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Cobalt is a heavy metal, that wasused between the 1940s and 1980s as a therapeutic agent to treat anemic diseases. Similar to hypoxia, cobalt stabilizes the HIFsubunits and stimulates the renal production of erythropoietin. For several decades, it has been suggested that cobalt is also used in sports to optimize oxygen transport via increased hemoglobin mass. In 2015, WADA put it in the list of banned substances. In various dietary supplements purporting to increase performance, cobalt was detected whilst incorrectly or not declared by the manufacturers. Our research suggests that an oral dose of 5mg/day exceeds the erythropoietic threshold. As a result, a 3-week supplementation period at this dose leads to an increase in Hb mass of 2% and to a tendency of higher performance, which corresponds to the effects of a training camp lasting200h at 2000m. About 10% of the administered cobalt is absorbed by the body and excreted in urine with a half-life of 4-12 hours. In order to detect doping with cobalt,a reference limit of 14ng/ml in urine has been suggested, which is 4 standard deviations higher than the normal urine cobalt concentration. This value is clearly exceeded during and until one week after a 3-week supplementation period at 5 mg/day. Since it is possible that athletes use higher amounts of cobalt for doping purposes in hopes of achieving greater gains in performance, WADA must set appropriate reference limits and introduce regular test procedures to avoid serious health risks to these athletes.KEY WORDS: Hemoglobin Mass, Performance, Erythropoietin, Nutritional Supplement, Blood Manipulation

Background: The World Anti-Doping Agency (WADA) did not publish the number of anti-doping rule violations (ADRVs) in sports before 2013, leading to a lack of information regarding ADRVs in certain countries and sporting disciplines. The present study aimed to provide an overview of the number and distribution of ADRVs among elite athletes of Olympic sports. Methods: A database of ADRVs was created for Olympic sports between 2000 and 2013based on an Internet search. The inclusion criterion was success of the athlete at the international level. The data were analyzed using descriptive statistics. Results: A total of 1,236 cases were found. The most frequent violations were the use of anabolic substances (>38%), followed by blood doping (15.3%) and stimulant use (14.2%). ADRVs were found in 120 countries; the countries that accounted for most cases were Russia (10.4%), the USA (6.8%), and Italy (4.9%). The most affected sports were track and field (29.4%), weightlifting (21.8%), and cycling (13.0%). Related to Olympic disciplines, however, weightlifting was by far in front. Numerous ADRVs were observed among Russian women athletes. The highest numbers of ADRVs in track and field were committed by athletes from Russia (n=53), the USA (n=37), and Jamaica (n=19). The prevalence of ADRVs among Russian track and field athletes was 4.1 times higher during Olympic versus non-Olympic years. Conclusion: Targeted and organized doping can be assumed to occur in certain disciplines and countries.Problemstellung: Bis zum Jahr 2013 wurde von der WADA die Anzahl der sanktionierten Dopingbefunde (anti-doping rule violations, ADRVs) nicht verffentlicht und es konnte somit keine Zuordnung zu bestimmten Lndern und hufig auch nicht zu bestimmten Sportarten erfolgen. Das Ziel der vorliegenden Studie war es, eine bersicht ber die Anzahl und Verteilung von ADRVs bei Weltklasse-Athleten in den olympischen Disziplinen zu erstellen.KEY WORDS: Anti-Doping Rule Violation, Olympic Disciplines, Athletics, Doping Prevalence, Russia

Elite rowers are highly endurance trained and present with a large lean body mass (LBM), which is closely related to total haemoglobin mass (tHbmass), a major determinant of blood O2 -transport. This study aims to determine the magnitude of tHbmass in elite rowers and its relation to performance parameters that are common in rowing worldwide. 13 rowers (3 lightweight) performed a 2 000 m test to evaluate maximal performance on the rowing ergometer (P2k) and an incremental test to evaluate power output at lactate 2 and 4 mmol/l (N = 15). tHbmass was measured by CO-rebreathing. tHbmass amounted to 1 285 ± 123 g (open weight) and 1 059 ± 48 g (lightweight). Coefficients of correlation between tHbmass and power output increased with intensity, being highest for P2k (r = 0.80). An increase of 100 g tHbmass is associated with an increase of 24 W in P2k between subjects. The ratio between tHbmass/ LBM amounted to approximately 16 g/kg. Absolute tHbmass in elite rowers of open weight class is very high. In relation to body mass or LBM, data is similar to other endurance athletes. The relation between P2k performance and tHbmass is very large. However, it is partly mediated by body composition. [ABSTRACT FROM AUTHOR]

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Aims: To investigate how a change in body position with light-intensity physical activity (PA) 'snacks' (LIPAS, alternate sitting and standing, walking or standing continuously) compared with uninterrupted prolonged sitting affects glucose metabolism and heart rate variability (HRV) parameters in young adults with overweight and obesity., Materials and Methods: We conducted a four-arm randomized controlled crossover trial. The following conditions were tested during an 8-h simulated workday: uninterrupted prolonged sitting (SIT), alternate sitting and standing (SIT-STAND; 2.5 h total), continuous standing (STAND), and continuous walking (1.0 mph; WALK). The primary outcome was to investigate how a change in body position (alternate sitting and standing, walking or standing continuously) compared with uninterrupted sitting affects mean 8-h glucose metabolism. Secondary outcomes included the effects on 2-h postprandial glucose concentrations, as well as on 8-h/24-h heart rate and HRV parameters, in the respective study arms. Capillary blood samples were drawn from an hyperemised earlobe in the fasted state and once every hour during each trial intervention by puncturing the earlobe with a lancet and collecting 20 μL of blood (Biosen S-Line Lab+; EKF diagnostics, Barleben, Germany). HRV was assessed for 24 h including the 8-h intervention phase, and a home phase by means of a Holter electrocardiogram. All participants received the same standardized non-relativised breakfast and lunch during the four trial visits., Results: Seventeen individuals (eight women, mean age 23.4 ± 3.3 years, body mass index 29.7 ± 3.8 kg/m 2 , glycated haemoglobin level 34.8 ± 3.1 mmol/mol [5.4 ± 0.3%], body fat 31.8 ± 8.2%) completed all four trial arms. Compared with SIT (89.4 ± 6.8 mg/dL), 8-h mean glucose was lower in all other conditions (p < 0.05) and this was statistically significant compared with WALK (86.3 ± 5.2 mg/dL; p = 0.034). Two-hour postprandial glucose after breakfast was approximately 7% lower for WALK compared with SIT (p = 0.002). Furthermore, significant time × condition effects on HRV parameters favouring light-intensity walking were observed (p < 0.001)., Conclusions: Replacement and interruption of prolonged sitting with light-intensity walking showed a significant blood glucose-lowering effect and improved HRV during an 8-h work environment in young adults with overweight and obesity., (© 2024 The Author(s). Diabetes, Obesity and Metabolism published by John Wiley & Sons Ltd.)

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 (t 0-120 ) 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 t 120 were found ( p > 0.05). In the ISO trial arm, PV was significantly increased at t 70 (+138 mL, p = 0.01), t 80 (+191 mL, p < 0.01), and t 110 (+182 mL, p = 0.01) when compared to t 0 . Moreover, PV in the ISO trial arm was significantly higher at t 70 ( p = 0.02), t 110 ( p = 0.04), and t 120 ( 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 t 70 and t 90 (+183 mL, p = 0.01) and between t 110 (+194 mL, p = 0.03) and t 120 (+186 mL, p < 0.01) when compared to t 0 . 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.

Physical activity and exercise have many beneficial effects on general and type 1 diabetes (T1D) specific health and are recommended for individuals with T1D. Despite these health benefits, many people with T1D still avoid exercise since glycemic management during physical activity poses substantial glycemic and psychological challenges - which hold particularly true for unannounced exercise when using an AID system. Automated insulin delivery (AID) systems have demonstrated their efficacy in improving overall glycemia and in managing announced exercise in numerous studies. They are proven to increase time in range (70-180 mg/dL) and can especially counteract nocturnal hypoglycemia, even when evening exercise was performed. AID-systems consist of a pump administering insulin as well as a CGM sensor (plus transmitter), both communicating with a control algorithm integrated into a device (insulin pump, mobile phone/smart watch). Nevertheless, without manual pre-exercise adaptions, these systems still face a significant challenge around physical activity. Automatically adapting to the rapidly changing insulin requirements during unannounced exercise and physical activity is still the Achilles' heel of current AID systems. There is an urgent need for improving current AID-systems to safely and automatically maintain glucose management without causing derailments - so that going forward, exercise announcements will not be necessary in the future. Therefore, this narrative literature review aimed to discuss technological strategies to how current AID-systems can be improved in the future and become more proficient in overcoming the hurdle of unannounced exercise. For this purpose, the current state-of-the-art therapy recommendations for AID and exercise as well as novel research approaches are presented along with potential future solutions - in order to rectify their deficiencies in the endeavor to achieve fully automated AID-systems even around unannounced exercise.

Aims: To investigate the seroconversion following first and second COVID-19 vaccination in people with type 1 and type 2 diabetes in relation to glycaemic control prior to vaccination and to analyse the response in comparison to individuals without diabetes., Materials and Methods: This prospective, multicentre cohort study analysed people with type 1 and type 2 diabetes and a glycated haemoglobin level ≤58 mmol/mol (7.5%) or >58 mmol/mol (7.5%), respectively, and healthy controls. Roche's Elecsys anti-SARS-CoV-2 S immunoassay targeting the receptor-binding domain was used to quantify anti-spike protein antibodies 7 to 14 days after the first and 14 to 21 days after the second vaccination., Results: A total of 86 healthy controls were enrolled in the study, as well as 161 participants with diabetes, of whom 150 (75 with type 1 diabetes and 75 with type 2 diabetes) were eligible for the analysis. After the first vaccination, only 52.7% of participants in the type 1 diabetes group and 48.0% of those in the type 2 diabetes group showed antibody levels above the cut-off for positivity. Antibody levels after the second vaccination were similar in participants with type 1 diabetes, participants with type 2 diabetes and healthy controls after adjusting for age, sex and multiple testing (P > 0.05). Age (r = -0.45, P < 0.001) and glomerular filtration rate (r = 0.28, P = 0.001) were significantly associated with antibody response., Conclusions: Anti-SARS-CoV-2 S receptor-binding domain antibody levels after the second vaccination were comparable in healthy controls and in participants with type 1 and type 2 diabetes, irrespective of glycaemic control. Age and renal function correlated significantly with the extent of antibody levels., (© 2022 The Authors. Diabetes, Obesity and Metabolism published by John Wiley & Sons Ltd.)

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 O 2 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]., Competing Interests: WS. is a managing partner of the company Blood tec GmbH, but he is unaware of any direct or indirect conflict of interest with the contents of this paper. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Schmidt, Wachsmuth, Jimenez and Soria.)

The aim of this study was to investigate the impact of glucose (Glu), fructose (Fru), glucose and fructose (GluFru) and sucralose on blood glucose response in healthy individuals. Fifteen healthy individuals (five females, age of 25.4 ± 2.5 years, BMI of 23.7 ± 1.7 kg/m 2 with a body mass (BM) of 76.3 ± 12.3 kg) participated in this double-blind randomized crossover placebo-controlled trial. Participants received a mixture of 300 mL of water with 1 g/kg BM of Glu, 1 g/kg BM of Fru, 0.5 g/kg BM of GluFru (each), and 0.2 g sucralose as a placebo. Peak BG values Glu were reached after 40 ± 13 min (peak BG: 141 ± 20 mg/dL), for Fru after 36 ± 22 min (peak BG: 98 ± 7 mg/dL), for GluFru after 29 ± 8 min (BG 128 ± 18 mg/dL), and sucralose after 34 ± 27 min (peak BG: 83 ± 5 mg/dL). Significant differences regarding the time until peak BG were found only between Glu and GluFru supplementation ( p = 0.02). Peak blood glucose levels were significantly lower following the ingestion of Fru compared to the supplementation of Glu and GluFru ( p < 0.0001) while Glu and GluFru supplementation showed no difference in peak values ( p = 0.23). All conditions led to a significantly higher peak BG value compared to sucralose ( p < 0.0001). Blood lactate increased in Glu ( p = 0.002), Fru and GluFru (both p < 0.0001), whereas sucralose did not increase compared to the baseline ( p = 0.051). Insulin levels were significantly higher in all conditions at peak compared to sucralose ( p < 0.0001). The findings of this study prove the feasibility of combined carbohydrate supplementations for many applications in diabetic or healthy exercise cohorts.

New Findings: What is the central question of this study? Is it necessary to modify the CO-rebreathing method to acquire reliable measurements of haemoglobin mass in patients with chronic mountain sickness? What is the main finding and its importance? The CO-rebreathing method must be modified because of the prolonged CO-mixing time in patients with chronic mountain sickness. After adaptation of the blood sampling method, reliable and valid results were attained. With this modification, it is possible to quantify the extent of polycythaemia and to distinguish between a haemoconcentration and an exclusive enhancement of erythrocyte volume., Abstract: Patients suffering from chronic mountain sickness (CMS) exhibit extremely high haemoglobin concentrations. Their haemoglobin mass (Hbmass), however, has rarely been investigated. The CO-rebreathing protocol for Hbmass determination in those patients might need to be modified because of restricted peripheral perfusion. The aim of this study was to evaluate the CO uptake and carboxyhaemoglobin-mixing time in the blood of CMS patients and to adapt the CO-rebreathing method for this group. Twenty-five male CMS patients living at elevations between 3600 and 4100 m above sea level were compared with ethnically matched healthy control subjects from identical elevations (n = 11) and near sea level (n = 9) and with a Caucasian group from sea level (n = 6). CO rebreathing was performed for 2 min, and blood samples were taken for the subsequent 30 min. After the method was modified, its reliability was evaluated in test-retest experiments (n = 28), and validity was investigated by measuring the Hbmass before and after the phlebotomy of 500 ml (n = 4). CO uptake was not affected by CMS. The carboxyhaemoglobin mixing was completed after 8 min in the Caucasian group but after 14 min in the groups living at altitude. When blood was sampled 14-20 min after inhalation, the typical error of the method was 1.6% (confidence limits 1.2-2.5%). After phlebotomy, Hbmass decreased from 1779 ± 123 to 1650 ± 129 g, and no difference was found between the measured and calculated Hbmass (1666 ± 122 g). When the time of blood sampling was adapted to accommodate a prolonged carboxyhaemoglobin-mixing time, the CO-rebreathing method became a reliable and valid tool to determine Hbmass in CMS patients., (© 2019 The Authors. Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

Cobaltous ions (Co 2+ ) 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 Co 2+ 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 Co 2+ administration. In a second study, the same daily Co 2+ 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 Co 2+ administration (p < 0.001). Urine [Co 2+ ] transiently increased, with maximum values 3-5 hours after Co 2+ 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 Co 2+ 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 Co 2+ dosage of 10 mg/day exerts clear erythropoietic effects, and 5 mg/day tended to increase plasma EPO concentration., (© 2018 John Wiley & Sons, Ltd.)

Introduction: Cobalt ions (Co 2+ ) stabilize HIFα and increase endogenous erythropoietin (EPO) production creating the possibility that Co 2+ 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 [Co 2+ ] 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 Co 2+ 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 Co 2+ 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 [Co 2+ ] 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 Co 2+ dosage of 5 mg/day for 3 weeks effectively increases Hbmass with a tendency to increase hemoglobin concentration ([Hb]) and hematocrit (Hct). Because urine Co 2+ concentration remains increased for 2 weeks after cessation, upper limit threshold values for monitoring CoSupp can be established.

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.

Gastrointestinal (GI) blood loss is a possible reason for anemia in athletes. To quantify the impact on endurance performance, we present data of a world-class rower who developed anemia due to GI blood loss but maintained his training volume. Eight months after recording four normal hematological values over 6 months, an anemic state was detected. Total hemoglobin mass (tHbmass) was reduced from 1267 g to 917 g (-28%) and [Hb] was reduced from 176 g/L to 122 g/L (-31%). Blood volume (BV) remained largely unchanged at 8162 mL and 8261 mL, respectively. VO2max was decreased from 5.8 L/min to 4.8 L/min (-17%), but remained ~0.4 L/min higher than calculated from tHbmass. Power at [lactate] 2 mmol/L (P2) and 4 mmol/L (P4) decreased by 12% and 14%, respectively. Ten months after detection of the anemic state, the athlete had recovered and tHbmass (9%) as well as VO2max (3%), P2 (7%) and P4 (5%) were higher than before anemia. GI blood loss was most likely caused by the intake of non steroidal anti-inflammatory drugs and/or a bleeding Meckel's diverticulum, the latter been diagnosed and surgically removed 3 years later after two rapid bleedings had occurred. Data demonstrate the impact of a tHbmass reduction leading to a substantial but mitigated decrease in submaximal performance and VO2max in an elite athlete. 10 months later, higher levels of tHbmass, VO2max, and endurance performance were observed. However, the underlying mechanisms for the apparent increase in tHbmass remain unclear.

Objectives: To examine the time course of wellness, fatigue and performance during an altitude training camp (La Paz, 3600 m) in two groups of either sea-level (Australian) or altitude (Bolivian) native young soccer players., Methods: Wellness and fatigue were assessed using questionnaires and resting heart rate (HR) and HR variability. Physical performance was assessed using HR responses to a submaximal run, a Yo-Yo Intermittent recovery test level 1 (Yo-YoIR1) and a 20 m sprint. Most measures were performed daily, with the exception of Yo-YoIR1 and 20 m sprints, which were performed near sea level and on days 3 and 10 at altitude., Results: Compared with near sea level, Australians had moderate-to-large impairments in wellness and Yo-YoIR1 relative to the Bolivians on arrival at altitude. The acclimatisation of most measures to altitude was substantially slower in Australians than Bolivians, with only Bolivians reaching near sea-level baseline high-intensity running by the end of the camp. Both teams had moderately impaired 20 m sprinting at the end of the camp. Exercise HR had large associations (r>0.5-0.7) with changes in Yo-YoIR1 in both groups., Conclusions: Despite partial physiological and perceptual acclimatisation, 2 weeks is insufficient for restoration of physical performance in young sea-level native soccer players. Because of the possible decrement in 20 m sprint time, a greater emphasis on speed training may be required during and after altitude training. The specific time course of restoration for each variable suggests that they measure different aspects of acclimatisation to 3600 m; they should therefore be used in combination to assess adaptation to altitude.

Background: We describe here the 3-year process underpinning a multinational collaboration to investigate soccer played at high altitude--La Paz, Bolivia (3600 m). There were two main aims: first, to quantify the extent to which running performance would be altered at 3600 m compared with near sea level; and second, to characterise the time course of acclimatisation of running performance and underlying physiology to training and playing at 3600 m. In addition, this project was able to measure the physiological changes and the effect on running performance of altitude-adapted soccer players from 3600 m playing at low altitude., Methods: A U20 Bolivian team ('The Strongest' from La Paz, n=19) played a series of five games against a U17 team from sea level in Australia (The Joeys, n=20). 2 games were played near sea level (Santa Cruz 430 m) over 5 days and then three games were played in La Paz over the next 12 days. Measures were (1) game and training running performance--including global positioning system (GPS) data on distance travelled and velocity of movement; (2) blood--including haemoglobin mass, blood volume, blood gases and acid-base status; (3) acclimatisation--including resting heart rate variability, perceived altitude sickness, as well as heart rate and perceived exertion responses to a submaximal running test; and (4) sleep patterns., Conclusions: Pivotal to the success of the project were the strong professional networks of the collaborators, with most exceeding 10 years, the links of several of the researchers to soccer federations, as well as the interest and support of the two head coaches.

Objectives: The optimal strategy for soccer teams playing at altitude is not known, that is, 'fly-in, fly-out' versus short-term acclimatisation. Here, we document changes in blood gas and vascular volumes of sea-level (Australian, n=20) and altitude (Bolivian, n=19) native soccer players at 3600 m., Methods: Haemoglobin-oxygen saturation (Hb-sO₂), arterial oxygen content (CaO₂), haemoglobin mass (Hbmass), blood volume (BV) and blood gas concentrations were measured before descent (Bolivians only), together with aerobic fitness (via Yo-YoIR1), near sea-level, after ascent and during 13 days at 3600 m., Results: At baseline, haemoglobin concentration [Hb] and Hbmass were higher in Bolivians (mean ± SD; 18.2 ± 1.0 g/dL, 12.8 ± 0.8 g/kg) than Australians (15.0 ± 0.9 g/dL, 11.6 ± 0.7 g/kg; both p ≤ 0.001). Near sea-level, [Hb] of Bolivians decreased to 16.6 ± 0.9 g/dL, but normalised upon return to 3600 m; Hbmass was constant regardless of altitude. In Australians, [Hb] increased after 12 days at 3600 m to 17.3 ± 1.0 g/dL; Hbmass increased by 3.0 ± 2.7% (p ≤ 0.01). BV decreased in both teams at altitude by ∼400 mL. Arterial partial pressure for oxygen (PaO₂), Hb-sO₂ and CaO₂ of both teams decreased within 2 h of arrival at 3600 m (p ≤ 0.001) but increased over the following days, with CaO₂ overcompensated in Australians (+1.7 ± 1.2 mL/100 mL; p ≤ 0.001). Yo-YoIR1 was lower on the 3rd versus 10th day at altitude and was significantly related to CaO₂., Conclusions: The marked drop in PaO₂ and CaO₂ observed after ascent does not support the 'fly-in, fly-out' approach for soccer teams to play immediately after arrival at altitude. Although short-term acclimatisation was sufficient for Australians to stabilise their CaO₂ (mostly due to loss of plasma volume), 12 days appears insufficient to reach chronic levels of adaption.

Objectives: We investigated the effect of high altitude on the match activity profile of elite youth high altitude and sea level residents., Methods: Twenty Sea Level (Australian) and 19 Altitude-resident (Bolivian) soccer players played five games, two near sea level (430 m) and three in La Paz (3600 m). Match activity profile was quantified via global positioning system with the peak 5 min period for distance ((D₅(peak)) and high velocity running (>4.17 m/s, HIVR₅(peak)); as well as the 5 min period immediately subsequent to the peak for both distance (D₅(sub)) and high-velocity running (HIVR₅(sub)) identified using a rolling 5 min epoch. The games at 3600 m were compared with the average of the two near sea-level games., Results: The total distance per minute was reduced by a small magnitude in the first match at altitude in both teams, without any change in low-velocity running. There were variable changes in HiVR, D₅(peak) and HiVR₅(peak) from match to match for each team. There were within-team reductions in D₅(peak) in each game at altitude compared with those at near sea level, and this reduction was greater by a small magnitude in Australians than Bolivians in game 4. The effect of altitude on HiVR₅(peak) was moderately lower in Australians compared with Bolivians in game 3. There was no clear difference in the effect of altitude on maximal accelerations between teams., Conclusions: High altitude reduces the distance covered by elite youth soccer players during matches. Neither 13 days of acclimatisation nor lifelong residence at high altitude protects against detrimental effects of altitude on match activity profile.

Background: Altitude training is used by elite athletes to improve sports performance, but it may also disrupt sleep. The aim of this study was to examine the effects of 2 weeks at high altitude on the sleep of young elite athletes., Methods: Participants (n=10) were members of the Australian under-17 soccer team on an 18-day (19-night) training camp in Bolivia, with six nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was monitored using polysomnography during a baseline night at 430 m and three nights at 3600 m (immediately after ascent, 1 week after ascent and 2 weeks after ascent). Data were analysed using effect size statistics., Results: All results are reported as comparisons with baseline. Rapid eye movement (REM) sleep was likely lower immediately upon ascent to altitude, possibly lower after 1 week and similar after 2 weeks. On all three nights at altitude, hypopneas and desaturations were almost certainly higher; oxygen saturation was almost certainly lower; and central apnoeas, respiratory arousals and periodic breathing were very likely higher. The effects on REM sleep were common to all but one participant, but the effects on breathing were specific to only half the participants., Conclusions: The immediate effects of terrestrial altitude of 3600 m are to reduce the amount of REM sleep obtained by young elite athletes, and to cause 50% of them to have impaired breathing during sleep. REM sleep returns to normal after 2 weeks at altitude, but impaired breathing does not improve.

Background: Altitude exposure causes acute sleep disruption in non-athletes, but little is known about its effects in elite athletes. The aim of this study was to examine the effects of altitude on two groups of elite athletes, that is, sea-level natives and high-altitude natives., Methods: Sea-level natives were members of the Australian under-17 soccer team (n=14). High-altitude natives were members of a Bolivian under-20 club team (n=12). Teams participated in an 18-day (19 nights) training camp in Bolivia, with 6 nights at near sea level in Santa Cruz (430 m) and 13 nights at high altitude in La Paz (3600 m). Sleep was assessed on every day/night using activity monitors., Results: The Australians' sleep was shorter, and of poorer quality, on the first night at altitude compared with sea level. Sleep quality returned to normal by the end of the first week at altitude, but sleep quantity had still not stabilised at its normal level after 2 weeks. The quantity and quality of sleep obtained by the Bolivians was similar, or greater, on all nights at altitude compared with sea level. The Australians tended to obtain more sleep than the Bolivians at sea level and altitude, but the quality of the Bolivians' sleep tended to be better than that of the Australians at altitude., Conclusions: Exposure to high altitude causes acute and chronic disruption to the sleep of elite athletes who are sea-level natives, but it does not affect the sleep of elite athletes who are high-altitude natives.

We compared changes in performance and total haemoglobin mass (tHb) of elite swimmers in the weeks following either Classic or Live High:Train Low (LHTL) altitude training. Twenty-six elite swimmers (15 male, 11 female, 21.4 ± 2.7 years; mean ± SD) were divided into two groups for 3 weeks of either Classic or LHTL altitude training. Swimming performances over 100 or 200 m were assessed before altitude, then 1, 7, 14 and 28 days after returning to sea-level. Total haemoglobin mass was measured twice before altitude, then 1 and 14 days after return to sea-level. Changes in swimming performance in the first week after Classic and LHTL were compared against those of Race Control (n = 11), a group of elite swimmers who did not complete altitude training. In addition, a season-long comparison of swimming performance between altitude and non-altitude groups was undertaken to compare the progression of performances over the course of a competitive season. Regardless of altitude training modality, swimming performances were substantially slower 1 day (Classic 1.4 ± 1.3% and LHTL 1.6 ± 1.6%; mean ± 90% confidence limits) and 7 days (0.9 ± 1.0% and 1.9 ± 1.1%) after altitude compared to Race Control. In both groups, performances 14 and 28 days after altitude were not different from pre-altitude. The season-long comparison indicated that no clear advantage was obtained by swimmers who completed altitude training. Both Classic and LHTL elicited ~4% increases in tHb. Although altitude training induced erythropoeisis, this physiological adaptation did not transfer directly into improved competitive performance in elite swimmers.

Unlabelled: Several East Africans are among the most successful runners worldwide. The physiological reasons underlying this superiority are, however, not yet known., Purpose: To evaluate the total hemoglobin mass (tHb-mass) and blood volume (BV) of Kenyan runners and their adaptation to near sea level., Methods: tHb-mass, BV, and VO2max were determined in 10 male Kenyan runners (10-km best time = 28:29 ± 00:27 min) residing at an altitude of 2090 m over the course of a 6-wk training camp at sea level. Their values were compared with those of elite German runners (10-km best time = 30:39 ± 00:24 min)., Results: Kenyans are characterized by significantly lower body mass (Kenyans = 57.2 ± 7.0 kg; Germans = 66.5 ± 6.3 kg) and body mass index (Kenyans = 18.5 ± 0.9; Germans = 20.4 ± 0.9). Relative tHb-mass (Kenyans = 14.2 ± 1.0 g·kg(-1); Germans = 14.0 ± 0.7 g·kg(-1)) and BV (Kenyans = 101.9 ± 4.5 mL·kg(-1); Germans = 99.6 ± 5.8 mL·kg(-1)) were similar in both groups but were decreased in Kenyans during the stay at near sea level (absolute tHb-mass from 813 ± 90 g·mL(-1) to 767 ± 90 g, P < 0.001; BV from 5828 ± 703 g·mL(-1) to 5513 ± 708 mL, P < 0.01). Relative VO2max was similar in both groups (Kenyans 71.5 ± 5.0 mL·kg(-1)·min(-1); Germans 70.7 ± 3.7 mL·kg(-1)·min(-1))., Conclusion: The oxygen transport of the blood cannot explain the superior endurance performance of Kenyan runners. Most measured parameters are in the same range as those of elite German runners, and tHb-mass even deteriorates after an adaptation to near sea level.