Corrected whole blood biomarkers - the equation of Dill and Costill revisited

Acute natural killer cells response to a continuous moderate intensity and a work-matched high intensity interval exercise session in metastatic cancer patients treated with chemotherapy

Background

It has been suggested that the acute natural killer (NK) cell response to aerobic exercise might contribute to the tumor suppressor effect of regular exercise observed in preclinical studies. Moreover, because this response is modulated by exercise intensity, high-intensity intervals exercise (HIIE) might represent an interesting therapeutic approach in cancer patients. However, this immune response remains unstudied in cancer patients currently undergoing chemotherapy.

Objective

To characterize the acute NK cell response following a moderate-intensity continuous aerobic exercise session (MOD), and a HIIE session in metastatic cancer patients treated with chemotherapy.

Methods

Twelve cancer patients (45-65 years old) underwent a MOD and a duration and work-matched HIIE trial, in a block-randomized order. Peripheral blood mononuclear cells (PBMC) were isolated before, after and 1h after each trial. NK cell subsets were enumerated using flow cytometry and complete blood counts. The surface expression of the cytotoxic NK cell (cNK; CD56dimCD16+) subset was evaluated for its expression of the differentiation markers CD57 and CD158a, the activating receptor NKG2D, the immune checkpoints TIM-3 and PD-1, and the chemokine receptors CXCR3, CXCR4 and CCR2.

Results

cNK cell blood counts increased immediately following MOD (p < 0.001) and decreased back to pre-exercise values 1 h after exercise cessation (p < 0.001). The most responsive cNK cell subsets were expressing CD57, CD158a, NKG2D, TIM-3 and CXCR3. The HIIE trial elicited a similar biphasic response, without any difference between trials (all p ≥ 0.38). However, significant changes in the MFI values of CXCR4 and NKG2D were observed in the cNK cell subset following HIIE (all p ≤ 0.038), but not MOD.

Conclusion

In metastatic cancer patients undergoing chemotherapy, both MOD and HIIE can elicit an acute mobilisation and egress of NK cells exhibiting phenotypic characteristics associated with high cytotoxicity and tumor homing. Future longitudinal trials are needed to determine if combining aerobic exercise training and chemotherapy will translate towards favorable immune and clinical outcomes.

Changes in Plasma Concentration of Free Proteinogenic and Non-Proteinogenic Amino Acids in High-Performance Sprinters over a 6-Month Training Cycle

Background/Objectives: Free amino acids substantially contribute to energy metabolism. Also, their profile may identify (over)training status and effectiveness. The long-term effects of speed-power training on plasma free amino acid (PFAA) profiles are not known. We aimed to observe variations in PFAA levels in high-performance sprinters in a six-month training cycle. Methods: Ten male athletes (24.6 ± 3.3 years) were examined during four training phases: transition (1 month), general preparation (2 months), specific preparation (1 month), and pre-competition/competition (2 months). Venous blood was collected at rest, after exhaustive exercise, and recovery. Forty-two PFAAs were analyzed by the LC-ESI-MS/MS method. Results: Significant decreases in resting concentrations were observed between the transition and competition phases for glutamine (762 ± 117 vs. 623 ± 53 μmol∙L-1; p < 0.001, η2 = 0.47) and histidine (89 ± 15 vs. 75 ± 10 μmol∙L-1; p = 0.010, η2 = 0.27), whereas β-alanine (30 ± 7 vs. 41 ± 9 μmol∙L-1; p = 0.024, η2 = 016) and sarcosine (3.6 ± 0.4 vs. 4.8 ± 0.6 μmol∙L-1; p = 0.006, η2 = 0.188) levels increased. Between the specific and competition phases, significant decreases in the resting levels of 1-methylhistidine (22.1 ± 19.4 vs. 9.6 ± 8.8 μmol∙L-1; p = 0.14, η2 = 0.19), 3-methylhistidine (7.1 ± 1.5 vs. 6.5 ± 1.6 μmol∙L-1; p = 0.009, η2 = 0.18), citrulline (40 ± 10 vs. 29 ± 4 μmol∙L-1; p = 0.05, η2 = 0.29), and ornithine (74 ± 15 vs. 56 ± 10 μmol∙L-1; p = 0.015, η2 = 185) were noticed. Also, for β-alanine and sarcosine, the pattern of response to exercise strongly changed between the training phases. Blood ammonia levels at exhaustion decreased between the transition and competition phases (32 ± 4 vs. 23 ± 5 μmol∙L-1; p < 0.001, η2 = 0.67), while lactate, the phenylalanine-tyrosine ratio, the glutamine-glutamate ratio, hematological parameters, and cardiorespiratory indices remained at similar levels. Conclusions: Speed-power training seems to affect PFAAs involved in skeletal muscle metabolic pathways responsible for neutralizing toxic ammonia (glutamine, arginine, citrulline, ornithine), attenuating the deleterious effects of H+ ions (histidine, β-alanine), and reducing exercise-induced protein breakdown (1- and 3-methylhistidine). Our findings suggest that sprint-oriented training supports metabolic pathways that are responsible for the removal of harmful metabolites produced during exercise.

Exercise-induced response of proteinogenic and non-proteinogenic plasma free amino acids is sport-specific: A comparison of sprint and endurance athletes

Circulating blood is an important plasma free amino acids (PFAAs) reservoir and a pivotal link between metabolic pathways. No comparisons are available between athletes with opposite training adaptations that include a broader spectrum of both proteinogenic and non-proteinogenic amino acids, and that take into account skeletal muscle mass. We hypothesized that the levels of the exercise-induced PFAAs concentration are related to the type of training-related metabolic adaptation. We compared highly trained endurance athletes (n = 11) and sprinters (n = 10) aged 20‒35 years who performed incremental exercise until exhaustion. Venous blood was collected before and during the test and 30-min recovery (12 samples). Forty-two PFAAs were assayed using LC-ESI-MS/MS technique. Skeletal muscle mass was estimated using dual X-ray absorptiometry method. Glutamine and alanine were dominant PFAAs throughout the whole exercise and recovery period (~350‒650 μmol∙L-1). Total, combined proteinogenic, non-essential, and non-proteinogenic PFAAs levels were significantly higher in endurance athletes than sprinters (ANOVA group effects: p = 0.007, η2 = 0.321; p = 0.011, η2 = 0.294; p = 0.003, η2 = 0.376; p = 0.001, η2 = 0.471, respectively). The exercise response was more pronounced in endurance athletes, especially for non-proteinogenic PFAAs (ANOVA interaction effect: p = 0.038, η2 = 0.123). Significant between-group differences were observed for 19 of 33 PFAAs detected, including 4 essential, 7 non-essential, and 8 non-proteinogenic ones. We demonstrated that the PFAAs response to incremental aerobic exercise is associated with the type of training-related metabolic adaptation. A greater turnover and availability of circulating PFAAs for skeletal muscles and other body tissues is observed in endurance- than in sprint-trained individuals. Non-proteinogenic PFAAs, despite low concentrations, also respond to exercise loads, indicating their important, though less understood role in exercise metabolism. Our study provides additional insight into the exercise-induced physiological response of PFAAs, and may also provide a rationale in discussions regarding dietary amino acid requirements in high-performance athletes with respect to sports specialization.

Brief cycling intervals incrementally increase the number of hematopoietic stem and progenitor cells in human peripheral blood

Introduction

Peripheral blood stem cell (PBSC) donation is the primary procedure used to collect hematopoietic stem and progenitor cells (HSPCs) for hematopoietic stem cell transplantation. Single bouts of exercise transiently enrich peripheral blood with HSPCs and cytolytic natural killer cells (CD56dim), which are important in preventing post-transplant complications. To provide a rationale to investigate the utility of exercise in a PBSC donation setting (≈3 h), this study aimed to establish whether interval cycling increased peripheral blood HSPC and CD56dim concentrations to a greater degree than continuous cycling.

Methods

In a randomised crossover study design, eleven males (mean ± SD: age 25 ± 7 years) undertook bouts of moderate intensity continuous exercise [MICE, 30 min, 65%-70% maximum heart rate (HRmax)], high-volume high intensity interval exercise (HV-HIIE, 4 × 4 min, 80%-85% HRmax) and low-volume HIIE (LV-HIIE, 4 × 2 min, 90%-95% HRmax). The cumulative impact of each interval on circulating HSPC (CD34+CD45dimSSClow) and CD56dim concentrations (cells/µL), and the bone marrow homing potential of HSPCs (expression of CXCR-4 and VLA-4) were determined.

Results

There was an increase in HSPC concentration after two intervals of LV-HIIE (Rest: 1.84 ± 1.55 vs. Interval 2: 2.94 ± 1.34, P = 0.01) and three intervals of HV-HIIE only (Rest: 2.05 ± 0.86 vs. Interval 3: 2.51 ± 1.05, P = 0.04). The concentration of all leukocyte subsets increased after each trial, with this greatest for CD56dim NK cells, and in HIIE vs. MICE (LV-HIIE: 4.77 ± 2.82, HV-HIIE: 4.65 ± 2.06, MICE: 2.44 ± 0.77, P < 0.0001). These patterns were observed for concentration, not frequency of CXCR-4+ and VLA-4+ HSPCs, which was unaltered. There was a marginal decrease in VLA-4, but not CXCR-4 expression on exercise-mobilised HSPCs after all trials (P < 0.0001).

Discussion

The results of the present study indicate that HIIE caused a more marked increase in HSPC and CD56dim NK cell concentrations than MICE, with mobilised HSPCs maintaining their bone marrow homing phenotype. LV-HIIE evoked an increase in HSPC concentration after just 2 × 2-minute intervals. The feasibility and clinical utility of interval cycling in a PBSC donation context should therefore be evaluated.

Changes in Plasma Free Amino Acid Profile in Endurance Athletes over a 9-Month Training Cycle

We aimed to evaluate long-term changes in proteinogenic and non-proteinogenic plasma free amino acids (PFAA). Eleven male endurance triathletes participated in a 9-month study. Blood was collected at rest, immediately after exhaustive exercise, and during 30-min recovery, in four consecutive training phases: transition, general, specific, and competition. Twenty proteinogenic and 22 non-proteinogenic PFAAs were assayed using the LC-ESI-MS/MS technique. The structured training modified the patterns of exercise-induced PFAA response, with the competition phase being the most distinct from the others. Branched-chain amino acids (p = 0.002; η2 = 0.216), phenylalanine (p = 0.015; η2 = 0.153), methionine (p = 0.002; η2 = 0.206), and lysine (p = 0.006; η2 = 0.196) declined more rapidly between rest and exhaustion in the competition phase. Glutamine (p = 0.008; η2 = 0.255), glutamate (p = 0.006; η2 = 0.265), tyrosine (p = 0.001; η2 = 0.195), cystine (p = 0.042; η2 = 0.183), and serine (p < 0.001; η2 = 0.346) levels were reduced in the competition phase. Arginine (p = 0.046; η2 = 0.138) and aspartate (p = 0.011; η2 = 0.171) levels were highest during exercise in the transition phase. During the competition phase, α-aminoadipic acid (p = 0.023; η2 = 0.145), β-aminoisobutyric acid (p = 0.007; η2 = 0.167), β-alanine (p < 0.001; η2 = 0.473), and sarcosine (p = 0.017; η2 = 0.150) levels increased, whereas phosphoethanolamine (p = 0.037; η2 = 0.189) and taurine (p = 0.008; η2 = 0.251) concentrations decreased. Overtraining indicators were not elevated. The altered PFAA profile suggests adaptations within energy metabolic pathways such as the tricarboxylic acid cycle, oxidative phosphorylation, ammonia neutralization, the purine nucleotide cycle, and buffering of intracellular H+ ions. The changes seem to reflect normal adaptations.

Molecular biomarkers for assessing the heat-adapted phenotype: a narrative scoping review

Heat acclimation/acclimatisation (HA) mitigates heat-related decrements in physical capacity and heat-illness risk and is a widely advocated countermeasure for individuals operating in hot environments. The efficacy of HA is typically quantified by assessing the thermo-physiological responses to a standard heat acclimation state test (i.e. physiological biomarkers), but this can be logistically challenging, time consuming, and expensive. A valid molecular biomarker of HA would enable evaluation of the heat-adapted state through the sampling and assessment of a biological medium. This narrative review examines candidate molecular biomarkers of HA, highlighting the poor sensitivity and specificity of these candidates and identifying the current lack of a single 'standout' biomarker. It concludes by considering the potential of multivariable approaches that provide information about a range of physiological systems, identifying a number of challenges that must be overcome to develop a valid molecular biomarker of the heat-adapted state, and highlighting future research opportunities.

Early Human Pathophysiological Responses to Exertional Hypobaric Decompression Stress

INTRODUCTION: Consistent blood biomarkers of hypobaric (altitude) decompression stress remain elusive. Recent laboratory investigation of decompression sickness risk at 25,000 ft (7620 m) enabled evaluation of early pathophysiological responses to exertional decompression stress.METHODS: In this study, 15 healthy men, aged 20-50 yr, undertook 2 consecutive (same-day) ascents to 25,000 ft (7620 m) for 60 and 90 min, breathing 100% oxygen, each following 1 h of prior denitrogenation. Venous blood was sampled at baseline (T0), immediately after the second ascent (T8), and next morning (T24). Analyses encompassed whole blood hematology, endothelial microparticles, and soluble markers of cytokine response, endothelial function, inflammation, coagulopathy, oxidative stress, and brain insult, plus cortisol and creatine kinase.RESULTS: Acute hematological effects on neutrophils (mean 72% increase), eosinophils (40% decrease), monocytes (37% increase), and platelets (7% increase) normalized by T24. Consistent elevation (mean five-fold) of the cytokine interleukin-6 (IL-6) at T8 was proinflammatory and associated with venous gas emboli (microbubble) load. Levels of C-reactive protein and complement peptide C5a were persistently elevated at T24, the former by 100% over baseline. Additionally, glial fibrillary acidic protein, a sensitive marker of traumatic brain injury, increased by a mean 10% at T24.CONCLUSIONS: This complex composite environmental stress, comprising the triad of hyperoxia, decompression, and moderate exertion at altitude, provoked pathophysiological changes consistent with an IL-6 cytokine-mediated inflammatory response. Multiple persistent biomarker disturbances at T24 imply incomplete recovery the day after exposure. The elevation of glial fibrillary acidic protein similarly implies incomplete resolution following recent neurological insult.Connolly DM, Madden LA, Edwards VC, D'Oyly TJ, Harridge SDR, Smith TG, Lee VM. Early human pathophysiological responses to exertional hypobaric decompression stress. Aerosp Med Hum Perform. 2023; 94(10):738-749.

Plasma procalcitonin kinetics in healthy dogs and dogs undergoing tibial plateau leveling osteotomy

BACKGROUND

Procalcitonin (PCT) is a well-established biomarker for bacterial infection in human patients.

OBJECTIVES

We aimed to analyze the kinetics of plasma PCT (pPCT) in healthy dogs and dogs with canine cranial cruciate ligament (CCL) rupture undergoing tibial plateau leveling osteotomy (TPLO).

METHODS

This prospective, longitudinal study included 15 healthy dogs and 25 dogs undergoing TPLO. Hematology, pPCT, and C-reactive protein (CRP) were assessed on 3 consecutive days in healthy dogs and 1 day preoperatively and days 1, 2, 10, and 56 postoperatively. Inter- and intraindividual variability of pPCT were assessed in healthy dogs. Median pPCT concentrations of dogs with CCL rupture preoperatively were compared with healthy controls, and median pPCT concentrations, as well as percentage change post anesthesia, arthroscopy, and TPLO, were compared with baseline. For the correlation analysis, the Spearman rank correlation test was used.

RESULTS

Inter- and intraindividual variabilities of pPCT in healthy dogs were 36% and 15%, respectively. Median baseline pPCT concentrations were not significantly different between healthy dogs (118.9 pg/mL; IQR: 75.3-157.3 pg/mL) and dogs undergoing TPLO (95.9 pg/mL; IQR: 63.8-117.0 pg/mL). Plasma PCT concentrations were significantly lower immediately post- than preoperatively (P < 0.001). CRP, WBC, and neutrophil concentrations increased significantly on post-OP day 2 and had normalized by day 10.

CONCLUSIONS

These results indicate that CCL rupture, as well as anesthesia, arthroscopy, and TPLO combined, are not associated with increased pPCT concentrations in dogs with uncomplicated recovery. Considering the high intraindividual variability, individual serial measurements rather than a population-based reference interval should be considered.

Extended Match Time Exacerbates Fatigue and Impacts Physiological Responses in Male Soccer Players

PURPOSE

This study evaluated how extended match time (90 + 30 min) affected physiological responses and fatigue in male soccer players.

METHODS

Twenty competitive players (mean ± SD: age, 20 ± 1 yr; maximal oxygen uptake, 59 ± 4 mL·min -1 ·kg -1 ) completed an experimental match with their activity pattern and heart rate assessed throughout the game, whereas countermovement jump performance and repeated sprint ability were tested and quadriceps muscle biopsies and venous blood samples were taken at baseline and after 90 and 120 min of match play.

RESULTS

Less high-intensity running (12%) was performed in extra time in association with fewer intense accelerations and decelerations per minute compared with normal time. Peak sprint speed was 11% lower in extra time compared with normal time, and fatigue also manifested in impaired postmatch repeated sprint ability and countermovement jump performance (all P < 0.05). Muscle glycogen declined from 373 ± 59 mmol·kg -1 dry weight (dw) at baseline to 266 ± 64 mmol·kg -1 dw after 90 min, with a further decline to 186 ± 56 mmol·kg -1 dw after extra time ( P < 0.05) and with single-fiber analyses revealing depleted or very low glycogen levels in ~75% of both slow and fast twitch fibers. Blood glucose did not change during the first 90-min but declined ( P < 0.05) to 81 ± 8 mg·dL -1 after extra time. Plasma glycerol and ammonia peaked at 236 ± 33 mg·dL -1 and 75 ± 21 μmol·L -1 after the extra period.

CONCLUSIONS

These findings demonstrate exacerbated fatigue after extra time compared with normal time, which seems to be associated with muscle glycogen depletion, reductions in blood glucose levels, and hyperammonemia. Together, this points to metabolic disturbances being a major part of the integrated and multifaceted fatigue response during extended soccer match play.

Lymphocytes are less sensitive to autophagy than monocytes during fasting and exercise conditions

The concomitant investigation of apoptosis (a regulated cell death) and autophagy (a conserved cell survival mechanism) in immune cells is rare. More detailed knowledge of these two types of self-consumption in circulating lymphocytes and monocytes would be important, since conditions such as fasting and acute exercise could promote health by a coordinated/linked modulation of autophagy and apoptosis in these mononuclear cells. In this study we performed flow cytometry to quantify numbers of apoptotic and autophagic mononuclear cells, lymphocytes and monocytes in fasting, standardized fed, and exercise conditions, using Annexin V, LC3B, and p62, respectively. We show that within total mononuclear cells lymphocytes are less apoptotic and autophagic than monocytes during fasting (p < 0.001, p < 0.05, respectively) and after acute exercise (p < 0.01, p < 0.05, respectively). Fasting increased circulating autophagic monocyte concentrations, but not lymphocytes compared to the fed control condition. Acute exercise elevated circulating autophagic lymphocyte concentrations, but not monocytes. Interestingly, Western blotting analysis of the fasting samples showed that higher LC3BII/I ratios were correlated with lower numbers of autophagic mononuclear cells (r = − 0.74, p = 0.02, n = 8), which could be attributed to the monocyte subgroup, but not lymphocytes. These results extend the current knowledge of the two types of self-consumption in circulating immune cells and underline their possible importance in pro-inflammatory monocytes during fasting and exercise as health promoting interventions.

Resistance exercise with different workloads have distinct effects on cellular respiration of peripheral blood mononuclear cells

Little is known how acute exercise-induced inflammation and metabolic stress affect immune cell bioenergetics and the portion of its components. Therefore, we investigated acute effects of eccentric-only (E), concentric-only (C) and combined eccentric-concentric resistance exercise (E + C) bouts on cellular respiration of peripheral blood mononuclear cells (PBMCs). Twelve strength-trained young men performed bench press resistance exercises in randomized order. Venous blood samples were drawn at pre-, 5 min post- and 24 h post-exercise. Several PBMC respiration states were measured using high-resolution respirometry. Levels of leukocytes, interleukin 6 (IL-6), C-reactive protein (CRP), creatine kinase (CK), blood lactate and maximum voluntary isometric force were measured from the same time points. Effects of blood lactate and pH change on bioenergetics of PBMCs were investigated ex vivo. PBMC routine respiration (p = 0.017), free routine capacity (p = 0.025) and ET-capacity (p = 0.038) decreased immediately after E + C. E responded in opposite manner 5 min post-exercise compared to E + C (p = 0.013) and C (p = 0.032) in routine respiration, and to E + C in free routine activity (p = 0.013). E + C > C > E was observed for increased lactate levels and decreased isometric force that correlated with routine respiration (R = -0.369, p = 0.035; R = 0.352, p = 0.048). Lactate and pH change did not affect bioenergetics of PBMCs. Acute resistance exercise affected cellular respiration of PBMCs, with training volume and the amount of metabolic stress appear influential. Results suggest that acute inflammation response does not contribute to changes seen in cellular respiration, but the level of peripheral muscle fatigue and metabolic stress could be explaining factors.

Influence of exercise duration on respiratory function and systemic immunity among healthy, endurance-trained participants exercising in sub-zero conditions

Background

Strenuous endurance exercise in sub-zero temperatures can cause airway damage that may lead to EIB. Prolonged exercise can also elicit greater immune perturbations than short-duration exercise. However, the influence of exercise duration on lung function and systemic immunity in sub-zero temperatures has not been established. Additionally, it is currently unknown whether atopic disposition, which is risk factor for EIB, influences respiratory responses in a sub-zero climate. The aim of this study was to compare respiratory and systemic immune responses to two cold air running trials of short and long duration, as well as to examine whether the responses differed between atopic and non-atopic subjects.

Methods

Eighteen healthy, endurance-trained subjects (males/females: 14/4; age: 29.4 ± 5.9 years old; BMI: 23.1 ± 1.7; atopic/non-atopic: 10/8) completed two moderate-intensity climate chamber running trials at − 15 °C, lasting 30 and 90 min, in a randomized, cross-over design. Lung function (spirometry and impulse oscillometry), serum CC16, respiratory symptoms, and blood leukocyte counts were examined before and after the trials.

Results

Lung function was not significantly affected by exercise or exercise duration. CC16 concentration increased after both trials (p = 0.027), but the response did not differ between trials. Respiratory symptom intensity was similar after each trial. There was a greater increase in neutrophils (p < 0.001), and a decrease in eosinophils (p < 0.001) after the 90-min bout. The 90-min protocol increased X5 compared to the 30-min protocol only in atopic subjects (p = 0.015) while atopy increased lower airway symptoms immediately after the 90-min session (p = 0.004).

Conclusions

Our results suggest that a 90-min bout of moderate-intensity exercise at − 15 °C does not cause substantial lung function decrements, airway epithelial damage or respiratory symptoms compared to 30 min running in the same environment, despite a heightened redistribution of white blood cells. However, exercise at − 15 °C may cause airway injury and evoke respiratory symptoms, even at moderate intensity. Atopic status may lead to greater peripheral bronchodilation and higher frequency of respiratory symptoms after long-duration exercise in cold.

Trial registration: 01/02/2022 ISRCTN13977758. This trial was retrospectively registered upon submission to satisfy journal guidelines. The authors had not initially registered the study, as the intervention was considered to be a controlled simulation of exercise in a naturally occurring environment (i.e. sub-zero air) for healthy volunteers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-022-02029-2.

Heat Acclimation with or without Normobaric Hypoxia Exposure Leads to Similar Improvements in Endurance Performance in the Heat

Background: Combining the key adaptation of plasma volume (PV) expansion with synergistic physiological effects of other acclimation interventions to maximise endurance performance in the heat has potential. The current study investigated the effects of heat acclimation alone (H), combined with normobaric hypoxia exposure (H+NH), on endurance athletic performance. Methods: Well-trained participants completed a heat-stress trial (30 °C, 80% relative humidity (RH), 20.8% fraction of inspired oxygen (FiO2)) of a 75 min steady-state cycling (fixed workload) and a subsequent 15 min cycling time trial for distance before and after intervention. Participants completed 12 consecutive indoor training days with either heat acclimation (H; 60 min·day−1, 30 °C, 80% RH; 20.8% FiO2) or heat acclimation and overnight hypoxic environment (H+NH; ~12 h, 60% RH; 16% FiO2 simulating altitude of ~2500 m). Control (CON) group trained outdoors with average maximum daily temperature of 16.5 °C and 60% RH. Results: Both H and H+NH significantly improved time trial cycling distance by ~5.5% compared to CON, with no difference between environmental exposures. PV increased (+3.8%) and decreased (−4.1%) following H and H+NH, respectively, whereas haemoglobin concentration decreased (−2%) and increased (+3%) in H and H+NH, respectively. Conclusion: Our results show that despite contrasting physiological adaptations to different environmental acclimation protocols, heat acclimation with or without hypoxic exposure demonstrated similar improvements in short-duration exercise performance in a hot environment.

Heterogeneity of Hematological Response to Hypoxia and Short-Term or Medium-Term Bed Rest

Hematological changes are commonly observed following prolonged exposure to hypoxia and bed rest. Typically, such responses have been reported as means and standard deviations, however, investigation into the responses of individuals is insufficient. Therefore, the present study retrospectively assessed individual variation in the hematological responses to severe inactivity (bed rest) and hypoxia. The data were derived from three-bed rest projects: two 10-d (LunHab project: 8 males; FemHab project: 12 females), and one 21-d (PlanHab project: 11 males). Each project comprised a normoxic bed rest (NBR; P_IO₂=133mmHg) and hypoxic bed rest (HBR; P_IO₂=91mmHg) intervention, where the subjects were confined in the Planica facility (Rateče, Slovenia). During the HBR intervention, subjects were exposed to normobaric hypoxia equivalent to an altitude of 4,000m. NBR and HBR interventions were conducted in a random order and separated by a washout period. Blood was drawn prior to (Pre), during, and post bed rest (R1, R2, R4) to analyze the individual variation in the responses of red blood cells (RBC), erythropoietin (EPO), and reticulocytes (Rct) to bed rest and hypoxia. No significant differences were found in the mean ∆(Pre-Post) values of EPO across projects (LunHab, FemHab, and PlanHab; p>0.05), however, female EPO responses to NBR (Range - 17.39, IQR – 12.97 mIU^.ml⁻¹) and HBR (Range – 49.00, IQR – 10.91 mIU^.ml⁻¹) were larger than males (LunHab NBR Range – 4.60, IQR – 2.03; HBR Range – 7.10, IQR – 2.78; PlanHab NBR Range – 7.23, IQR – 1.37; HBR Range – 9.72, IQR – 4.91 mIU^.ml⁻¹). Bed rest duration had no impact on the heterogeneity of EPO, Rct, and RBC responses (10-d v 21-d). The resultant hematological changes that occur during NBR and HBR are not proportional to the acute EPO response. The following cascade of hematological responses to NBR and HBR suggests that the source of variability in the present data is due to mechanisms related to hypoxia as opposed to inactivity alone. Studies investigating hematological changes should structure their study design to explore these mechanistic responses and elucidate the discord between the EPO response and hematological cascade to fully assess heterogeneity.

Extreme Ultra-Trail Race Induces Muscular Damage, Risk for Acute Kidney Injury and Hyponatremia: A Case Report

A case study involving a healthy trained male athlete who completed a 786 km multi-stage ultra-trail race. Several markers were analyzed in blood and urine samples: creatinine (SCR) for kidney damage, sodium ([Na⁺]) for hyponatremia, creatine kinase (CK) for exertional rhabdomyolysis, as well as other hematological values. Samples were taken before and after the race and during the recovery period (days 2 and 9 after the race). Results showed: SCR = 1.13 mg/dl, [Na⁺] =139 mmol/l and CK = 1.099 UI/l. Criteria for the determination of acute kidney damage were not met, and [Na+] concentration was above 135 mEq/L, indicating the absence of hyponatremia. Exertional rhabdomyolysis was suffered by the athlete (baseline CK increased fivefold), though this situation was reverted after 9 days of recovery. Ultra-trail races cause biochemical changes in athletes, which should be known about by healthcare professionals.

Biological Responses to Short-Term Maximal Exercise in Male Police Officers

The specifics of short-term physical exercise are similar to the immediate reaction demands placed on police officers. Identifying the physiological predisposition to short-term high-intensity exercise in male law enforcement officers will assist in understanding their metabolism and make a significant contribution to a much more personal and individualized workout program. This will improve physical fitness of individual officers, improving their preparedness for such times of emergency. This cross-sectional study was conducted to investigate the responses of hematological (erythrocytes, hemoglobin, hematocrit, leucocytes, monocytes, neutrophils, lymphocytes), hormonal (testosterone, cortisol, melatonin), biochemical (glucose, uric-acid, lactate, creatine-phosphokinase) data to short-term maximal exercise in male police officers (n = 20). Blood samples were collected before- and after- the running-based anaerobic sprint test (RAST), and biological values were corrected for fluid shifts. Data were mean ± standard deviation of differences (= after minus before RAST). After the RAST, values of cortisol, lactate, neutrophils, lymphocytes, and monocytes increased significantly by 7.01 ± 37.36 mmol/l, 7.55 ± 1.67 mmol/l, 0.17 ± 0.26 103/µl, 0.61 ± 0.28 103/µl, and 0.10 ± 0.13 103/µl, respectively. After the RAST, values of melatonin, uric-acid, creatine-phosphokinase, hemoglobin, and hematocrit decreased significantly by -13.24 ± 4.60 pg/ml, -13.28 ± 14.35 µmol/l, -10.23 ± 10.13 IU/l, -2.01 ± 0.81 g/dl, and -4.46 ± 0.59%, respectively. Biological data of male police officers were affected by sprint test. Understanding changes in biological data following short-term maximal exercise can further assist in a better understanding of anaerobic metabolism, which will be helpful to find available methods for coaches to quantify training loads.

Effects of Prior Voluntary Hyperventilation on the 3-min All-Out Cycling Test in Men

INTRODUCTION

The ergogenic effects of respiratory alkalosis induced by prior voluntary hyperventilation (VH) are controversial. This study examined the effects of prior VH on derived parameters from the 3-min all-out cycling test (3MT).

METHODS

Eleven men ( = 46 ± 8 mL·kg-1·min-1) performed a 3MT preceded by 15 min of rest (CONT) or VH ( = 38 ± 5 L·min-1) with PETCO2 reduced to 21 ± 1 mm Hg (HYP). End-test power (EP; synonymous with critical power) was calculated as the mean power output over the last 30 s of the 3MT, and the work done above EP (WEP; synonymous with W') was calculated as the power-time integral above EP.

RESULTS

At the start of the 3MT, capillary blood PCO2 and [H+] were lower in HYP (25.2 ± 3.0 mm Hg, 27.1 ± 2.6 nmol·L-1) than CONT (43.2 ± 2.0 mm Hg, 40.0 ± 1.5 nmol·L-1) (P < 0.001). At the end of the 3MT, blood PCO2 was still lower in HYP (35.7 ± 5.4 mm Hg) than CONT (40.6 ± 5.0 mm Hg) (P < 0.001). WEP was 10% higher in HYP (19.4 ± 7.0 kJ) than CONT (17.6 ± 6.4 kJ) (P = 0.006), whereas EP was 5% lower in HYP (246 ± 69 W) than CONT (260 ± 74 W) (P = 0.007). The ΔWEP (J·kg-1) between CONT and HYP correlated positively with the PCO2 immediately before the 3MT in HYP (r = 0.77, P = 0.006).

CONCLUSION

These findings suggest that acid-base changes elicited by prior VH increase WEP but decrease EP during the all-out 3MT.

Effects of Padel Competition on Brain Health-Related Myokines

Padel is becoming one of the most widespread racket sports that may have potential health benefits. Considering that several myokines mediate the cross-talk between skeletal muscles and the brain, exerting positive effects on brain health status, this study was designed to evaluate the responses of brain-derived neurotrophic factor (BDNF), leukemia inhibitory factor (LIF), and irisin (IR) to padel competition in trained players and to determine whether these responses were sex-dependent. Twenty-four trained padel players (14 women and 10 men with a mean age of 27.8 ± 6.3 years) participated voluntarily in this study. Circulating levels of BDNF, LIF, and IR were assessed before and after simulated padel competition (real playing time, 27.8 ± 8.49 min; relative intensity, 75.2 ± 7.9% maximum heart rate). Except for BDNF responses observed in female players (increasing from 1531.12 ± 269.09 to 1768.56 ± 410.75 ng/mL), no significant changes in LIF and IR concentrations were reported after padel competition. In addition, no sex-related differences were found. Moreover, significant associations between IR and BDNF were established at both pre- and post-competition. Our results suggest that while competitive padel practice stimulates BDNF response in female players, padel competition failed to boost the release of LIF and IR. Future studies are needed to further explore the role of these exercise-induced myokines in the regulation of brain functions and to identify the field sports that can contribute to myokine-mediated muscle–brain crosstalk.

The effects of interval training on peripheral brain derived neurotrophic factor (BDNF) in young adults: a systematic review and meta-analysis

The aim of the current meta-analysis was to determine the effects of acute and chronic interval training (IT) on serum and plasma BDNF concentrations in healthy young adults. A literature search was performed using six databases until February 2020. The TESTEX scale was used to assess the quality of studies. Effect sizes (ES) were computed and two-tailed α values < 0.05 and non-overlapping 95% confidence intervals (95% CI) were considered statistically significant. Heterogeneity, inconsistency (I²), and small-study effects using the Luis Furuya-Kanamori (LFK) index were examined. Fifteen studies (n = 277 participants, age = 24 ± 3 years) were included. The overall effects of IT on circulating BDNF concentrations were moderate and significant (ES = 0.62, 95% CI 0.00, 1.24, heterogeneous (p < 0.001), highly inconsistent (I² = 90%), and with major asymmetry (LFK index = 2.76). The acute effect of IT on peripheral BDNF levels was large and significant (ES = 1.10, 95% CI 0.07, 2.14), heterogeneous (p < 0.001), highly inconsistent (I² = 92%), and with major asymmetry (LFK index = 3.34). The chronic effect of IT on circulating BDNF was large and significant (ES = 0.93, 95% CI 0.40, 1.46), heterogeneous (p < 0.001), with moderate inconsistency (I² = 70%), and minor asymmetry (LFK index = 1.21). Acute and chronic IT elicited a moderate increase in serum and plasma BDNF concentrations in a healthy young population.

Effects of short duration high intensity competition on cardiac and cell damage biomarkers

The purpose of this study was to investigate the cardiac biomarkers like cardiac troponin T (cTnT), cardiac troponin I, and creatine kinase-MB (CK-MB) and the cell damage biomarkers including creatine phosphokinase (CPK), C-reactive protein (CRP), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) in response to a short-duration high-intensity competition with correction of the post-exercise raw data with the plasma volume loss in trained athletes. Thirty-two male athletes (age, 26.9±4.7 years) competed in 8 min high-intensity competition. The competition items included: running for 400 meters; three-stage deadlifting; bar pulling up; and 30 kg kettlebell swinging. Venous blood samples were obtained before and immediately after the competition and biomarkers analysed. Plasma volume changes were estimated from haemoglobin and haematocrit readings before and after the competition. A significant increase was shown immediately after the competition compared to resting in cTnT, AST, ALT, CPK, and CRP (P<0/001). CK-MB showed no significant difference. When raw data were corrected for plasma volume loss, CPK showed a significant increase (P<0.001), and LDH and CK-MB a significant decrease (P<0.001), however cTnT, AST, ALT and CRP showed no significant difference. The plasma volume loss can affect the response of cardiac and cellular damage biomarkers to exercise. High-intensity competition for 8 min did not elevate the cardiac biomarkers, but elevated the muscle biomarkers.

Effect of oral rehydration solution versus spring water intake during exercise in the heat on muscle cramp susceptibility of young men

Background

Muscle cramp is a painful, involuntary muscle contraction, and that occurs during or following exercise is referred to as exercise-associated muscle cramp (EAMC). The causes of EAMC are likely to be multifactorial, but dehydration and electrolytes deficits are considered to be factors. This study tested the hypothesis that post-exercise muscle cramp susceptibility would be increased with spring water ingestion, but reduced with oral rehydration solution (ORS) ingestion during exercise.

Methods

Ten men performed downhill running (DHR) in the heat (35–36 °C) for 40–60 min to reduce 1.5–2% of their body mass in two conditions (spring water vs ORS) in a cross-over design. The body mass was measured at 20 min and every 10 min thereafter during DHR, and 30 min post-DHR. The participants ingested either spring water or ORS for the body mass loss in each period. The two conditions were counter-balanced among the participants and separated by a week. Calf muscle cramp susceptibility was assessed by a threshold frequency (TF) of an electrical train stimulation to induce cramp before, immediately after, 30 and 65 min post-DHR. Blood samples were taken before, immediately after and 65 min after DHR to measure serum sodium, potassium, magnesium and chroride concentrations, hematocrit (Hct), hemoglobin (Hb), and serum osmolarity. Changes in these varaibles over time were compared between conditions by two-way repeated measures of analysis of variance.

Results

The average (±SD) baseline TF (25.6 ± 0.7 Hz) was the same between conditions. TF decreased 3.8 ± 2.7 to 4.5 ± 1.7 Hz from the baseline value immediately to 65 min post-DHR for the spring water condition, but increased 6.5 ± 4.9 to 13.6 ± 6.0 Hz in the same time period for the ORS condition (P < 0.05). Hct and Hb did not change significantly (P > 0.05) for both conditions, but osmolarity decreased (P < 0.05) only for the spring water condition. Serum sodium and chloride concentrations decreased (< 2%) at immediately post-DHR for the spring water condition only (P < 0.05).

Conclusions

These results suggest that ORS intake during exercise decreased muscle cramp susceptibility. It was concluded that ingesting ORS appeared to be effective for preventing EAMC.

Acute and delayed hormonal and blood cell count responses to high-intensity exercise before and after short-term high-intensity interval training

The acute and delayed hormonal and blood cell responses to a high-intensity interval training (HIIT) session, were examined before and after a 3-week intervention (9 HIIT sessions of 4-6 × 30 s high-intensity cycling bouts) in eight recreationally active male volunteers (age: 24.3 ± 1.4 y, VO₂max: 41.2 ± 3.2 ml/kg/min). Blood samples were collected before and 0.5, 24, 48 h following the first and last training session. Before training, the HIIT session induced acute increases in cortisol, prolactin and TSH concentration, while free-T4 peaked 24 h later (p < 0.001) and testosterone remained unchanged. White blood cell count was increased 0.5 h after exercise (p < 0.001), while lymphocyte percentage decreased 24 h post exercise (p < 0.01). After three weeks of HIIT, cortisol, WBC and lymphocyte responses were decreased by ~42% (p = 0.002), 8.6% (p = 0.032) and 9.6% (p = 0.039), respectively, despite an increase in total work. These findings show that short-term HIIT may induce rapid adaptations of the hypothalamic-pituitary-adrenal axis and may blunt exercise-induced immune responses.

Cooling During Endurance Cycling in the Heat: Blunted Core Temperature but Not Inflammatory Responses

PURPOSE

This study assessed the effects of cooling during endurance cycling (percooling) on changes in core body temperature (Tcore), inflammatory, and metabolic responses.

METHODS

A total of 12 male cyclists (peak oxygen uptake 60 [4] mL·kg-1·min-1) completed a 60-minute constant workload trial (55% of peak power output and ambient temperature 30.4°C [0.6°C]) in a randomized order both with (ICE) and without (CON) an ice vest. An ingestible capsule was used to measure Tcore. Blood samples were collected immediately before and after each trial to determine concentrations of blood lactate, serum cortisol, interleukin-6, and reactive oxygen and nitrogen species.

RESULTS

Tcore increased statistically (P < .001) both in CON (7.0% [1.4%], effect size [ES] = 6.3) and ICE (5.1% [1.1%], ES = 5.7). The increase in CON was statistically larger compared with ICE (P = .006, ES = 1.4). Concentrations of blood lactate (CON: 163% [63%], ES = 1.3; ICE: 149% [91%], ES = 1.3), cortisol (CON: 138% [123%], ES = 1.7; ICE: 81% [102%], ES = 1.0), and interleukin-6 (CON: 661% [324%], ES = 2.1; ICE: 624% [368%], ES = 1.2) statistically increased in both conditions (P < .01) to a similar extent. In addition, reactive oxygen and nitrogen species statistically decreased in both conditions (CON: -19.2% [14.9%], P = .002, ES = 0.9; ICE: -15.1% [16.5%], P = .02, ES = 0.9). No correlations were found between the changes of Tcore and blood parameters across the conditions.

CONCLUSIONS

Despite attenuated Tcore, similar inflammatory and metabolic responses were observed. Our findings suggest percooling to be a promising strategy to attenuate thermal strain without compromising physiological function.

The effect of Omega-3 polyunsaturated fatty acid supplementation on exercise-induced muscle damage

Background

Exercise-induced muscle damage (EIMD) results in transient muscle inflammation, strength loss, muscle soreness and may cause subsequent exercise avoidance. Omega-3 (n-3) supplementation may minimise EIMD via its anti-inflammatory properties, however, its efficacy remains unclear.

Methods

Healthy males (n = 14, 25.07 ± 4.05 years) were randomised to 3 g/day n-3 supplementation (N-3, n = 7) or placebo (PLA, n = 7). Following 4 weeks supplementation, a downhill running protocol (60 min, 65% V̇O₂max, − 10% gradient) was performed. Creatine kinase (CK), interleukin (IL)-6 and tumour necrosis factor (TNF)-α, perceived muscle soreness, maximal voluntary isometric contraction (MVIC) and peak power were quantified pre, post, and 24, 48 and 72 h post-EIMD.

Results

Muscle soreness was significantly lower in N-3 vs PLA group at 24 h post-EIMD (p = 0.034). IL-6 was increased in PLA (p = 0.009) but not in N-3 (p = 0.434) following EIMD, however, no significant differences were noted between groups. Peak power was significantly suppressed in PLA relative to pre-EIMD but not in N-3 group at 24 h post-EIMD. However, no significant difference in peak power output was observed between groups. MVIC, CK and TNF-α were altered by EIMD but did not differ between groups.

Conclusion

N-3 supplementation for 4 weeks may successfully attenuate minor aspects of EIMD. Whilst not improving performance, these findings may have relevance to soreness-associated exercise avoidance.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12970-020-00405-1.

Simulated Hypergravity Activates Hemostasis in Healthy Volunteers

Background

Hypergravity may promote human hemostasis thereby increasing thrombotic risk. Future touristic suborbital spaceflight will expose older individuals with chronic medical conditions, who are at much higher thromboembolic risk compared with professional astronauts, to hypergravity. Therefore, we tested the impact of hypergravity on hemostasis in healthy volunteers undergoing centrifugation.

Methods and Results

We studied 20 healthy seated men before and after 15 minutes under 3 Gz hypergravity on a long‐arm centrifuge. We obtained blood samples for hemostasis testing before, immediately after, and 30 minutes after centrifugation. Tests included viscoelastic thromboelastometry, platelet impedance aggregometry, endothelial activation markers, blood rheology testing, microparticle analyses, and clotting factor analysis. Exposure to hypergravity reduced plasma volume by 12.5% (P=0.002) and increased the red blood cell aggregation index (P<0.05). With hypergravity, thrombelastographic clotting time of native blood shortened from 719±117 seconds to 628±89 seconds (P=0.038) and platetet reactivity increased (P=0.045). Hypergravity shortened partial thromboplastin time from 28 (26–29) seconds to 25 (24–28) seconds (P<0.001) and increased the activity of coagulation factors (eg, factor VIII 117 [93–134] versus 151 [133–175] %, P<0.001). Tissue factor concentration was 188±95 pg/mL before and 298±136 pg/mL after hypergravity exposure (P=0.023). Antithrombin (P=0.005), thrombin‐antithrombin complex (P<0.001), plasmin‐alpha2‐antiplasmin complex (0.002), tissue‐plasminogen activatior (P<0.001), and plasminogen activator inhibitor‐1 (P=0.002) increased with centrifugation. Statistical adjustment for plasma volume attenuated changes in coagulation.

Conclusions

Hypergravity triggers low‐level hemostasis activation through endothelial cell activation, increased viscoelasticity, and augmented platelet reactivity, albeit partly counteracted through endogenous coagulation inhibitors release. Hemoconcentration may contribute to the response.

Biomarkers of neuronal damage in saturation diving-a controlled observational study

Purpose

A prospective and controlled observational study was performed to determine if the central nervous system injury markers glial fibrillary acidic protein (GFAp), neurofilament light (NfL) and tau concentrations changed in response to a saturation dive.

Methods

The intervention group consisted of 14 submariners compressed to 401 kPa in a dry hyperbaric chamber. They remained pressurized for 36 h and were then decompressed over 70 h. A control group of 12 individuals was used. Blood samples were obtained from both groups before, during and after hyperbaric exposure, and from the intervention group after a further 25–26 h.

Results

There were no statistically significant changes in the concentrations of GFAp, NfL and tau in the intervention group. During hyperbaric exposure, GFAp decreased in the control group (mean/median − 15.1/ − 8.9 pg·mL⁻¹, p < 0.01) and there was a significant difference in absolute change of GFAp and NfL between the groups (17.7 pg·mL⁻¹, p = 0.02 and 2.34 pg·mL⁻¹, p = 0.02, respectively). Albumin decreased in the control group (mean/median − 2.74 g/L/ − 0.95 g/L, p = 0.02), but there was no statistically significant difference in albumin levels between the groups. In the intervention group, haematocrit and mean haemoglobin values were slightly increased after hyperbaric exposure (mean/median 2.3%/1.5%, p = 0.02 and 4.9 g/L, p = 0.06, respectively).

Conclusion

Hyperbaric exposure to 401 kPa for 36 h was not associated with significant increases in GFAp, NfL or tau concentrations. Albumin levels, changes in hydration or diurnal variation were unlikely to have confounded the results. Saturation exposure to 401 kPa seems to be a procedure not harmful to the central nervous system.

Trial registration

ClinicalTrials.gov NCT03192930.

Changes in Novel AKI Biomarkers after Exercise. A Systematic Review

More than 100 substances have been identified as biomarkers of acute kidney injury. These markers can help to diagnose acute kidney injury (AKI) in its early phase, when the creatinine level is not increased. The two markers most frequently studied in plasma and serum are cystatin C and neutrophil gelatinase-associated lipocalin (NGAL). The former is a marker of kidney function and the latter is a marker of kidney damage. Some other promising serum markers, such as osteopontin and netrin-1, have also been proposed and studied. The list of promising urinary markers is much longer and includes cystatin C, NGAL, kidney injury molecule-1 (KIM-1), liver-type fatty-acid-binding protein (L-FABP), interleukin 18, insulin-like growth factor binding protein 7 (IGFBP-7), tissue inhibitor of metalloproteinases-2 (TIMP-2) and many others. Although these markers are increased in urine for no longer than a few hours after nephrotoxic agent action, they are not widely used in clinical practice. Only combined IGFBP-7/TIMP-2 measurement was approved in some countries as a marker of AKI. Several studies have shown that the levels of urinary AKI biomarkers are increased after physical exercise. This systematic review focuses on studies concerning changes in new AKI biomarkers in healthy adults after single exercise. Twenty-seven papers were identified and analyzed in this review. The interpretation of results from different studies was difficult because of the variety of study groups, designs and methodology. The most convincing data concern cystatin C. There is evidence that cystatin C is a better indicator of glomerular filtration rate (GFR) in athletes after exercise than creatinine and also at rest in athletes with a lean mass lower or higher than average. Serum and plasma NGAL are increased after prolonged exercise, but the level also depends on inflammation and hypoxia; therefore, it seems that in physical exercise, it is too sensitive for AKI diagnosis. It may, however, help to diagnose subclinical kidney injury, e.g., in rhabdomyolysis. Urinary biomarkers are increased after many types of exercise. Increases in NGAL, KIM-1, cystatin-C, L-FABP and interleukin 18 are common, but the levels of most urinary AKI biomarkers decrease rapidly after exercise. The importance of this short-term increase in AKI biomarkers after exercise is doubtful. It is not clear if it is a sign of mild kidney injury or physiological metabolic adaptation to exercise.

Acute Exercise in Hypobaric Hypoxia Attenuates Endothelial Shedding in Subjects Unacclimatized to High Altitudes

Travel of unacclimatized subjects to a high altitude has been growing in popularity. Changes in endothelial shedding [circulating endothelial cells (ECs)] and hematopoietic stem and progenitor cells (CPCs) during physical exercise in hypobaric hypoxia, however, are not well understood. We investigated the change in ECs and CPCs when exposed to high altitude, after acute exercise therein, and after an overnight stay in hypobaric hypoxia in 11 healthy unacclimatized subjects. Blood withdrawal was done at baseline (520 m a.s.l.; baseline), after passive ascent to 3,883 m a.s.l. (arrival), after acute physical exercise (±400 m, postexercise) and after an overnight stay at 3,883 m a.s.l. (24 h). Mature blood cells, ECs, and CPCs were assessed by a hematology analyzer and flow cytometry, respectively. The presence of matrix metalloproteinases (MMPs), their activity, and hematopoietic cytokines were assessed in serum and plasma. EC and CPC concentrations significantly decreased after exercise (p = 0.019, p = 0.007, respectively). CPCs remained low until the next morning (24 h, p = 0.002), while EC concentrations returned back to baseline. MMP-9 decreased at arrival (p = 0.021), stayed low postexercise (p = 0.033), and returned to baseline at 24 h (p = 0.035 to postexercise). MMP-activity did not change throughout the study. Circulating MMP-9 concentrations, but not MMP-activity, were associated with EC concentrations (r_rm = 0.48, p = 0.010). CPC concentrations were not linked to hematopoietic cytokines. Acute exercise at high altitude attenuated endothelial shedding, but did not enhance regenerative CPCs. Results were not linked to endothelial matrix remodeling or CPC mobilization. These results provide information to better understand the endothelium and immature immune system during an active, short-term sojourn at high altitude.