Regulation of mitochondrial morphology and cristae architecture by the TLR4 pathway in human skeletal muscle

In skeletal muscle (SkM), a reduced mitochondrial elongate phenotype is associated with several metabolic disorders like type 2 diabetes mellitus (T2DM). However, the mechanisms contributing to this reduction in mitochondrial elongate phenotype in SkM have not been fully elucidated. It has recently been shown in a SkM cell line that toll-like receptor 4 (TLR4) contributes to the regulation of mitochondrial morphology. However, this has not been investigated in human SkM. Here we found that in human SkM biopsies, TLR4 protein correlated negatively with Opa1 (pro-mitochondrial fusion protein). Moreover, the incubation of human myotubes with LPS reduced mitochondrial size and elongation and induced abnormal mitochondrial cristae, which was prevented with the co-incubation of LPS with TAK²⁴². Finally, T2DM myotubes were found to have reduced mitochondrial elongation and mitochondrial cristae density. Mitochondrial morphology, membrane structure, and insulin-stimulated glucose uptake were restored to healthy levels in T2DM myotubes treated with TAK²⁴². In conclusion, mitochondrial morphology and mitochondrial cristae seem to be regulated by the TLR4 pathway in human SkM. Those mitochondrial alterations might potentially contribute to insulin resistance in the SkM of patients with T2DM.

Ursodeoxycholic acid induces sarcopenia associated with decreased protein synthesis and autophagic flux

BACKGROUND

Skeletal muscle generates force and movements and maintains posture. Under pathological conditions, muscle fibers suffer an imbalance in protein synthesis/degradation. This event causes muscle mass loss and decreased strength and muscle function, a syndrome known as sarcopenia. Recently, our laboratory described secondary sarcopenia in a chronic cholestatic liver disease (CCLD) mouse model. Interestingly, the administration of ursodeoxycholic acid (UDCA), a hydrophilic bile acid, is an effective therapy for cholestatic hepatic alterations. However, the effect of UDCA on skeletal muscle mass and functionality has never been evaluated, nor the possible involved mechanisms.

METHODS

We assessed the ability of UDCA to generate sarcopenia in C57BL6 mice and develop a sarcopenic-like phenotype in C₂C₁₂ myotubes and isolated muscle fibers. In mice, we measured muscle strength by a grip strength test, muscle mass by bioimpedance and mass for specific muscles, and physical function by a treadmill test. We also detected the fiber's diameter and content of sarcomeric proteins. In C₂C₁₂ myotubes and/or isolated muscle fibers, we determined the diameter and troponin I level to validate the cellular effect. Moreover, to evaluate possible mechanisms, we detected puromycin incorporation, p70S6K, and 4EBP1 to evaluate protein synthesis and ULK1, LC3 I, and II protein levels to determine autophagic flux. The mitophagosome-like structures were detected by transmission electron microscopy.

RESULTS

UDCA induced sarcopenia in healthy mice, evidenced by decreased strength, muscle mass, and physical function, with a decline in the fiber's diameter and the troponin I protein levels. In the C₂C₁₂ myotubes, we observed that UDCA caused a reduction in the diameter and content of MHC, troponin I, puromycin incorporation, and phosphorylated forms of p70S6K and 4EBP1. Further, we detected increased levels of phosphorylated ULK1, the LC3II/LC3I ratio, and the number of mitophagosome-like structures. These data suggest that UDCA induces a sarcopenic-like phenotype with decreased protein synthesis and autophagic flux.

CONCLUSIONS

Our results indicate that UDCA induces sarcopenia in mice and sarcopenic-like features in C₂C₁₂ myotubes and/or isolated muscle fibers concomitantly with decreased protein synthesis and alterations in autophagic flux.

Mitochondria-SR interaction and mitochondrial fusion/fission in the regulation of skeletal muscle metabolism

Mitochondria-endoplasmic/sarcoplasmic reticulum (ER/SR) interaction and mitochondrial fusion/fission are critical processes that influence substrate oxidation. This narrative review summarizes the evidence on the effects of substrate availability on mitochondrial-SR interaction and mitochondria fusion/fission dynamics to modulate substrate oxidation in human skeletal muscle. Evidence shows that an increase in mitochondria-SR interaction and mitochondrial fusion are associated with elevated fatty acid oxidation. In contrast, a decrease in mitochondria-SR interaction and an increase in mitochondrial fission are associated with an elevated glycolytic activity. Based on the evidence reviewed, we postulate two hypotheses for the link between mitochondrial dynamics and insulin resistance in human skeletal muscle. First, glucose and fatty acid availability modifies mitochondria-SR interaction and mitochondrial fusion/fission to help the cell to adapt substrate oxidation appropriately. Individuals with an impaired response to these substrate challenges will accumulate lipid species and develop insulin resistance in skeletal muscle. Second, a chronically elevated substrate availability (e.g. overfeeding) increases mitochondrial production of reactive oxygen species and induced mitochondrial fission. This decreases fatty acid oxidation, thus leading to the accumulation of lipid species and insulin resistance in skeletal muscle. Altogether, we propose mitochondrial dynamics as a potential target for disturbances associated with low fatty acid oxidation.

Neither Chia Flour nor Whey Protein Supplementation Further Improves Body Composition or Strength Gains after a Resistance Training Program in Young Subjects with a Habitual High Daily Protein Intake

The aim of this study was to compare the potential additional effect of chia flour, whey protein, and a placebo juice to resistance training on fat-free mass (FFM) and strength gains in untrained young men. Eighteen healthy, untrained young men underwent an 8-week whole-body resistance training program, comprising three sessions per week. Subjects were randomized into three groups that after each training session consumed: (1) 30 g whey protein concentrate containing 23 g protein (WG), (2) 50 g chia flour containing 20 g protein (CG), or (3) a placebo not containing protein (PG). Strength tests (lower- and upper-limb one repetition maximum (1 RM) tests) and body composition analyses (dual-energy X-ray absorptiometry; DXA) were performed before (PRE) and after (POST) the intervention. Resistance training increased FFM and the 1 RM for each of the strength tests similarly in the three groups. FFM increased by 2.3% in WG (p = 0.04), by 3.6% in CG (p = 0.004), and by 3.0% in PG (p = 0.002)., and 1 RM increased in the different strength tests in the three groups (p < 0.05) with no difference between PG, CG, and WG. In conclusion, neither chia flour nor whey protein supplementation elicited an enhanced effect on FFM and strength gains after an 8-week resistance training program in healthy, untrained young men consuming a habitual high protein mixed diet (>1.2 g/kg/day).

Targeting mitochondria for the prevention and treatment of nonalcoholic fatty liver disease: polyphenols as a non-pharmacological approach

Scope:

Nonalcoholic fatty liver disease (NAFLD) has a high and growing prevalence globally. Mitochondria are fundamental in regulating cell energy homeostasis. Nevertheless, mitochondria control mechanisms can be exceeded in this context of energy overload. Damaged mitochondria worsen NAFLD progression. Diet and lifestyle changes are the main recommendations for NAFLD prevention and treatment. Some polyphenols have improved mitochondrial function in different NAFLD and obesity models.

Objective:

To discuss the potential role of polyphenols as a non-pharmacological approach targeting mitochondria to prevent and treat NAFLD, analyzing the influence of polyphenols' chemical structure, limitations and clinical projections.

Methods:

In vivo and in vitro NAFLD models were considered. Study searches were performed using the following keywords: nonalcoholic fatty liver disease, liver steatosis, mitochondria, mitochondrial activity, mitochondrial dynamics, mitochondrial dysfunction, mitochondrial morphology, mitochondrial cristae, fusion, fission, polyphenols, flavonoids, anthocyanins, AND/OR bioactive compounds.

Conclusion:

Polyphenols are a group of diverse bioactive molecules whose bioactive effects are highly determined by their chemical structure. These bioactive compounds could offer an interesting non-pharmacological approach to preventing and treating NAFLD, regulating mitochondrial dynamics and function. Nevertheless, the mitochondria' role in subjects with NAFLD treatment is not fully elucidated. The dosage and bioavailability of these compounds should be addressed when studied.

Concurrent training and interindividual response in women with a high number of metabolic syndrome risk factors

The non-responders (NRs) after exercise training have been poorly studied in populations with morbid obesity. The purpose of this study was to determine the NR prevalence after 20 weeks of concurrent training of morbidly obese women with a high or low number of metabolic syndrome (MetS) risk factors. Twenty-eight women with morbid obesity participated in an exercise training intervention and were allocated into two groups distributed based on a high (≥3, n = 11) or low number (<3, n = 17) of MetS risk factors. The main outcomes were waist circumference (WC), fasting plasma glucose (FPG), high-density lipids (HDL-c), triglycerides (Tg), and systolic (SBP) and diastolic (DBP) blood pressure, and secondary outcomes were body composition, anthropometric and physical fitness, determined before and after 20 weeks of concurrent training. NRs were defined as previously used technical error cut-off points for the MetS outcomes. Significantly different (all p < 0.05) prevalences of NRs between the H-MetS vs. L-MetS groups (respectively) in WC (NRs 18.2 % vs. 41.1 %, p < 0.0001), SBP (NRs 72.7 % vs. 47.0 %, p = 0.022), DBP (NRs 54.5 % vs. 76.4 %, p < 0.0001), FPG (NRs 100% vs. 64.8 %, p < 0.0001), and HDL-c (NRs 90.9 % vs. 64.7 %, p = 0.012) were observed. In addition, the H-MetS group evidenced significant changes on ΔSBP (−10.2 ± 11.4 mmHg), ΔFPG (−5.8 ± 8.2 mg/dl), ΔHDL-c (+4.0 ± 5.9 mg/dl), and ΔTg (−8.8 ± 33.8 mg/dl), all p < 0.05. The L-MetS group only showed significant changes in ΔWC (−3.8 ± 5.0 cm, p = 0.009). Comparing H-MetS vs. L-MetS groups, significant differences were observed in ∆FPG (−5.8 ± 8.2 vs. +0.3 ± 3.2 mg/dl, p = 0.027), but not in other MetS outcomes. In conclusion, 20 weeks of concurrent training promotes greater beneficial effects in morbidly obese patients with a high number of MetS risk factors. However, the NR prevalence for improving MetS outcomes was significantly superior in these more-diseased groups in SBP, FPG, and HDL-c, independent of their major training-induced effects.

Effect of epicatechin on skeletal muscle

:

Loss of skeletal muscle (SkM) quality is associated with different clinical conditions such as aging, diabetes, obesity, cancer and heart failure. Nutritional research has focused on identifying naturally occurring molecules that mitigate the loss of SkM quality induced by a pathology or syndrome. In this context, although few human studies have been conducted, Epicatechin (Epi) is a prime candidate that may positively affect SkM quality by its potential ability to mitigate muscle mass loss. This seems to be a consequence of its antioxidant, anti-inflammatory properties, and its stimulation of mitochondrial biogenesis to increase myogenic differentiation, as well as its modulation of key proteins involved in SkM structure, function, metabolism, and growth. In conclusion, the Epi could prevent, mitigate, delay, and even treat muscle-related disorders caused by aging and diseases, however, studies in humans are needed.

Low abundance of Mfn2 protein correlates with reduced mitochondria-SR juxtaposition and mitochondrial cristae density in human men skeletal muscle: Examining organelle measurements from TEM images

The role of mitofusin 2 (Mfn2) in the regulation of skeletal muscle (SM) mitochondria-sarcoplasmic (SR) juxtaposition, mitochondrial morphology, mitochondrial cristae density (MCD), and SM quality has not been studied in humans. In in vitro studies, whether Mfn2 increases or decreases mitochondria-SR juxtaposition remains controversial. Transmission electron microscopy (TEM) images are commonly used to measure the organelle juxtaposition, but the measurements are performed "by-hand," thus potentially leading to between-rater differences. The purposes of this study were to: (1) examine the repeatability and reproducibility of mitochondrial-SR juxtaposition measurement from TEM images of human SM between three raters with different experience and (2) compare the mitochondrial-SR juxtaposition, mitochondrial morphology, MCD (stereological-method), and SM quality (cross-sectional area [CSA] and the maximum voluntary contraction [MVC]) between subjects with high abundance (Mfn2-HA; n = 6) and low abundance (Mfn2-LA; n = 6) of Mfn2 protein. The mitochondria-SR juxtaposition had moderate repeatability and reproducibility, with the most experienced raters showing the best values. There were no differences between Mfn2-HA and Mfn2-LA groups in mitochondrial size, distance from mitochondria to SR, CSA, or MVC. Nevertheless, the Mfn2-LA group showed lower mitochondria-SR interaction, MCD, and VO_2max . In conclusion, mitochondrial-SR juxtaposition measurement depends on the experience of the rater, and Mfn2 protein seems to play a role in the metabolic control of human men SM, by regulating the mitochondria-SR interaction.

Acute and Chronic Effects of High Frequency Electric Pulse Stimulation on the Akt/mTOR Pathway in Human Primary Myotubes

Electrical pulse stimulation (EPS) has been suggested to be a useful method to investigate the mechanisms underlying the adaptations of human skeletal muscle to both endurance and resistance exercise. Although different myotube stimulation protocols mimicking acute and chronic endurance exercise have been developed, no convincing protocol mimicking resistance exercise exists. Adaptations to resistance exercise mainly ensue via the Akt/mTOR pathway. Therefore, the aim of this study was to develop a high frequency EPS protocol mimicking resistance exercise both acutely (100 Hz, 15 V, 0.4 ms with 4 s rest between each contraction for 30 min) and chronically (acute EPS protocol repeated on three consecutive days) on human myotubes. Compared to control conditions, the acute EPS protocol increased the phosphorylation of Akt^Ser473 at 0 h (+91%, p = 0.02) and 3 h (+95%, p = 0.01), and mTOR^Ser2448 at 0 h (+93%, p = 0.03), 1 h (+129%, p = 0.01), and 3 h (+104%, p = 0.0250) post-stimulation. The phosphorylation of ERK1/2^{Thr202/Tyr204} was increased at 0 h (+69%, p = 0.02) and 3 h (+117%, p = 0.003) post-stimulation compared to control conditions. In addition, both S6K1^Thr389 (+157%, p = 0.009) and S6^Ser240/244 (+153%, p = 0.003) phosphorylation increased 1 h after EPS compared to control conditions. Chronic EPS protocol increased the phosphorylation of S6K1^Thr389 1 h (+105%, p = 0.03) and 3 h (+126%, p = 0.02) and the phosphorylation of S6^Ser240/244 1 h (+32%, p = 0.02) after the end of the last stimulation. In conclusion, the present work shows that human muscle cells subjected to EPS can be used as an in vitro model of acute and chronic resistance exercise.

Hepatocyte expression of the micropeptide adropin regulates the liver fasting response and is enhanced by caloric restriction

The micropeptide adropin encoded by the clock-controlled energy homeostasis-associated gene is implicated in the regulation of glucose metabolism. However, its links to rhythms of nutrient intake, energy balance, and metabolic control remain poorly defined. Using surveys of Gene Expression Omnibus data sets, we confirm that fasting suppresses liver adropin expression in lean C57BL/6J (B6) mice. However, circadian rhythm data are inconsistent. In lean mice, caloric restriction (CR) induces bouts of compulsive binge feeding separated by prolonged fasting intervals, increasing NAD-dependent deacetylase sirtuin-1 signaling important for glucose and lipid metabolism regulation. CR up-regulates adropin expression and induces rhythms correlating with cellular stress-response pathways. Furthermore, adropin expression correlates positively with phosphoenolpyruvate carboxokinase-1 (Pck1) expression, suggesting a link with gluconeogenesis. Our previous data suggest that adropin suppresses gluconeogenesis in hepatocytes. Liver-specific adropin knockout (LAdrKO) mice exhibit increased glucose excursions following pyruvate injections, indicating increased gluconeogenesis. Gluconeogenesis is also increased in primary cultured hepatocytes derived from LAdrKO mice. Analysis of circulating insulin levels and liver expression of fasting-responsive cAMP-dependent protein kinase A (PKA) signaling pathways also suggests enhanced responses in LAdrKO mice during a glucagon tolerance test (250 µg/kg intraperitoneally). Fasting-associated changes in PKA signaling are attenuated in transgenic mice constitutively expressing adropin and in fasting mice treated acutely with adropin peptide. In summary, hepatic adropin expression is regulated by nutrient- and clock-dependent extrahepatic signals. CR induces pronounced postprandial peaks in hepatic adropin expression. Rhythms of hepatic adropin expression appear to link energy balance and cellular stress to the intracellular signal transduction pathways that drive the liver fasting response.

Tapering strategies applied to plyometric jump training: a systematic review with meta-analysis of randomized-controlled trials

INTRODUCTION

The purpose of this systematic review was to analyze the effect of plyometric jump training (PJT) applied in conjunction with tapering strategies on the jump performance of team-sport athletes.

EVIDENCE ACQUISITION

The meta-analysis included: 1) randomized-controlled studies that incorporated a PJT program; 2) cohorts of team-sport athletes; 3) jump performance assessments; and 4) studies that incorporated a programmed taper. A systematic search was conducted in distinct electronic databases for relevant studies. Aside from jump performance, the extracted data included characteristics of the participants, PJT, and tapering. Means and standard deviations were used to calculate the effect sizes (ES). To assess the effects of moderator variables, subgroup analyses were performed. The statistical significance level was set as P<0.05.

EVIDENCE SYNTHESIS

From 7020 records initially identified, 14 studies were eligible for meta-analysis. Across all included studies, there was a moderate, significant improvement in jump performance (ES=0.73; P<0.001). Additionally, the subgroup analysis demonstrated that the duration and intensity of the taper and the volume of the PJT induced similar improvements in jump performance (P<0.01).

CONCLUSIONS

In summary, PJT interventions that included a programmed taper induced significant improvements in jump performance in team-sport athletes. These effects were observed after different tapering strategies in terms of volume, taper duration, and the type of PJT prescribed.

Direct Relationship Between Metabolic Flexibility Measured During Glucose Clamp and Prolonged Fast in Men

OBJECTIVE

This study aimed to determine the relationship between metabolic flexibility (MetFlex) measured during a euglycemic-hyperinsulinemic clamp and a prolonged fast. This study also analyzed the association between MetFlex and metabolic health.

METHODS

Eighteen healthy men (mean [SD]: 22 [2] years old; BMI: 22 [1] kg/m² ) performed two sessions: (1) euglycemic-hyperinsulinemic clamp (2 mIU/kg of insulin per minute) and (2) ~20-hour fast. Clamp MetFlex corresponded to the change in (Δ) respiratory quotient (RQ) (ΔRQ = postchallenge RQ - prechallenge RQ) adjusted for M value and prechallenge RQ. Prolonged fast MetFlex corresponded to the ΔRQ adjusted for the Δβ-hydroxybutyrate and prechallenge RQ.

RESULTS

MetFlex during the clamp related directly with MetFlex during prolonged fast (r = 0.59, P = 0.014). Using the median of MetFlex for each challenge, this study split participants into high or low MetFlex. Participants with high or low MetFlex to both challenges were identified. Participants with high MetFlex had 3% lower serum low-density lipoprotein cholesterol than participants with low MetFlex (P = 0.021).

CONCLUSIONS

Measuring MetFlex during a clamp or a prolonged fast produces similar results, despite challenging the oxidation of different substrates. An impaired MetFlex in response to these challenges may be an early event in the development of abnormal lipid metabolism.

Effects of A High Intensity Interval Session on Mucosal Immune Function and Salivary Hormones in Male and Female Endurance Athletes

Although the effects of high intensity interval training (HIIT) on health and sports performance are well documented, the effects of this training type on mucosal immune function remain unclear. The aim of this study was to assess the impact of an acute HIIT session on salivary immune and endocrine marker levels (immunoglobulin A (sIgA), alpha amylase (sAA), cortisol (C), and testosterone (T)) in male and female endurance athletes. Twenty subjects (ten males and ten females) underwent ten bouts of treadmill running using a 4 min:2 min work:rest ratio at ~90% of peak oxygen uptake (VO_2peak). Saliva samples were collected 5 min before and 20 min post-exercise. During work intervals, female participants had a higher HR than male participants (+4.0 ± 5%; p = 0.008). Rating of perceived exertion (RPE) increased throughout the duration of the HIIT session in both males and females (main time effect: p < 0.001), but was higher in males than females (+17 ± 4%; time x gender main effect: p < 0.001). Lactate concentrations were similar in both males and females. Exercise increased the concentration of salivary IgA (males: +24 ± 6%, p = 0.004; females: +27 ± 3%, p = 0.03), salivary alpha-amylase (males: +44 ± 22%, p = 0.036; females: +71 ± 26%, p = 0.026) and salivary cortisol (males: +41 ± 24%, p = 0.015; females: +55 ± 24%, p = 0.005). Testosterone levels and the Testosterone/Cortisol ratio remained stable in both males and females. These findings suggest that the physiological stress produced by a HIIT session does not affect immune function and does not disturb the anabolic/catabolic balance.

Relative lipid oxidation associates directly with mitochondrial fusion phenotype and mitochondria-sarcoplasmic reticulum interactions in human skeletal muscle

Disturbances in skeletal muscle lipid oxidation might induce ectopic fat deposition and lipotoxicity. Nevertheless, the cellular mechanisms that regulate skeletal muscle lipid oxidation have not been fully determined. We aimed to determine whether there was an association between relative whole body lipid oxidation and mitochondrial size or mitochondria-sarcoplasmic reticulum interactions in the skeletal muscle. Twelve healthy men were included [mean (standard deviation), 24.7 (1.5) yr old, 24.4 (2.6) kg/m²]. The respiratory quotient (RQ) was used to estimate relative lipid oxidation at rest and during exercise (50% maximal oxygen consumption, 600 kcal expended). A skeletal muscle biopsy was obtained from the vastus lateralis at rest. Transmission electron microscopy was used to determine mitochondrial size and mitochondria-sarcoplasmic reticulum interactions (≤50 nm of distance between organelles). Protein levels of fusion/fission regulators were measured in skeletal muscle by Western blot. Resting RQ and exercise RQ associated inversely with intermyofibrillar mitochondrial size (r = -0.66 and r = -0.60, respectively, P < 0.05). Resting RQ also associated inversely with the percentage of intermyofibrillar mitochondria-sarcoplasmic reticulum interactions (r = -0.62, P = 0.03). Finally, intermyofibrillar mitochondrial size associated inversely with lipid droplet density (r = -0.66, P = 0.01) but directly with mitochondria fusion-to-fission ratio (r = 0.61, P = 0.03). Our results show that whole body lipid oxidation is associated with skeletal muscle intermyofibrillar mitochondrial size, fusion phenotype, and mitochondria-sarcoplasmic-reticulum interactions in nondiabetic humans.

Role of Basal Hormones on Sweat Rate and Sweat Na+ Loss in Elite Women Soccer Players

We aimed to determine whether basal concentrations of testosterone, cortisol or the ratio testosterone/cortisol were related to sweat Na⁺ loss, sweat Na⁺ concentration ([Na⁺]) and sweat rate during exercise. Twenty-two female elite soccer players participated in the study. Testosterone and cortisol were measured in blood samples before exercise. Sweat samples were collected during a training session (~20°C, ~30% RH, and ~0.55 m/s of wind speed) to measure sweat [Na⁺]. Sweat rate was determined by considering the difference between post-and pre-body weight, along with the amount of liquid consumed. During exercise, sweat Na⁺ loss (0.33[0.19] g/h) and sweat rate (0.49[0.20] L/h) were related to basal testosterone concentration (1.4[0.4] pg/mL) (r=0.54; r=0.55, respectively; p<0.05), but not with basal cortisol concentration (119.2[24.2] ng/mL) nor testosterone/cortisol ratio (0.012[0.003]) (p>0.05). However, when Na⁺ loss was adjusted to sweat rate, no association was found between Na⁺ loss and testosterone (p>0.05). In addition, no differences were found between players with high vs. low Na⁺ loss adjusted to sweat loss in menstrual phase or intensity during exercise (p>0.05). In conclusion, these results suggest that in these specific environmental conditions, basal levels of testosterone might increase sweat rate and therefore, the amount of Na⁺ lost during exercise in elite women soccer players.

Effects of skim milk and isotonic drink consumption before exercise on fluid homeostasis and time-trial performance in cyclists: a randomized cross-over study

BACKGROUND

Hydration status affects endurance performance. Pre-exercise hydration recommendations target the consumption of high carbohydrate and sodium beverages. Milk, due to its carbohydrate and sodium content, may be considered an effective pre-exercise hydration beverage.

PURPOSE

In a randomized cross-over trial, we compared the effects of an isotonic sport drink (SPD) with skim milk (SM) consumption before a race, on fluid homeostasis and time-trial performance in road cyclists.

METHODS

Male road cyclists (n = 9; age, 26.8 ± 4.78 years) with 10.8 ± 8.56 years of experience in national competitions, consumed either SPD or SM in doses of 350 mL at 3 h and 350 mL at 1.5 h before a 18.6 km time-trial race. Measurements of body mass, urine specific gravity (USG), urine color and time-trial were compared between drinks (group; g) before and after the race (time; t).

RESULTS

The two-way ANOVA showed no differences between SPD and SM in body mass (t, p < 0.0001; g, p = 0.89; t × g, p = 0.54), USG (t, p = 0.01; g, p = 0.63; t × g, p = 0.29) and urine color (t, p = 0.01; g, p = 0.54; t × g, p = 0.28) before or after race. Furthermore, no differences on water consumption during the race (p = 0.55) or time-trial performance (p = 0.84) were observed between trials.

CONCLUSION

Current results may help athletes with different beverages preferences to increase their options of hydration strategies.

Basal Mild Dehydration Increase Salivary Cortisol After a Friendly Match in Young Elite Soccer Players

A soccer match induce changes in physiological stress biomarkers as testosterone (T), cortisol (C), and testosterone:cortisol (T:C) ration. Hydration state may also modulate these hormones, and therefore may alter the anabolic/catabolic balance in response to soccer match. The role of hydration status before the match in this biomarkers has not yet been reported. The aim of this study was to compare the salivary T, C, and the T:C ratio responses after two friendly matches in well-hydrated and mild-dehydrated (MD) elite young male soccer player. Seventeen players (age, 16.8 ± 0.4 years; VO₂max 57.2 ± 3.6 ml/kg⁻¹/min⁻¹) were divided into two teams. Before the matches the athletes were assessed for hydration level by the urine specific gravity method and divided for the analysis into well-hydrated (WH; n = 9; USG < 1.010 g/mL⁻¹) and mild-dehydrated (MD; n = 8; USG 1.010 to 1.020 g/mL⁻¹) groups. Hormones were collected before and after each match by saliva samples. The mean (HRmean) and maximal (HRmax) heart rate were measured throughout the matches. A two-way ANOVA was used to compare T, C, and T:C between and within groups. Similar HRmean (WH, 83.1 ± 4.7%; MD, 87.0 ± 4.1; p = 0.12) and HRmax (WH, 93.2 ± 4.4%; MD, 94.7 ± 3.7%; p = 0.52) were found for both groups during the matches. No differences were found before the matches in the T (p = 0.38), C (p = 66), nor T:C (p = 0.38) between groups. No changes within groups were found after matches in neither group for T (WH, p = 0.20; MD, p = 0.36), and T:C (WH, p = 0.94; MD, p = 0.63). Regarding the C, only the MD group showed increases (28%) after the matches (MD, p = 0.03; WH, p = 0.13). In conclusion MD group exacerbate the C response to friendly matches in elite young male soccer players, suggesting that dehydration before match may be an added stress to be considered.

Effects of Beer, Non-Alcoholic Beer and Water Consumption before Exercise on Fluid and Electrolyte Homeostasis in Athletes

Fluid and electrolyte status have a significant impact on physical performance and health. Pre-exercise recommendations cite the possibility of consuming beverages with high amounts of sodium. In this sense, non-alcoholic beer can be considered an effective pre-exercise hydration beverage. This double-blind, randomized study aimed to compare the effect of beer, non-alcoholic beer and water consumption before exercise on fluid and electrolyte homeostasis. Seven male soccer players performed 45 min of treadmill running at 65% of the maximal heart rate, 45 min after ingesting 0.7 L of water (W), beer (AB) or non-alcoholic beer (NAB). Body mass, plasma Na⁺ and K⁺ concentrations and urine specific gravity (USG) were assessed before fluid consumption and after exercise. After exercise, body mass decreased (p < 0.05) in W (−1.1%), AB (−1.0%) and NAB (−1.0%). In the last minutes of exercise, plasma Na⁺ was reduced (p < 0.05) in W (−3.9%) and AB (−3.7%), plasma K⁺ was increased (p < 0.05) in AB (8.5%), and USG was reduced in W (−0.9%) and NAB (−1.0%). Collectively, these results suggest that non-alcoholic beer before exercise could help maintain electrolyte homeostasis during exercise. Alcoholic beer intake reduced plasma Na⁺ and increased plasma K⁺ during exercise, which may negatively affect health and physical performance, and finally, the consumption of water before exercise could induce decreases of Na⁺ in plasma during exercise.

Prevalence of Dehydration Before Training Sessions, Friendly and Official Matches in Elite Female Soccer Players

This study aimed to evaluate and compare the hydration states prior to different sporting events (training sessions, friendly and official matches) in elite female soccer players and relate that to the importance that the player attached to the hydration state as a determinant of sports performance. The hydration state of 17 female elite soccer players (age: 21.5 ± 3 years; body mass: 62 ± 6 kg; body height: 165 ± 9 cm) was determined by measuring their urine specific gravity (USG) prior to three different sports events: training sessions (PT), friendly (PF) and official (PO) matches. The importance that each player attached to the hydration state as a determinant of sports performance was evaluated through a simple questionnaire. An average of 47.05% of the soccer players were severely dehydrated (USG > 1.030), 33.33% were significantly dehydrated (USG > 1.020), 17.64% were mildly dehydrated (USG > 1.010) and 1.96% were euhydrated (USG < 1.010). The average USG was 1.027 ± 0.007 (PT = 1.029 ± 0.009; PF = 1.023 ± 0.010 and PO = 1.030 ± 0.006). Differences were found between urine specific gravity prior to a friendly and an official match (p = 0.03). No relationship was found between urine specific gravity and the importance each player attached to the hydration state as a determinant of sports performance. The results show that dehydration is the most prevalent hydration state of elite soccer players before training sessions, friendly and official matches. Players were most dehydrated prior to official matches, which was unlinked to the players’ perceived importance of hydration for sports performance.

MOTOR SKILLS AND NUTRITIONAL STATUS OUTCOMES FROM A PHYSICAL ACTIVITY INTERVENTION IN SHORT BREAKS ON PRESCHOOL CHILDREN CONDUCTED BY THEIR EDUCATORS: A PILOT STUDY

INTRODUCTION

childhood obesity is a worldwide health concern. For this issue different intervention have being planned to increase physical activity patterns and reduce the excess of weight in children with limited or no success.

OBJECTIVE

the aim of this study is to evaluate the results of a pilot intervention consisting in three 15-minute breaks conducted by educators and supervised by physical education teachers on motor skills and nutritional status in preschool children.

METHODS

sample was 70 preschool children (32 boys and 38 girls), age 4 ± 0,6 years. The physical activity classes were performed three times a week, 45 minutes daily, distributed in three 15 minutes breaks. The circuits were planned to have; jumps, sprints, carrying medicinal balls, gallops and crawling. Motor skill tests that were performed Standing long jump (SLJ) and Twelve meter run.

RESULTS

with the intervention no significant differences in nutritional status where found on mean Z score (boys p = 0.49, girls p = 0.77). An increment on weight and height was fount after the intervention (p < 0.0001). Regarding the 12 meter run test, we found significant changes after the intervention when we normalize by weight in boys (p = 0.002) and girls (p < 0.0001). Our results have shown than boys significantly increased their SLJ and SLJ normalized by weight (p < 0.0001); a similar result was found in girls after the intervention (p < 0.0001) suggesting the increment of power independent of weight gain.

CONCLUSIONS

in conclusion, this pilot study found that an intervention with more intense activities in small breaks (15 minutes), and guided by the educators could improve essential motor skills (running and jumping) in preschool children of a semi-rural sector independent of nutritional status. This gaining in motor skills is the first step to increase physical activity levels in preschool children.

Hydration status after exercise affect resting metabolic rate and heart rate variability

INTRODUCTION

Heart rate variability and resting metabolic rate are commonly to assess athlete's physiological status and energy requirements. Exercise-induced dehydration can reach up to 5% of body mass per hour. Consequently, dehydration may have a profound physiological effect on human's homeostasis.

OBJECTIVES

To compare the effects of dehydration and rehydration after exercise on heart rate variability and resting metabolic rate in college athletes.

METHODS

14 college athletes were divided into a dehydration group (n=7) and a rehydration group (n=7), both submitted to basal (T1) heart rate variability and resting metabolic rate measurements. After basal measurements both groups were actively dehydrated (-3.4 ± 0.4% of body mass for both groups). Afterwards, dehydration group rested, while rehydration group receive a fluid intake (during a 3 h period) equivalent to 150% of body mass loss achieved during active dehydration. Four hours after active dehydration heart rate variability and resting metabolic rate were re-assessed (T2).

RESULTS

At T2 both rehydration group (+13%) and dehydration group (+30%) achieve a significant (p<0.05) increase in resting metabolic rate, however, only dehydration group ..showed a significant reduction in heart rate variability. More so, the change in resting metabolic rate was significantly higher in dehydration group compared to rehydration group.

DISCUSSION

Hydric homeostasis after exercise affects resting metabolic rate and heart rate variability, highlighting the necessity to control hydration state before resting metabolic rate and heart rate variability assessment.