Endurance Exercise Capacity Research Articles

O.4.1-7 Recreational football training increases leg-extensor force production at high velocities in 55- to 70-year-old adults

Abstract Purpose Ageing coincides with a blunted ability to produce force at moderate to high velocities. Therefore, improving muscle power, especially at moderate to high velocities, is a crucial target for exercise interventions in middle-aged and older adults. We investigated the effects of 10 weeks of recreational football training on the leg-extensor force-velocity (F-V) profile in 55- to 70-year-old adults. Simultaneous effects on functional capacity, body composition and endurance exercise capacity were examined. In addition, feasibility and the physical demands of the training program were tracked. Methods Forty participants (age 63.5 ± 3.9 years) were randomized in a football training (FOOT, n = 20) and a control (CON, n = 20) group. FOOT performed 45-min to 1-h of football training sessions with small-sided games (SSG’s) twice a week. Pre and post intervention, leg-extensor F-V profile (maximal power (Pmax), maximal force (F0), maximal velocity (V0), the slope divided by F0 (SFV/F0)), functional capacity, body composition and endurance exercise capacity were measured. Results Results revealed an increase over time for Pmax (ptime = 0.009), but no interaction effect (pint = 0.221). A greater increase in V0 and in SFV/F0 was apparent in FOOT compared to CON (pint = 0.043 and pint = 0.065). No interaction effect was found for F0 (pint = 0.922). Three-step stair ascent power, 10m fast walk, body fat percentage and running speed at 2mM lactate improved significantly more in FOOT than in CON (all pint < 0.1). The SSG’s elicited intense muscular actions and high average heart rates of 85.7% of maximal heart rate. Despite the high training load, participants perceived the sessions as very enjoyable and feasible. Conclusions The present study emphasized that recreational football can be used as a feasible, enjoyable and effective training tool in middle-aged to older adults for improving force production at high velocities. This improvement is translated into a better performance on functional capacity tests that rely on high execution velocity. In addition, broad-spectrum health benefits can be realized with only 2 hours of training per week. Funding E. Van Roie was supported by the Research Foundation Flanders, Belgium (senior postdoctoral fellowship 12Z5720N).

Effect of ubiquinol on cardiorespiratory fitness during high-altitude acclimatization and de-acclimatization in healthy adults: the Shigatse CARdiorespiratory fitness study design.

Cardiorespiratory function influences exercise capacity and is an important determinant of high-altitude adaptation. Some studies have investigated the characteristics of changes in cardiorespiratory fitness during high-altitude acclimatization. However, studies on changes in cardiorespiratory fitness during high-altitude de-acclimatization are still lacking and have not yet been elucidated. Furthermore, few drugs have been studied to improve cardiorespiratory function during both processes. The Shigatse CARdiorespiratory Fitness (SCARF) study is a single-center, randomized, double-blind, placebo-control clinical trial to explore the effects of ubiquinol on cardiorespiratory fitness during high-altitude acclimatization and de-acclimatization in healthy adults. Participants will be randomly assigned 1:1 to ubiquinol 200 mg daily or a placebo for 14 days before departure until the end of data collection after return in 7 days. Cardiorespiratory fitness is the primary outcome, while acute mountain sickness and high-altitude de-acclimatization symptoms are secondary endpoints. In addition, laboratory measurements, including routine blood tests and serological measurements, will be performed. To the best of our knowledge, the SCARF study will be the first to reveal the changes in the cardiorespiratory fitness characteristics during high-altitude acclimatization and de-acclimatization. Furthermore, the results of this study will contribute to exploring whether ubiquinol supplementation could be beneficial for endurance exercise capacity at different altitudes and help improve adaptation to acute hypoxia and de-acclimatization. Clinical Trial Registration: This study has been registered in the Chinese Clinical Trial Register (www.chictr.org.cn) as ChiCTR2200059900 and ChiCTR2200066328.

Baf155 regulates skeletal muscle metabolism via HIF-1a signaling.

During exercise, skeletal muscle is exposed to a low oxygen condition, hypoxia. Under hypoxia, the transcription factor hypoxia-inducible factor-1α (HIF-1α) is stabilized and induces expressions of its target genes regulating glycolytic metabolism. Here, using a skeletal muscle-specific gene ablation mouse model, we show that Brg1/Brm-associated factor 155 (Baf155), a core subunit of the switch/sucrose non-fermentable (SWI/SNF) complex, is essential for HIF-1α signaling in skeletal muscle. Muscle-specific ablation of Baf155 increases oxidative metabolism by reducing HIF-1α function, which accompanies the decreased lactate production during exercise. Furthermore, the augmented oxidation leads to high intramuscular adenosine triphosphate (ATP) level and results in the enhancement of endurance exercise capacity. Mechanistically, our chromatin immunoprecipitation (ChIP) analysis reveals that Baf155 modulates DNA-binding activity of HIF-1α to the promoters of its target genes. In addition, for this regulatory function, Baf155 requires a phospho-signal transducer and activator of transcription 3 (pSTAT3), which forms a coactivator complex with HIF-1α, to activate HIF-1α signaling. Our findings reveal the crucial role of Baf155 in energy metabolism of skeletal muscle and the interaction between Baf155 and hypoxia signaling.

MCT4 Deficiency Enhances High-intensity Interval Training-induced Metabolic Adaptations in Skeletal Muscle

The purpose of this study was to understand the effect of increased lactate accumulation in skeletal muscle by MCT4 deficiency on the adaptation of skeletal muscle to high-intensity interval training. To address this challenge, we first developed MCT4-deficient mice with a genetic background of the Jcl:ICR strain which is capable of performing high-intensity exercise. We found that MCT4 deficiency enhances high-intensity interval training-induced improvement of endurance exercise capacity at high intensity. Furthermore, it was also shown that the combination of MCT4 deficiency and high-intensity interval training, coupled with the physiological context of such adaptation, increases enzyme activity of the glycolysis and the mitochondrial oxidative capacity of pyruvate. The findings of this study would help us understand the physiological significance of lactate accumulation in skeletal muscle with high-intensity exercise. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Aerobic exercise training-induced alteration of gut microbiota composition affects endurance capacity.

This study aimed to clarify whether aerobic exercise training-induced alterations in the gut microbiota affect physiological adaptation with endurance exercise capacity. In study 1, ICR mice were randomly divided into three groups: vehicle intake + sedentary (V+S), vehicle intake + exercise training (V+Ex) and antibiotic intake + exercise training (AB+Ex). In the exercise training groups, treadmill running was performed for 8weeks. During the exercise training intervention, the antibiotic-intake group freely drank water containing antibiotics. In study 2, ICR mice were randomly divided into three groups: Sham, transplantation of caecum microbiota from sedentary mice (Sed-CMT) and exercise training mice (Ex-CMT). In study 1, the treadmill running time to exhaustion, an index of maximal aerobic capacity, after aerobic exercise training in the V+Ex group was significantly longer than that in the V+S and AB+Ex groups. Gastrocnemius muscle citrate synthase (CS) activity and PGC-1α protein levels in the V+Ex group were significantly higher than in the V+S and AB+Ex groups. The bacterial Erysipelotrichaceae and Alcaligenaceae families were positively correlated with treadmill running time to exhaustion. In study 2, the treadmill running time to exhaustion after transplantation was significantly higher in the Ex-CMT group than in the Sham and Sed-CMT groups. Furthermore, CS activity and PGC-1α protein levels in the gastrocnemius muscle were significantly higher in the Ex-CMT group than in the Sham and Sed-CMT groups. Thus, gut microbiota altered by aerobic exercise training may be involved in the augmentation of endurance capacity and muscle mitochondrial energy metabolism. KEY POINTS: Aerobic exercise training changes gut microbiota composition, and the Erysipelotrichaceae and Alcaligenaceae families were among the altered gut bacteria. The gut microbiota was associated with endurance performance and metabolic regulator levels in skeletal muscle after aerobic exercise training. Continuous antibiotic treatment attenuated the increase in endurance performance, citrate synthase activity and PGC-1α levels in skeletal muscle induced by aerobic exercise training. Gut microbiota transplantation from exercise-trained mice improved endurance performance and metabolic regulator levels in recipient skeletal muscle, despite the absence of aerobic exercise training.

Rare Compound Heterozygous Missense Mutation of the SCN5A Gene with Childhood-Onset Sick Sinus Syndrome in Two Chinese Sisters.

Sick sinus syndrome (SSS) is a group of syndromes characterized by pathological changes in the sinoatrial node and its adjacent tissues. Although several mutations in the SCN5A gene have been associated with early-onset SSS, pediatric patients are still less common. Here, we report a rare compound missense mutation in the SCN5A gene [c.2893C>T (p. R965C) and c.2431C>T (p. R811C) ] in two sisters with childhood-onset SSS in Chinese population. The proband (5 years and 5 months old) was the second child of a clinically normal and nonconsanguineous couple. Her elder sister was 12 years old and had been implanted with a pacemaker because of the diagnosis of SSS at another hospital one year ago. The proband was presented to the hospital with a slowed heart rate and reduced endurance exercise capacity for more than three months. After a comprehensive clinical examination, she was diagnosed with SSS and underwent pacemaker implantation. Exome and Sanger sequencing were used to determine the compound heterozygous missense mutation of [c.2893C>T (p. R965C) and c.2431C>T (p. R811C) ] in the SCN5A in the patient and her elder sister. Each healthy parent carried a different heterozygous missense mutation. The compound heterozygous mutation of c.2893C>T (p. R965C) and c.2431C>T (p. R811C) rather than the single mutation might be the primary cause of familial early-onset SSS in Chinese population. Our current findings expanded the current understanding of the SCN5A gene mutations. We further confirmed the essential role of the SCN5A gene on the diagnosis, family cascade screening, early intervention, and prognostic evaluation of SSS.

Reliability and Responsiveness of Endurance Shuttle Walk Test to Estimate Functional Exercise Capacity in Patients with Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-analysis.

The endurance shuttle walk test (ESWT) is a simple, acceptable, field-based test first established in 1999 to measure endurance exercise capacity in patients with chronic obstructive pulmonary disease (COPD). The aim of this systematic review was to examine the reliability and responsiveness of ESWT in COPD. Of the 791 articles identified through electronic databases, 17 were included in this review. Qualitative and quantitative analyses were conducted according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses, and as per Consensus-Based Standards for the Selection of Health Status Measurements Instruments, the quality of the studies was graded as low for reliability and moderate for responsiveness. Qualitative analysis indicated inadequate evidence for the reliability of the ESWT in patients with COPD. The meta-analysis found strong evidence that ESWT was responsive to change following pulmonary rehabilitation with an estimated mean difference (ESWT time, seconds) 303.19 s (95% CI: 175.63-430.75; p< 0.001), ambulatory oxygen with a mean difference (ESWT time, seconds) 129.04 s (95% CI: 47.98-210.09; p = 0.002), and (ESWT mean distance, meters) 80.71 m (95% CI: 38.66-122.76; p < 0.001). The ESWT was also responsive to bronchodilation with a mean difference of 168.62 m (95% CI: 117.03-220.21; p < 0.001). Our findings suggest the strong potential of ESWT as a responsive test in COPD, but to draw a definitive conclusion regarding the reliability of the ESWT, further research is needed in this population.

Effects of carbohydrate and protein supplement strategies on endurance capacity and muscle damage of endurance runners: A double blind, controlled crossover trial.

ABSTRACTBackgroundThe purpose of this study is to explore the effect of carbohydrate only or carbohydrate plus protein supplementation on endurance capacity and muscle damage.MethodsTen recreationally active male runners (VO2max: 53.61 ± 3.86 ml/kg·min) completed run-to-exhaustion test three times with different intakes of intervention drinks. There was a 7-day wash-out period between tests. Each test started with 60 minutes of running at 70% VO2max (phase 1), followed by an endurance capacity test: time-to-exhaustion running at 80% VO2max (phase 2). Participants randomly ingested either 1) 0.4 g/kg BM carbohydrate before phase 1 and before phase 2 (CHO+CHO), 2) 0.4 g/kg BM protein before phase 1 and 0.4 g/kg BM carbohydrate before phase 2 (PRO+CHO), or 3) 0.4 g/kg BM carbohydrate before phase 1 and 0.4 g/kg BM protein before phase 2 (CHO+PRO). All subjects ingested carbohydrate (CHO) 1.2 g/kg BM during phase 1, and blood samples were obtained before, immediately, and 24 h after exercise for measurements of alanine aminotransferase (ALT), aspartate aminotransferase (AST), creatine kinase (CK), and myoglobin (MB).ResultsThere was no significant difference in time to exhaustion between the three supplement strategies (CHO+CHO: 432 ± 225 s; PRO+CHO: 463 ± 227 s; CHO+PRO: 461 ± 248 s). However, ALT and AST were significantly lower in PRO+CHO than in CHO+CHO 24 h after exercise (ALT: 16.80 ± 6.31 vs. 24.39 ± 2.54 U/L; AST: 24.06 ± 4.77 vs. 31.51 ± 7.53 U/L, p < 0.05). MB was significantly lower in PRO+CHO and CHO+PRO than in CHO+CHO 24 h after exercise (40.7 ± 15.2; 38.1 ± 14.3; 64.3 ± 28.9 ng/mL, respectively, p < 0.05). CK increased less in PRO+CHO compared to CHO+CHO 24 h after exercise (404.22 ± 75.31 VS. 642.33 ± 68.57 U/L, p < 0.05).ConclusionCarbohydrate and protein supplement strategies can reduce muscle damage caused by endurance exercise, but they do not improve endurance exercise capacity.

AKG/OXGR1 promotes skeletal muscle blood flow and metabolism by relaxing vascular smooth muscle

Abstract In response to contraction during exercise, skeletal muscle growth and metabolism are dynamically regulated by nerve action, blood flow, and metabolic feedback. α-Ketoglutarate (AKG), a bioactive intermediate in the tricarboxylic acid cycle released during exercise, has been shown to promote skeletal muscle hypertrophy. However, the underlying mechanism of AKG in regulating skeletal muscle development and metabolism is still less known. 2-Oxoglutarate receptor 1 (OXGR1), the endogenous AKG receptor, is found to be distributed in the vascular smooth muscle (VSM) of skeletal muscles. OXGR1 knockout results in skeletal muscle atrophy, accompanied by decreased expression of myosin heavy chain I (MyHC I), capillary density, and endurance exercise capacity. Furthermore, the study found that dietary AKG supplementation increased mice endurance exercise distance, MyHC I/MyHC IIb ratio, arteriole, and capillary densities in skeletal muscle. Meanwhile, acute AKG administration gradually increased the blood flow in the lower limbs. Further, by using OXGR1 global knockout and OXGR1 VSM-specific (MYH11-Cre × OXGR1-FloxP) knockdown models, we found that OXGR1 in VSM is essential for AKG-induced improvement of skeletal muscle performances. According to the in vitro study, AKG expanded the cell area in VSM with a decreased intracellular pH by OXGR1. Our results demonstrated a novel role of AKG/OXGR1 in VSM of skeletal muscle to regulate blood flow and then enhance slow muscle fiber conversion and capillarization. These findings provide a theoretical basis for the AKG/OXGR1 signaling pathway to maintain human muscle function and improve meat production and livestock and poultry meat quality.

Supplementation with Vitis vinifera Jingzaojing Leaf and Shoot Extract Improves Exercise Endurance in Mice.

Switching myofibers from the fast-glycolytic type to the slow-oxidative type is associated with an alleviation of the symptoms associated with various cardiometabolic diseases. This study investigates the effect of Vitis vinifera Jingzaojing leaf and shoot extract (JLSE), which is rich in phenolic compounds, on the regulation of skeletal muscle fiber-type switching, as well as the associated underlying mechanism. Male C57BL/6N mice were supplemented orally with vehicle or JLSE (300 mg/kg) and subjected to treadmill exercise training. After four weeks, mice in the JLSE-supplemented group showed significantly improved exercise endurance and mitochondrial oxidative capacity. JLSE supplementation increased the expression of sirtuin 6 and decreased Sox6 expression, thereby elevating the number of mitochondria and encouraging fast-to-slow myofiber switching. The results of our experiments suggest that JLSE supplementation reprograms myofiber composition to favor the slow oxidative type, ultimately enhancing exercise endurance.

Limonium tetragonum Promotes Running Endurance in Mice through Mitochondrial Biogenesis and Oxidative Fiber Formation.

The purpose of this study was to examine whether Limonium tetragonum, cultivated in a smart-farming system with LED lamps, could increase exercise capacity in mice. C57BL/6 male mice were orally administered vehicle or Limonium tetragonum water extract (LTE), either 30 or 100 mg/kg, and were subjected to moderate intensity treadmill exercise for 4 weeks. Running distance markedly increased in the LTE group (100 mg/kg) by 80 ± 4% compared to the vehicle group, which was accompanied by a higher proportion of oxidative fibers (6 ± 6% vs. 10 ± 4%). Mitochondrial DNA content and gene expressions related to mitochondrial biogenesis were significantly increased in LTE-supplemented gastrocnemius muscles. At the molecular level, the expression of PGC-1α, a master regulator of fast-to-slow fiber-type transition, was increased downstream of the PKA/CREB signaling pathway. LTE induction of the PKA/CREB signaling pathway was also observed in C2C12 cells, which was effectively suppressed by PKA inhibitors H89 and Rp-cAMP. Altogether, these findings indicate that LTE treatment enhanced endurance exercise capacity via an improvement in mitochondrial biosynthesis and the increases in the formation of oxidative slow-twitch fibers. Future study is warranted to validate the exercise-enhancing effect of LTE in the human.

Effects Of Broad-spectrum Antibiotic Administration And Germ-free Status On Biochemical And Endurance Adaptations To Regular Exercise In Mouse Muscle Tissue

PURPOSE: The gut microbiota modulates a variety of physiologic processes. Recent studies from our group have shown that regular endurance exercise alters the composition of the gut microbiome and metabolome in mice and humans, and we hypothesized that the presence of microbes would affect endurance training adaptations in muscular endurance capacity, mitochondrial activity and gene expression in mice. METHODS: To discern differences in adaptations from 6 wks of voluntary wheel running (VWR), we depleted microbes with antibiotics (ABX) and used germ free (GF) mice to compare to control (CON). Male and female C57Bl/6 mice of all groups underwent daily VWR or sedentary (SED) conditions in a 2 x 3 design (VWR/SED, CON/ABX/GF, n = 56). After the intervention, treadmill endurance was assessed and gastrocnemius and soleus tissue were harvested and analyzed for activity of key Krebs cycle enzyme Citrate Synthase (CS) and expression of genes indicating mitochondrial adaptations respectively. RESULTS: Two way ANOVA revealed that VWR increased treadmill endurance, ABX had no effect, and that GF status significantly reduced performance. Additionally, VWR increased Citrate Synthase enzyme activity in gastrocnemius muscle tissue in all groups, and ABX and GF status did not reduce VWR’s effect or have an effect of their own. VWR also tended to increase expression of genes associated with increased mitochondrial activity (PGC-1α, CS, Succinate Dehydrogenase) in soleus tissue, but ABX had no effect on these observations. CONCLUSIONS: We conclude that ABX treatment and GF status do not affect VWR induced adaptations in endurance capacity, gastrocnemius mitochondrial activity or expression of metabolic genes in soleus tissue, but that GF status significantly hinders endurance capacity. This indicates that removing gut microbes does not inhibit muscular endurance training adaptations, but that germ free mice possess hindered endurance exercise capacity.

Effects of Pulmonary Rehabilitation Including Inspiratory Muscle Training in Patients with Chronic Obstructive Pulmonary Disease after Stratification by the Degree of Static Hyperinflation

Inspiratory muscle training (IMT) improves inspiratory muscle strength, exercise capacity and health status in patients with chronic obstructive pulmonary disease (COPD). However, there is no additional effect on top of comprehensive pulmonary rehabilitation (PR). It is unclear whether patients with different baseline degrees of static hyperinflation respond differentially to IMT as part of a PR program. Therefore, the aim was to study the effects of IMT as an add-on on PR after stratification for baseline degrees of static hyperinflation. In this single center retrospective study data were extracted between June 2013 and October 2020 of COPD patients who participated in a comprehensive PR program including IMT. IMT was performed twice daily, one session consisted of 3 series of 10 breaths and training intensity was set initially at a load of approximately 50% of patients' maximal static inspiratory mouth pressure (MIP). The primary outcome measure was MIP. Secondary outcomes were the distance achieved on the 6-min walk test (6MWD), endurance cycling exercise capacity at 75% of the peak work rate (CWRT) and disease-specific health status using the COPD assessment test. 754 patients with COPD were screened for eligibility and 328 were excluded because of repeated PR programs, missing data or baseline residual volume (RV) > 350%. In total, 426 COPD patients were categorized into RV categories 50-130% (n = 84), 131-165% (n = 86), 166-197% (n = 86), 198-234% (n = 85) and 235-349% (n = 85). In the whole sample, MIP, endurance exercise capacity and health status improved significantly. The change in 6MWD was higher in the lowest baseline degree of static hyperinflation [+ 39 (9-92) m] compared with the baseline highest degree of static hyperinflation [+ 11 (- 18-54) m] (p < 0.05). IMT as part of a PR program in patients with COPD with different baseline degrees improved MIP irrespective of the degree of static lung hyperinflation. Improvement in functional exercise capacity was significantly higher in the group with the lowest degree of static hyperinflation compared with the patients with the highest degree of static hyperinflation.

Effects of COVID-19 Lockdown on Body Composition and Physical Performance of Elite Female Football Players

The COVID-19 pandemic led to an unusual situation in sports. Players were forced to stay at home for an undefined period of time and not allowed to use any training facilities or even exercise outdoors. Therefore, this study aimed to examine the effects of the COVID-19 lockdown on physical performance and body composition in elite female football players. During the confinement period, 19 players (n = 19, M = 27 years; SD = 4.19) volunteered to participate in the present study. Participants were confined during 5 months and performed six remotely guided sessions a week, designed and structured by a certified fitness coach. Pre- and postconfinement period, players were tested for body composition, strength in the squat exercise, vertical jump, 30-m sprint, kicking velocity, and intermittent endurance capacity (Yo-Yo Intermittent Recovery Level 1). Fat mass and muscle mass remained unaffected after the confinement period, while only body mass showed a significant increase between periods (1.19%; p = .014). In addition, physical performance measures postconfinement showed positive changes in kicking (p &lt; .001; effect size = 1.02), in contrast to a reduction in mean propulsive velocity against 40-kg load and Yo-Yo Intermittent Recovery Level 1 total distance covered (p: .041 and .010, respectively). Present findings indicate that the implementation of home-based training programs during confinement periods could be sufficient stimulus to maintain body composition and physical performance (i.e., strength, vertical jump, and sprint), although they might not be sufficient to maintain intermittent endurance capacity in elite female football players.

Whey Proteins-Fortified Milk with Adjusted Casein to Whey Proteins Ratio Improved Muscle Strength and Endurance Exercise Capacity without Lean Mass Accretion in Rats.

This study investigated the effects of the casein to whey proteins (CW) ratio in milk on body composition, muscle strength, and endurance exercise capacity in rats. Thirty rats were assigned into five groups, and each treatment was administered for eight weeks: (1) control (isocaloric lactose supplementation), (2) CW8:2 (regular milk), (3) CW6:4, (4) CW5:5, and (5) nitrogen-free (lactose). The milk concentration was converted from a human equivalent dose (400 mL/60 kg body weight/day). All the milk-administered groups showed significantly greater growth performance, including body weight and weight gain compared to the isocaloric lactose control (p < 0.05). However, different CW ratios in milk had no effect on growth performance. Additionally, body composition, i.e., lean body mass and adiposity, was not affected by the CW ratio. Interestingly, CW6:4 and CW5:5 had significantly higher plasma branched-chain amino acids concentrations than control and CW8:2 (p < 0.05). In addition, CW5:5 showed significantly increased grip strength by 12–24% and time to exhaustion by 8–62% compared to the other groups (p < 0.05), indicating that the higher whey proteins ratio improved physical performance. We concluded that whey proteins-fortified milk enhances muscle strength and endurance exercise capacity without altering lean mass in rats.

Sex differences in endurance exercise capacity and skeletal muscle lipid metabolism in mice.

Previous studies suggest that sex differences in lipid metabolism exist with females demonstrating a higher utilization of lipids during exercise, which is mediated partly by increased utilization of muscle triglycerides. However, whether these changes in lipid metabolism contribute directly to endurance exercise performance is unclear. Therefore, the objective of this study was to investigate the contribution of exercise substrate metabolism to sex differences in endurance exercise capacity (EEC) in mice. Male and female C57BL/6‐NCrl mice were subjected to an EEC test until exhaustion on a motorized treadmill. The treadmill was set at a 10% incline, and the speed gradually increased from 10.2 m/min to 22.2 m/min at fixed intervals for up to 2.5 h. Tissues and blood were harvested in mice immediately following the EEC. A cohort of sedentary, non‐exercised male and female mice were used as controls. Females outperformed males by ~25% on the EEC. Serum levels of both fatty acids and ketone bodies were ~50% higher in females at the end of the EEC. In sedentary female mice, skeletal muscle triglyceride content was significantly greater compared to sedentary males. Gene expression analysis demonstrated that genes involved in skeletal muscle fatty acid oxidation were significantly higher in females with no changes in genes associated with glucose uptake or ketone body oxidation. The findings suggest that female mice have a higher endurance exercise capacity and a greater ability to mobilize and utilize fatty acids for energy.

Curcuma longa L. Water Extract Enhances Endurance Exercise Capacity by Promoting Intramuscular Mitochondrial Biogenesis in Mice.

We investigated the effect of Curcuma longa L. extract on endurance exercise capacity (EEC). EEC is the ability to exercise continuously and recover quickly, even when tired. C. longa contains antioxidants that contribute beneficial effects on the body. We separated groups of nonexercise (CON), exercise control (Ex-CON), branched-chain amino acid (BCAA) intake, and C. longa water extract (CLW) intake (Ex-CLW). EEC increased on the 28th day of BCAA and CLW intake. Both treatment groups exhibited decreased lactate levels with increased levels of nonesterified fatty acids and muscular glycogen compared with the Ex-CON group. Also, the Ex-CLW group possessed higher intramuscular antioxidant enzyme activities (catalase, superoxide dismutase, and glutathione peroxidase) than the Ex-CON group. The expression of PGC-1α, NRF, and Tfam, which are factors related to mitochondrial biogenesis, increased in the Ex-CLW group. Results suggest that CLW intake elevated EEC by increasing intramuscular mitochondrial biogenesis through suppressing the accumulation of fatigue substances and increasing fat consumption, and antioxidant enzyme activity.

Luteolin increases slow muscle fibers via FLCN-AMPK-PGC-1α signaling pathway

• Luteolin may improve endurance exercise capacity of mice. • Luteolin may increase slow muscle fibers proportion both in mice and C2C12 myotubes. • Luteolin may activate FLCN-AMPK-PGC-1α axis in mice’s muscle and C2C12 myotubes. • FLCN-AMPK-PGC-1α axis may play key role in luteolin induced slow myofibers increasing. While the regulating mechanisms of slow myofibers have been gradually explored, there are currently a lack of effective means to increase slow myofibers proportion. Here, we have showed that luteolin could markedly improve endurance exercise performance and increase body oxygen consumption of mice, and activate aerobic enzyme activity and slow myofibers related genes and proteins expression in mice’s skeletal muscle. Meanwhile, folliculin (FLCN)-AMP-activated protein kinase (AMPK) -peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) pathway was activated by treatment luteolin in the tissues. Furthermore, by in vitro investigation and FLCN lentivirus infection, we have found that the over-expression of FLCN significantly reduces the effects of luteolin on slow myofibers expression and AMPK-PGC-1α axis activation. Together, our results indicate that luteolin can increase the proportion of slow myofibers probably by FLCN-AMPK-PGC-1α pathway. These findings provide a novel approach to increase slow muscle fibers proportion and improve skeletal muscle fitness.

Quercetin as a supplement improving endurance exercise capacity – review

Quercetin is a polyphenol found mainly in fruits and vegetables. Many studies show that its supplementation increases physical efficiency. The purpose of this review is to summarize to date literature on whether quercetin may increase athletes’ performance. Previous reports show that this polyphenol has an antioxidant, antidiabetic effect (by increasing GLUT4 expression in skeletal muscles), stimulates mitochondrial biogenesis, prevents obesity by, inter alia, inhibition of adipogenesis, and increases the maximal aerobic capacity. However, due to the many contradicting results, there is a need for further research especially with athletes as participants. La quercétine est un polyphénol présent principalement dans les fruits et légumes. De nombreuses études montrent que sa supplémentation améliore l’aptitude physique. Le but de cette revue est de résumer la littérature à ce jour sur la question de savoir si la quercétine peut augmenter les performances des athlètes. De précédentes publications suggèrent que ce polyphénol aurait un effet antioxydant et antidiabétique (en augmentant l’expression de GLUT4 dans les muscles squelettiques), stimulerait la biogenèse mitochondriale, préviendrait l’obésité, entre autres, par l’inhibition de l’adipogenèse et augmenterait la capacité aérobie maximale. Cependant, en raison des nombreux résultats contradictoires, il est nécessaire de poursuivre les recherches, en particulier en étudiant des sujets sportifs.

Treatments for skeletal muscle abnormalities in heart failure: sodium-glucose transporter 2 and ketone bodies.

Various skeletal muscle abnormalities are known to occur in heart failure (HF) and are closely associated with exercise intolerance. Particularly, abnormal energy metabolism caused by mitochondrial dysfunction in skeletal muscle is a cause of decreased endurance exercise capacity. However, to date, no specific drug treatment has been established for the skeletal muscle abnormalities and exercise intolerance occurring in patients with HF. Sodium-glucose transporter 2 (SGLT2) inhibitors promote glucose excretion by suppressing glucose reabsorption in the renal tubules, which has a hypoglycemic effect independent of insulin secretion. Recently, large clinical trials have demonstrated that treatment with SGLT2 inhibitors suppresses cardiovascular events in patients who have HF with systolic dysfunction. Mechanisms of the therapeutic effects of SGLT2 inhibitors for HF have been suggested to be diuretic, suppression of neurohumoral factor activation, renal protection, and improvement of myocardial metabolism, but this has not been clarified to date. SGLT2 inhibitors are known to increase blood ketone bodies. This suggests that they may improve the abnormal skeletal muscle metabolism in HF, that is, improve fatty acid metabolism, suppress glycolysis, and use ketone bodies in mitochondrial energy production. Ultimately, they may improve aerobic metabolism in skeletal muscle, suppress anaerobic metabolism, and improve aerobic exercise capacity at the level of the anaerobic threshold. The potential actions of such SGLT2 inhibitors explain their effectiveness in HF and may be candidates for new drug treatments aimed at improving exercise intolerance. In this review, we outlined the effects of SGLT2 inhibitors on skeletal muscle metabolism, with a particular focus on ketone metabolism.