mRNA biomarkers sensitive and specific to micro-dose erythropoietin treatment at sea level and altitude

Recombinant human erythropoietin (rhEPO) is prohibited by the World Anti-Doping Agency. rhEPO abuse can be indirectly detected via the athlete biological passport (ABP). However, altitude exposure challenges interpretation of the ABP. This study investigated whether 5'-aminolevulinate synthase 2 (ALAS2) and carbonic anhydrase 1 (CA1) in capillary dried blood spots (DBSs) are sensitive and specific markers of rhEPO treatment at altitude. ALAS2 and CA1 expression was monitored in DBS collected weekly before, during, and after a 3-week period at sea level or altitude. Participants were randomly assigned to receive 20 IU kg bw-1 epoetin alpha (rhEPO) or placebo injections every second day for 3 weeks while staying at sea level (rhEPO, n = 25; placebo, n = 9) or altitude (rhEPO, n = 12; placebo, n = 27). ALAS2 and CA1 expression increased up to 300% and 200%, respectively, upon rhEPO treatment at sea-level and altitude (P-values <0.05). When a blinded investigator interpreted the results, ALAS2 and CA1 expression had a sensitivity of 92%. Altitude did not confound the interpretation. Altitude affected ALAS2 and CA1 expression less than actual ABP markers when compared between sea level and altitude results. An individual athlete passport-like approach simulation confirmed the biomarker potential of ALAS2 and CA1. ALAS2 and CA1 were sensitive and specific biomarkers of micro-dose rhEPO treatment at sea level and altitude. Altitude seemed less a confounding factor for these biomarkers, especially when they are combined. Thus, micro-dose rhEPO injections can be detected in a longitudinal blinded setting using mRNA biomarkers in DBS.

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.

Contemporary blood doping-Performance, mechanism, and detection

Blood doping is prohibited for athletes but has been a well-described practice within endurance sports throughout the years. With improved direct and indirect detection methods, the practice has allegedly moved towards micro-dosing, that is, reducing the blood doping regime amplitude. This narrative review evaluates whether blood doping, specifically recombinant human erythropoietin (rhEpo) treatment and blood transfusions are performance-enhancing, the responsible mechanism as well as detection possibilities with a special emphasis on micro-dosing. In general, studies evaluating micro-doses of blood doping are limited. However, in randomized, double-blinded, placebo-controlled trials, three studies find that infusing as little as 130 ml red blood cells or injecting 9 IU × kg bw-1 rhEpo three times per week for 4 weeks improve endurance performance ~4%-6%. The responsible mechanism for a performance-enhancing effect following rhEpo or blood transfusions appear to be increased O2 -carrying capacity, which is accompanied by an increased muscular O2 extraction and likely increased blood flow to the working muscles, enabling the ability to sustain a higher exercise intensity for a given period. Blood doping in micro-doses challenges indirect detection by the Athlete Biological Passport, albeit it can identify ~20%-60% of the individuals depending on the sample timing. However, novel biomarkers are emerging, and some may provide additive value for detection of micro blood doping such as the immature reticulocytes or the iron regulatory hormones hepcidin and erythroferrone. Future studies should attempt to validate these biomarkers for implementation in real-world anti-doping efforts and continue the biomarker discovery.

Changes in Immature Reticulocytes Aid the Indirect Detection of Microdose Recombinant Erythropoietin Use in Men and Women

PURPOSE

We investigated whether immature reticulocyte fraction (IRF) and the immature reticulocytes to red blood cells ratio (IR/RBC) are sensitive and specific biomarkers for microdose recombinant human erythropoietin (rHuEPO) and whether the inclusion of reticulocyte percentage (RET%) and the algorithm "abnormal blood profile score (ABPS)" increased the athlete biological passport (ABP) sensitivity compared with hemoglobin concentration ([Hb]) and the OFF-hr score ([Hb]-60 × √RET%).

METHODS

Forty-eight (♀ = 24, ♂ = 24) participants completed a 2-wk baseline period followed by a 4-wk intervention period with three weekly intravenous injections of 9 IU·kg -1 ·bw -1 epoetin β (♀ = 12, ♂ = 12) or saline (0.9% NaCl, ♀ = 12, ♂ = 12) and a 10-d follow-up. Blood samples were collected weekly during baseline and intervention as well as 3, 5, and 10 d after treatment.

RESULTS

The rHuEPO treatment increased [Hb] (time-treatment, P < 0.001), RET% (time-treatment, P < 0.001), IRF (time-treatment, P < 0.001) and IR/RBC (time-treatment, P < 0.001). IRF and IR/RBC were up to ~58% ( P < 0.001) and ~141% ( P < 0.001) higher compared with placebo, and calculated thresholds provided a peak sensitivity across timepoints of 58% and 54% with ~98% specificity, respectively. To achieve >99% specificity for IRF and IR/RBC, sensitivity was reduced to 46% and 50%, respectively. Across all timepoints, the addition of RET% and ABPS to the ABP increased sensitivity from 29% to 46%. Identification of true-positive outliers obtained via the ABP and IRF and IR/RBC increased sensitivity across all timepoints to 79%.

CONCLUSIONS

In summary, IRF, IR/RBC, RET% and ABPS are sensitive and specific biomarkers for microdose rHuEPO in both men and women and complement the ABP.

Moderate hypoxic exposure for 4 weeks reduces body fat percentage and increases fat-free mass in trained individuals: a randomized crossover study

PURPOSE

We evaluated whether or not changes in body composition following moderate hypoxic exposure for 4 weeks were different compared to sea level exposure.

METHODS

In a randomized crossover design, nine trained participants were exposed to 2320 m of altitude or sea level for 4 weeks, separated by > 3 months. Body fat percentage (BF%), fat mass (FM), and fat-free mass (FFM) were determined before and after each condition by dual X-ray absorptiometry (DXA) and weekly by a bioelectrical impedance scanner to determine changes with a high resolution. Training volume was quantified during both interventions.

RESULTS

Hypoxic exposure reduced (P < 0.01) BF% by 2 ± 1 percentage points and increased (P < 0.01) FFM by 2 ± 2% determined by DXA. A tending time × treatment effect existed for FM determined by DXA (P = 0.06), indicating a reduced FM in hypoxia by 8 ± 7% (P < 0.01). Regional body analysis revealed reduced (P < 0.01) BF% and FFM and an increased (P < 0.01) FFM in the truncus area. No changes were observed following sea level. Bioelectrical impedance determined that BF%, FM, and FFM did not reveal any differences between interventions. Urine specific gravity measured simultaneously as body composition was identical. Training volume was similar between interventions (509 ± 70 min/week vs. 432 ± 70 min/week, respectively).

CONCLUSIONS

Four weeks of altitude exposure reduced BF% and increased FFM in trained individuals as opposed to sea level exposure. The results also indicate that a decrease in FM is greater at altitude compared to sea level. Changes were specifically observed in the truncus area.

Glucocorticoids Accelerate Erythropoiesis in Healthy Humans-Should the Use in Sports Be Reevaluated?

PURPOSE

The World Anti-Doping Agency prohibits glucocorticoid administration in competition but not in periods out of competition. Glucocorticoid usage is controversial as it may improve performance, albeit debated. A hitherto undescribed but performance-relevant effect of glucocorticoids in healthy humans is accelerated erythropoiesis. We investigated whether a glucocorticoid injection accelerates erythropoiesis, increases total hemoglobin mass, and improves exercise performance.

METHODS

In a counterbalanced, randomized, double-blinded, placebo-controlled crossover design (3 months washout), 10 well-trained males (peak oxygen uptake, 60 ± 3 mL O 2 ·min -1 ·kg -1 ) were injected with 40 mg triamcinolone acetonide (glucocorticoid group) or saline (placebo group) in the gluteal muscles. Venous blood samples collected before and 7-10 h, 1, 3, 7, 14, and 21 d after treatment were analyzed for hemoglobin concentration and reticulocyte percentage. Hemoglobin mass and mean power output in a 450-kcal time trial were measured before as well as 1 and 3 wk after treatment.

RESULTS

A higher reticulocyte percentage was evident 3 d (19% ± 30%, P < 0.05) and 7 d (48% ± 38%, P < 0.001) after glucocorticoid administration, compared with placebo, whereas hemoglobin concentration was similar between groups. Additionally, hemoglobin mass was higher ( P < 0.05) 7 d (glucocorticoid, 886 ± 104 g; placebo, 872 ± 103 g) and 21 d (glucocorticoid, 879 ± 111 g; placebo, 866 ± 103 g) after glucocorticoid administration compared with placebo. Mean power output was similar between groups 7 d (glucocorticoid, 278 ± 64 W; placebo, 275 ± 62 W) and 21 d (glucocorticoid, 274 ± 62 W; placebo, 275 ± 60 W) after treatment.

CONCLUSIONS

Intramuscular injection of 40 mg triamcinolone acetonide accelerates erythropoiesis and increases hemoglobin mass but does not improve aerobic exercise performance in the present study. The results are important for sport physicians administering glucocorticoids and prompt a reconsideration of glucocorticoid usage in sport.

Stability and detectability of testosterone esters in dried blood spots after intramuscular injections

While misuse of testosterone esters is widespread in elite and recreational sports, direct detection of intact testosterone esters in doping control samples is hampered by the rapid hydrolysis by esterases present in the blood. With dried blood spot (DBS) as sample matrix, continued degradation of the esters is avoided due to inactivation of the hydrolase enzymes in dried blood. Here, we have developed the method further for detection of testosterone esters in DBS with focus on robustness and applicability in doping control. To demonstrate the method's feasibility, DBS samples from men receiving two intramuscular injections of Sustanon® 250 (n = 9) or placebo (n = 10) were collected, transported, and stored prior to analysis, to mimic a doping control scenario. The presented nanoLC-HRMS/MS method appeared reliable and suitable for direct detection of four testosterone esters (testosterone decanoate, isocaproate, phenylpropionate, and propionate) after extraction from DBS. Sustanon® was detected in all subjects for at least 5 days, with detection window up to 14 days for three of the esters. Evaluation of analyte stability showed that while storage at room temperature is tolerated well for a few days, testosterone esters are highly stable (>18 months) in DBS when stored in frozen conditions. Collectively, these findings demonstrate the applicability of DBS sampling in doping control for detection of steroid esters. The fast collection and reduced shipment costs of DBS compared with urine and standard blood samples, respectively, will allow more frequent and/or large-scale testing to increase detection and deterrence.

EpoR stimulates rapid cycling and larger red cells during mouse and human erythropoiesis

The erythroid terminal differentiation program couples sequential cell divisions with progressive reductions in cell size. The erythropoietin receptor (EpoR) is essential for erythroblast survival, but its other functions are not well characterized. Here we use Epor-/- mouse erythroblasts endowed with survival signaling to identify novel non-redundant EpoR functions. We find that, paradoxically, EpoR signaling increases red cell size while also increasing the number and speed of erythroblast cell cycles. EpoR-regulation of cell size is independent of established red cell size regulation by iron. High erythropoietin (Epo) increases red cell size in wild-type mice and in human volunteers. The increase in mean corpuscular volume (MCV) outlasts the duration of Epo treatment and is not the result of increased reticulocyte number. Our work shows that EpoR signaling alters the relationship between cycling and cell size. Further, diagnostic interpretations of increased MCV should now include high Epo levels and hypoxic stress.

Cerebral lactate uptake during exercise is driven by the increased arterial lactate concentration

Exercise facilitates cerebral lactate uptake, likely by increasing arterial lactate concentration and hence the diffusion gradient across the blood brain barrier. However, non-specific β-adrenergic blockade by propranolol has previously reduced the arterio-jugular venous lactate difference (AV_Lac) during exercise, suggesting β-adrenergic control of cerebral lactate uptake. Alternatively, we hypothesize that propranolol reduces cerebral lactate uptake by decreasing arterial lactate concentration. To test that hypothesis, we evaluated cerebral lactate uptake taking changes in arterial concentration into account. Nine healthy males performed incremental cycling exercise to exhaustion with and without intravenous propranolol (18.7 ± 1.9 mg). Lactate concentration was determined in arterial and internal jugular venous blood at the end of each workload. To take changes in arterial lactate into account we calculated the fractional extraction (FE_Lac) defined as AV_Lac divided by the arterial lactate concentration. Arterial lactate concentration was reduced by propranolol at any workload (p<0.05), reaching 14 ± 3 and 11 ± 3 mmol l^-1 during maximal exercise without and with propranolol, respectively. While AV_Lac and FE_Lac increased during exercise (both p<0.05), they were both unaffected by propranolol at any workload (p=0.68 and p=0.26) or for any given arterial lactate concentration (p=0.78 and p=0.22). These findings support that, while propranolol may reduce cerebral lactate uptake, this effect reflects the propranolol-induced reduction in arterial lactate concentration and not inhibition of a β-adrenergic mechanism within the brain. We hence conclude that cerebral lactate uptake during exercise is directly driven by the increasing arterial concentration with work rate.

Effects of altitude and recombinant human erythropoietin on iron metabolism: a randomized controlled trial

Current markers of iron deficiency (ID), such as ferritin and hemoglobin, have shortcomings, and hepcidin and erythroferrone (ERFE) could be of clinical relevance in relation to early assessment of ID. Here, we evaluate whether exposure to altitude-induced hypoxia (2,320 m) alone, or in combination with recombinant human erythropoietin (rHuEPO) treatment, affects hepcidin and ERFE levels before alterations in routine ID biomarkers and stress erythropoiesis manifest. Two interventions were completed, each comprising a 4-wk baseline, a 4-wk intervention at either sea level or altitude, and a 4-wk follow-up. Participants (n = 39) were randomly assigned to 20 IU·kg body wt^-1 rHuEPO or placebo injections every second day for 3 wk during the two intervention periods. Venous blood was collected weekly. Altitude increased ERFE (P ≤ 0.001) with no changes in hepcidin or routine iron biomarkers, making ERFE of clinical relevance as an early marker of moderate hypoxia. rHuEPO treatment at sea level induced a similar pattern of changes in ERFE (P < 0.05) and hepcidin levels (P < 0.05), demonstrating the impact of accelerated erythropoiesis and not of other hypoxia-induced mechanisms. Compared with altitude alone, concurrent rHuEPO treatment and altitude exposure induced additive changes in hepcidin (P < 0.05) and ERFE (P ≤ 0.001) parallel with increases in hematocrit (P < 0.001), demonstrating a relevant range of both hepcidin and ERFE. A poor but significant correlation between hepcidin and ERFE was found (R² = 0.13, P < 0.001). The findings demonstrate that hepcidin and ERFE are more rapid biomarkers of changes in iron demands than routine iron markers. Finally, ERFE and hepcidin may be sensitive markers in an antidoping context.

Immature reticulocytes are sensitive and specific to low-dose erythropoietin treatment at sea level and altitude

We investigated whether immature reticulocyte fraction (IRF) and immature reticulocytes to red blood cells ratio (IR/RBC) are sensitive biomarkers for low-dose recombinant human erythropoietin (rhEpo) treatment at sea level (SL) and moderate altitude (AL) and whether multi (FACS) or single (Sysmex-XN) fluorescence flow cytometry is superior for IRF and IR/RBC determination. Thirty-nine participants completed two interventions, each containing a 4-week baseline, a 4-week SL or AL (2,230 m) exposure, and a 4-week follow-up. During exposure, rhEpo (20 IU kg^-1 ) or placebo (PLA) was injected at SL (SL_rhEpo , n = 25, SL_PLA n = 9) and AL (AL_rhEpo , n = 12, AL_PLA n = 27) every second day for 3 weeks. Venous blood was collected weekly. Sysmex measurements revealed that IRF and IR/RBC were up to ~70% (P < 0.01) and ~190% (P < 0.001) higher in SL_rhEpo than SL_PLA during treatment and up to ~45% (P < 0.001) and ~55% (P < 0.01) lower post-treatment, respectively. Compared with AL_PLA , IRF and IR/RBC were up to ~20% (P < 0.05) and ~45% (P < 0.001) lower post-treatment in SL_rhEpo , respectively. In AL_rhEpo , IRF and IR/RBC were up to ~40% (P < 0.05) and ~110% (P < 0.001) higher during treatment and up to ~25% (P < 0.05) and ~40% (P < 0.05) lower post-treatment, respectively, compared with AL_PLA . Calculated thresholds provided ~90% sensitivity for both biomarkers at SL and 33% (IRF) and 66% (IR/RBC) at AL. Specificity was >99%. Single-fluorescence flow cytometry coefficient of variation was >twofold higher at baseline (P < 0.001) and provided larger or similar changes compared to multi-fluorescence, albeit with smaller precision. In conclusion, IRF and IR/RBC were sensitive and specific biomarkers for low-dose rhEpo misuse at SL and AL.

An Untargeted Urine Metabolomics Approach for Autologous Blood Transfusion Detection

PURPOSE

Autologous blood transfusion is performance enhancing and prohibited in sport but remains difficult to detect. This study explored the hypothesis that an untargeted urine metabolomics analysis can reveal one or more novel metabolites with high sensitivity and specificity for detection of autologous blood transfusion.

METHODS

In a randomized, double-blinded, placebo-controlled, crossover design, exercise-trained men (n = 12) donated 900 mL blood or were sham phlebotomized. After 4 wk, red blood cells or saline were reinfused. Urine samples were collected before phlebotomy and 2 h and 1, 2, 3, 5, and 10 d after reinfusion and analyzed by ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry. Models of unique metabolites reflecting autologous blood transfusion were attained by partial least-squares discriminant analysis.

RESULTS

The strongest model was obtained 2 h after reinfusion with a misclassification error of 6.3% and 98.8% specificity. However, combining only a few of the strongest metabolites selected by this model provided a sensitivity of 100% at days 1 and 2 and 66% at day 3 with 100% specificity. Metabolite identification revealed the presence of secondary di-2-ethylhexyl phtalate metabolites and putatively identified the presence of (iso)caproic acid glucuronide as the strongest candidate biomarker.

CONCLUSIONS

Untargeted urine metabolomics revealed several plasticizers as the strongest metabolic pattern for detection of autologous blood transfusion for up to 3 d. Importantly, no other metabolites in urine seem of value for antidoping purposes.

A 3-min All-out Upper-body Ergometer Test For Competitive Swimmers

We examined the application of a land-based swimming ergometer 3-min all-out test to determine physiological predictors of swimming performance. Fourteen young elite swimmers participated (males: n=6; females: n=8). The swimmers completed two 3-min upper-body all-out tests on a swimming ergometer. Additionally, the swimmers completed freestyle swim races ranging from 50 m to 1500 m. High test-retest reproducibility (r=0.98 and coefficient of variation values <7.5%) was evident for ergometer derived peak, mean and critical power. Very strong correlations (r>0.87, p<0.001) were obtained between the 200-, 400-, 800- and 1500-m swimming performances and derived critical speed. Moreover, correlations were found between peak force and peak power and 50-m performance, in addition to critical power and performance for all distances. The critical speed was the dominant predictor of 200- to 1500-m performances (r=0.84-0.99). In conclusion, the land-based 3-min all-out swimming ergometer test is reliable and valid in predicting swimming performance in competitive swimmers and evaluates important physiological components in swimmers independent of technical abilities.

The central blood volume as measured by thoracic electrical impedance and plasma proANP is not compromised by donation of 900 mL of blood in men

OBJECTIVES

To evaluate whether the donation of 900 mL of blood reduces the central blood volume (CBV) assessed by thoracic electrical impedance (TI) and plasma pro-atrial natriuretic peptide (proANP).

BACKGROUND

Donation of 450 mL of blood carries a 1% risk of a vasovagal reaction. Withdrawal of 900 mL of blood decreases cardiac output; however, the effect on CBV remains unknown.

METHODS/MATERIALS

A randomised, single-blinded, placebo-controlled, crossover design was used, where 21 healthy semi-recumbent men donated 2 × 450 mL blood or were sham-phlebotomised. Changes in CBV were estimated by proANP and TI at 1.5 (TI_1.5 ) and 100 (TI₁₀₀ ) kHz, reflecting extracellular volume and (regional) total body water, respectively, and the index value (IDX; 1/T_1.5 -1/TI₁₀₀ ) was used to estimate changes in intracellular (red cell) volume. Systolic, diastolic and mean arterial blood pressure; heart rate; stroke volume; cardiac output; and systemic vascular resistance were monitored. After completion of the study, 1000 mL of isotonic saline was infused.

RESULTS

Changes (mean% ± SD) in TI_1.5 , TI₁₀₀ and IDX were similar after 450 mL (-0.2 ± 1.6%, 0.0 ± 1.1%, -0.4 ± 10.1%) and 900 mL (0.1 ± 1.6%, 0.2 ± 1.5% and -2.0 ± 15.8%) of blood donation compared to after a sham donation of 450 mL (-0.9 ± 1.2%, -0.5 ± 1.5% and -0.1 ± 6.1%) and 900 mL (-1.2 ± 1.5%, -0.6 ± 1.3% and 0.5 ± 9.9%). In addition, changes in plasma proANP were similar after 450 and 900 mL of blood donation (-0.8 ± 6.7% and -7.6 ± 7.9%) as after sham donations (1.3 ± 7.3% and -4.5 ± 5.6%). Monitoring haemodynamic variables revealed that stroke volume decreased after the donation of 900 mL of blood (-12 ± 12 mL) compared to sham donations.

CONCLUSION

During a 900-mL blood loss in semi-recumbent men, CBV measured by TI and plasma proANP is not affected.

Distribution of concurrent training sessions does not impact endurance adaptation

OBJECTIVES

Optimized concurrent training regimes are warranted in physical training of military-, law enforcement- and rescue-personnel. This study investigated if four 15-min endurance training sessions weekly improve aerobic capacity and performance more than one 60-min endurance session weekly during the initial phase of a Basic Military Training program.

DESIGN

A randomized training intervention study with functional and physiological tests before and after the intervention.

METHODS

Military conscripts (n=290) were randomly allocated to three groups completing 9 weeks training. Weekly training consisted of four endurance and four strength training sessions lasting 15min each ('Micro-training': MIC); one strength and one endurance session lasting 60min each ('Classical-training': CLA) or two 60min sessions of standard military training ('Control-training': CON).

RESULTS

Both 12-min (∼7-10%) and shuttle run performance (∼35-42%) improved (P≤0.001) similarly in all groups. Likewise, functional 2-min maximal repetition exercise capacity increased (P≤0.05) similarly in all groups (Lunges ∼17-24 %; PushUp ∼10-20%; AbdominalFlexions∼21-23%). Peak oxygen uptake changes depended on group (P≤0.05) with increases (P≤0.01) in MIC (7±7%, n=23) and CON (12±18%, n=17) and no changes in CLA. Maximal m. vastus lateralis citrate synthase activity decreased 14±26% (P≤0.001, n=18) in CLA. Likewise, maximal m. vastus lateralis 3-hydroxyacyl-CoA dehydrogenase activity decreased 8±17% in MIC (n=28) and 14±24% in CLA (n=18).

CONCLUSIONS

Four 15-min endurance training sessions weekly improves running performance and strength-endurance similarly to one 60min session. Peak oxygen uptake only increases with more than one endurance session weekly and leg muscle oxidative capacity appears reduced after basic military training.

Hematological adaptations and detection of recombinant human erythropoietin combined with chronic hypoxia

This study evaluated whether recombinant human erythropoietin (rhEpo) treatment combined with chronic hypoxia provided an additive erythropoietic response and whether the athlete biological passport (ABP) sensitivity improved with hypoxia. Two interventions were completed, each containing 4 weeks baseline, 4 weeks exposure at sea level or 2,320 m of altitude, and 4 weeks follow-up. Participants were randomly assigned to 20 IU·kg bw^-1 rhEpo or placebo injections every second day for 3 weeks during the exposure period at sea level (rhEpo n = 25, placebo n = 9) or at altitude (rhEpo n = 12, placebo n = 27). Venous blood was analyzed weekly. Combining rhEpo and hypoxia induced larger changes compared with rhEpo or hypoxia alone for [Hb] (p < 0.001 and p > 0.05, respectively), reticulocyte percentage (p < 0.001), and OFF-hr score (p < 0.01 and p < 0.001, respectively). The most pronounced effect was observed for reticulocyte percentage with up to ~35% (p < 0.001) and ~45% (p < 0.001) higher levels compared with rhEpo or hypoxia only, respectively. The ABP sensitivity for the combined treatment was 54 and 35 percentage points higher for [Hb] (p < 0.05) and reticulocyte percentage (p < 0.05), respectively, but similar for OFF-hr score, compared with rhEpo at sea level. Across any time point, [Hb] and OFF-hr score combined identified 14 unique true-positive participants (56%) at sea level and 12 unique true-positive participants (100%) at altitude. However, a concurrent reduction in specificity existed at altitude. In conclusion, rhEpo treatment combined with hypoxic exposure provided an additive erythropoietic response compared with rhEpo or hypoxic exposure alone. Correspondingly, ABP was more sensitive to rhEpo at altitude than at sea level, but a compromised specificity existed with hypoxic exposure.

An Intramuscular Injection of Mixed Testosterone Esters Does Not Acutely Enhance Strength and Power in Recreationally Active Young Men

Purpose: Limited data are available on the acute performance-enhancing effects of single-dose administration of testosterone in healthy humans. Studies of testosterone administrations to healthy humans are rare due to the difficult nature and necessity of close clinical monitoring. However, our unique physiological experimental facilities combined with close endocrinological collaboration have allowed us to safely complete such a study. We tested the hypothesis that an intramuscular injection of 250 mg mixed testosterone esters (TEs) enhances physical performance in strength and power exercises acutely, measured 24 h after injection. Additionally, we investigated whether the basal serum testosterone concentration influences the performance in countermovement jump (CMJ), 30-s all out cycle sprint, and one-arm isometric elbow flexion.

Methods: In a randomized, double-blind, placebo-controlled design, 19 eugonadal men received either a TE (n = 9, 23 ± 1 years, 183 ± 7 cm, 83 ± 10 kg) or a PLA (n = 10, 25 ± 2 years, 186 ± 6 cm, 82 ± 14 kg) injection. Hormonal levels and the performance in CMJ, 30-s all out cycle sprint, and one-arm isometric elbow flexion were measured before and 24 h after injection.

Results: Firstly, an intramuscular injection of 250 mg mixed TEs did not enhance the vertical jump height in a CMJ test, peak power, mean power, and fatigue index in a 30-s all-out cycle sprint or rate of force development and maximal voluntary contraction in a one-arm isometric elbow flexion 24 h post-injection. Secondly, baseline testosterone levels appeared not to influence performance in strength and power exercises to a large extent in healthy, recreationally active young men.

Conclusion: A single intramuscular injection of 250 mg mixed TEs has no acute ergogenic effects on strength and power performance in recreationally active, young men. This novel information has implication for basic physiological understanding. Whether the same applies to an elite athlete population remains to be determined. If so, this would have implications for anti-doping efforts aiming to determine the most cost-efficient testing programs.

Reproducibility of the CO rebreathing technique with a lower CO dose and a shorter rebreathing duration at sea level and at 2320 m of altitude

Total hemoglobin mass (Hb_mass) is routinely assessed in studies by the carbon monoxide (CO) rebreathing. Its clinical application is often hindered due to the consequent rise in carboxyhemoglobin (%HbCO) and the concern of CO toxicity. We tested the reproducibility of the CO rebreathing with a CO dose of 0.5 mL/kg body mass (CO_0.5) compared to 1.5 mL/kg (CO_1.5) and when shortening the CO rebreathing protocol. Therefore, CO rebreathing was performed 1×/day in eight healthy individuals on four consecutive days. On each day, either CO_0.5 (CO_0.5-1 and CO_0.5-2) or CO_1.5 (CO_1.5-1 and CO_1.5-2) was administered. Venous blood samples to determine %HbCO and quantify Hb_mass were obtained prior to, and at 6 (T₆), 8 (T₈) and 10 min (T₁₀) of CO rebreathing. This protocol was tested at sea level and at 2320 m to investigate the altitude-related measurement error. At sea level, the mean difference (95% limits of agreement) in Hb_mass between CO_0.5-1 and CO_0.5-2 was 26 g (-26; 79 g) and between CO_1.5-1 and CO_1.5-2, it was 17 g (-18; 52 g)_. The respective typical error (TE) corresponded to 2.4% (CO_0.5) and 1.5% (CO_1.5), while it was 6.5% and 3.0% at 2320 m. With CO_0.5, shortening the CO rebreathing resulted in a TE for Hb_mass of 4.4% (T₈ vs. T₁₀) and 14.1% (T₆ vs T₁₀) and with CO_1.5, TE was 1.6% and 5.8%. In conclusion, the CO dose and rebreathing time for the CO rebreathing procedure can be decreased at the cost of a measurement error ranging from 1.5-14.1%.

Impact of low-volume concurrent strength training distribution on muscular adaptation

OBJECTIVES

Military-, rescue- and law-enforcement personnel require a high physical capacity including muscular strength. The present study hypothesized that 9 weeks of volume matched concurrent short frequent training sessions increases strength more efficiently than less frequent longer training sessions.

DESIGN

A randomized training intervention study with functional and physiological tests before and after the intervention.

METHODS

Military conscripts (n=290) were assigned to micro-training (four 15-min strength and four 15-min endurance bouts weekly); classical-training (one 60-min strength and one 60-min endurance training session weekly) or a control-group (two 60-min standard military physical training sessions weekly).

RESULTS

There were no group difference between micro-training and classical-training in measures of strength. Standing long jump remained similar while shotput performance was reduced (P≤0.001) in all three groups. Pull-up performance increased (P≤0.001) in micro-training (7.4±4.6 vs. 8.5±4.0 repetitions, n=59) and classical-training (5.7±4.1 vs. 7.1±4.2 repetitions, n=50). Knee extensor MVC increased (P≤0.01) in all groups (micro-training, n=30, 11.5±8.9%; classical-training, n=24, 8.3±11.5% and control, n=19, 7.5±11.8%) while elbow flexor and hand grip MVC remained similar. Micro-training increased (P≤0.05) type IIa percentage from 32.5±11.0% to 37.6±12.3% (n=20) and control-group increased (P≤0.01) type IIax from 4.4±3.0% to 11.6±7.9% (n=8). In control-group type I, fiber size increased (P≤0.05) from 5121±959μm to 6481±2084μm (n=5). Satellite cell content remained similar in all groups.

CONCLUSIONS

Weekly distribution of low-volume concurrent training completed as either eight 15-min bouts or two 60-min sessions of which 50% was strength training did not impact strength gains in a real-world setting.

Autologous Blood Transfusion Enhances Exercise Performance-Strength of the Evidence and Physiological Mechanisms

This review critically evaluates the magnitude of performance enhancement that can be expected from various autologous blood transfusion (ABT) procedures and the underlying physiological mechanisms. The review is based on a systematic search, and it was reported that 4 of 28 studies can be considered of very high quality, i.e. placebo-controlled, double-blind crossover studies. However, both high-quality studies and other studies have generally reported performance-enhancing effects of ABT on exercise intensities ranging from ~70 to 100% of absolute peak oxygen uptake (VO_2peak) with durations of 5–45 min, and the effect was also seen in well-trained athletes. A linear relationship exists between ABT volume and change in VO_2peak. The likely correlation between ABT volume and endurance performance was not evident in the few available studies, but reinfusion of as little as 135 mL packed red blood cells has been shown to increase time trial performance. Red blood cell reinfusion increases endurance performance by elevating arterial oxygen content (C_aO₂). The increased C_aO₂ is accompanied by reduced lactate concentrations at submaximal intensities as well as increased VO_2peak. Both effects improve endurance performance. Apparently, the magnitude of change in haemoglobin concentration ([Hb]) explains the increase in VO_2peak associated with ABT because blood volume and maximal cardiac output have remained constant in the majority of ABT studies. Thus, the arterial-venous O₂ difference during exercise must be increased after reinfusion, which is supported by experimental evidence. Additionally, it remains a possibility that ABT can enhance repeated sprint performance, but studies on this topic are lacking. The only available study did not reveal a performance-enhancing effect of reinfusion on 4 × 30 s sprinting. The reviewed studies are of importance for both the physiological understanding of how ABT interacts with exercise capacity and in relation to anti-doping efforts. From an anti-doping perspective, the literature review demonstrates the need for methods to detect even small ABT volumes.

Physiological determinants of elite mountain bike cross-country Olympic performance

Detailed physiological phenotyping was hypothesized to have predictive value for Olympic distance cross-country mountain bike (XCO-MTB) performance. Additionally, mean (MPO) and peak power output (PPO) in 4 × 30 s all-out sprinting separated by 1 min was hypothesized as a simple measure with predictive value for XCO-MTB performance. Parameters indicative of body composition, cardiovascular function, power and strength were determined and related to XCO-MTB national championship performance (n = 11). Multiple linear regression demonstrated 98% of the variance (P < 0.001) in XCO-MTB performance (t_XCO-MTB; [min]) is explained by maximal oxygen uptake relative to body mass (VO_2peak,rel; [ml/kg/min]), 30 s all-out fatigue resistance (FI; [%]) and with a minor contribution from quadriceps femoris maximal torque (T_max; [Nm]): t_XCO-MTB = -0.217× VO_2peak,rel.-0.201× FI+ 0.012× T_max+ 85.4. Parameters with no additional predictive value included hemoglobin mass, leg peak blood flow, femoral artery diameter, knee-extensor peak workload, jump height, quadriceps femoris maximal voluntary contraction force and rate of force development. Additionally, multiple linear regression demonstrated parameters obtained from 4x30s repeated sprinting explained 88% of XCO-MTB variance (P < 0.001) with t_XCO-MTB = -5.7× MPO+ 5.0× PPO+ 55.9. In conclusion, XCO-MTB performance is predictable from VO_2peak,rel and 30 s all-out fatigue resistance. Additionally, power variables from a repeated sprint test provides a cost-effective way of monitoring athletes XCO-MTB performance.

Skeletal muscle and performance adaptations to high-intensity training in elite male soccer players: speed endurance runs versus small-sided game training

Purpose

To examine the skeletal muscle and performance responses across two different exercise training modalities which are highly applied in soccer training.

Methods

Using an RCT design, 39 well-trained male soccer players were randomized into either a speed endurance training (SET; n = 21) or a small-sided game group (SSG; n = 18). Over 4 weeks, thrice weekly, SET performed 6–10 × 30-s all-out runs with 3-min recovery, while SSG completed 2 × 7–9-min small-sided games with 2-min recovery. Muscle biopsies were obtained from m. vastus lateralis pre and post intervention and were subsequently analysed for metabolic enzyme activity and muscle protein expression. Moreover, the Yo–Yo Intermittent Recovery level 2 test (Yo–Yo IR2) was performed.

Results

Muscle CS maximal activity increased (P < 0.05) by 18% in SET only, demonstrating larger (P < 0.05) improvement than SSG, while HAD activity increased (P < 0.05) by 24% in both groups. Na⁺–K⁺ ATPase α₁ subunit protein expression increased (P < 0.05) in SET and SSG (19 and 37%, respectively), while MCT4 protein expression rose (P < 0.05) by 30 and 61% in SET and SSG, respectively. SOD2 protein expression increased (P < 0.05) by 28 and 37% in SET and SSG, respectively, while GLUT-4 protein expression increased (P < 0.05) by 40% in SSG only. Finally, SET displayed 39% greater improvement (P < 0.05) in Yo–Yo IR2 performance than SSG.

Conclusion

Speed endurance training improved muscle oxidative capacity and exercise performance more pronouncedly than small-sided game training, but comparable responses were in muscle ion transporters and antioxidative capacity in well-trained male soccer players.

Reliable and sensitive physical testing of elite trapeze sailors

It was investigated whether a newly developed discipline-specific test for elite-level trapeze sailors is reliable and sensitive. Furthermore, the physical demands of trapeze sailing were examined. In part 1, 9 national team athletes were accustomed to a simulated sailing test, which subsequently was completed on 4 occasions to determine test reliability and sensitivity to manipulations in body weight. Rope-pulling mean power output (MPO), oxygen consumption (VO₂ ), heart rate (HR), and blood lactate values were acquired in all trials. In part 2, 6 sailors completed on-water racing with concurrent measurements of VO₂ , HR, and blood lactate. VO_2max was determined during an incremental treadmill running test. Typical error, minimal difference, and ICC for average MPO in the test were 1.3%, 1.7%, and 0.99%, respectively. Adding 4 kg of external body weight caused a decrease in average MPO (270 ± 45W vs 265 ± 45W, P < .05) and an increase in VO₂ (2.44 ± 0.23 L·min^-1 vs 2.55 ± 0.26 L·min^-1 , P < .01). VO₂ , HR, and blood lactate during on-water sailing were 54.5% ± 7.2% VO_2max , 75.1% ± 3.1% HR_max , and 5.8 ± 2.7 mmol·L^-1 , respectively. However, VO₂ and HR were substantially higher for periods of the race as peak values were 83.5% ± 11.4% and 89.9% ± 1.7% of max, respectively. In conclusion, the present test is reliable and sensitive, thus providing a sailing-specific alternative to traditional physical testing of elite trapeze sailors. Additionally, on-water racing requires moderate aerobic energy production, although oxygen consumption can approach maximal levels for short periods of time.

No Effect of β-alanine on Muscle Function and Kayak Performance

PURPOSE

If β-alanine supplementation counteracts muscular fatigue development or improves athletic performance was investigated.

METHODS

Elite kayak rowers (10 men and 7 women) were supplemented with either 80 mg·kg body mass·d of β-alanine or placebo for 8 wk. Muscular fatigue development was investigated by applying a 2-min elbow flexor maximal voluntary contraction (MVC). EMG was recorded continuously, and voluntary activation was determined 30, 60, 90, and 115 s into the 2-min MVC. In addition, performance was evaluated as 1000-m and 5 × 250-m kayak ergometer rowing.

RESULTS

Force reduction during the 2-min MVC was similar before and after supplementation with β-alanine (30.9% ± 10.3% vs 36.0% ± 14.1%) and placebo (35.5% ± 7.7% vs 35.1% ± 8.0%). No time effect was apparent in voluntary activation during the 2-min MVC. In addition, there was no detectable effect of β-alanine supplementation on 1000-m kayak ergometer performance (β-alanine: 0.26% ± 0.02% vs placebo: -0.18% ± 0.02%) or accumulated 5 × 250-m time (β-alanine: -1.0% ± 0.3% vs placebo: -1.0% ± 0.2%). In 5 × 250 m, mean power output was reduced to a similar extent from first to fifth interval before and after supplementation with β-alanine (23% ± 11% vs 22% ± 10%) and placebo (26% ± 13% vs 20% ± 5%).

CONCLUSIONS

Two-minute MVC characteristics are unaffected by β-alanine supplementation in elite kayakers, and likewise, both a 1000-m kayak ergometer time trial lasting 4-5 min and a 5 × 250-m repeated sprint ability were unaltered by supplementation.

Validity of physical activity and cardiorespiratory fitness in the Danish cohort "Diet, Cancer and Health-Next Generations"

Valid assessments of physical activity (PA) and cardiorespiratory fitness (CRF) are essential in epidemiological studies to define dose-response relationship for formulating thorough recommendations of an appropriate pattern of PA to maintain good health. The aim of this study was to validate the Danish step test, the physical activity questionnaire Active-Q, and self-rated fitness against directly measured maximal oxygen uptake (VO₂ max). A population-based subsample (n=125) was included from the "Diet, Cancer and Health-Next Generations" (DCH-NG) cohort which is under establishment. Validity coefficients, which express the correlation between measured and "true" exposure, were calculated, and misclassification across categories was evaluated. The validity of the Danish step test was moderate (women: r=.66, and men: r=.56); however, men were systematically underestimated (43% misclassification). When validating the questionnaire-derived measures of PA, leisure-time physical activity was not correlated with VO₂ max. Positive correlations were found for sports overall, but these were only significant for men: total hours per week of sports (r=.26), MET-hours per week of sports (r=.28) and vigorous sports (0.28) alone were positively correlated with VO₂ max. Finally, the percentage of misclassification was low for self-rated fitness (women: 9% and men: 13%). Thus, self-rated fitness was found to be a superior method to the Danish step test, as well as being less cost prohibitive and more practical than the VO₂ max method. Finally, even if correlations were low, they support the potential for questionnaire outcomes, particularly sports, vigorous sports, and self-rated fitness to be used to estimate CRF.

Hiking strap force decreases during sustained upwind sailing

The hypothesis, that sailing upwind in wind speeds above 12 knots causes fatigue, which manifests as a reduction in exerted hiking strap force and/or maximal isometric voluntary contraction force (MVC) of the knee extensors, was evaluated. Additionally, it was investigated if a relationship exists between maximal exerted hiking force (hMVC) and sailing performance. In part 1 of the study, 12 national level athletes sailed upwind for 2 × 10 min while hiking strap forces were continuously acquired. Before, in between and after sailing periods, the MVC of the knee extensors was measured. In part 2 of the study, hMVC was measured dry land in a hiking bench and correlated with the overall results at a national championship. Hiking strap force decreased from the first to the last minute in both 10 min sailing periods (430 ± 131 vs. 285 ± 130 N, P < .001 and 369 ± 74 vs. 267 ± 97 N, P < .001, respectively), but MVC was similar before, between and after the two 10 min sailing periods (878 ± 215 vs. 852 ± 202 vs. 844 ± 211 130 N). In part 2, a significant positive correlation (r² = 0.619, P < .01) was observed between hMVC and regatta results. In conclusion, upwind sailing in wind speeds above 12 knots causes sailing-specific fatigue as evidenced by a marked reduction in exerted hiking strap force. However, MVC of the knee extensors was not compromised ∼45 s after hiking was terminated. Additionally, sailing performance is related to maximal hiking force.

Use of nutritional supplements by Danish elite athletes and fitness customers

The nutritional supplement (NS) industry is one of the fastest growing in the world, and NS use in Denmark is among the highest in Europe. However, the exact use in elite athletes and fitness customers targeted for doping control is unknown. Information from 634 doping control forms obtained in 2014 was evaluated (elite athletes: n = 361; fitness customers: n = 273). The majority of female (92.6%) and male (85.0%) elite athletes and female (100.0%) and male (94.0%) fitness customers declared using one or more NS. The use of non-ergogenic NS was more prevalent in women than in men and in younger (15-34 years) compared with older (35-49 years) subjects, but it was less prevalent in intermittent compared with endurance and power/strength sports. Additionally, fitness customers who tested positive for doping also reported using more NS than subjects testing negative, indicating an association between NS and doping abuse. The present results demonstrate a very high prevalence of NS usage in both elite athletes and fitness customers. This highlights the importance of a strong national regulation of NS to avoid contamination of NS with doping substances.

Acute hyperhydration reduces athlete biological passport OFF-hr score

Anecdotal evidence suggests that athletes hyperhydrate to mask prohibited substances in urine and potentially counteract suspicious fluctuations in blood parameters in the athlete biological passport (ABP). It is examined if acute hyperhydration changes parameters included in the ABP. Twenty subjects received recombinant human erythropoietin (rhEPO) for 3 weeks. After 10 days of rhEPO washout, 10 subjects ingested normal amount of water (∼ 270 mL), whereas the remaining 10 ingested a 1000 mL bolus of water. Blood variables were measured 20, 40, 60, and 80 min after ingestion. Three days later, the subjects were crossed-over with regard to water ingestion and the procedure was repeated. OFF-hr was reduced by ∼ 4%, ∼ 3%, and ∼ 2% at 40, 60, and 80 min, respectively, after drinking 1000 mL of water, compared with normal water ingestion (P < 0.05). Forty percent of the subjects were identified with atypical blood profiles (99% specificity level) before drinking 1000 mL of water, whereas 11% (n = 18), 10% and 11% (n = 18) were identified 40, 60, and 80 min, respectively, after ingestion. This was different (P < 0.05) compared with normal water intake, where 45% of the subjects were identified before ingestion, and 54% (n = 19), 45%, and 47% (n = 19) were identified 40, 60, and 80 min, respectively, after ingestion. In conclusion, acute hyperhydration reduces ABP OFF-hr and reduces ABP sensitivity.

High-intensity intermittent swimming improves cardiovascular health status for women with mild hypertension

To test the hypothesis that high-intensity swim training improves cardiovascular health status in sedentary premenopausal women with mild hypertension, sixty-two women were randomized into high-intensity (n = 21; HIT), moderate-intensity (n = 21; MOD), and control groups (n = 20; CON). HIT performed 6-10 × 30 s all-out swimming interspersed by 2 min recovery and MOD swam continuously for 1 h at moderate intensity for a 15-week period completing in total 44 ± 1 and 43 ± 1 sessions, respectively. In CON, all measured variables were similar before and after the intervention period. Systolic BP decreased (P < 0.05) by 6 ± 1 and 4 ± 1 mmHg in HIT and MOD; respectively. Resting heart rate declined (P < 0.05) by 5 ± 1 bpm both in HIT and MOD, fat mass decreased (P < 0.05) by 1.1 ± 0.2 and 2.2 ± 0.3 kg, respectively, while the blood lipid profile was unaltered. In HIT and MOD, performance improved (P < 0.05) for a maximal 10 min swim (13 ± 3% and 22 ± 3%), interval swimming (23 ± 3% and 8 ± 3%), and Yo-Yo IE1 running performance (58 ± 5% and 45 ± 4%). In conclusion, high-intensity intermittent swimming is an effective training strategy to improve cardiovascular health and physical performance in sedentary women with mild hypertension. Adaptations are similar with high- and moderate-intensity training, despite markedly less total time spent and distance covered in the high-intensity group.

Oral quercetin supplementation hampers skeletal muscle adaptations in response to exercise training

We aimed to test exercise-induced adaptations on skeletal muscle when quercetin is supplemented. Four groups of rats were tested: quercetin sedentary, quercetin exercised, placebo sedentary, and placebo exercised. Treadmill exercise training took place 5 days a week for 6 weeks. Quercetin groups were supplemented with quercetin, via gavage, on alternate days throughout the experimental period. Sirtuin 1 (SIRT1), peroxisome proliferator-activated receptor γ coactivator-1α mRNA levels, mitochondrial DNA (mtDNA) content, and citrate synthase (CS) activity were measured on quadriceps muscle. Redox status was also quantified by measuring muscle antioxidant enzymatic activity and oxidative damage product, such as protein carbonyl content (PCC). Quercetin supplementation increased oxidative damage in both exercised and sedentary rats by inducing higher amounts of PCC (P < 0.001). Quercetin supplementation caused higher catalase (P < 0.001) and superoxide dismutase (P < 0.05) activity in the non-exercised animals, but not when quercetin is supplemented during exercise. Quercetin supplementation increased SIRT1 expression, but when quercetin is supplemented during exercise, this effect is abolished (P < 0.001). The combination of exercise and quercetin supplementation caused lower (P < 0.05) mtDNA content and CS activity when compared with exercise alone. Quercetin supplementation during exercise provides a disadvantage to exercise-induced muscle adaptations.

Thigh oxygen uptake at the onset of intense exercise is not affected by a reduction in oxygen delivery caused by hypoxia

In response to hypoxic breathing most studies report slower pulmonary oxygen uptake (V̇o2) kinetics at the onset of exercise, but it is not known if this relates to an actual slowing of the V̇o2 in the active muscles. The aim of the present study was to evaluate whether thigh V̇o2 is slowed at the onset of intense exercise during acute exposure to hypoxia. Six healthy male subjects (25.8 ± 1.4 yr, 79.8 ± 4.0 kg, means ± SE) performed intense (100 ± 6 watts) two-legged knee-extensor exercise for 2 min in normoxia (NOR) and hypoxia [fractional inspired oxygen concentration (FiO2) = 0.13; HYP]. Thigh V̇o2 was measured by frequent arterial and venous blood sampling and blood flow measurements. In arterial blood, oxygen content was reduced ( P < 0.05) from 191 ± 5 ml O2/l in NOR to 180 ± 5 ml O2/l in HYP, and oxygen pressure was reduced ( P < 0.001) from 111 ± 4 mmHg in NOR to 63 ± 4 mmHg in HYP. Thigh blood flow was the same in NOR and HYP, and thigh oxygen delivery was consequently reduced ( P < 0.05) in HYP, but femoral arterial-venous oxygen difference and thigh V̇o2 were similar in NOR and HYP. In addition, muscle lactate release was the same in NOR and HYP, and muscle lactate accumulation during the first 25 s of exercise determined from muscle biopsy sampling was also similar (0.35 ± 0.07 and 0.36 ± 0.07 mmol·kg dry wt−1·s−1 in NOR and HYP). Thus the increase in thigh V̇o2 was not attenuated at the onset of intense knee-extensor exercise despite a reduction in oxygen delivery and pressure.

Four weeks of normobaric "live high-train low" do not alter muscular or systemic capacity for maintaining pH and K⁺ homeostasis during intense exercise

It was investigated if athletes subjected to 4 wk of living in normobaric hypoxia (3,000 m; 16 h/day) while training at 800-1,300 m ["live high-train low" (LHTL)] increase muscular and systemic capacity for maintaining pH and K(+) homeostasis as well as intense exercise performance. The design was double-blind and placebo controlled. Mean power during 30-s all-out cycling was similar before and immediately after LHTL (650 ± 31 vs. 628 ± 32 W; n = 10) and placebo exposure (658 ± 22 vs. 660 ± 23 W; n = 6). Supporting the performance data, arterial plasma pH, lactate, and K(+) during submaximal and maximal exercise were also unaffected by the intervention in both groups. In addition, muscle buffer capacity (in mmol H(+)·kg dry wt(-1)·pH(-1)) was similar before and after in both the LHTL (140 ± 12 vs. 140 ± 16) and placebo group (145 ± 2 vs. 140 ± 3). The expression of sarcolemmal H(+) transporters (Na(+)/H(+) exchanger 1, monocarboxylate transporters 1 and 4), as well as expression of Na(+)-K(+) pump subunits-α(1), -α(2), and -β(1) was also similar before and after the intervention. In conclusion, muscular and systemic capacity for maintaining pH and K(+) balance during exercise is similar before and after 4 wk of placebo-controlled normobaric LHTL. In accordance, 30-s all-out sprint ability was similar before and after LHTL.

Determinants of time trial performance and maximal incremental exercise in highly trained endurance athletes

Human endurance performance can be predicted from maximal oxygen consumption (Vo(2max)), lactate threshold, and exercise efficiency. These physiological parameters, however, are not wholly exclusive from one another, and their interplay is complex. Accordingly, we sought to identify more specific measurements explaining the range of performance among athletes. Out of 150 separate variables we identified 10 principal factors responsible for hematological, cardiovascular, respiratory, musculoskeletal, and neurological variation in 16 highly trained cyclists. These principal factors were then correlated with a 26-km time trial and test of maximal incremental power output. Average power output during the 26-km time trial was attributed to, in order of importance, oxidative phosphorylation capacity of the vastus lateralis muscle (P = 0.0005), steady-state submaximal blood lactate concentrations (P = 0.0017), and maximal leg oxygenation (sO(2LEG)) (P = 0.0295), accounting for 78% of the variation in time trial performance. Variability in maximal power output, on the other hand, was attributed to total body hemoglobin mass (Hb(mass); P = 0.0038), Vo(2max) (P = 0.0213), and sO(2LEG) (P = 0.0463). In conclusion, 1) skeletal muscle oxidative capacity is the primary predictor of time trial performance in highly trained cyclists; 2) the strongest predictor for maximal incremental power output is Hb(mass); and 3) overall exercise performance (time trial performance + maximal incremental power output) correlates most strongly to measures regarding the capability for oxygen transport, high Vo(2max) and Hb(mass), in addition to measures of oxygen utilization, maximal oxidative phosphorylation, and electron transport system capacities in the skeletal muscle.

Relative workload determines exercise-induced increases in PGC-1alpha mRNA

INTRODUCTION

The hypothesis that brief intermittent exercise-induced increases in human skeletal muscle metabolic mRNA is dependent on relative workload was investigated.

METHODS

Trained (n = 10) and untrained (n = 8) subjects performed exhaustive intermittent cycling exercise (4 x 4 min at 85% of VO(2peak), interspersed by 3 min). Trained subjects also performed the intermittent exercise at the same absolute workload as the untrained subjects, corresponding to 70% of VO(2peak) (n = 6).

RESULTS

Exercise at 85% of V(O2peak) elevated (P < 0.001) venous plasma lactate to 10.1 +/- 0.4 and 10.8 +/- 0.5 mM in the trained and untrained subjects, respectively. Peroxisome proliferator-activated receptor gamma coactivator 1alpha (PGC-1alpha) mRNA expression was increased (P < 0.001) approximately four- to fivefold for several hours after exercise in both groups. After exercise at 70% of VO(2peak), venous plasma lactate was less (P < 0.001) elevated (3.1 +/- 0.7 mM) and PGC-1alpha mRNA content was less (P < 0.05) increased (approximately threefold) than after exercise at 85% of VO(2peak). Likewise, pyruvate dehydrogenase kinase 4 and hexokinase II mRNA expressions were increased (P < 0.05) only after exercise performed at 85% of VO(2peak) in the trained subjects. Hypoxia-inducible factor 2alpha mRNA only increased (P < 0.05) 3 h into recovery in trained subjects, with no difference between the 70% and 85% of VO(2peak) trial. No change in hypoxia-inducible factor 1alpha, phosphofructokinase, citrate synthase, or lactate dehydrogenase, heart and muscle isoforms, mRNA expressions was detected after any of the exercise trials.

CONCLUSIONS

The relative intensity of brief intermittent exercise is of major importance for the exercise-induced increase of several mRNA, including PGC-1alpha.