Training Surface and Intensity

Current iron therapy in the light of regulation, intestinal microbiome, and toxicity: are we prescribing too much iron?

Iron deficiency is a widespread global health concern with varying prevalence rates across different regions. In developing countries, scarcity of food and chronic infections contribute to iron deficiency, while in industrialized nations, reduced food intake and dietary preferences affect iron status. Other causes that can lead to iron deficiency are conditions and diseases that result in reduced intestinal iron absorption and blood loss. In addition, iron absorption and its bioavailability are influenced by the composition of the diet. Individuals with increased iron needs, including infants, adolescents, and athletes, are particularly vulnerable to deficiency. Severe iron deficiency can lead to anemia with performance intolerance or shortness of breath. In addition, even without anemia, iron deficiency leads to mental and physical fatigue, which points to the fundamental biological importance of iron, especially in mitochondrial function and the respiratory chain. Standard oral iron supplementation often results in gastrointestinal side effects and poor compliance. Low-dose iron therapy seems to be a valid and reasonable therapeutic option due to reduced hepatic hepcidin formation, facilitating efficient iron resorption, replenishment of iron storage, and causing significantly fewer side effects. Elevated iron levels influence gut microbiota composition, favoring pathogenic bacteria and potentially disrupting metabolic and immune functions. Protective bacteria, such as bifidobacteria and lactobacilli, are particularly susceptible to increased iron levels. Dysbiosis resulting from iron supplementation may contribute to gastrointestinal disorders, inflammatory bowel disease, and metabolic disturbances. Furthermore, gut microbiota alterations have been linked to mental health issues. Future iron therapy should consider low-dose supplementation to mitigate adverse effects and the impact on the gut microbiome. A comprehensive understanding of the interplay between iron intake, gut microbiota, and human health is crucial for optimizing therapeutic approaches and minimizing potential risks associated with iron supplementation.

Sports Supplement Consumption in 316 Federated Female Road Cyclists

Although the extensive use of sports supplements (SSs) is prevalent among cyclists, this area has been poorly explored; in fact, no studies have been conducted on this topic regarding women cyclists to date. This descriptive, cross-sectional study, which included 316 federated female road cyclists, aimed to analyze SS consumption patterns in relation to scientific evidence and various categories. SSs were categorized according to the groups and subgroups established by the Australian Sport Institute (AIS, 2023) based on the level of evidence supporting their use. The analysis found that 85.1% of the female road cyclists surveyed used SSs, with an average consumption of 7 ± 6 supplements per individual. Pharmacies (60.8%), dietitian-nutritionists (58.9%), and health status (60.1%) were the primary purchase location, source of information, and reason for use, respectively. The most frequently consumed supplements were sports bars (77.5%), sports gels (61.4%), and caffeine (49.1%). Significantly, 80% of the ten most commonly used supplements were from the group with the highest evidence level, as classified by the AIS, with an average intake of 5 ± 3 supplements per cyclist. In summary, the use of SSs is prevalent among female road cyclists, with reliable sources for both purchasing and obtaining advice on supplements.

International society of sports nutrition position stand: nutritional concerns of the female athlete

Based on a comprehensive review and critical analysis of the literature regarding the nutritional concerns of female athletes, conducted by experts in the field and selected members of the International Society of Sports Nutrition (ISSN), the following conclusions represent the official Position of the Society: 1. Female athletes have unique and unpredictable hormone profiles, which influence their physiology and nutritional needs across their lifespan. To understand how perturbations in these hormones affect the individual, we recommend that female athletes of reproductive age should track their hormonal status (natural, hormone driven) against training and recovery to determine their individual patterns and needs and peri and post-menopausal athletes should track against training and recovery metrics to determine the individuals' unique patterns. 2. The primary nutritional consideration for all athletes, and in particular, female athletes, should be achieving adequate energy intake to meet their energy requirements and to achieve an optimal energy availability (EA); with a focus on the timing of meals in relation to exercise to improve training adaptations, performance, and athlete health. 3. Significant sex differences and sex hormone influences on carbohydrate and lipid metabolism are apparent, therefore we recommend first ensuring athletes meet their carbohydrate needs across all phases of the menstrual cycle. Secondly, tailoring carbohydrate intake to hormonal status with an emphasis on greater carbohydrate intake and availability during the active pill weeks of oral contraceptive users and during the luteal phase of the menstrual cycle where there is a greater effect of sex hormone suppression on gluconogenesis output during exercise. 4. Based upon the limited research available, we recommend that pre-menopausal, eumenorrheic, and oral contraceptives using female athletes should aim to consume a source of high-quality protein as close to beginning and/or after completion of exercise as possible to reduce exercise-induced amino acid oxidative losses and initiate muscle protein remodeling and repair at a dose of 0.32-0.38 g·kg-1. For eumenorrheic women, ingestion during the luteal phase should aim for the upper end of the range due to the catabolic actions of progesterone and greater need for amino acids. 5. Close to the beginning and/or after completion of exercise, peri- and post-menopausal athletes should aim for a bolus of high EAA-containing (~10 g) intact protein sources or supplements to overcome anabolic resistance. 6. Daily protein intake should fall within the mid- to upper ranges of current sport nutrition guidelines (1.4-2.2 g·kg-1·day-1) for women at all stages of menstrual function (pre-, peri-, post-menopausal, and contraceptive users) with protein doses evenly distributed, every 3-4 h, across the day. Eumenorrheic athletes in the luteal phase and peri/post-menopausal athletes, regardless of sport, should aim for the upper end of the range. 7. Female sex hormones affect fluid dynamics and electrolyte handling. A greater predisposition to hyponatremia occurs in times of elevated progesterone, and in menopausal women, who are slower to excrete water. Additionally, females have less absolute and relative fluid available to lose via sweating than males, making the physiological consequences of fluid loss more severe, particularly in the luteal phase. 8. Evidence for sex-specific supplementation is lacking due to the paucity of female-specific research and any differential effects in females. Caffeine, iron, and creatine have the most evidence for use in females. Both iron and creatine are highly efficacious for female athletes. Creatine supplementation of 3 to 5 g per day is recommended for the mechanistic support of creatine supplementation with regard to muscle protein kinetics, growth factors, satellite cells, myogenic transcription factors, glycogen and calcium regulation, oxidative stress, and inflammation. Post-menopausal females benefit from bone health, mental health, and skeletal muscle size and function when consuming higher doses of creatine (0.3 g·kg-1·d-1). 9. To foster and promote high-quality research investigations involving female athletes, researchers are first encouraged to stop excluding females unless the primary endpoints are directly influenced by sex-specific mechanisms. In all investigative scenarios, researchers across the globe are encouraged to inquire and report upon more detailed information surrounding the athlete's hormonal status, including menstrual status (days since menses, length of period, duration of cycle, etc.) and/or hormonal contraceptive details and/or menopausal status.

Factors Influencing the Hepcidin Response to Exercise: An Individual Participant Data Meta-analysis

BACKGROUND

Hepcidin, the master iron regulatory hormone, has been shown to peak 3-6 h postexercise, and is likely a major contributor to the prevalence of iron deficiency in athletes. Although multiple studies have investigated the hepcidin response to exercise, small sample sizes preclude the generalizability of current research findings.

OBJECTIVE

The aim of this individual participant data meta-analysis was to identify key factors influencing the hepcidin-exercise response.

METHODS

Following a systematic review of the literature, a one-stage meta-analysis with mixed-effects linear regression, using a stepwise approach to select the best-fit model, was employed.

RESULTS

We show that exercise is associated with a 1.5-2.5-fold increase in hepcidin concentrations, with pre-exercise hepcidin concentration accounting for ~ 44% of the variance in 3 h postexercise hepcidin concentration. Although collectively accounting for only a further ~ 3% of the variance, absolute 3 h postexercise hepcidin concentrations appear higher in males with lower cardiorespiratory fitness and higher pre-exercise ferritin levels. On the other hand, a greater magnitude of change between the pre- and 3 h postexercise hepcidin concentration was largely attributable to exercise duration (~ 44% variance) with a much smaller contribution from VO2max, pre-exercise ferritin, sex, and postexercise interleukin-6 (~ 6% combined). Although females tended to have a lower absolute 3 h postexercise hepcidin concentration [1.4 nmol·L-1, (95% CI [- 2.6, - 0.3]), p = 0.02] and 30% less change (95% CI [-54.4, - 5.1]), p = 0.02) than males, with different explanatory variables being significant between sexes, sample size discrepancies and individual study design biases preclude definitive conclusions.

CONCLUSION

Our analysis reveals the complex interplay of characteristics of both athlete and exercise session in the hepcidin response to exercise and highlights the need for further investigation into unaccounted-for mediating factors.

Iron deficiency in young basketball players: Is a 100 μg/L ferritin cut-off appropriate for iron supplementation?: Results of a randomized placebo-controlled study

BACKGROUND

Iron deficiency (ID) is one of the most common factors that may reduce sports performance, supplementation forms and doses are still not standardized in athletes. Our aim was to assess the iron status of young male basketball players and to study the effect of iron supplementation in a randomized placebo-controlled study.

HYPOTHESIS

We hypothesized that due to the higher iron demand of athletes, the 100 μg/L ferritin cut-off may be appropriate to determine the non-anemic ID.

METHODS

During a sports cardiology screening, questionnaires, laboratory tests, electrocardiograms, echocardiography exams, and cardiopulmonary exercise tests were performed. Athletes with ID (ferritin <100 μg/L) were randomized into iron and placebo groups. Ferrous sulfate (containing 100 mg elemental iron [II] and 60 mg ascorbic acid) or placebo (50 mg vitamin C) was administered for 3 months. All exams were repeated after the supplementation period.

RESULTS

We included 65 (age 15.8 ± 1.7 years) basketball players divided into four age groups. Non-anemic ID was observed in 60 (92%) athletes. After supplementation, ferritin levels were higher in the iron group (75.5 ± 25.9 vs. 54.9 ± 10.4 μg/L, p < .01). Ferritin >100 μg/L level was achieved only in 15% of the athletes. There were no differences in performance between the groups (VO2 max: 53.6 ± 4.3 vs. 54.4 ± 5.7 mL/kg/min, p = .46; peak lactate: 9.1 ± 2.2 vs. 9.1 ± 2.6 mmol/L, p = .90).

CONCLUSIONS

As a result of the 3-month iron supplementation, the ferritin levels increased; however, only a small portion of the athletes achieved the target ferritin level, while performance improvement was not detectable.

Effect of Supplementation with Black Chokeberry (Aronia melanocarpa) Extract on Inflammatory Status and Selected Markers of Iron Metabolism in Young Football Players: A Randomized Double-Blind Trial

The use of herbal medicinal products and supplements in amateur and professional sports has increased in the last decades. This is because most of these products and supplements contain bioactive compounds with a variety of biological properties that exert a physiological effect on the human body. The aim of this study was to analyze the effect of dietary supplementation with lyophilized black chokeberry extract on the levels of pro-inflammatory cytokines, hepcidin, and selected markers of iron metabolism in a group of young football players. This double-blind study included 22 male football players (mean = 19.96 ± 0.56), divided into two groups: supplemented and placebo. Before and after a 90-day period of training combined with supplementation (6 g of lyophilized black chokeberry extract), participants performed maximal multistage 20-m shuttle run tests at the beginning and at the end of the supplementation period, with blood sampled for analysis at different times before and after exercise. The levels of IL-6, IL-10, ferritin, myoglobin, hepcidin, 8-OHdG, albumin, and TAC were analyzed. The analysis of variance revealed a significant effect of 90-day supplementation with the lyophilized extract on changes in the IL-6 and IL-10 levels, and TAC induced by maximal aerobic effort. In conclusion, supplementation with lyophilized black chokeberry extract improves the performance and antioxidant status of serum in humans and induces protective changes in inflammatory markers.

Managing Female Athlete Health: Auditing the Representation of Female versus Male Participants among Research in Supplements to Manage Diagnosed Micronutrient Issues

Micronutrient deficiencies and sub-optimal intakes among female athletes are a concern and are commonly prevented or treated with medical supplements. However, it is unclear how well women have been considered in the research underpinning current supplementation practices. We conducted an audit of the literature supporting the use of calcium, iron, and vitamin D. Of the 299 studies, including 25,171 participants, the majority (71%) of participants were women. Studies with exclusively female cohorts (37%) were also more prevalent than those examining males in isolation (31%). However, study designs considering divergent responses between sexes were sparse, accounting for 7% of the literature. Moreover, despite the abundance of female participants, the quality and quantity of the literature specific to female athletes was poor. Just 32% of studies including women defined menstrual status, while none implemented best-practice methodologies regarding ovarian hormonal control. Additionally, only 10% of studies included highly trained female athletes. Investigations of calcium supplementation were particularly lacking, with just two studies conducted in highly trained women. New research should focus on high-quality investigations specific to female athletes, alongside evaluating sex-based differences in the response to calcium, iron, and vitamin D, thus ensuring the specific needs of women have been considered in current protocols involving medical supplements.

Heat acclimation does not attenuate hepcidin elevation after a single session of endurance exercise under hot condition

Purpose

We sought to determine the effects of heat acclimation on endurance exercise-induced hepcidin elevation under hot conditions.

Methods

Fifteen healthy men were divided into two groups: endurance training under hot conditions (HOT, 35 °C, n = 8) and endurance training under cool conditions (CON, 18 °C, n = 7). All subjects completed 10 days of endurance training (8 sessions in total), consisting of 60 min of continuous exercise at 50% of maximal oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2\max }$$\end{document}V˙O2max) under their assigned environment condition. Subjects completed a heat stress exercise test (HST, 60 min exercise at 60% \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}{\text{O}}_{2\max }$$\end{document}V˙O2max) to evaluate the exercise-induced thermoregulatory and hepcidin responses under hot conditions (35 °C) before (pre-HST) and after (post-HST) the training period.

Results

Core temperature during exercise in the post-HST decreased significantly in the HOT group compared to pre-HST (P = 0.004), but not in the CON group. The HOT and CON groups showed augmented exercise-induced plasma interleukin-6 (IL-6) elevation in the pre-HST (P = 0.002). Both groups had significantly attenuated increases in exercise-induced IL-6 in the post-HST; however, the reduction of exercise-induced IL-6 elevation was not different significantly between both groups. Serum hepcidin concentrations increased significantly in the pre-HST and post-HST in both groups (P = 0.001), no significant difference was observed between both groups during each test or over the study period.

Conclusion

10 days of endurance training period under hot conditions improved thermoregulation, whereas exercise-induced hepcidin elevation under hot conditions was not attenuated following the training.

Iron Metabolism following Twice a Day Endurance Exercise in Female Long-Distance Runners

Iron deficiency anemia (IDA) and iron deficiency (ID) are frequently observed among endurance athletes. The iron regulatory hormone hepcidin may be involved in IDA and/or ID. Endurance athletes incorporate multiple training sessions, but the influence of repeated bouts of endurance exercise within the same day on iron metabolism remains unclear. Therefore, the purpose of the present study was to investigate the influence of twice a day endurance exercise on iron metabolism, including the hepcidin level, in female long-distance runners. Thirteen female long-distance runners participated in this study. They completed the twice-a-day endurance exercise in the morning and afternoon. Blood samples were collected four times in total: at 06:00 (P0), 14:00 (P8), 20:00 (P14), and 06:00 the next day (P24). In addition to the blood variables, nutritional intake was assessed throughout the exercise day. Serum hepcidin levels were significantly elevated (compared to P0) until the following morning (P24). Moreover, dietary analysis revealed that subjects consumed a low volume of carbohydrates (<6 g/kg body mass/day). In conclusion, twice a day endurance exercise resulted in significant elevation of serum hepcidin level 24 h after completion of the exercise in female long-distance runners. Therefore, athletes with a high risk of anemia should pay attention to training frequency and nutritional intake in order to maintain optimal iron metabolism.

A Bioinformatics-Assisted Review on Iron Metabolism and Immune System to Identify Potential Biomarkers of Exercise Stress-Induced Immunosuppression

The immune function is closely related to iron (Fe) homeostasis and allostasis. The aim of this bioinformatics-assisted review was twofold; (i) to update the current knowledge of Fe metabolism and its relationship to the immune system, and (ii) to perform a prediction analysis of regulatory network hubs that might serve as potential biomarkers during stress-induced immunosuppression. Several literature and bioinformatics databases/repositories were utilized to review Fe metabolism and complement the molecular description of prioritized proteins. The Search Tool for the Retrieval of Interacting Genes (STRING) was used to build a protein-protein interactions network for subsequent network topology analysis. Importantly, Fe is a sensitive double-edged sword where two extremes of its nutritional status may have harmful effects on innate and adaptive immunity. We identified clearly connected important hubs that belong to two clusters: (i) presentation of peptide antigens to the immune system with the involvement of redox reactions of Fe, heme, and Fe trafficking/transport; and (ii) ubiquitination, endocytosis, and degradation processes of proteins related to Fe metabolism in immune cells (e.g., macrophages). The identified potential biomarkers were in agreement with the current experimental evidence, are included in several immunological/biomarkers databases, and/or are emerging genetic markers for different stressful conditions. Although further validation is warranted, this hybrid method (human-machine collaboration) to extract meaningful biological applications using available data in literature and bioinformatics tools should be highlighted.

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

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

Hepcidin as a Prospective Individualized Biomarker for Individuals at Risk of Low Energy Availability

Hepcidin, a peptide hormone with an acknowledged evolutionary function in iron homeostasis, was discovered at the turn of the 21st century. Since then, the implications of increased hepcidin activity have been investigated as a potential advocate for the increased risk of iron deficiency in various health settings. Such implications are particularly relevant in the sporting community where peaks in hepcidin postexercise (∼3-6 hr) are suggested to reduce iron absorption and recycling, and contribute to the development of exercise-induced iron deficiency in athletes. Over the last decade, hepcidin research in sport has focused on acute and chronic hepcidin activity following single and repeated training blocks. This research has led to investigations examining possible methods to attenuate postexercise hepcidin expression through dietary interventions. The majority of macronutrient dietary interventions have focused on manipulating the carbohydrate content of the diet in an attempt to determine the health of athletes adopting the low-carbohydrate or ketogenic diets, a practice that is a growing trend among endurance athletes. During the process of these macronutrient dietary intervention studies, an observable coincidence of increased cumulative hepcidin activity to low energy availability has emerged. Therefore, this review aims to summarize the existing literature on nutritional interventions on hepcidin activity, thus, highlighting the link of hepcidin to energy availability, while also making a case for the use of hepcidin as an individualized biomarker for low energy availability in males and females.

Lower Level of Interleukin-6 and Hepcidin Found in Lower Density of Physical Exercise among Athlete During Pandemic of Covid-19

The pandemic of Covid-19 affected entire daily human life worldwide, including sports activities among athletes. An athlete was pushed to suit their routine activities with a new health protocol for Covid-19 prevention. Some of them were programmed to train at home with a moderate density of exercise, but others were still in a high density of exercise. This study compared the serum level of hemoglobin (Hb), interleukin-6 (IL-6), and hepcidin among athletes with a high versus moderate exercise density training program during the pandemic. Thirty-four indoor soccer athletes of a soccer football school in Malang voluntarily registered as a subject. Half of them received moderate exercise density exercise programs, and others received high-density exercise programs during June-July 2020. Interleukin-6 and hepcidin level mean was found significantly lower in the moderate group compared to the high-density group. Hemoglobin level mean was found not different between those groups. The lower density of exercise influenced on IL-6 and hepcidin serum level of athlete, but not on hemoglobin level.

Synbiotic Supplementation Improves Response to Iron Supplementation in Female Athletes during Training

OBJECTIVE

Iron deficiency (ID) affects ∼30% of female athletes, and its consequences are highly relevant to athletic performance. Poor iron (Fe) uptake remains a major factor in the development of ID. While studies suggest that consumption of either prebiotics or probiotics may improve Fe uptake, consumption of synbiotics has not been well-studied. The main objective of this study was to determine the effects of synbiotic supplementation on the Fe status of female athletes during Fe repletion.

METHODS

The Fe status of 32 female athletes was screened early in the season. Twenty eligible athletes (hemoglobin:12.3 ± 0.9g/dL; serum ferritin, sFer:18.1 ± 9.2 µg/L) were randomized to receive either a daily synbiotic supplement (5 g prebiotic fiber + 8 billion colony forming units, CFU probiotic B. lactis) or placebo, along with Fe supplementation (140 mg ferrous sulfate, FeSO4/d) for 8 weeks using a double-blind design. Fe status was assessed again at mid-point and after the trial.

RESULTS

Nineteen athletes (n = 9 supplement, 10 placebo) completed the trial and there were no differences in compliance or GI symptoms reported between groups. After controlling for baseline Fe status, regression analyses revealed improvements in log sFer in the supplement group after both 4 and 8 weeks (p = 0.01 and p = 0.05, respectively), compared to placebo.

CONCLUSIONS

Synbiotic supplementation along with FeSO4 improved athletes' Fe status over 8 weeks. This data is essential to advancing our understanding of how dietary and supplemental Fe uptake in active women can be enhanced by synbiotic supplementation, as well as by foods containing pre- and probiotics.

Hepcidin response to three consecutive days of endurance training in hypoxia

PURPOSE

The purpose of this study was to determine the effects of 3 consecutive days of endurance training in hypoxia on hepcidin responses.

METHOD

Nine active healthy males completed two trials, consisting of 3 consecutive days of endurance training in either hypoxia [fraction of inspired oxygen (F_iO₂): 14.5%) or normoxia (F_iO₂: 20.9%). On days 1-3, participants performed one 90 min session of endurance training per day, consisting of high-intensity endurance interval exercise [10 × 4 min of pedaling at 80% of maximal oxygen uptake ([Formula: see text]O_2max) with 2 min of active rest at 30% of [Formula: see text]O_2max] followed by 30 min of continuous exercise at 60% of [Formula: see text]O_2max. Venous blood samples were collected prior to exercise each day during the experimental period (days 1-4) to determine serum hepcidin, iron, ferritin, haptoglobin, and ketone body concentrations.

RESULT

Serum iron (p < 0.0001), ferritin (p = 0.005) and ketone body (p < 0.0001) concentrations increased significantly in both trials on days 2-4 compared with day 1, with no significant differences between trials. No significant changes in serum haptoglobin concentrations were observed throughout the experimental period in either trial. Serum hepcidin concentrations also increased significantly on days 2-4 compared with day 1 in both trials (p = 0.004), with no significant differences observed between trials.

CONCLUSION

3 consecutive days of endurance training in hypoxia did not affect hepcidin concentrations compared with endurance training in normoxia.

Association of Serum Hepcidin Levels with Aerobic and Resistance Exercise: A Systematic Review

BACKGROUND

Prevalence of iron deficiency is commonly reported among athletic population groups. It impairs physical performance due to insufficient oxygen delivery to target organs and low energy production. This is due to the high demand of exercise on oxygen delivery for systemic metabolism by the erythrocytes in the blood. Hepcidin, the key regulator of iron homeostasis, decreases to facilitate iron efflux into the circulation during enhanced erythropoiesis. However, acute anaemia of exercise is caused by increased hepcidin expression that is induced by stress and inflammatory signal. The study aimed to systematically review changes in serum hepcidin levels during resistance and aerobic exercise programmes.

METHODS

A systemic literature search from 2010 to April 2020 across seven databases comprised of Cochrane library, PubMed, Web of Science, Scopus, Embase, MEDLINE, and OpenGrey. The primary outcome was increased or decreased serum hepcidin from baseline after the exercise activity. Risks of bias were evaluated by using the National Institutes of Health (NIH) for quality assessment of before and after different exercise programmes.

RESULTS

Overall, twenty-three studies met the inclusion criteria. Out of the 23 studies, 16 studies reported significantly exercise-induced serum hepcidin elevation. Of the 17 studies that evaluated serum interleukin (IL)-6 levels, 14 studies showed significant exercise-induced serum IL-6 elevation. Changes in exercise-induced serum hepcidin and IL-6 levels were similar in both resistance and endurance exercise. Significant correlations were observed between post-exercise hepcidin and baseline ferritin levels (r = 0.69, p < 0.05) and between post-exercise hepcidin and post-exercise IL-6 (r = 0.625, p < 0.05).

CONCLUSION

Resistance and endurance training showed significant increase in serum hepcidin and IL-6 levels in response to exercise. Baseline ferritin and post-exercise IL-6 elevation are key determining factors in the augmentation of hepcidin response to exercise.

Six weeks of dynamic apnoeic training stimulates erythropoiesis but does not increase splenic volume

Purpose

This study examined the influence of dynamic apnoea training on splenic volume and haematological responses in non-breath-hold divers (BHD).

Methods

Eight non-BHD performed ten maximal dynamic apnoeas, four times a week for  six weeks. Splenic volumes were assessed ultrasonically, and blood samples were drawn for full blood count analysis, erythropoietin, iron, ferritin, albumin, protein and osmolality at baseline, 24 h post the completion of each week’s training sessions and seven days post the completion of the training programme. Additionally, blood samples were drawn for haematology at 30, 90, and 180 min post session one, twelve and twenty-four.

Results

Erythropoietin was only higher than baseline (6.62 ± 3.03 mlU/mL) post session one, at 90 (9.20 ± 1.88 mlU/mL, p = 0.048) and 180 min (9.04 ± 2.35 mlU/mL, p = 0.046). Iron increased from baseline (18 ± 3 µmol/L) post week five (23 ± 2 µmol/L, p = 0.033) and six (21 ± 6 µmol/L; p = 0.041), whereas ferritin was observed to be lower than baseline (111 ± 82 µg/L) post week five (95 ± 75 µg/L; p = 0.016), six (84 ± 74 µg/L; p = 0.012) and one week post-training (81 ± 63 µg/L; p = 0.008). Reticulocytes increased from baseline (57 ± 12 × 10⁹/L) post week one (72 ± 17 × 10⁹/L, p = 0.037) and six (71 ± 17 × 10⁹/L, p = 0.021) while no changes were recorded in erythrocytes (p = 0.336), haemoglobin (p = 0.124) and splenic volumes (p = 0.357).

Conclusions

Six weeks of dynamic apnoeic training increase reticulocytes without altering mature erythrocyte concentration and splenic volume.

Hepcidin and interleukin-6 responses to endurance exercise over the menstrual cycle

The aim of the current study was to investigate iron metabolism in endurance trained women through the interleukin-6, hepcidin and iron responses to exercise along different endogenous hormonal states. Fifteen women performed 40 min treadmill running trials at 75% vVO2peak during three specific phases of the menstrual cycle: early follicular phase (day 3 ± 0.85), mid-follicular phase (day 8 ± 1.09) and luteal phase (day 21 ± 1.87). Venous blood samples were taken pre-, 0 h post- and 3 h post-exercise. Interleukin-6 reported a significant interaction for menstrual cycle phase and time (p=0.014), showing higher interleukin-6 levels at 3 h post-exercise during luteal phase compared to the early follicular phase (p=0.004) and the mid-follicular phase (p=0.002). Iron levels were significantly lower (p=0.009) during the early follicular phase compared to the mid-follicular phase. However, hepcidin levels were not different across menstrual cycle phases (p>0.05). The time-course for hepcidin and interleukin-6 responses to exercise was different from the literature, since hepcidin peak levels occurred at 0 h post-exercise, whereas the highest interleukin-6 levels occurred at 3 h post-exercise. We concluded that menstrual cycle phases may alter interleukin-6 production causing a higher inflammation when progesterone levels are elevated (days 19-21). Moreover, during the early follicular phase a significant reduction of iron levels is observed potentially due to a loss of haemoglobin through menses. According to our results, high intensity exercises should be carefully monitored in these phases in order not to further compromise iron stores.

Partial sleep deprivation after an acute exercise session does not augment hepcidin levels the following day

The purpose of the present study was to determine the effects of partial sleep deprivation (PSD) after an exercise session in the evening on the endurance exercise-induced hepcidin response the following morning. Ten recreationally trained males participated under two different conditions. Each condition consisted of 2 consecutive days of training (days 1 and 2). On day 1, participants ran for 60 min at 75% of maximal oxygen uptake ( V ˙ O2max ) followed by 100 drop jumps. Sleep duration at night was manipulated, with a normal length of sleep (CON condition, 23:00-07:00 hr) or a shortened length of sleep (PSD condition). On the morning of day 2, the participants ran for 60 min at 65% of V ˙ O2max . Sleep duration was significantly shorter under the PSD condition (141.2 ± 13.3 min) than under the CON condition (469.0 ± 2.3 min, p < .0001). Serum hepcidin, plasma interleukin (IL)-6, serum haptoglobin, iron, and myoglobin levels did not differ significantly between the conditions (p > .05) on the morning (before exercise) of day 2. Additionally, the 3-hr postexercise levels for the hematological variables were not significantly different between the two conditions (p > .05). In conclusion, the present study demonstrated that a single night of PSD after an exercise session in the evening did not affect baseline serum hepcidin level the following morning. Moreover, a 60 min run the following morning increased serum hepcidin and plasma IL-6 levels significantly, but the exercise-induced elevations were not affected by PSD.

Diagnosis and management of iron deficiency in children with or without anemia: consensus recommendations of the SPOG Pediatric Hematology Working Group

Iron deficiency is the most prevalent nutritional deficiency affecting children and adolescents worldwide. A consistent body of epidemiological data demonstrates an increased incidence of iron deficiency at three timepoints: in the neonatal period, in preschool children, and in adolescents, where it particularly affects females.Conclusion: This narrative review focuses on the most suggestive symptoms of iron deficiency in childhood, describes the diagnostic procedures in situations with or without anemia, and provides Swiss expert-based management recommendations for the pediatric context.What is Known:• Iron deficiency (ID) is one of the most common challenges faced by pediatricians.• Significant progress in the diagnosis and therapy of ID has been made over the last decade.What is New:• Our expert panel provides ID management recommendations based on the best available evidence.• They include strategies for ID diagnosis and therapy, both oral and intravenous.

Resistance exercise causes greater serum hepcidin elevation than endurance (cycling) exercise

BACKGROUND

Hepcidin is an iron regulating hormone, and exercise-induced hepcidin elevation is suggested to increase the risk of iron deficiency among athletes.

OBJECTIVE

We compared serum hepcidin responses to resistance exercise and endurance (cycling) exercise.

METHODS

Ten males [mean ± standard error: 172 ± 2 cm, body weight: 70 ± 2 kg] performed three trials: a resistance exercise trial (RE), an endurance exercise trial (END), and a rest trial (REST). The RE consisted of 60 min of resistance exercise (3-5 sets × 12 repetitions, 8 exercises) at 65% of one repetition maximum, while 60 min of cycling exercise at 65% of [Formula: see text] was performed in the END. Blood samples were collected before exercise and during a 6-h post-exercise (0h, 1h, 2h, 3h, 6h after exercise).

RESULTS

Both RE and END significantly increased blood lactate levels, with significantly higher in the RE (P < 0.001). Serum iron levels were significantly elevated immediately after exercise (P < 0.001), with no significant difference between RE and END. Both the RE and END significantly increased serum growth hormone (GH), cortisol, and myoglobin levels (P < 0.01). However, exercise-induced elevations of GH and cortisol were significantly greater in the RE (trial × time: P < 0.001). Plasma interleukin-6 (IL-6) levels were significantly elevated after exercise (P = 0.003), with no significant difference between the trials. Plasma hepcidin levels were elevated after exercise (P < 0.001), with significantly greater in the RE (463 ± 125%) than in the END (137 ± 27%, P = 0.03). During the REST, serum hepcidin and plasma IL-6 levels did not change significantly.

CONCLUSION

Resistance exercise caused a greater exercise-induced elevation in hepcidin than did endurance (cycling) exercise. The present findings indicate that caution will be required to avoid iron deficiency even among athletes in strength (power) types of events who are regularly involved in resistance exercise.

Beneficial Effect of Ubiquinol on Hematological and Inflammatory Signaling during Exercise

Strenuous exercise (any activity that expends six metabolic equivalents per minute or more causing sensations of fatigue and exhaustion to occur, inducing deleterious effects, affecting negatively different cells), induces muscle damage and hematological changes associated with high production of pro-inflammatory mediators related to muscle damage and sports anemia. The objective of this study was to determine whether short-term oral ubiquinol supplementation can prevent accumulation of inflammatory mediators and hematological impairment associated to strenuous exercise. For this purpose, 100 healthy and well-trained firemen were classified in two groups: Ubiquinol (experimental group), and placebo group (control). The protocol was two identical strenuous exercise tests with rest period between tests of 24 h. Blood samples were collected before supplementation (basal value) (T1), after supplementation (T2), after first physical exercise test (T3), after 24 h of rest (T4), and after second physical exercise test (T5). Hematological parameters, pro- and anti-inflammatory cytokines and growth factors were measured. Red blood cells (RBC), hematocrit, hemoglobin, VEGF, NO, EGF, IL-1ra, and IL-10 increased in the ubiquinol group while IL-1, IL-8, and MCP-1 decreased. Ubiquinol supplementation during high intensity exercise could modulate inflammatory signaling, expression of pro-inflammatory, and increasing some anti-inflammatory cytokines. During exercise, RBC, hemoglobin, hematocrit, VEGF, and EGF increased in ubiquinol group, revealing a possible pro-angiogenic effect, improving oxygen supply and exerting a possible protective effect on other physiological alterations.

Epidemiological, biological and clinical update on exercise-induced hemolysis

Exercise-induced hemolysis can be conventionally defined as rupture and destruction of erythrocytes during physical exercise. The currently available epidemiologic information attests that a substantial degree of exercise-induced hemolysis is commonplace after short-, medium-, long- and ultra-long distance running, as reflected by significant decrease of serum or plasma haptoglobin and significant increase of plasma concentration (or overall blood content) of free hemoglobin. This paraphysiological intravascular hemolysis is typically mild (average variations of hemolysis biomarkers are usually comprised between 1.2- and 1.8-fold), almost self-limiting (completely resolving within 24-48 hours), with severity depending on athlete population, analytical technique used for detecting intravascular hemolysis, as well as on number, frequency and intensity of ground contacts, but not on running technique. Additional lines of evidence support the notion that both osmotic fragility and membrane structure of erythrocytes are considerably modified during endurance exercise. This fact goes hand in hand with findings that erythrocyte lifespan in runners is approximately 40% shorter than in sedentary controls. Direct mechanical injury caused by forceful ground contacts, repeated muscle contractile activity or vasoconstriction in internal organs are three potential sources of exercise-induced hemolysis, whilst metabolic abnormalities developing while exercising (e.g., hyperthermia, dehydration, hypotonic shock, hypoxia, lactic acidosis, shear stress, oxidative damage, proteolysis, increased concentration of catecholamines and lysolecithin) may actively contribute to trigger, accelerate or amplify this phenomenon. Although no systematic evidence is available, it seems also reasonable to hypothesize that patients bearing erythrocyte disorders may be particularly vulnerable to developing exercise-induced hemolysis.

An intensified training schedule in recreational male runners is associated with increases in erythropoiesis and inflammation and a net reduction in plasma hepcidin

Background

Iron status is a determinant of physical performance, but training may induce both low-grade inflammation and erythropoiesis, exerting opposing influences on hepcidin and iron metabolism. To our knowledge, the combined effects on iron absorption and utilization during training have not been examined directly in humans.

Objective

We hypothesized that 3 wk of exercise training in recreational male runners would decrease oral iron bioavailability by increasing inflammation and hepcidin concentrations.

Design

In a prospective intervention, nonanemic, iron-sufficient men (n = 10) completed a 34-d study consisting of a 16-d control phase and a 22-d exercise-training phase of 8 km running every second day. We measured oral iron absorption and erythroid iron utilization using oral 57Fe and intravenous 58Fe tracers administered before and during training. We measured hemoglobin mass (mHb) and total red blood cell volume (RCV) by carbon monoxide rebreathing. Iron status, interleukin-6 (IL-6), plasma hepcidin (PHep), erythropoietin (EPO), and erythroferrone were measured before, during, and after training.

Results

Exercise training induced inflammation, as indicated by an increased mean ± SD IL-6 (0.87 ± 1.1 to 5.17 ± 2.2 pg/mL; P < 0.01), while also enhancing erythropoiesis, as indicated by an increase in mean EPO (0.66 ± 0.42 to 2.06 ± 1.6 IU/L), mHb (10.5 ± 1.6 to 10.8 ± 1.8 g/kg body weight), and mean RCV (30.7 ± 4.3 to 32.7 ± 4.6 mL/kg) (all P < 0.05). Training tended to increase geometric mean iron absorption by 24% (P = 0.083), consistent with a decreased mean ± SD PHep (7.25 ± 2.14 to 5.17 ± 2.24 nM; P < 0.05). The increase in mHb and erythroid iron utilization were associated with the decrease in PHep (P < 0.05). Compartmental modeling indicated that iron for the increase in mHb was obtained predominantly (>80%) from stores mobilization rather than from increased dietary absorption.

Conclusions

In iron-sufficient men, mild intensification of exercise intensity increases both inflammation and erythropoiesis. The net effect is to decrease hepcidin concentrations and to tend to increase oral iron absorption. This trial was registered at clinicaltrials.gov as NCT01730521.

Exercise and Redox Status Responses Following Alpha-Lipoic Acid Supplementation in G6PD Deficient Individuals

G6PD deficiency renders cells more susceptible to oxidative insults, while antioxidant dietary supplementation could restore redox balance and ameliorate exercise-induced oxidative stress. To examine the effects of alpha-lipoic acid (ALA) supplementation on redox status indices in G6PD deficient individuals, eight male adults with G6PD deficiency (D) participated in this randomized double-blind placebo-controlled crossover trial. Participants were randomly assigned to receive ALA (600 mg/day) or placebo for 4 weeks separated by a 4-week washout period. Before and at the end of each treatment period, participants exercised following an exhaustive treadmill exercise protocol. Blood samples were obtained before (at rest), immediately after and 1h after exercise for later analysis of total antioxidant capacity (TAC), uric acid, bilirubin, thiobarbituric acid reactive substances (TBARS) and protein carbonyls (PC). ALA resulted in significantly increased resting TAC and bilirubin concentrations. Moreover, TAC increased immediately and 1h after exercise following both treatment periods, whereas bilirubin increased immediately after and 1h after exercise following only ALA. No significant change in uric acid, TBARS or PC was observed at any time point. ALA supplementation for 4 weeks may enhance antioxidant status in G6PD individuals; however, it does not affect redox responses to acute exercise until exhaustion or exercise performance.

Repressed Exercise-Induced Hepcidin Levels after Danggui Buxue Tang Supplementation in Male Recreational Runners

This study was to investigate the protective and recovery effects of Danggui Buxue Tang (DBT) supplementation on exercise performance, hepcidin, iron status, and other related biochemical parameters after being challenged by a single bout of intense aerobic exercise. A total of 36 recreationally active males were pair-matched and randomly assigned to receive DBT or a placebo for 11 days, while using clusters based on their aerobic capacities. On the eighth day of the supplementation, the participants performed a 13-km run with maximal effort. Blood and urine samples were collected and analysed before treatment (Pre-Tre) and immediately after (Post-Ex), 24 h after (24-h Rec), and 72 h after (72-h Rec) the run. DBT supplementation dramatically shortened the finish times by 14.0% (12.3 min) when compared with that in the placebo group. Significant group × time effects were observed in serum hepcidin and iron levels. DBT supplementation repressed hepcidin levels at Post-Ex and 24-h Rec, thereby causing a significant increase in iron levels by 63.3% and 31.4% at Post-Ex and 72-h Rec, respectively. However, DBT supplementation had no significant anti-inflammatory or haemolysis-preventative effects. Short-term DBT supplementation shortened the running time and repressed exercise-induced hepcidin levels, thereby boosting iron levels and accelerating iron homeostasis during recovery.

Acute effects of high-intensity exercise on hematological and iron metabolic parameters in elite male and female dragon boating athletes

OBJECTIVE

To investigate the acute effects of high-intensity exercise on blood hepcidin levels and other iron metabolic and hematological parameters in highly trained athletes of dragon boating as a sport performed in a sitting position.

METHODS

We conducted an exercise intervention study with a pre- and posttest blood measurement to determine the effects of high-intensity training on hematological and iron metabolic parameters in both male (n = 19) and female (n = 12) elite athletes of the German national dragon boating team. The study took place during the final training camp before the European championships. Blood samples were collected at baseline and 3 h after 3 consecutive high-intensity training bouts at the same day, each one lasting 1 h in duration.

RESULTS

After exercise, leukocytes, CPK, CKMB, and hepcidin levels increased significantly both in men and women. In contrast, iron concentrations decreased significantly. No gender-related differences were found. Compared with baseline, the postexercise concentrations of serum iron decreased significantly both in men [99.3 ± 46.3 to 61.2 ± 20.9 µg/dL (p < 0.001)] and in women [116.3 ± 34 to 67.1 ± 21.8 µg/dL (p < 0.001)] without a gender difference (p = 0.28). Hepcidin levels increased significantly both in men [9.1 ± 6.5 to 12.2 ± 5.8 ng/mL (p < 0.001)] and in women [8.0 ± 4.6 to 11.7 ± 5.7 ng/mL (p < 0.001)] without a significant gender difference in hepcidin changes (p = 0.34).

CONCLUSIONS

In conclusion, three consecutive high-intensity training bouts lead to elevated hepcidin levels and decreased iron levels in elite athletes of dragon boating. The increase in hepcidin levels may contribute to the risk of anemia in these athletes.

Stability in post-seasonal hematological profiles in response to high-competitive match-play loads within elite top-level European soccer players: implications from a pilot study

INTRODUCTION

The stability of hematological status indices is a key determinant of optimal sport performance. The capacity to monitor hematological behaviors of elite soccer players may better explain the stresses placed upon physiological systems and the potential decrements in performance and physical capacity. The primary aim of this investigation was to examine the post-seasonal hematological status of professional top-level soccer players in response to seasonal match-play and training demands, in terms of the training practices, intensity, and loadings that they experience before, during, and after each season.

METHODS

Seventeen male elite European soccer players participated in the study (mean±SD: age 26.8±4.6 years, weight 78.1±5.7 kg, height 182.4±4.8 cm, body fat 9.8%±2.9%, and maximal aerobic capacity 56.5±4.2 mL kg-1 min-1). The season culminated in 74 competitive matches including domestic, Champions League, and UEFA Cup matches. Blood samples were collected between 9:00 and 10:30 am after an overnight fast (~10 hours), 72 hours post conclusion of the final match of the competitive season.

RESULTS

Near-perfect correlations between white blood cells, neutrophils, the period of season, training availability, and total competitive minutes were found. When adjusting for all the confounding variables, a stability of the hematological profile was noticed. Only mean cell volume and mean cell hemoglobin values were associated with the requirement for elite European soccer teams to fulfill excessive competitive loadings. The reported lower mean cell volume and mean cell hemoglobin values may highlight the accumulative effects of seasonal training and match-play demands.

CONCLUSION

Regular blood testing could identify the need for both squad rotation and the implementation of interventions to assist in stabilizing transient hematological behaviors in order to optimize performance and sports output.

Biomarkers in Sports and Exercise: Tracking Health, Performance, and Recovery in Athletes

Lee, EC, Fragala, MS, Kavouras, SA, Queen, RM, Pryor, JL, and Casa, DJ. Biomarkers in sports and exercise: tracking health, performance, and recovery in athletes. J Strength Cond Res 31(10): 2920–2937, 2017—Biomarker discovery and validation is a critical aim of the medical and scientific community. Research into exercise and diet-related biomarkers aims to improve health, performance, and recovery in military personnel, athletes, and lay persons. Exercise physiology research has identified individual biomarkers for assessing health, performance, and recovery during exercise training. However, there are few recommendations for biomarker panels for tracking changes in individuals participating in physical activity and exercise training programs. Our approach was to review the current literature and recommend a collection of validated biomarkers in key categories of health, performance, and recovery that could be used for this purpose. We determined that a comprehensive performance set of biomarkers should include key markers of (a) nutrition and metabolic health, (b) hydration status, (c) muscle status, (d) endurance performance, (e) injury status and risk, and (f) inflammation. Our review will help coaches, clinical sport professionals, researchers, and athletes better understand how to comprehensively monitor physiologic changes, as they design training cycles that elicit maximal improvements in performance while minimizing overtraining and injury risk.

Postexercise serum hepcidin response to repeated sprint exercise under normoxic and hypoxic conditions

We determined the effects of repeated sprint exercise under normoxic and hypoxic conditions on serum hepcidin levels. Ten male athletes (age: 20.9 ± 0.3 years; height: 175.7 ± 6.0 cm; weight: 67.3 ± 6.3 kg) performed 2 exercise trials under normoxic (NOR; fraction of inspiratory oxygen (FiO₂): 20.9%) or hypoxic conditions (HYPO; FiO₂: 14.5%). The exercise consisted of 3 sets of 5 × 6 s of maximal pedaling (30-s rest periods between sprints, 10-min rest periods between sets). Blood samples were collected before exercise, immediately after exercise, and 1 and 3 h after exercise. Serum hepcidin levels were significantly elevated after exercise in both trials (both P < 0.01), with no significant difference between the trials. The postexercise blood lactate levels were significantly higher in the HYPO than the NOR (P < 0.05). Both trials caused similar increases in plasma interleukin-6 and serum iron levels (P < 0.001), with no significant difference between the trials. A significant interaction (trial × time) was apparent in terms of serum erythropoietin (EPO) levels (P = 0.003). The EPO level was significantly higher in the HYPO than the NOR at 3 h after exercise (P < 0.05). In conclusion, repeated sprint exercise significantly increased serum hepcidin levels to similar extent in 2 trials, despite differences in the inspired oxygen concentrations during both the exercise and the 3-h postexercise period.

Post-exercise serum hepcidin levels were unaffected by hypoxic exposure during prolonged exercise sessions

The purpose of the present study was to determine the influence of hypoxic exposure during prolonged endurance exercise sessions (79 min in total) on post-exercise hepcidin levels in trained male endurance athletes. Ten endurance athletes (mean ± standard deviation; height: 169.8 ± 7.1 cm, weight: 57.1 ± 5.0 kg) conducted two endurance exercise sessions under either a normobaric hypoxic condition [inspired O2 fraction (FiO2) = 14.5%] or a normoxic condition (FiO2 = 20.9%). Exercise consisted of 10 × 3 min running on a treadmill at 95% of maximal oxygen uptake ([Formula: see text]) with 60s of active rest at 60% of [Formula: see text]. After 10 min of rest, they subsequently performed 30 min of continuous running at 85% of [Formula: see text]. Running velocities were significantly lower in the HYPO than in the NOR (P < 0.0001). Exercise-induced blood lactate elevation was significantly greater in the HYPO (P < 0.01). There were significant increases in plasma interleukin-6, serum iron, and blood glucose levels after exercise, with no significant difference between the trials [interaction (trial × time) or main effect for trial, P > 0.05]. Serum hepcidin levels increased significantly 120 min after exercise (HYPO: from 10.7 ± 9.4 ng/mL to 15.8 ± 11.2 ng/mL; NOR: from 7.9 ± 4.7 ng/mL to 13.2 ± 7.9 ng/mL, P < 0.05), and no difference was observed between the trials. In conclusion, endurance exercise at lower running velocity in hypoxic conditions resulted in similar post-exercise hepcidin elevations as higher running velocity in normoxic conditions.

Iron Supplementation during Three Consecutive Days of Endurance Training Augmented Hepcidin Levels

Iron supplementation contributes an effort to improving iron status among athletes, but it does not always prevent iron deficiency. In the present study, we explored the effect of three consecutive days of endurance training (twice daily) on the hepcidin-25 (hepcidin) level. The effect of iron supplementation during this period was also determined. Fourteen male endurance athletes were enrolled and randomly assigned to either an iron-treated condition (Fe condition, n = 7) or a placebo condition (Control condition; CON, n = 7). They engaged in two 75-min sessions of treadmill running at 75% of maximal oxygen uptake on three consecutive days (days 1-3). The Fe condition took 12 mg of iron twice daily (24 mg/day), and the CON condition did not. On day 1, both conditions exhibited significant increases in serum hepcidin and plasma interleukin-6 levels after exercise (p < 0.05). In the CON condition, the hepcidin level did not change significantly throughout the training period. However, in the Fe condition, the serum hepcidin level on day 4 was significantly higher than that of the CON condition (p < 0.05). In conclusion, the hepcidin level was significantly elevated following three consecutive days of endurance training when moderate doses of iron were taken.

Factors influencing the post-exercise hepcidin-25 response in elite athletes

PURPOSE

The extent to which hepcidin regulation after acute bouts of exercise is influenced by baseline (resting) concentrations of key iron parameters remains uncertain. This investigation explored the influence of selected iron parameters and 25-km race walk time on 3-h post-exercise hepcidin-25 levels in international-level race walkers.

METHODS

Twenty-four male race walkers completed a graded exercise test and a 25-km race-walk trial. Throughout the 25-km race-walk, venous blood samples were collected pre-exercise, immediately post-exercise, and at 3-h post-exercise. Blood was analysed for serum ferritin, serum iron, Interleukin-6 (IL-6), and hepcidin-25 concentration.

RESULTS

IL-6 and hepcidin-25 increased (7.6- and 7.5-fold, respectively) in response to the 25-km race-walk trial (both p < 0.01). Significant individual relationships were evident between 3-h post-exercise hepcidin-25, baseline serum ferritin and serum iron (r > 0.62; p < 0.05). Multiple regression analysis showed that these two iron parameters, in addition to post-exercise IL-6 concentration and 25-km race-walk time, accounted for ~77% of the variance in 3-h post-exercise hepcidin-25 (p < 0.01). A median split by the cohort's baseline serum ferritin concentration (LOW: 58.0 vs. HIGH: 101.8 µg/L; p < 0.01) showed a significant between group difference in the 3-h post-exercise hepcidin-25 (LOW: 6.0 ± 3.6 vs. 11.3 ± 5.4 nM; p = 0.01), despite no differences in baseline serum iron, post-exercise IL-6, or 25-km race-walk time (all p > 0.05).

CONCLUSION

Despite exercise activating numerous hepcidin regulators, baseline iron status appears to play a dominant role in the regulation of hepcidin-25 in elite-level athletes subsequent to endurance exercise.

The effect of 8-week different-intensity walking exercises on serum hepcidin, IL-6, and iron metabolism in pre-menopausal women

Objective

Hepcidin may be an important mediator in exercise-induced iron deficiency. Despite the studies investigating acute exercise effects on hepcidin and markers of iron metabolism, we found no studies examining the chronic effects of walking exercises (WE) on hepcidin and markers of iron metabolism in premenopausal women. The chronic effects of two 8-week different-intensity WE on hepcidin, interleukin 6 (IL-6), and markers of iron metabolism in pre-menopausal women were examined.

Methods

Exercise groups (EG) [moderate tempo walking group (MTWG), n = 11; brisk walking group (BWG), n = 11] walked 3 days/week, starting from 30 to 51 min. Control group (CG; n = 8) did not perform any exercises. BWG walked at ∼70%–75%; MTWG at ∼50%–55% of HRRmax. VO2max, hepcidin, IL-6, and iron metabolism markers were determined before and after the intervention.

Results

VO2max increased in both EGs, favoring the BWG. Hepcidin increased in the BWG (p < 0.01) and CG (p < 0.05). IL-6 decreased in the BWG and the MTWG (p < 0.05; p < 0.01). While iron, ferritin, transferrin, and transferrin saturation levels did not change in any group, total iron binding capacity (p < 0.05), red blood cells (p < 0.05), and hematocrit (p < 0.01) increased only in the BWG.

Conclusion

Both WE types may be useful to prevent inflammation. However, brisk walking is advisable due to the positive changes in VO2max and some iron metabolism parameters, which may contribute to prevent iron deficiency. The increase in hepcidin levels remains unclear and necessitates further studies.

Elevated Serum Hepcidin Levels during an Intensified Training Period in Well-Trained Female Long-Distance Runners

Iron is essential for providing oxygen to working muscles during exercise, and iron deficiency leads to decreased exercise capacity during endurance events. However, the mechanism of iron deficiency among endurance athletes remains unclear. In this study, we compared iron status between two periods involving different training regimens. Sixteen female long-distance runners participated. Over a seven-month period, fasting blood samples were collected during their regular training period (LOW; middle of February) and during an intensified training period (INT; late of August) to determine blood hematological, iron, and inflammatory parameters. Three-day food diaries were also assessed. Body weight and lean body mass did not differ significantly between LOW and INT, while body fat and body fat percentage were significantly lower in INT (p < 0.05). Blood hemoglobin, serum ferritin, total protein, and iron levels, total iron-binding capacity, and transferrin saturation did not differ significantly between the two periods. Serum hepcidin levels were significantly higher during INT than LOW (p < 0.05). Carbohydrate and iron intakes from the daily diet were significantly higher during INT than LOW (p < 0.05). In conclusion, an elevated hepcidin level was observed during an intensified training period in long-distance runners, despite an apparently adequate daily intake of iron.

Live high, train low - influence on resting and post-exercise hepcidin levels

The post-exercise hepcidin response during prolonged (>2 weeks) hypoxic exposure is not well understood. We compared plasma hepcidin levels 3 h after exercise [6 × 1000 m at 90% of maximal aerobic running velocity (vVO_2max )] performed in normoxia and normobaric hypoxia (3000 m simulate altitude) 1 week before, and during 14 days of normobaric hypoxia [196.2 ± 25.6 h (median: 200.8 h; range: 154.3-234.8 h) at 3000 m simulated altitude] in 10 well-trained distance runners (six males, four females). Venous blood was also analyzed for hepcidin after 2 days of normobaric hypoxia. Hemoglobin mass (Hb_mass ) was measured via CO rebreathing 1 week before and after 14 days of hypoxia. Hepcidin was suppressed after 2 (Cohen's d = -2.3, 95% confidence interval: [-2.9, -1.6]) and 14 days of normobaric hypoxia (d = -1.6 [-2.6, -0.6]). Hepcidin increased from baseline, 3 h post-exercise in normoxia (d = 0.8 [0.2, 1.3]) and hypoxia (d = 0.6 [0.3, 1.0]), both before and after exposure (normoxia: d = 0.7 [0.3, 1.2]; hypoxia: d = 1.3 [0.4, 2.3]). In conclusion, 2 weeks of normobaric hypoxia suppressed resting hepcidin levels, but did not alter the post-exercise response in either normoxia or hypoxia, compared with the pre-exposure response.

Single dose of intra-muscular platelet rich plasma reverses the increase in plasma iron levels in exercise-induced muscle damage: A pilot study

BACKGROUND

Platelet rich plasma (PRP) therapy is widely used in enhancing the recovery of skeletal muscle from injury. However, the impact of intramuscular delivery of PRP on hematologic and biochemical responses has not been fully elucidated in exercise-induced muscle damage. The purpose of this investigation the effects of intramuscular delivery of PRP on hematologic and biochemical responses and recovery strategy muscle damage induced by high intensity muscle exercise (exercise-induced muscle damage, EIMD).

METHODS

Moderately active male volunteers participated in this study and were assigned to a control group (control, n = 6) and PRP administration group (PRP, n = 6). The subjects performed exercise with a load of 80% one repetition maximum (1RM) maximal voluntary contraction of the elbow flexors until point of exhaustion of the non-dominant arm was reached. The arms were treated with saline or autologous PRP post-24 h EIMD. Venous blood samples were obtained in the morning to establish a baseline value and 1-4 days post-exercise and were analyzed for serum ferritin, iron, iron binding capacity (IBC), creatinine kinase (CK), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), and alanine aminotransferase (ALT).

RESULTS

The baseline levels of plasma iron, ferritin, IBC, CK, LDH, AST, and ALT were similar in both the control and PRP groups. However, 24-h following exercise a significant increase in these parameters was observed in both groups between 1 and 4 days during the recovery period. Interestingly, PRP administration decreased plasma iron levels compared to the control on the second day post-exercise. Plasma IBC increased in PRP group from Days 2 to 4 post-exercise compared to the control group whilst PRP administration had no effect on plasma ferritin, CK, AST, ALT, or LDH.

CONCLUSION

Acute exhaustive exercise increased muscle damage markers, including plasma iron, IBC, and ferritin levels, indicating muscle damage induced by exercise. PRP administration improves inflammation by reversing the increase in the iron levels post-exercise without displaying any myotoxicity and may have a role to play in the recovery of exercise-induced muscle damage.

A comparison of haemolytic responses in fore-foot and rear-foot distance runners

This study examined the haemolytic effects of an interval-based running task in fore-foot and rear-foot striking runners. Nineteen male distance runners (10 fore-foot, 9 rear-foot) completed 8 × 3 min repeats at 90% vVO2peak on a motorised treadmill. Pre- and post-exercise venous blood samples were analysed for serum haptoglobin to quantify the haemolytic response to running. Vertical ground reaction forces were also captured via a force plate beneath the treadmill belt. Haptoglobin levels were significantly decreased following exercise (P = 0.001) in both groups (but not between groups), suggesting that the running task created a haemolytic stress. The ground reaction force data showed strong effect sizes for a greater peak force (d = 1.20) and impulse (d = 1.37) in fore-foot runners, and a greater rate of force development (d = 2.74) in rear-foot runners. The lack of difference in haptoglobin response between groups may be explained by the trend for fore-foot runners to experience greater peak force and impulse during the stance phase of their running gait, potentially negating any impact of the greater rate of force development occurring from the rear-foot runners' heel strike. Neither type of runner (fore-foot or rear-foot) appears more susceptible to technique-related foot-strike haemolysis.

Acute dietary carbohydrate manipulation and the subsequent inflammatory and hepcidin responses to exercise

PURPOSE

To examine the effects of 24-h controlled carbohydrate intake on next day pre- and post-exercise inflammatory and hepcidin responses.

METHODS

In a crossover design, 12 well-trained endurance athletes (Ht 181.08 ± 7.68 cm; Wt 74.8 ± 11.5 kg, VO 2peak 68.9 ± 7.2 ml kg(-1) min(-1)) completed two experimental (2-day) trials. On day 1, participants completed a glycogen depletion task, including a 16-km run (80 % vVO 2peak) and 5 × 1 min efforts (130 % vVO 2peak) separated by 2-min recovery. Subsequently, strict dietary control was enforced for 24 h, where low carbohydrate (LCHO 3 g kg(-1)) or high carbohydrate (HCHO 10 g kg(-1)) diets were provided. Twenty-four hours later, participants completed an 8 × 3 min interval running session at 85 % vVO 2peak followed by 3-h monitored recovery. Venous blood samples were collected pre-, immediately post- and 3-h post-exercise, which were analyzed for interleukin-6, serum iron, ferritin and hepcidin.

RESULTS

Interleukin-6 was elevated (p < 0.001) immediately post-exercise compared to baseline in both conditions, but was lower in HCHO (p = 0.015). Hepcidin levels were also lower at baseline (p = 0.049) in HCHO, and a large effect (d = 0.72) indicated a trend for lower levels at 3-h post-exercise compared to LCHO. Serum iron was increased post-exercise for both trials (p = 0.001), whereas serum ferritin remained unchanged.

CONCLUSIONS

Twenty-four hours of controlled low carbohydrate intake resulted in higher baseline hepcidin levels and post-exercise IL-6 responses than a high carbohydrate intake. Such hormone increases may be induced by gluconeogenic signaling of the liver, and may negatively impact an athlete's iron metabolism.

Adaptation of iron requirement to hypoxic conditions at high altitude

Adequate acclimatization time to enable adjustment to hypoxic conditions is one of the most important aspects for mountaineers ascending to high altitude. Accordingly, most reviews emphasize mechanisms that cope with reduced oxygen supply. However, during sojourns to high altitude adjustment to elevated iron demand is equally critical. Thus in this review we focus on the interaction between oxygen and iron homeostasis. We review the role of iron 1) in the oxygen sensing process and erythropoietin (Epo) synthesis, 2) in gene expression control mediated by the hypoxia-inducible factor-2 (HIF-2), and 3) as an oxygen carrier in hemoglobin, myoglobin, and cytochromes. The blood hormone Epo that is abundantly expressed by the kidney under hypoxic conditions stimulates erythropoiesis in the bone marrow, a process requiring high iron levels. To ensure that sufficient iron is provided, Epo-controlled erythroferrone that is expressed in erythroid precursor cells acts in the liver to reduce expression of the iron hormone hepcidin. Consequently, suppression of hepcidin allows for elevated iron release from storage organs and enhanced absorption of dietary iron by enterocytes. As recently observed in sojourners at high altitude, however, iron uptake may be hampered by reduced appetite and gastrointestinal bleeding. Reduced iron availability, as observed in a hypoxic mountaineer, enhances hypoxia-induced pulmonary hypertension and may contribute to other hypoxia-related diseases. Overall, adequate systemic iron availability is an important prerequisite to adjust to high-altitude hypoxia and may have additional implications for disease-related hypoxic conditions.

Timing of post-exercise carbohydrate ingestion: influence on IL-6 and hepcidin responses

PURPOSE

Carbohydrate ingestion prior and during exercise attenuates exercise-induced interleukin-6. This investigation examined if an analogous effect was evident for interleukin-6 and hepcidin response when carbohydrates were ingested post-exercise.

METHODS

In a crossover design, 11 well-trained endurance athletes completed two experimental trials. Participants completed an 8 × 3 min interval running session at 85 % vVO2peak followed by 5 h of monitored recovery. During this period, participants were provided with two 1.2 g kg(-1) carbohydrate beverages at either an early feeding time (immediately post-exercise and 2 h post-exercise) or delayed feeding time (2 h post-exercise and 4 h post-exercise). Venous blood samples were collected pre-, immediately post-, 3 and 5 h post-exercise. Samples were analysed for Interleukin-6, serum iron, serum ferritin and hepcidin.

RESULTS

Interleukin-6 was significantly elevated (p = 0.004) immediately post-exercise compared to baseline for both trials. Hepcidin levels were significantly elevated at 3 h post-exercise (p = 0.001) and 5 h post-exercise (p = 0.002) compared to baseline levels in both trials, with no significant difference between the two conditions and any time point. Serum iron was significantly increased from baseline to immediately post-exercise (p = 0.001) for both trials, with levels decreasing by 3 h (p = 0.025) and 5 h post-exercise (p = 0.001). Serum ferritin levels increased immediately post-exercise compared to baseline (p = 0.006) in both conditions.

CONCLUSIONS

The timing and ingestion of post-exercise carbohydrate ingestion do not appear to impact post-exercise interleukin-6 and hepcidin responses; this is likely a result of the interval running task inducing an inflammatory response and subsequent up-regulation of hepcidin.

Frontier impact of microRNAs in skeletal muscle research: a future perspective

MicroRNAs (miRNAs) are non-coding RNAs that can regulate the expression of mRNAs and proteins by degrading mRNA molecules or by inhibiting their translation. It has been predicted that miRNAs regulate approximately 60% of protein-coding genes that could be involved in a wide range of biological processes. Research over the last 5 years suggests that miRNAs play important roles in skeletal muscle function and several miRNAs have been identified as modulators of myogenesis, muscle mass, and nutrient metabolism in physiological and pathological states. In addition, some miRNAs can be incorporated into intracellular vesicles, released into the circulation, transported to other cells, and possibly function in other organs in an endocrine manner. This phenomenon might explain the interactions between skeletal muscles and other organs. Thus, far, several muscle-secreted miRNAs have been identified and their involvement in muscle biology has been debated. Based on the recent understanding, this perspective article describes the potential valuable role of miRNAs in skeletal muscle function, delineates its limitations, and outlines its future perspectives.

Effect of supplementation with chokeberry juice on the inflammatory status and markers of iron metabolism in rowers

Background

The aim of this study was to analyze the effect of supplementation with chokeberry (Aronia melanocarpa) juice on the levels of pro-inflammatory cytokines, hepcidin, and selected markers of iron metabolism in rowers subjected to exhaustive exercise.

Methods

This double-blind study included 19 members of the Polish Rowing Team. The subjects were randomly assigned to the supplemented group (n = 10), receiving 150 mL of chokeberry juice for 8 weeks, or to the placebo group (n = 9). The participants performed a 2000-m test on a rowing ergometer at the beginning and at the end of the preparatory camp. Blood samples were obtained from the antecubital vein prior to each exercise test, one minute after completing the test, and after a 24-hour recovery period. The levels of hepcidin, interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), ferritin, iron, uric acid, and myoglobin were determined, as well as the total iron-binding capacity, unbound iron-binding capacity, and total antioxidant capacity (TAC).

Results

Post-exercise, there was a significant increase in IL-6 and a significant decrease in the TAC in both groups, prior to and after supplementation with chokeberry juice. At the end of the experiment, the supplemented athletes showed significantly lower post-exercise levels of TNF-alpha and significantly higher TACs and iron levels than the controls.

Conclusion

Supplementation with chokeberry juice results in an increase in the antioxidant activity of plasma and contributes significantly to reducing the TNF-alpha level.