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.

ActivPAL accuracy in determining metabolic rate during walking, running and cycling.

To evaluate the ActivPAL's (AcP) ability to estimate METs during walking, running and cycling. Twenty physically active participants performed two submaximal exercises using a treadmill and cycle ergometer. The treadmill session involved varying speeds with a fixed grade and varying grade at fixed walking and running speeds. The cycling session involved fixed power, while cadence was varied and fixed cadence, while power was varied. Four AcPs (two AcP3 & two AcP4) were worn. ActivPAL MET estimations were compared to METS determined via indirect calorimetry. The AcP MET estimations between units and models did not differ. The AcP underestimated (-15% to -61%) METs with increasing speed and was unable to detect an increase in metabolic rate with a change in grade for walking and running. The AcP underestimated (-33% to -60%) METs during cycling and was unable to detect increases in metabolic rate when cadence was fixed, while power increased. The AcP can identify when exercise occurs and provides consistent information across units/models. However, the current AcP algorithm does not provide accurate estimates of METs during walking, running and cycling in a controlled laboratory setting, which would suggest limited accuracy in the field.

A Retrospective Analysis of Collegiate Athlete Blood Biomarkers at Moderate Altitude.

Morris, KL, Widstrom, L, Goodrich, J, Poddar, S, Rueda, M, Holliday, M, San Millian, I, and Byrnes, WC. A retrospective analysis of collegiate athlete blood biomarkers at moderate altitude. J Strength Cond Res 33(11): 2913-2919, 2019-Blood biomarkers are used to assess overall health and determine positive/negative adaptations to training/environmental stimuli. This study aimed to describe the changes in blood biomarkers in collegiate football (FB) (n = 31) and cross-country (XC) (n = 29; 16 women [FXC], 13 men [MXC]) athletes across a competitive season while training and living at a moderate altitude (1,655 m). This study used a database of previously collected hematological (complete blood count and serum ferritin) and muscle damage (lactate dehydrogenase and creatine kinase) blood biomarkers. Data were analyzed both within and between groups using linear mixed-model and variance component analyses, alpha = 0.05. All 3 groups had significant but different patterns of change in the measured biomarkers. Hematological blood biomarkers increased at different time points but remained within the normal reference ranges with greater between-subject vs. within-subject variability, suggesting no significant decrements to oxygen-carrying capacity across the season for FB, MXC, or FXC. Muscle damage biomarkers increased over time and exceeded the normal reference ranges, indicating cell damage pathology. However, it is also possible that the demands of training and competition might alter baseline values in these athletes, although this cannot be confirmed with the current experimental design. The patterns of change in the hematological and muscle damage biomarkers varied by sport discipline, suggesting that the training/competitive environments of these athletes influence these changes. Further studies should assess how much training, altitude, and nutrition influence these changes by using a more comprehensive set of biomarkers and related performance parameters.

Breathing valve resistance alters physiological responses during a graded exercise test.

PURPOSE: To determine the impact of breathing valve resistance on peak aerobic capacity ([Formula: see text]) and running economy (RE) in endurance-trained and recreationally active individuals. METHODS: Ten endurance-trained males (ETM), 10 endurance-trained females (ETF), 10 recreationally active males (RAM), and 10 recreationally active females (RAF) participated in this study. On two separate occasions, subjects performed identical graded exercise treadmill protocols using either a Hans Rudolph 2700 (high resistance) or a Daniels' (low resistance) two-way non-rebreathing valve. Parameters obtained from these protocols included energy expenditure (EE), ventilation ([Formula: see text]), heart rate, respiratory exchange ratio, RE, [Formula: see text], and time to exhaustion (TTE). RESULTS: When using the Daniels' valve, all groups had lower submaximal EE (- 2.4, - 3.4, - 2.7, and - 2.0% for ETM, ETF, RAM, and RAF) and better RE (- 2.7, - 3.5, - 1.9, and - 1.8% for ETM, ETF, RAM and RAF) across all submaximal speeds. Only the ET groups had lower submaximal [Formula: see text] (4.6 and 3.8% for ETM and ETF) when using the Daniels' valve. TTE increased when using the Daniels' valve for all groups (6.0, 10.9, 6.2 and 9.8% for ETM, ETF, RAM and RAF), but [Formula: see text] was unaltered. CONCLUSION: Compared to the Daniels' valve, the Hans Rudolph 2700 valve altered the assessment of RE, submaximal EE, and TTE regardless of fitness level or sex, but did not change [Formula: see text]. Therefore, airflow resistance of a breathing valve must be considered when assessing and comparing EE, RE and TTE in the applied and research settings.

Beneficial Effects of Cooling during Constant Power Non-steady State Cycling.

This study compared the effects of cooling on the energetic and associated physiological and perceptual responses to constant power, non-steady state cycling. Twelve males cycled at their lactate threshold power for 60 min or until exhaustion under 3 conditions: wearing a cooling vest and sleeves (COOL), a synthetic shirt embedded with an active particle technology claimed to facilitate evaporative heat loss (EVAP), and a standard synthetic shirt (CON). When adjusted for time, the increase in gastrointestinal temperature from baseline was reduced during COOL and EVAP compared to CON (1.44±0.45 and 1.52±0.43 vs. 1.66±0.45°C, p<0.05). Sweat rate was reduced during COOL compared to EVAP and CON (1 312±331 vs. 1 525±393 and 1 550±548 mL·h-1, p<0.01). Gross efficiency decreased over time across conditions (p<0.01), but COOL attenuated this decrease by 22% compared to CON (p<0.05). The rating of perceived exertion was reduced during COOL and EVAP compared to CON (p<0.01). In conclusion, cooling using a vest and sleeves or wearing an active particle technology shirt reduced the rise in gastrointestinal temperature and rating of perceived exertion compared to a standard synthetic shirt. Cooling using a vest and sleeves also reduced the decrease in gross efficiency and sweat rate compared to wearing the standard synthetic shirt.

Decreased arterial PO2, not O2 content, increases blood flow through intrapulmonary arteriovenous anastomoses at rest.

KEY POINTS: The mechanism(s) that regulate hypoxia-induced blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) are currently unknown. Our previous work has demonstrated that the mechanism of hypoxia-induced QIPAVA is not simply increased cardiac output, pulmonary artery systolic pressure or sympathetic nervous system activity and, instead, it may be a result of hypoxaemia directly. To determine whether it is reduced arterial PO2 (PaO2) or O2 content (CaO2) that causes hypoxia-induced QIPAVA , individuals were instructed to breathe room air and three levels of hypoxic gas at rest before (control) and after CaO2 was reduced by 10% by lowering the haemoglobin concentration (isovolaemic haemodilution; Low [Hb]). QIPAVA , assessed by transthoracic saline contrast echocardiography, significantly increased as PaO2 decreased and, despite reduced CaO2 (via isovolaemic haemodilution), was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA , although where and how this is detected remains unknown. ABSTRACT: Alveolar hypoxia causes increased blood flow through intrapulmonary arteriovenous anastomoses (QIPAVA ) in healthy humans at rest. However, it is unknown whether the stimulus regulating hypoxia-induced QIPAVA is decreased arterial PO2 (PaO2) or O2 content (CaO2). CaO2 is known to regulate blood flow in the systemic circulation and it is suggested that IPAVA may be regulated similar to the systemic vasculature. Thus, we hypothesized that reduced CaO2 would be the stimulus for hypoxia-induced QIPAVA . Blood volume (BV) was measured using the optimized carbon monoxide rebreathing method in 10 individuals. Less than 5 days later, subjects breathed room air, as well as 18%, 14% and 12.5% O2 , for 30 min each, in a randomized order, before (CON) and after isovolaemic haemodilution (10% of BV withdrawn and replaced with an equal volume of 5% human serum albumin-saline mixture) to reduce [Hb] (Low [Hb]). PaO2 was measured at the end of each condition and QIPAVA was assessed using transthoracic saline contrast echocardiography. [Hb] was reduced from 14.2 ± 0.8 to 12.8 ± 0.7 g dl(-1) (10 ± 2% reduction) from CON to Low [Hb] conditions. PaO2 was no different between CON and Low [Hb], although CaO2 was 10.4%, 9.2% and 9.8% lower at 18%, 14% and 12.5% O2 , respectively. QIPAVA significantly increased as PaO2 decreased and, despite reduced CaO2, was similar at iso-PaO2. These data suggest that, with alveolar hypoxia, low PaO2 causes the hypoxia-induced increase in QIPAVA . Whether the low PO2 is detected at the carotid body, airway and/or the vasculature remains unknown.

Haemoglobin mass alterations in healthy humans following four-day head-down tilt bed rest.

NEW FINDINGS: What is the central question of this study? Is haemoglobin mass (Hbmass) decreased following 4 days of head-down tilt bed rest (HDTBR), and does increased red blood cell (RBC) destruction mediate this adaptation? What is the main finding and its importance? Haemoglobin mass was increased immediately following HDTBR, before decreasing below baseline 5 days after return to normal living conditions. The transient increase in Hbmass might be the result of decreased RBC destruction, but it is also possible that spleen contraction after HDTBR contributed to this adaptation. Our data suggest that the decreased Hbmass 5 days following HDTBR resulted from decreased RBC production, not increased RBC destruction. Rapid decreases in haemoglobin mass (Hbmass) have been reported in healthy humans following spaceflight and descent from high altitude. It has been proposed that a selective increase in the destruction of young red blood cells (RBCs) mediates these decreases, but conclusive evidence demonstrating neocytolysis in humans is lacking. Based on the proposed triggers and time course of adaptation during spaceflight, we hypothesized that Hbmass would be reduced after 4 days of -6 deg head-down tilt bed rest (HDTBR) and that this would be associated with evidence for increased RBC destruction. We assessed Hbmass in seven healthy, recreationally active men before (PRE), 5 h after (POST) and 5 days after (POST5) 4 days of HDTBR. The concentration of erythropoietin decreased from 7.1 ± 1.8 mIU ml(-1) at PRE to 5.2 ± 2.8 mIU ml(-1) at POST (mean ± SD; P = 0.028). Contrary to our hypothesis, Hbmass was increased from 817 ± 135 g at PRE to 849 ± 141 g at POST (P = 0.014) before decreasing below PRE to 789 ± 139 g at POST5 (P = 0.027). From PRE to POST, the concentration of haptoglobin increased from 0.54 ± 0.32 to 0.68 ± 0.28 g l(-1) (P = 0.013) and the concentration of bilirubin decreased from 0.50 ± 0.24 to 0.32 ± 0.11 mg dl(-1) (P = 0.054), suggesting that decreased RBC destruction might have contributed to the increased Hbmass. However, it is possible that spleen contraction following HDTBR also played a role in the increase in Hbmass at POST, but as the transient increase in Hbmass was unexpected, we did not collect data that would provide direct evidence for or against spleen contraction. From PRE to POST5, the concentration of soluble transferrin receptor decreased from 20.7 ± 3.9 to 17.1 ± 3.3 nmol l(-1) (P = 0.018) but the concentrations of ferritin, haptoglobin and bilirubin were not significantly altered, suggesting that the decrease in Hbmass was mediated by decreased RBC production rather than increased RBC destruction. Peak oxygen uptake decreased by 0.31 ± 0.16 l min(-1) from PRE to POST (P = 2 × 10(-4) ) but was not significantly altered at POST5 compared with PRE. Overall, these findings indicate that 4 days of HDTBR does not increase RBC destruction and that re-examination of the time course and mechanisms of Hbmass alterations following short-term spaceflight and simulated microgravity is warranted.

Pedelecs as a physically active transportation mode.

INTRODUCTION: Pedelecs are bicycles that provide electric assistance only when a rider is pedaling and have become increasingly popular. PURPOSE: Our purpose was to quantify usage patterns over 4 weeks of real-world commuting with a pedelec and to determine if pedelec use would improve cardiometabolic risk factors. METHODS: Twenty sedentary commuters visited the laboratory for baseline physiological measurements [body composition, maximum oxygen consumption ([Formula: see text]), mean arterial blood pressure (MAP), blood lipid profile, and 2-h oral glucose tolerance test (OGTT)]. The following 4 weeks, participants were instructed to commute using a pedelec at least 3 days week(-1) for 40 min day(-1) while wearing a heart rate monitor and a GPS device. Metabolic equivalents (METS) were estimated from heart rate data. Following the intervention, we repeated the physiological measurements. RESULTS: Average total distance and time were 317.9 ± 113.8 km and 15.9 ± 3.4 h, respectively. Participants averaged 4.9 ± 1.2 METS when riding. Four weeks of pedelec commuting significantly improved 2-h post-OGTT glucose (5.53 ± 1.18-5.03 ± 0.91 mmol L(-1), p < 0.05), [Formula: see text] (2.21 ± 0.48-2.39 ± 0.52 L min(-1), p < 0.05), and end of [Formula: see text] test power output (165.1 ± 37.1-189.3 ± 38.2 W, p < 0.05). There were trends for improvements in MAP (84.6 ± 10.5-83.2 ± 9.4 mmHg, p = 0.15) and fat mass (28.6 ± 11.3-28.2 ± 11.4 kg, p = 0.07). CONCLUSION: Participants rode a pedelec in the real world at a self-selected moderate intensity, which helped them meet physical activity recommendations. Pedelec commuting also resulted in significant improvements in 2-h post-OGTT glucose, [Formula: see text], and power output. Pedelecs are an effective form of active transportation that can improve some cardiometabolic risk factors within only 4 weeks.

Revisiting the Force-Joint Angle Relationship After Eccentric Exercise.

The purpose of this study was to evaluate force-angle curve fitting techniques pre-eccentric exercise, quantify changes in curve characteristics postexercise, and examine the relationship between curve changes and markers of muscle damage. Fourteen males unaccustomed to eccentric exercise performed 60 eccentric muscle actions of the elbow flexors. Maximal voluntary isometric force was measured throughout a range of angles pre- (Pre1 and Pre2), immediately post (IP), and 1, 2, 4, and 7 days postexercise. Force-angle curves for each visit were constructed using second-order polynomials. Changes in curve characteristics (optimal angle, peak force, curve height), range of motion, soreness, and creatine kinase activity were quantified. Optimal joint angle and force at optimal angle were significantly correlated from Pre1 to Pre2 (ICC = 0.821 and 0.979, respectively). Optimal angle was significantly right shifted (p = 0.035) by 10.4 ± 12.9° from Pre2 to IP and was restored by 1 day post exercise. Interestingly, the r value for curve fit was significantly decreased (p < 0.001) from Pre2 (r = 0.896) to IP (r = 0.802) and 1 day post exercise (r = 0.750). Curve height was significantly decreased (39%) IP and restored to pre-exercise height by 4 days postexercise. There was no correlation between optimal angle or curve height and other damage markers. In conclusion, force-angle relationships can be accurately described using second-order polynomials. After eccentric exercise, the force-angle curve is flattened and shifted (downward and rightward), but these changes are not correlated to other markers of muscle damage. Changes in the force-angle relationship are multifaceted, but determining the physiological significance of these changes requires further investigation.

Factors affecting the increased energy expenditure during passive cycling.

Short-duration passive cycling, during which a motor drives the pedals, elevates metabolic energy expenditure. Our purpose was to investigate the feasibility of passive cycling as a physical inactivity countermeasure by quantifying how the number of legs involved, cycling cadence, and habituation influence energy expenditure. Eleven non-cyclists participated. We compared one- and two-leg passive cycling at cadences of 60 and 90 RPM. To investigate if there are habituation effects, we conducted multiple 5-min trials and a prolonged 30-min passive cycling trial. The increase in energy expenditure above rest during passive cycling was significantly greater for two legs compared to one leg (39 vs. 16% at 60 RPM and 96 vs. 45% at 90 RPM). The increase in energy expenditure above rest was greater for 90 versus 60 RPM two-leg passive cycling (96 vs. 39%; p < 0.001). Repeated trials showed no evidence of habituation and the increase in energy expenditure was maintained for the duration of the 30-min trial. In conclusion, energy expenditure during passive cycling is directly related to the number of legs involved and cycling cadence. Two-leg passive cycling at 90 RPM resulted in energy expenditures similar to the walking workstation, suggesting its potential as a physical inactivity countermeasure.

Iron Status and Homeostasis Across 2 Competitive Seasons in NCAA Division I Collegiate Cross-Country Runners Residing at Low Altitude.

PURPOSE: Inflammatory cytokines including interleukin-6 can upregulate hepcidin and decrease iron absorption. Endurance exercise is associated with transient increases in cytokines, which may alter the risk of iron deficiency (ID). This study examined whether chronic elevations in basal levels of cytokines and hepcidin were associated with ID in highly trained runners. METHODS: Fifty-four collegiate runners (26 males and 28 females) living at ∼1625 m were recruited from an NCAA Division I cross-country team for this prospective cohort study. Over 2 seasons, fasted, preexercise blood draws were performed in the morning 4 times per season and were analyzed for hemoglobin concentration, ferritin, soluble transferrin receptor (sTfR), hepcidin, and 10 cytokines. Stages of ID were defined using ferritin, sTfR, and hemoglobin concentration. During the study, a registered dietician provided all runners with iron supplements using athletic department-created guidelines. RESULTS: Fifty-seven percent of females and 35% of males exhibited stage 2 ID (ferritin <20 ng/mL or sTfR >29.5 nmol/L) at least once. Cytokines, ferritin, and sTfR exhibited changes through the 2 years, but changes in cytokines were not associated with alterations in hepcidin, ferritin, or sTfR. In males and females, lower ferritin was associated with lower hepcidin (both P < .0001). One female exhibited higher hepcidin and lower iron stores compared with other individuals, suggesting a different etiology of ID. CONCLUSION: ID is common in highly trained collegiate runners. In general, the high prevalence of ID in this population is not associated with alterations in basal hepcidin or cytokine levels.

Matrix metalloproteinase-9 deficiency results in decreased fiber cross-sectional area and alters fiber type distribution in mouse hindlimb skeletal muscle.

Matrix metalloproteinases (MMPs) play a major role in the degradation of the extracellular matrix (ECM) of skeletal muscle, and the inducible gelatinase MMP-9 in particular appears to be critical for the remodeling of muscle ECM during growth and repair. Here we determined the effects of MMP-9 gene inactivation on fiber type and size in the tibialis anterior (TA), gastrocnemius (GAST), and soleus (SOL) muscles in female mice. In the TA, the cross-sectional area (CSA) of the myosin heavy chain (MyHC) IIb-expressing fibers was significantly smaller in MMP-9 null mice while in the GAST, CSA of all three fast fiber types was decreased. In the SOL, MyHC type I-expressing fibers were significantly smaller in the MMP-9 null mice. The percentage of MyHC type IIb-expressing fibers was significantly increased in the TA and GAST of MMP-9 null mice, while the percentage of MyHC IId-expressing fibers significantly decreased in the GAST of MMP-9 null mice. Fiber percentages in the SOL were not significantly different between the two lines. Despite these changes in fiber size and type, in vivo hindlimb force production was not changed in MMP-9 null mice. Meanwhile, neither expression of the constitutive gelatinase MMP-2 nor immunohistochemical staining for type IV collagen was significantly altered by MMP-9 inactivation in any muscles examined. The present study demonstrates that MMP-9 inactivation results in changes in fiber size and type in adult mouse hindlimb muscles that may depend on indirect mechanisms involving reduced bone growth or nerve changes in response to MMP-9 inactivation.

Influence of carbon monoxide leaks on the measurement error of total haemoglobin mass.

Total haemoglobin mass (Hb(mass)) can be assessed with low measurement error using carbon monoxide (CO) rebreathing. However, variability in measurement error of Hb(mass) has been reported across laboratories and it has previously been suggested that CO leaks contribute to this variability. As a result of employing a standardized leak monitoring procedure using two CO detectors, we were able to retrospectively examine the impact of CO leaks on Hb(mass) values from past test-retest studies in our laboratory using the optimized CO rebreathing method. Test-retest data were collected to determine measurement error, with subjects tested twice within 5 days. Test-retest data were placed into separate categories based on magnitude and duration of CO leak observed during one of the two tests. The No Leak category contained test-retest data in which no leak occurred during either test. The Minor Leak category contained test-retest data in which one of the tests had a CO leak of magnitude less than 30 ppm and less than 5 seconds duration, whereas the Major Leak category included test-retest data in which a leak greater than this magnitude or duration occurred. Measurement error was lowest in the No Leak category (1.9%; 95%CI: 1.6-2.3%; n = 56), approximately doubled in the Minor Leaks category (3.6%; 95%CI: 2.6-6.1%; n = 13), and dramatically increased in the Major Leaks category (9.3%; 95%CI: 6.3-17.6%; n = 10). We recommend careful monitoring of potential CO leaks using multiple detectors. To minimize measurement error, tests in which any CO leak is detected should be excluded.

Plasma matrix metalloproteinase-9 response to eccentric exercise of the elbow flexors.

Recent efforts to establish a role for plasma matrix metalloproteinase-9 (MMP-9) as a marker of exercise-induced muscle damage have been inconsistent. Methodological and experimental design issues have contributed to confusion in this area. The purpose of this study was to use a damaging eccentric arm task to evaluate the relationship between activity-induced muscle damage and plasma MMP-9 levels in humans while controlling for physical activity history and quantifying day-to-day variability of the dependent variables. Fourteen physically inactive males performed 6 sets of 10 eccentric contractions of the elbow flexors at 120% of their voluntary concentric maximum. Soreness ratings, maximum voluntary isometric strength, range of motion (ROM), limb circumference, and plasma creatine kinase (CK) and MMP-9 levels were measured at 2 time points before, immediately after, and 1, 2, 4, and 7 days post-exercise. Changes in traditional markers of muscle damage mirrored patterns previously reported in the literature, but plasma MMP-9 concentration and activity measured by ELISA and gelatin zymography were unchanged at all time points examined. Plasma levels of the MMP-9 inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), were also unchanged post-exercise. Finally, although mean MMP-9 levels were not significantly different between the two pre-exercise timepoints, the high total error of measurement and low day-to-day correlation suggest substantial within and between subject variability. Plasma MMP-9 levels are not a robust or reliable marker for eccentric exercise-induced damage of the elbow flexor musculature, though this may not preclude a role for MMPs in skeletal muscle remodeling in response to injury.

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 (HbmassBM) but only 7.5% higher Hbmass relative to lean mass (HbmassLEAN) (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. HbmassLEAN was 5% lower in ID vs. non-ID female subjects; HbmassBM 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 HbmassLEAN and hepcidin but not with differences in HbmassBM 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.

Chronic Exposure to Low-Dose Carbon Monoxide Alters Hemoglobin Mass and V˙O2max.

By blocking the oxygen binding sites on the hemoglobin molecule, chronic low-dose carbon monoxide (CO) administration may produce similar effects to those of exposure to altitude. PURPOSE: This study aimed to determine the effect of chronic low-dose CO application on hemoglobin mass (Hbmass) and V˙O2max. METHODS: For 3 wk, 11 healthy and moderately trained male subjects inhaled a CO bolus five times per day to increase their HbCO concentration by ~5%. Another 11 subjects received a placebo. Hbmass, serum erythropoietin concentration, ferritin, and basic hematological parameters were determined before and weekly during and until 3 wk after the CO inhalation period. V˙O2max tests on a cycle ergometer were performed before and after the CO administration period. RESULTS: In the CO group, Hbmass increased from 919 ± 69 to 962 ± 78 g in week 3 (P < 0.001) and was maintained for the following 3 wk. Reticulocytes (%) and immature reticulocyte fraction significantly increased after 1 wk. Serum erythropoietin concentration tended to increase after 1 wk (P = 0.07) and was suppressed in the postperiod (P < 0.01). Ferritin decreased during the inhalation period (from 106 ± 37 to 72 ± 37 ng·mL, P < 0.001). V˙O2max tended to increase from 4230 ± 280 to 4350 ± 350 mL·min (P < 0.1) immediately after the inhalation period and showed a significant relationship to the change in Hbmass (y = 4.1x - 73.4, r = 0.70, P < 0.001). CONCLUSIONS: Chronic continuous exposure to low-dose CO enhances erythropoietic processes resulting in a 4.8% increase in Hbmass. The individual changes in Hbmass were correlated to the corresponding changes in V˙O2max. Examination of ethical and safety concerns is warranted before the implementation of low-dose CO inhalation in the clinical/athletic setting as a tool for modifying Hbmass.

Cardiometabolic Effects of a Workplace Cycling Intervention.

BACKGROUND: In laboratory settings, cycling workstations improve cardiometabolic risk factors. Our purpose was to quantify risk factors following a cycling intervention in the workplace. METHODS: Twenty-one office workers who sat at work ≥6 hours per day underwent baseline physiological measurements (resting blood pressure, blood lipid profile, maximum oxygen consumption [V˙O2max], body composition, and 2-h oral glucose tolerance test). Participants were randomly assigned to a 4-week intervention only group (n = 12) or a delayed intervention group (n = 9) that involved a 4-week control condition before beginning the intervention. During the intervention, participants were instructed to use the cycling device a minimum of 15 minutes per hour, which would result in a total use of ≥2 hours per day during the workday. Following the intervention, physiological measurements were repeated. RESULTS: Participants averaged 1.77 (0.48) hours per day of cycling during the intervention with no changes in actigraphy-monitored noncycling physical activity. Four weeks of the workplace intervention increased V˙O2max (2.07 [0.44] to 2.17 [0.44] L·min-1, P < .01); end of V˙O2max test power output (166.3 [42.2] to 176.6 [46.1] W, P < .01); and high-density lipoprotein cholesterol (1.09 [0.17] to 1.17 [0.24] mmol·L-1, P = .04). CONCLUSIONS: A stationary cycling device incorporated into a sedentary workplace for 4 weeks improves some cardiometabolic risk factors with no compensatory decrease in noncycling physical activity.

Erythropoietic effects of low-dose cobalt application.

Cobaltous ions (Co2+ ) stabilize HIFα, increase endogenous erythropoietin (EPO) production, and may, therefore, be used as a performance-enhancing substance. To date, the dosage necessary to stimulate erythropoiesis is unknown. The aim of this study was, therefore, to determine the minimum dosage necessary to increase erythropoietic processes. In a first double-blind placebo-controlled study (n = 5), single oral Co2+ dosages of 5 mg (n = 6) and 10 mg (n = 7) were administered to healthy young men. Cubital venous blood and urine samples were collected before and up to 24 hours after Co2+ administration. In a second study, the same daily Co2+ dosages were administered for five days (placebo: n = 5, 5 mg: n = 9, 10 mg: n = 7). Blood and urine samples were taken the day before administration and at day 3 and day 5. Plasma [EPO] was elevated by 20.5 ± 16.9% at 5 hours after the single 5-mg administration (p < 0.05) and by 52.8 ± 23.5% up to 7 hours following the 10-mg Co2+ administration (p < 0.001). Urine [Co2+ ] transiently increased, with maximum values 3-5 hours after Co2+ ingestion (5 mg: from 0.8 ± 1.1 to 153.6 ± 109.4 ng/mL, 10 mg: from 1.3 ± 1.7 to 338.0 ± 231,5 ng/mL). During the five days of Co2+ application, 5 mg showed a strong tendency to increase [EPO], while the 10-mg application significantly increased [EPO] at day 5 by 27.2 ± 26.4% (p < 0.05) and the immature reticulocyte fraction by 49.9 ± 21.7% (p < 0.01). [Ferritin] was decreased by 12.4 ± 10.4 ng/mL (p < 0.05). An oral Co2+ dosage of 10 mg/day exerts clear erythropoietic effects, and 5 mg/day tended to increase plasma EPO concentration.

Calculating metabolic energy expenditure across a wide range of exercise intensities: the equation matters.

We compared 10 published equations for calculating energy expenditure from oxygen consumption and carbon dioxide production using data for 10 high-caliber male distance runners over a wide range of running velocities. We found up to a 5.2% difference in calculated metabolic rate between 2 widely used equations. We urge our fellow researchers abandon out-of-date equations with published acknowledgments of errors or inappropriate biochemical/physical assumptions.