BV during exercise were calculated from hematocrit, hemoglobin concentration, and hemoglobin mass (carbon monoxide rebreathing).

RESULTS

The reduction in V˙O2max per milliliter of BVR was 2.5-fold larger after BVR450mL compared with BVR150mL (-0.7 ± 0.3 vs -0.3 ± 0.6 mL·min-1·mL-1, P = 0.029). V˙O2max was not significantly changed after BVR150mL (-1% ± 2%, P = 0.124) but reduced by 7% ± 3% after BVR450mL (P < 0.001) compared with control. Peak power output only decreased after BVR450mL (P < 0.001). At maximal exercise, BV was restored after BVR150mL compared with control (-50 ± 185 mL, P = 0.375) attributed to PV restoration, which was, however, insufficient in restoring BV after BVR450mL (-281 ± 184 mL, P < 0.001). The peak heart rate tended to increase (3 ± 5 bpm, P = 0.062), whereas the O2 pulse (-2 ± 1 mL per beat, P < 0.001) and vastus lateralis tissue oxygenation index (-4% ± 8% points, P = 0.080) were reduced after BVR450mL, suggesting decreased stroke volume and increased leg O2 extraction.

CONCLUSION

The deteriorations of V˙O2max and of maximal exercise capacity accelerate with the magnitude of acute blood loss, likely because of a rapid PV restoration sufficient to establish euvolemia after a small but not after a moderate blood loss.

Effect of Exercise-Induced Reductions in Blood Volume on Cardiac Output and Oxygen Transport Capacity

We wanted to demonstrate the relationship between blood volume, cardiac size, cardiac output and maximum oxygen uptake (V.O_2max) and to quantify blood volume shifts during exercise and their impact on oxygen transport. Twenty-four healthy, non-smoking, heterogeneously trained male participants (27 ± 4.6 years) performed incremental cycle ergometer tests to determine V.O_2max and changes in blood volume and cardiac output. Cardiac output was determined by an inert gas rebreathing procedure. Heart dimensions were determined by 3D echocardiography. Blood volume and hemoglobin mass were determined by using the optimized CO-rebreathing method. The V.O_2max ranged between 47.5 and 74.1 mL⋅kg^–1⋅min^–1. Heart volume ranged between 7.7 and 17.9 mL⋅kg^–1 and maximum cardiac output ranged between 252 and 434 mL⋅kg^–1⋅min^–1. The mean blood volume decreased by 8% (567 ± 187 mL, p = 0.001) until maximum exercise, leading to an increase in [Hb] by 1.3 ± 0.4 g⋅dL^–1 while peripheral oxygen saturation decreased by 6.1 ± 2.4%. There were close correlations between resting blood volume and heart volume (r = 0.73, p = 0.002), maximum blood volume and maximum cardiac output (r = 0.68, p = 0.001), and maximum cardiac output and V.O_2max (r = 0.76, p < 0.001). An increase in maximum blood volume by 1,000 mL was associated with an increase in maximum stroke volume by 25 mL and in maximum cardiac output by 3.5 L⋅min^–1. In conclusion, blood volume markedly decreased until maximal exhaustion, potentially affecting the stroke volume response during exercise. Simultaneously, hemoconcentrations maintained the arterial oxygen content and compensated for the potential loss in maximum cardiac output. Therefore, a large blood volume at rest is an important factor for achieving a high cardiac output during exercise and blood volume shifts compensate for the decrease in peripheral oxygen saturation, thereby maintaining a high arteriovenous oxygen difference.

Quantification of testosterone-dependent erythropoiesis during male puberty

NEW FINDINGS

What is the central question of this study? To what extent does testosterone influence haemoglobin formation during male puberty? What is the main finding and its importance? In boys, testosterone might be responsible for about 65% of the increase in haemoglobin mass during puberty. The underlying mechanisms are assumed to be twofold: (i) indirectly, mediated by the increase in lean body mass, and (ii) directly by immediate testosterone effects on erythropoiesis. Thereby, an increase in testosterone of 1 ng/ml is associated with an increase in haemoglobin mass of ∼65 g. These processes are likely to determine endurance performance in adulthood.

ABSTRACT

The amount of haemoglobin during puberty is related to endurance performance in adulthood. During male puberty, testosterone stimulates erythropoiesis and could therefore be used as a marker for later endurance performance. This cross-sectional study aimed to determine the relationship between serum testosterone concentration and haemoglobin mass (Hbmass) in both male and female children and adolescents and to evaluate the possible influences of altitude and training. Three-hundred and thirteen differentially trained boys and girls aged from 9 to 18 years and living at altitudes of 1000 and 2600 m above sea level entered the study. The stage of sexual maturation was determined according to the classification of Tanner. Testosterone was measured by ELISA. Hbmass was determined by CO-rebreathing. Haemoglobin concentration did not change during maturation in girls and was 11% higher during puberty in boys, while Hbmass was elevated by 33% in Tanner stage V compared to stage II in girls (498 ± 77 vs. 373 ± 88 g) and by 95% in boys (832 ± 143 vs. 428 ± 95 g). This difference can most likely be attributed to indirect testosterone influences through an increase in lean body mass (LBM) and to direct testosterone effects on erythropoiesis, which increase the Hbmass by ∼65 g per 1 ng/ml. Altitude and training statuses were not associated with testosterone, but with an increase in Hbmass (altitude by 1.1 g/kg LBM, training by 0.8 g/kg LBM). Changes in Hbmass are closely related to testosterone levels during male puberty. Further studies will show whether testosterone and Hbmass during childhood and adolescence can be used as diagnostic tools for endurance talents.

Blood Volume, Hemoglobin Mass, and Peak Oxygen Uptake in Older Adults: The Generation 100 Study

Purpose: To investigate the association between blood volume, hemoglobin mass (Hb_mass), and peak oxygen uptake (VO_2peak) in healthy older adults.

Methods: Fifty fit or unfit participants from the prospective randomized Generation 100 Study (n = 1,566) were included (age- and sex-specific VO_2peak above or below average values). Blood, plasma, and erythrocyte volume and Hb_mass were tested using the carbon monoxide rebreathing method within 1 week after VO_2peak testing.

Results: Mean age, BMI, Hb_mass, blood volume, and VO_2peak were 73.0 ± 2.1 years, 24.8 ± 3.3 kg·m², 10.0 ± 1.7 g·kg⁻¹, 76.4 ± 11.8 mL·kg⁻¹, and 33.5 ± 8.4 mL·kg⁻¹·min⁻¹. VO_2peak in fit and unfit participants and women and men were 38.6 ± 6.5 and 25.8 ± 3.8 mL·kg⁻¹·min⁻¹, 30.7 ± 7.6 mL·kg⁻¹·min⁻¹, and 35.5 ± 8.5 mL·kg⁻¹·min⁻¹, respectively. Women were shorter (Δ14 cm), leaner (Δ13 kg), and with less muscle mass (Δ9%) than men (P < 0.05). Relative erythrocyte volume and Hb_mass were lower in women, and blood and erythrocyte volume and Hb_mass were higher in the fit participants (P < 0.05). Hb_mass and erythrocyte volume explained 40 and 37%, respectively, of the variability in VO_2peak, with a limited effect of physical-activity adjustment (40 and 38%, respectively). Blood and plasma volume explained 15 and 25%, respectively, of VO_2peak variability, and the association was strengthened adjusting for physical activity (25 and 31%, respectively), indicating a training-dependent adaptation in plasma but not erythrocyte volume (p ≤ 0.006).

Conclusions: Blood and plasma volumes were moderately associated with VO_2peak in healthy older men and women, and the association was strengthened after adjustment for physical activity. Hb_mass and erythrocyte volume were strongly associated with VO_2peak but unrelated to physical activity.

A carbon monoxide 'single breath' method to measure total haemoglobin mass: a feasibility study

NEW FINDINGS

What is the central question of this study? Is it possible to modify the CO-rebreathing method to acquire reliable measurements of haemoglobin mass in ventilated patients? What is the main finding and its importance? A 'single breath' of CO with a subsequent 30 s breath hold provides almost as exact a measure of haemoglobin mass as the established optimized CO-rebreathing method when applied to healthy subjects. The modified method has now to be checked in ventilated patients before it can be used to quantify the contributions of blood loss and of dilution to the severity of anaemia.

ABSTRACT

Anaemia is defined by the concentration of haemoglobin (Hb). However, this value is dependent upon both the total circulating haemoglobin mass (tHb-mass) and the plasma volume (PV) - neither of which is routinely measured. Carbon monoxide (CO)-rebreathing methods have been successfully used to determine both PV and tHb-mass in various populations. However, these methods are not yet suitable for ventilated patients. This study aimed to modify the CO-rebreathing procedure such that a single inhalation of a CO bolus would enable its use in ventilated patients. Eleven healthy volunteers performed four CO-rebreathing tests in a randomized order, inhaling an identical CO volume. In two tests, CO was rebreathed for 2 min (optimized CO rebreathing; oCOR), and in the other two tests, a single inhalation of a CO bolus was conducted with a subsequent breath hold of 15 s (Proc_new 15s) or 30 s (Proc_new 30s). Subsequently, the CO volume in the exhaled air was continuously determined for 20 min. The amount of CO exhaled after 7 and 20 min was respectively 3.1 ± 0.3 and 5.9 ± 1.1 ml for oCOR, 8.7 ± 3.6 and 12.0 ± 4.4 ml for Proc_new 15s and 5.1 ± 2.0 and 8.4 ±2.6 ml for Proc_new 30s. tHb-mass was 843 ± 293 g determined by oCOR, 821 ± 288 g determined by Proc_new 15s (difference: P < 0.05) and 849 ± 311 g determined by Proc_new 30s. Bland-Altman plots demonstrated slightly lower tHb-mass values for Proc_new 15s compared with oCOR (-21.8 ± 15.3 g) and similar values for Proc_new 30s. In healthy volunteers, a single inhalation of a CO bolus, preferably followed by a 30 s breath hold, can be used to determine tHb-mass. These results must now be validated for ventilated patients.

The importance of lean mass and iron deficiency when comparing hemoglobin mass in male and female athletic groups

Hemoglobin mass (Hbmass) is important for athletes because it helps determine maximal aerobic power. This study examined how lean mass, iron deficiency (ID), and sex influence Hbmass in athletic and nonathletic groups. NCAA Division I student athletes (21 men, 75 women; altitude: 1,625 m) were recruited from six athletic teams; 14 male and 12 female full-time students (non-varsity athletes) served as control subjects. Hbmass, body composition, and iron homeostasis parameters, including ferritin, soluble transferrin receptor (sTfR), hepcidin, erythroferrone, and 10 inflammatory cytokines, were measured two to four times across a competitive/training season. ID was defined as ferritin < 25 ng/mL. Hbmass was more closely related to lean mass (r² = 0.90) than body mass (r² = 0.69, P < 0.01). Compared with female subjects, male subjects had 19.9% higher Hbmass relative to body mass (Hbmass_BM) but only 7.5% higher Hbmass relative to lean mass (Hbmass_LEAN) (both P < 0.001). Prevalence of ID was higher in female than male subjects (47% vs. 9%, P < 0.01) but did not vary between groups. Hbmass_LEAN was 5% lower in ID vs. non-ID female subjects; Hbmass_BM was not different. ID was associated with lower hepcidin, elevated sTfR, and elevated erythroferrone but not with differences in inflammatory cytokines. Hbmass varied significantly between athletic groups and across sex, but the majority of these differences are explained by differences in lean mass. ID was common in female subjects and was associated with lower Hbmass_LEAN and hepcidin but not with differences in Hbmass_BM or inflammatory cytokines. Hbmass relative to lean mass seems advantageous when monitoring iron deficiency.NEW & NOTEWORTHY Differences in hemoglobin mass (Hbmass) between groups and across sex are primarily due to differences in lean mass. Iron deficiency (ID) independently decreases Hbmass; this effect is best characterized with Hbmass relative to lean mass. ID is common in females and is associated with lower hepcidin and elevated erythroferrone but not with differences in inflammatory cytokines. Hbmass relative to lean mass accurately quantifies hematological alterations secondary to iron deficiency.

Blood volume expansion does not explain the increase in peak oxygen uptake induced by 10 weeks of endurance training

Purpose

The endurance training (ET)-induced increases in peak oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak) and cardiac output (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{Q}$$\end{document}Q˙_peak) during upright cycling are reversed to pre-ET levels after removing the training-induced increase in blood volume (BV). We hypothesised that ET-induced improvements in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{Q}$$\end{document}Q˙_peak are preserved following phlebotomy of the BV gained with ET during supine but not during upright cycling. Arteriovenous O₂ difference (a-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{\text{v}}$$\end{document}v¯O₂diff; \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂/\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{Q}$$\end{document}Q˙), cardiac dimensions and muscle morphology were studied to assess their role for the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak improvement.

Methods

Twelve untrained subjects (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak: 44 ± 6 ml kg⁻¹ min⁻¹) completed 10 weeks of supervised ET (3 sessions/week). Echocardiography, muscle biopsies, haemoglobin mass (Hb_mass) and BV were assessed pre- and post-ET. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{Q}$$\end{document}Q˙_peak during upright and supine cycling were measured pre-ET, post-ET and immediately after Hb_mass was reversed to the individual pre-ET level by phlebotomy.

Results

ET increased the Hb_mass (3.3 ± 2.9%; P = 0.005), BV (3.7 ± 5.6%; P = 0.044) and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak during upright and supine cycling (11 ± 6% and 10 ± 8%, respectively; P ≤ 0.003). After phlebotomy, improvements in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak compared with pre-ET were preserved in both postures (11 ± 4% and 11 ± 9%; P ≤ 0.005), as was \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{Q}$$\end{document}Q˙_peak (9 ± 14% and 9 ± 10%; P ≤ 0.081). The increased \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{Q}$$\end{document}Q˙_peak and a-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{\text{v}}$$\end{document}v¯O₂diff accounted for 70% and 30% of the \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak improvements, respectively. Markers of mitochondrial density (CS and COX-IV; P ≤ 0.007) and left ventricular mass (P = 0.027) increased.

Conclusion

The ET-induced increase in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak was preserved despite removing the increases in Hb_mass and BV by phlebotomy, independent of posture. \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2peak increased primarily through elevated \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{Q}$$\end{document}Q˙_peak but also through a widened a-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{\text{v}}$$\end{document}v¯O₂diff, potentially mediated by cardiac remodelling and mitochondrial biogenesis.

Application of the optimized carbon monoxide rebreathing method for the measurement of total haemoglobin mass in chronic liver disease

BACKGROUND

Anemia is common in liver cirrhosis. This generally infers a fall in total hemoglobin mass (tHb-mass). However, hemoglobin concentration ([Hb]) may fall due to an expansion in plasma volume (PV). The "optimized carbon monoxide rebreathing method" (oCOR) measures tHb-mass directly and PV (indirectly using hematocrit). It relies upon carboxyhemoglobin (COHb) distribution throughout the entire circulation. In healthy subjects, such distribution is complete within 6-8 min. Given the altered circulatory dynamics in cirrhosis, we sought in this pilot study, to assess whether this was true in cirrhosis. The primary aim was to ascertain if the standard timings for the oCOR were applicable to patients with chronic liver disease and cirrhosis. The secondary aim was to explore the applicability of standard CO dosing methodologies to this patient population.

METHODS

Sixteen patients with chronic liver parenchymal disease were studied. However, tHb-mass was determined using the standard oCOR technique before elective paracentesis. Three subjects had an inadequate COHb% rise. In the remaining 13 (11 male), mean ± standard deviation (SD) age was 52 ± 13.8 years, body mass 79.1 ± 11.4 kg, height 175 ± 6.8 cm. To these, mean ± SD dose of carbon monoxide (CO) gas administered was 0.73 ± 0.13 ml/kg COHb values at baseline, 6 and 8 min (and "7-min value") were compared to those at 10, 12, 15 and 20 min after CO rebreathing.

RESULTS

The "7-min value" for median COHb% (IQR) of 6.30% (6.21%-7.47%) did not differ significantly from those at subsequent time points (8 min: 6.30% (6.21%-7.47%), 10 min: 6.33% (6.00%-7.50%), 12 min: 6.33% (5.90%-7.40%), 15 min: 6.37% (5.80%-7.33%), 20 min: 6.27% (5.70%-7.20%)). Mean difference in calculated tHb-mass between minute 7 and minute 20 was only 4.1 g, or 0.6%, p = .68. No subjects reported any adverse effects.

CONCLUSIONS

The oCOR method can be safely used to measure tHb-mass in patients with chronic liver disease and ascites, without adjustment of blood sample timings. Further work might refine and validate appropriate dosing regimens.

Factors Contributing to CO Uptake and Elimination in the Body: A Critical Review

BACKGROUND

Carbon monoxide (CO) poisoning is an important public health issue around the world. Research indicates that many factors may be related to the rate of CO uptake and elimination in the human body. However, some factors related to CO uptake and elimination are considered controversial. Relatively little attention has been devoted to review and synthesis of factors affecting CO uptake and elimination.

PURPOSE

This paper provides a critical scoping review of the factors and divides them into four aspects, including environmental, demographic, physiological and treatment factors.

METHODS

We searched the scientific databases for research that has proposed a mathematical equation as a synthesis of quantities related to CO poisoning, CO elimination, CO uptake, CO half-life, CO uptake and elimination and their relationships. After excluding the studies that did not meet the study criteria, there were 39 studies included in the review and the search was completed before 16 December 2019.

RESULTS AND CONCLUSION

This review discusses most of the factors that impact the rate of CO uptake and elimination. Several factors may be related to CO uptake and elimination, such as CO concentration, the duration of exposure to CO, age, sex, exercise, minute ventilation, alveolar ventilation, total haemoglobin mass and different treatments for CO poisoning. Although some potential factors were not included in the review, the findings are useful by presenting an overview for discussing factors affecting CO uptake and elimination and provide a starting point for further study regarding strategies for CO poisoning and the environmental standard of CO.

Heat therapy vs. supervised exercise therapy for peripheral arterial disease: a 12-wk randomized, controlled trial

Peripheral arterial disease (PAD) is characterized by lower limb atherosclerosis impairing blood supply and causing walking-induced leg pain or claudication. Adherence to traditional exercise training programs is poor due to these symptoms despite exercise being a mainstay of conservative treatment. Heat therapy improves many cardiovascular health outcomes, so this study tested if this was a viable alternative cardiovascular therapy for PAD patients. Volunteers with PAD were randomized to 12 wk of heat ( n = 11; mean age 76 ± 8 yr, BMI 28.7 ± 3.5 kg/m2, 4 females) or exercise ( n = 11; 74 ± 10 yr, 28.5 ± 6.8 kg/m2, 3 females). Heat involved spa bathing at ∼39°C, 3–5 days/wk for ≤30 min, followed by ≤30 min of callisthenics. Exercise involved ≤90 min of supervised walking and gym-based exercise, 1–2 days/wk. Following the interventions, total walking distance during a 6-min walk test increased (from ∼350 m) by 41 m (95% CI: [13, 69], P = 0.006) regardless of group, and pain-free walking distance increased (from ∼170 m) by 43 m ([22, 63], P < 0.001). Systolic blood pressure was reduced more following heat (−7 mmHg, [−4, −10], P < 0.001) than following exercise (−3 mmHg, [0, −6], P = 0.078), and diastolic and mean arterial pressure decreased by 4 mmHg in both groups ( P = 0.002). There were no significant changes in blood volume, ankle-brachial index, or measures of vascular health. There were no differences in the improvement in functional or blood pressure outcomes between heat and exercise in individuals with PAD.

NEW & NOTEWORTHY Heat therapy via hot-water immersion and supervised exercise both improved walking distance and resting blood pressure in peripheral arterial disease (PAD) patients over 12 wk. Adherence to heat therapy was excellent, and the heat intervention was well tolerated. The results of the current study indicate that heat therapy can improve functional ability and has potential as an effective cardiovascular conditioning tool for individuals with PAD.

Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/heat-therapy-vs-exercise-in-peripheral-arterial-disease/ .

Greater blood volume and Hb mass in obese women quantified by the carbon monoxide-rebreathing method affects interpretation of iron biomarkers and iron requirements

BACKGROUND/OBJECTIVE

Iron deficiency (ID) is common in overweight and obese individuals (OW/OB) but the mechanism is uncertain. Greater blood volume (BV) in OW/OB may increase hemoglobin (Hb) mass and iron requirements, and confound iron biomarkers by hemodilution. Quantification of BV/PV changes in OW/OB is challenging and a formula to estimate BV/PV based on anthropometric indices would be valuable. In normal weight (NW) and OW/OB women, we aimed at: (1) measure BV and assess whether differences in BV affect concentrations and total circulating mass of Hb and iron biomarkers; (2) develop an algorithm describing BV in OW/OB.

SUBJECTS/METHODS

In a cross-sectional study, we measured BV in NW, OW, and OB non-anemic women (n = 62) by using the carbon monoxide-rebreathing method, body composition by dual energy X-ray absorptiometry, and iron and inflammatory status.

RESULTS

OW and OB women had 11 and 16% higher mean BV and PV compared to NW (P < 0.05), respectively. In OW/OB compared to NW, total circulating masses of IL-6, hepcidin, Hb, and sTfR were higher, while total mass of serum iron was lower (for all, P < 0.05). An equation including height, body mass and lean mass to estimate BV in all BMI groups (R2 = 0.76).

CONCLUSION

An equation based on anthropometric indices provides a good estimate of increased BV in OW/OB women. In OW/OB women, there is an increase in Hb mass that likely increases iron requirements for erythropoiesis and circulating TfR mass. At the same time, higher hepcidin concentrations may lower serum iron mass. Both these mechanisms may increase risk for ID in OW/OB women.

Effects of 3 Weeks of Oral Low-Dose Cobalt on Hemoglobin Mass and Aerobic Performance

Introduction: Cobalt ions (Co²⁺) stabilize HIFα and increase endogenous erythropoietin (EPO) production creating the possibility that Co²⁺ supplements (CoSupp) may be used as performance enhancing substances. The aim of this study was to determine the effects of a small oral dosage of CoSupp on hemoglobin mass (Hbmass) and performance with the objective of providing the basis for establishing upper threshold limits of urine [Co²⁺] to detect CoSupp misuse in sport.

Methods: Twenty-four male subjects participated in a double-blind placebo-controlled study. Sixteen received an oral dose of 5 mg of ionized Co²⁺ per day for 3 weeks, and eight served as controls. Blood and urine samples were taken before the study, during the study and up to 3 weeks after CoSupp. Hbmass was determined by the CO-rebreathing method at regular time intervals, and VO_2max was determined before and after the CoSupp administration period.

Results: In the Co²⁺ group, Hbmass increased by 2.0 ± 2.1% (p < 0.001) while all the other analyzed hematological parameters did not show significant interactions of time and treatment. Hemoglobin concentration ([Hb]) and hematocrit (Hct) tended to increase (p = 0.16, p = 0.1) and also [EPO] showed a similar trend (baseline: 9.5 ± 3.0, after 2 weeks: 12.4 ± 5.2 mU/ml). While mean VO_2max did not change, there was a trend for a positive relationship between changes in Hbmass and changes in VO_2max immediately after CoSupp (r = 0.40, p = 0.11). Urine [Co²⁺] increased from 0.4 ± 0.3 to 471.4 ± 384.1 ng/ml (p < 0.01) and remained significantly elevated until 2 weeks after cessation.

Conclusion: An oral Co²⁺ dosage of 5 mg/day for 3 weeks effectively increases Hbmass with a tendency to increase hemoglobin concentration ([Hb]) and hematocrit (Hct). Because urine Co²⁺ concentration remains increased for 2 weeks after cessation, upper limit threshold values for monitoring CoSupp can be established.

Blood volume measurement using cardiovascular magnetic resonance and ferumoxytol: preclinical validation

BACKGROUND

The hallmark of heart failure is increased blood volume. Quantitative blood volume measures are not conveniently available and are not tested in heart failure management. We assess ferumoxytol, a marketed parenteral iron supplement having a long intravascular half-life, to measure the blood volume with cardiovascular magnetic resonance (CMR).

METHODS

Swine were administered 0.7 mg/kg ferumoxytol and blood pool T1 was measured repeatedly for an hour to characterize contrast agent extraction and subsequent effect on Vblood estimates. We compared CMR blood volume with a standard carbon monoxide rebreathing method. We then evaluated three abbreviated acquisition protocols for bias and precision.

RESULTS

Mean plasma volume estimated by ferumoxytol was 61.9 ± 4.3 ml/kg. After adjustment for hematocrit the resultant mean blood volume was 88.1 ± 9.4 ml/kg, which agreed with carbon monoxide measures (91.1 ± 18.9 ml/kg). Repeated measurements yielded a coefficient of variation of 6.9%, and Bland-Altman repeatability coefficient of 14%. The blood volume estimates with abbreviated protocols yielded small biases (mean differences between 0.01-0.06 L) and strong correlations (r2 between 0.97-0.99) to the reference values indicating clinical feasibility.

CONCLUSIONS

In this swine model, ferumoxytol CMR accurately measures plasma volume, and with correction for hematocrit, blood volume. Abbreviated protocols can be added to diagnostic CMR examination for heart failure within 8 min.

EFFECTS OF MODEST IRON LOADING ON IRON INDICES IN HEALTHY INDIVIDUALS

Intravenous (iv) iron administration is typically indicated in individuals who have iron deficiency refractory to oral iron. However, in certain chronic disease states, it may be beneficial to administer iv iron to individuals who are not strictly iron deficient. The purpose of this study was to define a dose-response relationship between clinical indices of iron status and modest loading with iv iron in healthy, iron-replete participants. This was a double-blind, controlled study involving 18 male participants. Participants were block randomised 2:1 to the iron and saline (control) groups. Participants in the iron group received 250 mg of iv iron, once a month for six months, provided that their ferritin remained < 300 µg/L and their transferrin saturation remained < 45%. Otherwise they received a saline infusion, as did the control participants. Iron indices were measured monthly during the study. The pulmonary vascular response to sustained hypoxia and total hemoglobin mass were measured before, at three months (hemoglobin mass only) and at six months, as variables that may be affected by iron loading. Serum ferritin was robustly elevated by iv iron by 0.21 µg/L/mg of iron delivered (95% CI: 0.15-0.26 µg/L/mg), but the effects on all other iron indices did not reach statistical significance. The pulmonary vascular response to sustained hypoxia was significantly suppressed by iron loading at six months, but the hemoglobin mass was unaffected. We conclude that the robust effect on ferritin provides a quantitative measure for the degree of iron loading in iron-replete individuals.

The Influence of Oxygen Saturation on the Relationship Between Hemoglobin Mass and VO 2 max

Hemoglobin mass (tHb) is a key determinant of maximal oxygen uptake (VO ₂ max). We examined whether oxyhemoglobin desaturation (ΔS _a O ₂ ) at VO ₂ max modifies the relationship between tHb and VO ₂ max at moderate altitude (1,625 m). Seventeen female and 16 male competitive, endurance-trained moderate-altitude residents performed two tHb assessments and two graded exercise tests on a cycle ergometer to determine VO ₂ max and ΔS _a O ₂ . In males and females respectively, VO ₂ max (ml·kg ⁻¹ ·min ⁻¹ ) ranged from 62.5–83.0 and 44.5–67.3; tHb (g·kg ⁻¹ ) ranged from 12.1–17.5 and 9.1–13.0; and S _a O ₂ at VO ₂ max (%) ranged from 81.7–94.0 and 85.7–95.0. tHb was related to VO ₂ max when expressed in absolute terms and after correcting for body mass (r=0.94 and 0.86, respectively); correcting by ΔS _a O ₂ did not improve these relationships (r=0.93 and 0.83). Additionally, there was a negative relationship between tHb and S _a O ₂ at VO ₂ max (r=–0.57). In conclusion, across a range of endurance athletes at moderate altitude, the relationship between tHb and VO ₂ max was found to be similar to that observed at sea level. However, correcting tHb by ΔS _a O ₂ did not explain additional variability in VO ₂ max despite significant variability in ΔS _a O ₂ ; this raises the possibility that tHb and exercise-induced ΔS _a O ₂ are not independent in endurance athletes.

Determination of hemoglobin mass in humans by measurement of CO uptake during inhalation of a CO-air mixture: a proof of concept study

Measuring hemoglobin mass (Hbmass) using the carbon monoxide (CO) bolus rebreathing method is frequently used in research but has yet to be widely used in the clinical practice. The estimation of an adequate CO bolus may be difficult in patients with unknown Hbmass. In the present pilot study, a progressive inhalation technique for CO that leads to a linear individual adjusted COHb increase was evaluated. Sixteen healthy test subjects participated in the study (preliminary investigation: six; main study: ten). The reliability and validity of the new method were evaluated using multiple measurements of Hbmass with and without a defined blood donation and compared to a CO bolus method. The participants inhaled a CO-air mixture (CO concentration: 1500 ppm) for a specific breathing duration. The CO uptake and COHb change were determined simultaneously. The typical error (reliability) in the repeated measurements was 2.4% (CI ± 4.7). The mean difference between the new method and the bolus method was 34 g (±41; P = 0.026). The measured hemoglobin loss in 490 mL of blood was 74 g (±35), and the calculated hemoglobin loss was 77 g (±4) (mean difference 3 g ± 34; P = 0.820). The new method was reliable and valid in a proof of concept study with healthy subjects. The total amount of CO and as a result the COHb increase is individually adjustable. Future studies in clinical settings are needed to determine if the method could be used in disease-specific pathologies associated with changes in Hbmass.

Influence of Endurance Training During Childhood on Total Hemoglobin Mass

Elite endurance athletes are characterized by markedly increased hemoglobin mass (Hbmass). It has been hypothesized that this adaptation may occur as a response to training at a very young age. Therefore, the aim of this study was to monitor changes in Hbmass in children aged 8–14 years following systematic endurance training. In the first study, Hbmass, VO2max, and lean body mass (LBM) were measured in 17 endurance-trained children (13 boys and 4 girls; aged 9.7 ± 1.3 years; training history 1.5±1.8 years; training volume 3.5 ± 1.6 h) twice a year for up to 3.5 years. The same parameters were measured once in a control group of 18 age-matched untrained children. Hbmass and blood volume (BV) were measured using the optimized CO-rebreathing technique, VO2max by an incremental test on a treadmill, and LBM by skin-fold measurements. In the second pilot study, the same parameters were measured in 9 young soccer athletes (aged 7.8 ± 0.2 years), and results were assessed in relation to soccer performance 2.5 years later. The increase in mean Hbmass during the period of study was 50% which was closely related to changes in LBM (r = 0.959). A significant impact of endurance training on Hbmass was observed in athletes exercising more than 4 h/week [+25.4 g compared to the group with low training volume (<2 h/week)]. The greatest effects were related to LBM (11.4 g·kg⁻¹ LBM) and overlapped with the effects of age. A strong relationship was present between absolute Hbmass and VO2max (r = 0.939), showing that an increase of 1 g hemoglobin increases VO2max by 3.6 ml·min⁻¹. Study 2 showed a positive correlation between Hbmass and soccer performance 2.5 years later at age 10.3 ± 0.3 years (r = 0.627, p = 0.035). In conclusion, children with a weekly training volume of more than 4 h show a 7% higher Hbmass than untrained children. Although this training effect is significant and independent of changes in LBM, the major factor driving the increase in Hbmass is still LBM.

Spot Sample Urine Specific Gravity Does Not Accurately Represent Small Decreases in Plasma Volume in Resting Healthy Males

BACKGROUND

Urine specific gravity (U_SG) is often used to assess hydration status, particularly around athletic competition, but it is unknown whether high U_SG is indicative of plasma volume (PV) reduction (i.e., hypohydration). We tested the hypothesis that if high U_SG is reflective of reduced PV, subsequent fluid ingestion would increase PV.

PURPOSE

The purpose of this study was to examine 24-hour changes in U_SG and PV in individuals presenting with high and low spot U_SG.

METHODS

Nineteen healthy males were provided food and water over 24 hours with a total water volume of 35 ml·kg^-1 body mass. Absolute PV and blood volume (BV), measured using the CO-rebreathe technique, along with U_SG were measured before and after a 24-hour intervention period. Based on a preintervention morning spot U_SG, subjects were post hoc assigned to groups according to U_SG (≤1.020 or >1.020; low and high U_SG, respectively).

RESULTS

Despite presenting with an elevated spot U_SG (1.026 ± 0.004), subsequent fluid ingestion over 24 hours did not lead to changes (∆) in PV (-75 ± 234 ml) or BV (-156 ± 370 ml) in the high U_SG group (p > 0.05). However, a spot U_SG after the 24-hour intervention in this group decreased (p = 0.018) to a level indicating improved hydration status (1.017 ± 0.007). In the low U_SG group, there were no changes in PV (-39 ± 274 ml), BV (-82 ± 396 ml), or U_SG (0.003 ± 0.007) over the 24-hour fluid intervention (all p > 0.05).

CONCLUSIONS

Despite a high preintervention U_SG and subsequent decrease after 24-hour fluid intake, measures of PV and BV were not indicative of this seemingly improved hydration status. This suggests that a highly concentrated spot sample U_SG and subsequent changes are not accurately representative of PV or BV.