Impact of Melatonin Supplementation on Sports Performance and Circulating Biomarkers in Highly Trained Athletes: A Systematic Review of Randomized Controlled Trials.

Melatonin (N-acetyl-5 methoxytryptamine) is an indolic neurohormone that modulates a variety of physiological functions due to its antioxidant, anti-inflammatory, and immunoregulatory properties. Therefore, the purpose of this study was to critically review the effects of melatonin supplementation in sports performance and circulating biomarkers related to the health status of highly trained athletes. Data were obtained by performing searches in the following three bibliography databases: Web of Science, PubMed, and Scopus. The terms used were "Highly Trained Athletes", "Melatonin", and "Sports Performance", "Health Biomarkers" using "Humans" as a filter. The search update was carried out in February 2024 from original articles published with a controlled trial design. The PRISMA rules, the modified McMaster critical review form for quantitative studies, the PEDro scale, and the Cochrane risk of bias were applied. According to the inclusion and exclusion criteria, 21 articles were selected out of 294 references. The dose of melatonin supplemented in the trials ranged between 5 mg to 100 mg administered before or after exercise. The outcomes showed improvements in antioxidant status and inflammatory response and reversed liver damage and muscle damage. Moderate effects on modulating glycemia, total cholesterol, triglycerides, and creatinine were reported. Promising data were found regarding the potential benefits of melatonin in hematological biomarkers, hormonal responses, and sports performance. Therefore, the true efficiency of melatonin to directly improve sports performance remains to be assessed. Nevertheless, an indirect effect of melatonin supplementation in sports performance could be evaluated through improvements in health biomarkers.

ß-Alanine Supplementation in Combat Sports: Evaluation of Sports Performance, Perception, and Anthropometric Parameters and Biochemical Markers-A Systematic Review of Clinical Trials.

ß-alanine does not have an ergogenic effect by itself, but it does as a precursor for the synthesis of carnosine in human skeletal muscle. ß-alanine and carnosine together help improve the muscles' functionality, especially in high-intensity exercises such as combat sports. Therefore, ß-alanine could be considered a nutritional ergogenic aid to improve sports performance in combat athletes. We aimed to critically review clinical trial evidence on the impact of ß-alanine supplementation on sports performance, perception, and anthropometric parameters, as well as circulating biochemical markers in combat athletes. This systematic review was conducted following the specific methodological guidelines of the Preferred Report Items for Systematic Reviews and Meta-Analyses guidelines (PRISMA), the PICOS question model, the Critical Review Form of McMaster, and the PEDro scale. Furthermore, the Cochrane risk-of-bias assessment tool was used. The search was carried out in the SCOPUS, Web of Science (WOS), and Medline (PubMed) databases for studies published from the beginning of the database until July 31, 2023. Of the 41 registers identified, only 7 met the established criteria and were included in this systematic review. Overall, performance parameters related to strength, power, total exercise work capacity, and combat-specific parameters were significantly improved (p < 0.05). Perception parameters increased non-significantly (p > 0.05). Regarding biochemical parameters, carnosine increased significantly (p < 0.05), pH decreased non-significantly (p > 0.05), and the results for blood bicarbonate and blood lactate were heterogeneous. Finally, there was a non-significant (p > 0.05) improvement in the anthropometric parameters of lean mass and fat mass. ß-alanine supplementation appears to be safe and could be a suitable nutritional ergogenic aid for combat athletes.

Influence of N-Acetylcysteine Supplementation on Physical Performance and Laboratory Biomarkers in Adult Males: A Systematic Review of Controlled Trials.

N-acetylcysteine (NAC) is used as a sports supplement for its ability to modulate exercise-induced oxidative damage through its antioxidant actions and maintenance of glutathione homeostasis, positioning NAC as a strategy to improve physical performance. We aimed to evaluate the current evidence on the benefits of NAC supplementation on physical performance and laboratory biomarkers in adult men. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we systematically reviewed studies indexed in the Web of Science, Scopus, and PubMed to assess the effects of NAC on physical performance, laboratory biomarkers, and adverse effects in adult men. Original articles published up to 30 April 2023 with a controlled trial design comparing NAC supplementation with a control group were included. The modified McMaster Critical Review Form for Quantitative Studies was used as an assessment tool and the Cochrane Risk of Bias was applied. Of the 777 records identified in the search, 16 studies met the inclusion and exclusion criteria. Overall, most of the trials reported beneficial effects of NAC supplementation and no serious adverse events were reported. Participants supplemented with NAC showed significant improvements in exercise performance, antioxidant capacity, and glutathione homeostasis. However, there was no clear evidence of beneficial effects of NAC supplementation on haematological markers, inflammatory response, and muscle behaviour. NAC supplementation appears to be safe and may regulate glutathione homeostasis, have antioxidant effects, and improve exercise performance. However, further studies are needed to clarify the relevance of its use.

Effects of L-Carnitine Intake on Exercise-Induced Muscle Damage and Oxidative Stress: A Narrative Scoping Review.

Exercise-induced muscle damage results in decreased physical performance that is accompanied by an inflammatory response in muscle tissue. The inflammation process occurs with the infiltration of phagocytes (neutrophils and macrophages) that play a key role in the repair and regeneration of muscle tissue. In this context, high intensity or long-lasting exercise results in the breakdown of cell structures. The removal of cellular debris is performed by infiltrated phagocytes, but with the release of free radicals as collateral products. L-carnitine is a key metabolite in cellular energy metabolism, but at the same time, it exerts antioxidant actions in the neuromuscular system. L-carnitine eliminates reactive oxygen and nitrogen species that, in excess, alter DNA, lipids and proteins, disturbing cell function. Supplementation using L-carnitine results in an increase in serum L-carnitine levels that correlates positively with the decrease in cell alterations induced by oxidative stress situations, such as hypoxia. The present narrative scoping review focuses on the critical evaluation of the efficacy of L-carnitine supplementation on exercise-induced muscle damage, particularly in postexercise inflammatory and oxidative damage. Although both concepts appear associated, only in two studies were evaluated together. In addition, other studies explored the effect of L-carnitine in perception of fatigue and delayed onset of muscle soreness. In view of the studies analyzed and considering the role of L-carnitine in muscle bioenergetics and its antioxidant potential, this supplement could help in postexercise recovery. However, further studies are needed to conclusively clarify the mechanisms underlying these protective effects.

Is Curcumine Useful in the Treatment and Prevention of the Tendinopathy and Myotendinous Junction Injury? A Scoping Review.

Physical activity in general and sports in particular, is a mechanism that produces stress and generates great force in the tendon and in the muscle-tendon unit, which increases the risk of injury (tendinopathies). Eccentric and repetitive contraction of the muscle precipitates persistent microtraumatism in the tendon unit. In the development of tendinopathies, the cellular process includes inflammation, apoptosis, vascular, and neuronal changes. Currently, treatments with oral supplements are frequently used. Curcumin seems to preserve, and even repair, damaged tendons. In this systematic review, we focus more especially on the benefits of curcumin. The biological actions of curcumin are diverse, but act around three systems: (a) inflammatory, (b) nuclear factor B (NF-κB) related apoptosis pathways, and (c) oxidative stress systems. A bibliographic search is conducted under the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) as a basis for reporting reliable systematic reviews to perform a Scoping review. After analysing the manuscripts, we can conclude that curcumin is a product that demonstrates a significant biological antialgic, anti-inflammatory, and antioxidant power. Therefore, supplementation has a positive effect on the inflammatory and regenerative response in tendinopathies. In addition, curcumin decreases and modulates the cell infiltration, activation, and maturation of leukocytes, as well as the production of pro-inflammatory mediators at the site of inflammation.

Effect of Vitamin C on Tendinopathy Recovery: A Scoping Review.

Tendinopathies represent 30-50% of all sports injuries. The tendon response is influenced by the load (volume, intensity, and frequency) that the tendon support, resulting in irritability and pain, among others. The main molecular component of tendons is collagen I (60-85%). The rest consist of glycosaminoglycans-proteoglycans, glycoproteins, and other collagen subtypes. This study's aim was to critically evaluate the efficacy of vitamin C supplementation in the treatment of tendinopathies. At the same time, the study aims to determine the optimal conditions (dose and time) for vitamin C supplementation. A structured search was carried out in the SCOPUS, Medline (PubMed), and Web of Science (WOS) databases. The inclusion criteria took into account studies describing optimal tendon recovery when using vitamin C alone or in combination with other compounds. The study design was considered, including randomized, double-blind controlled, and parallel designs in animal models or humans. The main outcome is that vitamin C supplementation is potentially useful as a therapeutic approach for tendinopathy recovery. Vitamin C supplementation, alone or in combination with other products, increases collagen synthesis with a consequent improvement in the patient's condition. On the other hand, vitamin C deficiency is mainly associated with a decrease in procollagen synthesis and reduced hydroxylation of proline and lysine residues, hindering the tendon repair process.

Nitric-Oxide-Inducing Factors on Vitamin D Changes in Older People Susceptible to Suffer from Sarcopenia.

Calcium and magnesium, together with vitamin D and the hormones testosterone and cortisol, are key elements in muscle function, to maintain physical fitness. This study aims to analyze if supplementation with NO precursors (L-arginine, L-citrulline and beetroot extract) modulates the circulating levels of calcium, magnesium, vitamin D and steroid hormones in elders. Sixty-one volunteers (65.1 years old, 164.6 cm of height and 71.2 kg of weight) susceptible to develop sarcopenia participated in a physical activity program for 6 weeks. Participants were divided into four groups: one placebo and three taking one of the indicated supplements. Physical capacity was assessed through the following tests: (a) distance covered in 6 min by walking (endurance indicator); (b) hand grip (upper-body strength indicator); (c) time to cover 4 m by walking (speed indicator); and (d) time to perform five full squats (lower-body strength indicator). We concluded that there is a disparity in the association of steroid hormones, vitamin D levels and physical fitness. However, a significant inverse correlation between speed and endurance indicators was observed. Higher circulating vitamin D levels were observed in the L-arginine- and beetroot-supplemented groups. In conclusion, vasodilators increase vitamin D circulating levels that, in the long term, could maintain mineral homeostasis, improving muscular function.

l-Arginine and Beetroot Extract Supplementation in the Prevention of Sarcopenia.

Aging is associated with a significant decline in neuromuscular function, leading to a reduction in muscle mass and strength. The aim of the present report was to evaluate the effect of supplementation with nitric oxide precursors (l-arginine and beetroot extract) in muscular function during a training period of 6 weeks in elderly men and women. The study (double-blind, placebo-controlled) involved 66 subjects randomly divided into three groups: placebo, arginine-supplemented and beetroot extract-supplemented. At the end of this period, no changes in anthropometric parameters were observed. Regarding other circulating parameters, urea levels were significantly (p < 0.05) lower in women of the beetroot-supplemented group (31.6 ± 5.9 mg/dL) compared to placebo (41.3 ± 8.5 mg/dL) after 6 weeks of training. In addition, the circulating creatine kinase activity, as an index of muscle functionality, was significantly (p < 0.05) higher in women of the arginine- (214.1 ± 162.2 mIU/L) compared to the beetroot-supplemented group (84.4 ± 36.8 mIU/L) at the end of intervention. No significant effects were noticed with l-arginine or beetroot extract supplementation regarding strength, endurance and SPPB index. Only beetroot extract supplementation improved physical fitness significantly (p < 0.05) in the sprint exercise in men after 6 weeks (2.33 ± 0.59 s) compared to the baseline (2.72 ± 0.41 s). In conclusion, beetroot seems to be more efficient during short-term training while supplementing, preserving muscle functionality in women (decreased levels of circulating creatine kinase) and with modest effects in men.

The Immunomodulatory Function of Vitamin D, with Particular Reference to SARS-CoV-2.

Vaccines are the only way to reduce the morbidity associated to SARS-CoV-2 infection. The appearance of new mutations urges us to increase the effectiveness of vaccines as a complementary alternative. In this context, the use of adjuvant strategies has improved the effectiveness of different vaccines against virus infections such as dengue, influenza, and common cold. Recent reports on patients infected by COVID-19 reveal that low levels of circulating vitamin D correlate with a severe respiratory insufficiency. The immunomodulatory activity of this micronutrient attenuates the synthesis of pro-inflammatory cytokines and at the same time, increases antibody production. Therefore, the present review proposes the use of vitamin D as adjuvant micronutrient to increase the efficacy of vaccines against SARS-CoV-2 infection.

Effects of Vitamin D in Post-Exercise Muscle Recovery. A Systematic Review and Meta-Analysis.

Vitamin D is a key micronutrient modulating function and health in skeletal muscle. Therefore, we sought to systematically review the role of vitamin D in muscle recovery. A search in different databases (PubMed/MEDLINE, WOS, Google Scholar, and Scopus) was carried out following PRISMA® and PICOS. The search period was from inception to April 2020. Changes in post-exercise muscle damage were quantified comparing experimental group vs. placebo in each study by using number of participants, standardized mean difference (SMD), and standard error of the SMD. Hedges's g was used to calculate the SMDs for each study group and biased by the inverse of variance that allows calculating an overall effect and the 95% confidence interval (CI). The net vitamin D supplementation effect was calculated by subtracting the placebo SMD from SMD of the experimental group. The DerSimonian and Laird method was used as a random effect model, taking into account that the effect of vitamin D on muscular damage may vary according to the dose administered and additional moderators. Six studies were selected. In conclusion, regarding circulating levels of muscle biomarkers and additional limitations of the studies, it cannot be concluded that vitamin D supplementation exerts an effect in post-exercise muscle recovery. Likely, the anti-inflammatory action of vitamin D is quicker than the recovery of tissue structure and function. This aspect is pending verification in future research.

Effect of Vitamin D Supplementation on Muscle Status in Old Patients Recovering from COVID-19 Infection.

Background and Objectives: Vitamin D, in addition to its effect on mineral homeostasis, plays a key role in muscle metabolism. Vitamin D supplementation is involved in muscle recovery after damage as a consequence of either pathology or after high-intensity exercise. In this context, the aim of this study was to analyze the effect of vitamin D on muscle fitness in elderly patients in the recovery phase after SARS-CoV-2 (COVID-19) infection. Materials and Methods: This pilot study was conducted at the Soria Norte Health Center. The study consisted of a double-blind trial with two groups of men (placebo and vitamin D-supplemented) (n = 15/group). Treatment with vitamin D (cholecalciferol: 2000 IU/day) and placebo was carried out for 6 weeks. Circulating hematological and biochemical parameters (total protein, glucose, vitamin D, urea, uric acid, aspartate aminotransferase/glutamic-oxaloacetic transaminase, alanine aminotransferase/glutamic-pyruvic transaminase, creatine kinase, lactate dehydrogenase, aldolase, gamma-glutamyl transferase and myoglobin) and the hormones cortisol and testosterone were determined. As for respiratory function tests, FEV1 and respiratory flow were also studied. For physical fitness tests, the "six-minute walk test" (6MWT) was used. Results: After vitamin D supplementation, we observed that serum creatine kinase levels returned to optimal values. This change suggests a protective role of vitamin D against muscle catabolism compared to placebo. In terms of physical test results, we observed only slight non-significant improvements, although patients reported feeling better. Conclusions: Vitamin D supplementation produces decreases in indicators of muscle damage, which may ultimately contribute to improving the health status and quality of life of patients who have suffered from COVID-19, during the recovery process.

Weight Loss Strategies in Male Competitors of Combat Sport Disciplines.

Background and objective: The use of suboptimal weight loss strategies in order to reach specific weight ranges as observed in combat sport disciplines can give rise to severe health problems. However, particular aspects regarding management of weight category comparing three sport disciplines remain to be investigated. Therefore, the aim of the present study was to obtain information regarding the weight loss strategies that competitors performed before a tournament. Materials and Methods: This article describes the most common dietary-nutritional strategies used by 140 national university male competitors of judo (n = 52), karate (n = 40) and taekwondo (n = 48) in order to achieve a specific weight, according to the rapid weight loss questionnaire (RWLQ) and the EAT-27 questionnaire. Results: Around 50% of participants were not involved in a weight loss process. Among the remaining participants, we considered three periods for weight reduction: less than 1 week (35% in judo, 8% in karate and 19% in taekwondo), less than 1 month (17% in judo, 15% in karate and 26% in taekwondo) and more than 1 month (0% in judo, 5% in karate and 21% in taekwondo). Severe fasting, focused on food/water restriction, was the most commonly used strategy, being more frequent in judo players. Light weight judo practitioners generally lost 2-5 kg before the contest. One third of participants avoided carbohydrate consumption when performing food restriction. Finally, individuals that reduced weight in the last week seemed to develop an unhealthy psychological relationship with food. Conclusion: All these aspects could be particularly relevant, providing information regarding how competitors manage basic nutritional concepts that guide dieting strategies. This information is relevant to prepare future educational interventions in the area of nutrition for competitors, coaches and technical staff.

L-Citrulline Supplementation and Exercise in the Management of Sarcopenia.

Sarcopenia is a process associated to aging. Persistent inflammation and oxidative stress in muscle favour muscle wasting and decreased ability to perform physical activity. Controlled exercise can optimize blood flux and moderate the production of reactive oxygen species. Therefore, supplements that can work as a vasodilators and control oxidative stress, might be beneficial for active elders. In this context, we have tested citrulline supplementation in a group of 44 participants aged from 60-73 years that followed a physical activity program adapted to their age and capacities. Volunteers were divided in two groups: placebo (n = 22) and citrullline supplemented (n = 22). Different physical tests and blood extractions were performed at the beginning and at the end of intervention (six weeks). Strength and endurance showed a tendency to increase in the citrulline supplemented group, with no significant differences respect to placebo. However, walking speed in the citrulline supplemented group improved significantly compared to placebo. Markers of muscle damage as well as circulating levels of testosterone, cortisol and vitamin D showed no significant changes, but a tendency to improve at the end of intervention in the supplemented group compared to placebo. Additional studies are necessary to confirm the effect of citrulline supplementation in sarcopenia delay.

Effect of Glutamine Supplementation on Muscular Damage Biomarkers in Professional Basketball Players.

Scientific evidence supports the role of L-glutamine in improving immune function. This could suggest a possible role of L-glutamine in recovery after intense exercise. To this end, the present report aimed to study if oral L-glutamine supplementation could attenuate muscle damage in a group of players of a mainly eccentric sport discipline such as basketball. Participants (n = 12) were supplemented with 6 g/day of glutamine (G group) or placebo (P group) for 40 days in a crossover study design (20 days with glutamine + 20 days with placebo and vice versa). Blood samples were obtained at the beginning and at the end of each period and markers from exercise-induced muscle damage were determined. The glutamine supplemented group displayed significantly low values of aspartate transaminase, creatine kinase and myoglobin in blood, suggesting less muscle damage compared to the placebo. In addition, adrenocorticotropic hormone levels were lower in the glutamine supplemented group than in the placebo. As a result, the circulating cortisol levels did not increase at the end of the study in the glutamine supplemented group. Altogether, the results indicate that glutamine could help attenuate exercise-induced muscle damage in sport disciplines with predominantly eccentric actions.

Antioxidant Supplementation Modulates Neutrophil Inflammatory Response to Exercise-Induced Stress.

The aim of the present report was to evaluate the inflammatory response to a 2000-m running test considering neutrophil myeloperoxidase as an inflammatory marker, and to verify if supplements rich in antioxidants could modulate Post-test antioxidant and anti-inflammatory responses. To this end, a 21-day homogenization period was carried out with three groups: a control group, a supplemented group taking an almond beverage enriched with vitamins C and E and a third group consuming the same beverage but enriched with Lippia citriodora extract. At the end of this period, participants performed a 2000-m run, and blood samples were obtained the day before and immediately after the running test. Plasma and neutrophils were isolated. As a result, plasma creatine kinase and myoglobin increased, indicating Post-test muscle damage. Plasma oxidative markers were increased in all groups, except in the group supplemented with the almond beverage. Neutrophil antioxidant enzymes were significantly increased only in the control group, suggesting an antioxidant effect of the supplements provided in the other groups. Myeloperoxidase activity was significantly increased after the test in the control group, while increased enzyme levels were detected in plasma of the supplement groups. Therefore, antioxidant consumption seems to favour myeloperoxidase release. The connection of this observation with post-exercise recovery will require further investigation.

Nutritional Ergogenic Aids in Racquet Sports: A Systematic Review.

A nutritional ergogenic aid (NEA) can help athletes optimize performance, but an evidence-based analysis is required in order to support training outcomes or competition performance in specific events. Racquet sports players are regularly exposed to a high-intensity workload throughout the tournament season. The activity during a match is characterized by variable durations (2-4 h) of repeated high-intensity bouts interspersed with standardized rest periods. Medline/PubMed, Scopus, and EBSCO were searched from their inception until February 2020 for randomized controlled trials (RCTs). Two independent reviewers extracted data, after which they assessed the risk of bias and the quality of trials. Out of 439 articles found, 21 met the predefined criteria: tennis (15 trials), badminton (three trials), paddle (one trial), and squash (two trials). Among all the studied NEAs, acute dosages of caffeine (3-6 mg/kg) 30-60 min before a match have been proven to improve specific skills and accuracy but may not contribute to improve perceived exertion. Currently, creatine, sodium bicarbonate, sodium citrate, beetroot juice, citrulline, and glycerol need more studies to strengthen the evidence regarding improved performance in racquet sports.

Quercetin metabolites from Hibiscus sabdariffa contribute to alleviate glucolipotoxicity-induced metabolic stress in vitro.

Polyphenols from Hibiscus sabdariffa (HS) alleviate obesity-related metabolic complications but the metabolites responsible for such effects are unknown. We aimed to elucidate which of the potential plasma metabolites from a polyphenol-enriched HS (PEHS) extract contributed for the reversion of glucolipotoxicity-induced metabolic stress using 3T3-L1 adipocyte and INS 832/13 pancreatic ß-cell models under glucolipotoxic conditions. PEHS extract, quercetin (Q) and quercetin-3-O-glucuronide (Q3GA) showed stronger capacity to decrease glucolipotoxicity-induced ROS generation than ascorbic acid or chlorogenic acid. PEHS extract, Q and Q3GA decreased secretion of cytokines (leptin, TNF-α, IGF-1, IL-6, VEGF, IL-1α, IL-1ß and CCL2) and reduced CCL2 expression at transcriptional level. In addition, PEHS extract, Q and Q3GA reduced triglyceride accumulation, which occurred through fatty acid synthase (FASN) downregulation, AMPK activation and mitochondrial mass and biogenesis restoration via PPARα upregulation. Electron microscopy confirmed that PEHS extract and Q3GA decreased mitochondrial remodeling and mitophagy. Virtual screening leads us to postulate that Q and Q3GA might act as agonists of these protein targets at specific sites. These data suggest that Q and Q3GA may be the main responsible compounds for the capacity of PEHS extract to revert glucolipotoxicity-induced metabolic stress through AMPK-mediated decrease in fat storage and increase in fatty acid oxidation, though other compounds of the extract may contribute to this capacity.

Impact of Magnesium Supplementation in Muscle Damage of Professional Cyclists Competing in a Stage Race.

Magnesium is a cofactor of different enzymatic reactions involved in anabolic and catabolic processes that affect muscular performance during exercise. In addition, it has been suggested that magnesium could participate in maintaining muscle integrity during demanding effort. The main purpose of this study was to analyze the effects of magnesium supplementation in preventing muscle damage in professional cyclists taking part in a 21-day cycling stage race. Eighteen male professional cyclists (n = 18) from two teams were recruited to participate in the research. They were divided into 2 groups: the control group (n = 9) and the magnesium-supplemented group (n = 9). The supplementation consisted of an intake of 400 mg/day of magnesium during the 3 weeks of competition. Blood samples were collected according to World Anti-Doping Agency rules at three specific moments during competition: immediately before the race; mid competition; and before the last stage. Levels of serum and erythrocyte magnesium, lactate dehydrogenase, creatinine kinase, aspartate transaminase, alanine transaminase, myoglobin, aldolase, total proteins, cortisol and creatinine were determined. Serum and erythrocyte magnesium levels decreased during the race. Circulating tissue markers increased at the end of the race in both groups. However, myoglobin increase was mitigated in the supplemented group compared with the controls. We conclude that magnesium supplementation seems to exert a protective effect on muscle damage.

Effect of Iron Supplementation on the Modulation of Iron Metabolism, Muscle Damage Biomarkers and Cortisol in Professional Cyclists.

BACKGROUND: The intense efforts made during 3-week stage races may reduce iron metabolism and hematological parameters. These efforts may increase the levels of circulating muscle damage markers and some hormones. All of these physiological changes may have negative consequences not only for the performance of athletes but also for their health. The main aim of this study was to evaluate the effects of supplementation with 80 mg/day of iron on haematological parameters, serum cortisol and biochemical muscle indicators on elite male cyclists during the 3-week stage race the Vuelta a España. Our secondary aim was to examine whether the hematological profile is associated with muscular damage parameters and cortisol. METHODS: Eighteen elite male cyclists from two teams were randomly assigned to one of two groups: (1) control group (CG, n = 9; age: 26.1 ± 4.6 years; maximum oxygen uptake per kg: 78.0 ± 5.4 mL/kg/min) or (2) group treated with 80 mg/day iron (800 mg of iron protein succinylate, ITG, n = 9; age: 25.7 ± 6.4 years; maximum oxygen uptake per kg: 77.6 ± 6.5 mL/kg/min). The cyclists were subjected to blood tests one week before the start of the race (T1) and after 4 weeks of treatment, coinciding with the end of the competition (T2). Iron metabolism parameters, muscle damage indicators and serum cortisol were assessed. Repeated-measures ANOVA with group as a factor (GC and ITG) were used to examine the differences between groups throughout the study (time × group) after iron supplementation treatment. RESULTS: Significant differences were observed between groups throughout the study in the group-by-time interaction and changes in serum iron (GC: -8.93 ± 10.35% vs. ITG: 0.60 ± 8.64%; p = 0.018), ferritin (GC: -13.88 ± 23.53% vs. ITG: 91.08 ± 118.30%; p = 0.004), haemoglobin (GC: 10.00 ± 3.32% vs. ITG: 13.04 ± 5.64%; p < 0.001), haematocrit (GC: -1.17 ± 3.78% vs. ITG: 7.32 ± 3.92%; p < 0.001) and cortisol (GC: 24.74 ± 25.84% vs. ITG: ⁻13.54 ± 13.61%; p = 0.005). However, no significant group-by-time interaction was observed for the circulating muscle biomarkers. Additionally, significant negative correlations of serum iron, haemoglobin and haematocrit with muscle circulating biomarkers and cortisol (p < 0.05) were observed. CONCLUSIONS: Oral iron supplementation with 80 mg/day iron (800 mg of iron protein succinylate) effectively prevented a decline in haematological parameters (serum iron, ferritin, haemoglobin and haematocrit) and maintained optimal levels of recovery in elite cyclists during the Vuelta a España. Moreover, the hematological values were shown to have relationship with muscular recovery parameters.

Differential effects of a combination of Hibiscus sabdariffa and Lippia citriodora polyphenols in overweight/obese subjects: A randomized controlled trial.

Plant-polyphenols have shown the capacity to ameliorate obesity-induced metabolic disturbances, both in cell and animal models, where most therapeutic approaches have failed. On the basis of previous research, a dietary supplement containing 500 mg of a combination of polyphenolic extracts from Lippia citriodora L. and Hibiscus sabdariffa L. (LC-HS), in the context of an equilibrated isocaloric diet, was evaluated in a double blind, placebo-controlled and randomized trial in 56 obese/overweight subjects for two months. Compared to controls, the consumption of the LC-HS polyphenols showed significant improvements in body weight, abdominal circumference of overweight subjects (-6.79 ± 0.80 cm in overweight LC-HS group vs -1.85 ± 0.83 cm in controls, p < 0.001) and body fat % (-1.33 ± 0.15% in overweight LC-HS group vs -0.66 ± 0.17% in controls, p < 0.05). Heart rate and systolic blood pressure also presented significant improvements in overweight LC-HS participants. However, changes were more modest in obese subjects. Further, LC-HS extract significantly reduced lipid content and increased AMPK activity in a hypertrophied adipocyte cell model. Therefore, consumption of 500 mg/day of LC-HS extracts enriched in polyphenols for two months in the context of an isocaloric diet by overweight subjects decreased symptoms associated to obesity-related diseases. Modulation of fat metabolism in adipose tissue, probably mediated by AMPK activation, is proposed as a molecular target to be explored in future research.