A Non-Weight Bearing Method for Measuring Hip Abduction Strength Overestimates Hip Abductor Muscle Fatigue During One-Leg Stance.

OCCUPATIONAL APPLICATIONSAssessing workers' strength capacities is a common practice prior to return to work following injury or illness, or assessing capabilities for strenuous jobs. Because it requires 50% or more of maximum strength capacity, hip abductor muscle strength is a strong predictor of both middle- and older-aged individuals' ability to reliably balance on one leg and of their risk of falls. Our results suggest subjects were able to augment their hip abductor moment during unipedal weight stance via gluteus maximus activity. Weight-bearing hip abduction strength measures are important for assessing worker capacity for jobs requiring reliable unipedal balance whether during lateral loading, while walking in gusty winds, on slippery footing or resisting lateral deck movements on board ship or train. Measurements of hip abductor strength should be made in a full unipedal weight bearing posture; non-weight-bearing measurements significantly underpredicted hip abductor strength as well as endurance.

Background: Unipedal stance time is a significant predictor of fall risk in middle- and older-aged individuals. Because muscle fatigue reduces muscle strength over a sustained contraction, muscle endurance time could limit maximum unipedal stance time. Purpose: We tested the hypothesis that hip abduction muscle endurance time, which depends on muscle strength, limits maximum unipedal stance time. Methods: We recruited 18 healthy young (10 females) and 17 older (10 females) adults who could stand on one leg for at least 10 s. Using a non-weight bearing test, we measured the left hip isometric maximum abduction strength and endurance time at 50% of that strength. We also measured subjects' maximum unipedal stance time, while force plate and full-body 3D motion capture signals were recorded. Subject-specific inverse dynamics biomechanical models were used to calculate the hip abduction moment required to stand on one leg. Results: Unipedal balance required a mean (SD) of 59 (19) % and 118 (53) % of the young and old adult hip abduction muscle strengths, respectively, which were consistent with published values. Mean (SD) hip muscle endurance times at 50% of abduction MVC were 63 (62) sec. and 147 (107) sec. for young and older adults, respectively. However, contrary to our hypothesis (above), the endurance time at 50% MVC failed to predict an upper limit for the maximum unipedal stance time. Conclusions: Our results show that standing on one leg requires over 50% of non-weight bearing hip abductor strength when young, and full strength when older. Because all younger individuals and four (out of 17) older individuals could balance on one leg longer than predicted during weight-bearing the gluteus maximus, a hip extensor, likely tensioned the iliotibial band to counteract abductor muscle fatigue with time. So, measurements of hip abduction strength should be made in the weight-bearing posture when middle- and older-aged workers' balance capacity is being assessed whether in a return-to-work assessment setting or evaluating workers for jobs requiring significant lateral loading, walking in gusty winds or on slippery surfaces, or on boat or train decks prone to sudden movements.

Demonstration of 1 V Reliable FeRAM Operation: Vc Engineering Using Quasi-Chirality of Hf1-xZrxO2 in a Nanolaminate Structure.

Hafnia thin films are known to demonstrate excellent performance with strong ferroelectricity and high scalability, making them promising candidates for CMOS-compatible materials. However, the reliability of ferroelectric devices must be further improved. This study developed a Hf1-xZrxO2 ferroelectric capacitor with a nanolaminate structure that operated at remarkably low voltages, demonstrating excellent retention (>10 years/85 °C) and endurance (>1010 cycles). The exceptional performance is attributed to the presence of thin tetragonal phase layers within the thick ferroelectric layers, which decreased the switching barrier in the nanolaminate films. Further, we verified phase crystallization via a detailed analysis of high-resolution transmission electron microscopy images. The improved switching propagation in the nanolaminate films was confirmed through switching speed measurements and theoretical models. Furthermore, we addressed pinching issues by precisely controlling the Hf/Zr ratio and O3 treatment. The initial imprint and retention characteristics were improved by interfacial engineering. Moreover, by reducing the thickness, we have achieved reliable operation at 1.0 V with a 5.5 nm-thick device while maintaining high retention and endurance. This study is a significant step toward the realization of the longstanding problem of ferroelectric random access memory operation voltage with respect to endurance and retention characteristics.

Resistance- and endurance-trained young men display comparable carotid artery strain parameters that are superior to untrained men.

PURPOSE: Central arterial stiffness, a predictor of cardiovascular risk, attenuates with endurance-exercise in ageing populations. However, in young individuals, this effect is inconsistent and emerging evidence suggests resistance-exercise may increase arterial stiffness. Two-dimensional (2D)-Strain imaging of the common carotid artery (CCA) is more sensitive at detecting endurance-training induced alterations in CCA stiffness than conventional methods, but has not been used to examine CCA stiffness in young resistance-trained individuals. Therefore, we compared CCA 2D-Strain parameters at rest, during acute exercise and recovery between resistance-trained, endurance-trained, and untrained young men. METHODS: Short-axis CCA ultrasound images were obtained from 12 endurance-trained [27yrs (95%CI; 24-29)], 14 resistance-trained [24yrs (23-26)] and 12 untrained [23yrs (22-24] men at rest, during isometric handgrip (IHG) exercise and recovery. 2D-Strain analysis quantified CCA peak circumferential strain (PCS) and systolic (S-SR) and diastolic (D-SR) strain rates. Conventional stiffness indices included aortic pulse-wave velocity, CCA ß-stiffness (ß1) and Petersons elastic modulus (Ep). RESULTS: Resting conventional stiffness indices were not different between groups (P > 0.05). Resting PCS and S-SR were comparable between resistance- [11.6% (10.6-12.5) and 1.46 s-1 (1.37-1.55), respectively] and endurance-trained [11.4% (10.7-12.2) and 1.5 s-1 (1.38-1.62)] men and superior to untrained men [9.5% (9.19-9.9); P < 0.004 and 1.24 s-1 (1.17 - 1.31); P < 0.018)]. Both trained groups displayed comparable reductions in PCS and S-SR during IHG, which returned to resting values during recovery (P < 0.001), whereas these parameters remained unchanged in untrained men. D-SR decreased during IHG in all groups (P < 0.001), but to a lesser extent in endurance-trained men (P < 0.023), whereas ß1 and Ep increased to a similar magnitude in all groups and returned to resting values during recovery (P < 0.001). CONCLUSION: Resistance- and endurance-trained men display comparable CCA 2D-Strain parameters that are superior to untrained men, which contends previous reports that resistance-training increases CCA stiffness.

Durability in recreational runners: effects of 90-min low-intensity exercise on the running speed at the lactate threshold.

PURPOSE: Recent studies have suggested that the capability to resist deterioration of physiological characteristics could be an independent factor contributing to endurance performance. This study aimed at investigating whether prolonged low-intensity exercise induces shifts in the lactate threshold, and whether fatigue-induced changes differ between the sexes. METHODS: A total of 31 (15 females) recreational runners performed an incremental treadmill test and a 90-min low-intensity exercise (LIT90) on two separate occasions. The LIT90 was performed at 90% of the first lactate threshold speed (LT1v), derived from the incremental treadmill test. The LT1v was determined from a 5-stage (3 min) submaximal threshold test (SubmaxLT), performed before and after LIT90. The SubmaxLTs were followed by a 10/5 reactivity jump test. Respiratory gases, heart rate (HR), and HR-derived detrended fluctuation analysis alpha 1 (DFA-a1) were assessed every 15 min during the LIT90. RESULTS: A significant decrease (p < 0.01) was observed in the LT1v in females (- 5.8 ± 4.4%) and in males (- 5.3 ± 6.4%). The HR increased (p < 0.001) similarly in females (5.9 ± 3.1%) and in males (5.5 ± 3.6%) during the LIT90, while energy expenditure increased (3.1 ± 4.5%, p = 0.013) in females but remained unchanged in males (0.9 ± 3.1%). Change in DFA-a1 during the LIT90 was the only marker that correlated significantly with the relative change of LT1v (r = 0.463, p = 0.013). CONCLUSION: LIT90 induced significant decreases in the LT1v, and the changes were comparable between sexes. DFA-a1 could be a potential intra-session marker of durability.

The higher the fraction of maximal oxygen uptake is during interval training, the greater is the cycling performance gain.

It has been suggested that time at a high fraction (%) of maximal oxygen uptake (VO2max) plays a decisive role for adaptations to interval training. Yet, no study has, to date, measured the % of VO2max during all interval sessions throughout a prolonged training intervention and subsequently related it to the magnitude of training adaptations. Thus, the present study aimed to investigate the relationship between % of VO2max achieved during an interval training intervention and changes in endurance performance and its physiological determinants in well-trained cyclists. Twenty-two cyclists (VO2max 67.1 (6.4) mL·min-1 ·kg-1; males, n = 19; females, n = 3) underwent a 9-week interval training intervention, consisting 21 sessions of 5 × 8-min intervals conducted at their 40-min highest sustainable mean power output (PO). Oxygen uptake was measured during all interval sessions, and the relationship between % of VO2max during work intervals and training adaptations were investigated using linear regression. A performance index was calculated from several performance measures. With higher % of VO2max during work intervals, greater improvements were observed for maximal PO during the VO2max test (R2 adjusted = 0.44, p = 0.009), PO at 4 mmol·L-1 [blood lactate] (R2 adjusted = 0.25, p = 0.035), the performance index (R2 adjusted = 0.36, p = 0.013), and VO2max (R2 adjusted = 0.54, p = 0.029). Other measures, such as % of maximal heart rate, were related to fewer outcome variables and exhibited poorer session-to-session repeatability compared to % of VO2max. In conclusion, improvements in endurance measures were positively related to the % of VO2max achieved during interval training. Percentage of VO2max was the measure that best reflected the magnitude of training adaptations.

Exercise to combat cancer: focusing on the ends.

Cancer remains a leading cause of death worldwide and although prognosis and survivorship after therapy has improved significantly, current cancer treatments have long-term health consequences. For decades telomerase-mediated telomere maintenance has been an attractive anti-cancer therapeutic target due to its abundance and role in telomere maintenance, pathogenesis and growth in neoplasms. Telomere maintenance-specific cancer therapies, however, are marred by off target side-effects that must be addressed before they reach clinical practice. Regular exercise training is associated with telomerase-mediated telomere maintenance in healthy cells, which is associated with healthy ageing. A single bout of endurance exercise training dynamically, but temporarily, increases TERT mRNA and telomerase activity, as well as several molecules that control genomic stability and telomere length (i.e., shelterin and TERRA). Considering the epidemiological findings and accumulating research highlighting that exercise significantly reduces the risk of many types of cancers and the anti-carcinogenic effects of exercise on tumour growth in vitro, investigating the governing molecular mechanisms of telomerase control in context with exercise and cancer may provide important new insights to explain these findings. Specifically, the molecular mechanisms controlling telomerase in both healthy cells and tumours after exercise could reveal novel therapeutic targets for tumour-specific telomere maintenance and offer important evidence that could refine current physical activity and exercise guidelines for all stages of cancer care.

Cross-sectional study of the optimal types of physical exercise for cognitive function in older Japanese adults.

AIM: This study aimed to determine whether practicing coordination exercises, compared with other physical exercise types, is associated with better cognitive function in older Japanese adults. METHODS: This cross-sectional study used data from a health checkup project carried out from 2015 to 2019 among older adults living in Kasama City, Ibaraki Prefecture, Japan. Data from 569 participants (mean age 74.0 ± 5.4 years, 53.8% women) were analyzed. The types of physical exercise practiced within the seven preceding days were identified. The Five-Cog test and Trail Making Test were used to evaluate general cognitive function and executive function, respectively. The cognitive functions of practitioners and non-practitioners of each type of physical exercise - coordination, endurance, resistance, and stretching - were examined using an analysis of covariance. RESULTS: Although practitioners of any physical exercise did not have significantly better cognitive function than non-practitioners, in an analysis stratified by exercise amount, those who practiced more coordination exercise had better general cognitive function than non-practitioners (P = 0.046), in a fully adjusted model. CONCLUSION: Those who practiced more coordination exercises had better general cognitive function. Geriatr Gerontol Int 2024; ••: ••-••.

Impact of resistance training on fatigue among breast cancer patients undergoing chemotherapy: a systematic review and meta-analysis.

PURPOSE: The effects of aerobic exercise interventions for reducing fatigue after cancer treatment are well-established, and the effect of resistance training remains uncertain. Therefore, this systematic review and meta-analysis aim to analyze the effect of resistance training and combined resistance and endurance training on cancer-related fatigue (CRF) in breast cancer patients. METHODS: A systematic search for randomized controlled trials (RCTs) was conducted on the PubMed, SPORTDiscus, Embase, and Cochrane databases, focusing on the effect of supervised resistance training and combined supervised resistance and endurance training on CRF. Random-effect models were employed for calculating the standardized mean difference (SMD). Risk of bias was assessed with risk of bias 2 (RoB2), and certainty of evidence was judged according to the GRADE approach. RESULTS: A total of 9 RCTs with 1512 participants were included, and data from 866 participants in 8 RCTs were used for the meta-analysis. The risk of bias was deemed low in seven studies, while one study exhibited attrition bias, and one showed possible selection bias. Resistance training probably reduce the total fatigue (SMD= -0.30, 95% CI -0.52, -0.08, p=0.008), with individual studies showing small effects on physical and emotional CRF. A combined resistance and endurance training reduce total fatigue (SMD= -0.34, 95% CI -0.51, -0.17, p= 0.0001), with individual studies indicating moderate effects on physical fatigue, in daily life fatigue, and small effects on emotional and cognitive CRF. CONCLUSION: Both supervised resistance training and combined resistance and endurance training have a small effect on total CRF. There is a trend towards an influence of intensity, with higher intensity potentially resulting in lower total CRF.

Corrigendum: Cardiac function and autonomic cardiac function during a multi-stage cycling event: a brief report.

[This corrects the article DOI: 10.3389/fspor.2024.1356577.].

A single-center, double-blind, randomized, placebo-controlled, two-arm study to evaluate the safety and efficacy of once-weekly sirolimus (rapamycin) on muscle strength and endurance in older adults following a 13-week exercise program.

BACKGROUND: Aging leads to a decline in muscle mass and strength, contributing to frailty and decreased quality of life. Sirolimus (rapamycin) , an mTOR inhibitor, has shown potential in preclinical studies to extend lifespan and improve health span. This study evaluates the safety and efficacy of once-weekly sirolimus (rapamycin) administration on muscle strength and endurance in older adults engaged in a 13-week exercise program. METHODS: This randomized, double-blind, placebo-controlled trial will enroll 40 participants aged 65-85. Participants will be randomly assigned to receive either sirolimus (rapamycin) 6 mg/week or placebo for 13 weeks, in conjunction with an at-home exercise program. The primary outcome measure is the change in muscle strength and endurance, assessed by the 30-Second Chair-Stand Test. Secondary outcome measures include adverse events, changes in muscle strength and endurance as measured by the 6-min walk test, handgrip strength, and participant-reported outcomes using the SF-36 survey. Assessments will be conducted at baseline, mid-intervention (week 6), and post-intervention (week 13). Blood samples will be collected for hematology and biochemistry analyses, including full blood count, urea and electrolytes, liver function tests, HbA1c, lipids, serum IGF-1, and hs-CRP. DNA methylation will be analyzed using TruDiagnostic™ to explore changes in biological age. DISCUSSION: This study aims to provide insights into the potential benefits of intermittent sirolimus (rapamycin) administration on muscle performance in older adults. By alternating periods of mTOR inhibition through rapamycin and activation via exercise, this study will explore a novel approach to enhancing muscle strength and endurance in the aging population. The results could have significant implications for developing interventions to improve physical function and overall health outcomes in older adults. Safety and tolerability will also be closely monitored to ensure the feasibility of this regimen for wider application. TRIAL REGISTRATION: Australia New Zealand Clinical Trials Registry, ACTRN12624000790549. Registered on 26 June 2024 https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12624000790549 .

Changes in the force-time curve during a repeat power ability assessment using loaded countermovement jumps.

Background: Repeat power ability (RPA) assessments traditionally use discrete variables, such as peak power output, to quantify the change in performance across a series of jumps. Rather than using a discrete variable, the analysis of the entire force-time curve may provide additional insight into RPA performance. The aims of this study were to (1) analyse changes in the force-time curve recorded during an RPA assessment using statistical parametric mapping (SPM) and (2) compare the differences in the force-time curve between participants with low and high RPA scores, as quantified by traditional analysis. Materials and Methods: Eleven well-trained field hockey players performed an RPA assessment consisting of 20 loaded countermovement jumps with a 30% one repetition maximum half squat load (LCMJ20). Mean force-time series data was normalized to 100% of the movement duration and analysed using SPM. Peak power output for each jump was also derived from the force-time data and a percent decrement score calculated for jumps 2 to 19 (RPA%dec). An SPM one-way ANOVA with significance accepted at α = 0.05, was used to identify the change in the force-time curve over three distinct series of jumps across the LCMJ20 (series 1 = jumps 2-5, series 2 = jumps 9-12 and series 3 = jumps 16-19). A secondary analysis, using an independent T-test with significance accepted at p < 0.001, was also used to identify differences in the force-time curve between participants with low and high RPA%dec. Results: Propulsive forces were significantly lower (p < 0.001) between 74-98% of the movement compared to 0-73% for changes recorded during the LCMJ20. Post hoc analysis identified the greatest differences to occur between jump series 1 and jump series 2 (p < 0.001) at 70-98% of the movement and between jump series 1 and jump series 3 (p < 0.001) at 86-99% of the movement. No significant differences were found between jump series 2 and jump series 3. Significant differences (p < 0.001) in both the braking phase at 44-48% of the jump and the propulsive phase at 74-94% of the jump were identified when participants were classified based on low or high RPA%dec scores (with low scores representing an enhanced ability to maintain peak power output than high scores). Conclusion: A reduction in force during the late propulsive phase is evident as the LCMJ20 progresses. SPM analysis provides refined insight into where changes in the force-time curve occur during performance of the LCMJ20. Participants with the lower RPA%dec scores displayed both larger braking and propulsive forces across the LCMJ20 assessment.

Home-based long-term physical endurance and inspiratory muscle training in children and adults with Fontan circulation.

Background and study aim: Regular physical activity is highly recommended for patients with Fontan hemodynamics. Our aim was to investigate the effects of a long-term individualized home-based endurance training (IHET) on a bicycle ergometer in combination with inspiratory muscle training (IMT) in pediatric and adult patients after Fontan palliation. Additionally, factors influencing the trainability of Fontan palliated patients were analyzed. Methods: From 2018 to 2021 a single-center prospective study was performed initially including 25 Fontan palliated patients. During study period nine patients were excluded due to incompliance. A Magbike® bicycle ergometer (DKN Technology, France) was used for IHET and a POWERbreathe® Medic plus device (HaB GmbH, Germany) was utilized for the IMT. Over the study period, bike training was increased from 90 min of basic endurance training per week to additional 25 min of interval training per week. IMT consisted of 30 breaths per day for 6-7 days per week with pressure adaption over time. Patients underwent cardiopulmonary exercise testing (CPET) and body plethysmography including measurement of respiratory muscle strength at baseline and at follow-up examinations at 4, 10 and 22 months. Results: Follow-up examinations were completed by 18/25 patients (72.0%) at 4 and 10 months and 16/25 patients (64.0%) at 22 months. Median exercise capacity slightly increased by 0.13 W/kg from baseline to last follow-up (p = 0.055, 95%CI: 0.0-0.36). However, a significant increase of oxygen pulse of 0.7 ml/beat (p = 0.006, 95%CI: 0.38-2.22) was detectable. IMT significantly improved respiratory function with an increase of inspiratory vital capacity (VCin/reference) by 4.0% (p = 0.016, 95%CI: 0.8-8). Median maximal inspiratory pressure increased by 1.2 kPa (p = 0.003, 95%CI: 0.64-3.19) and expiratory pressure by 1.5 kPa (p = 0.036, 95%CI: 0.08-2.29). No adverse events or unplanned interventions occurred during the study. Patients' subjective quality of life did not significantly change over the study period. Conclusion: In Fontan palliated patients, IHET in combination with IMT leads to a significant increase in oxygen pulse, inspiratory vital capacity as well as median maximal inspiratory and expiratory pressure but not to significant improvement of quality of life. Fontan patients should be encouraged to perform regular home-based exercise training.

Neural and Muscular Determinants of Performance Fatigability Are Independent of Work and Recovery Durations During High-Intensity Interval Exercise in Males.

The present study aimed to investigate the effect of two protocols of high-intensity interval exercise (HIIE) on performance fatigability and its neural and muscular determinants. On different days, 14 healthy males performed two HIIE protocols with different work and recovery durations (matched for total duration, work and recovery intensities, and density): 1) 4 × 4 min at 90% HRpeak,180-s recovery at 70% HRpeak; and 2) 16 × 1 min at 90% HRpeak, 45-s recovery at 70% HRpeak. Pre- to post-HIIE reduction in maximal voluntary isometric contraction (MVIC) was used as marker of performance fatigability, while voluntary activation (VA) and potentiated quadriceps twitch force (Qtw) as markers of the neural (i.e. central fatigue) and muscular (i.e. peripheral fatigue) determinants, respectively. In addition, pre- to post-HIIE reduction in twitch force stimulated at 100 Hz (Qtw100) and 10:100 Hz ratio (Qtw10:Qtw100) were used as markers of high- and low-frequency performance fatigability, respectively. The MVIC, VA, Tw, Qtw100, and Qtw10:Qtw100 ratio decreased similarly from pre- to post-HIIE in both HIIE protocols (p < .05). The rating of perceived effort, blood pH, and plasma lactate responses were similar between HIIE protocols (p > .05), but the heart rate was higher in the longer HIIE protocol (p < .05). In conclusion, performance fatigability and its neural and muscular determinants seemed to be independent of the work and recovery durations of the HIIE, at least when HIIE protocols were matched for total work duration, work and recovery intensities, and density. Further, HIIE with long work and recovery might be preferable when the intention is to stress the chronotropic response.

The influence of Sex on the Effects of Inorganic Nitrate Supplementation on Muscular Power and Endurance.

Inorganic nitrate (NO3-) supplementation increases nitric oxide (NO) bioavailability and may improve muscular power and endurance, although most studies are in males. Therefore, the present double-blind, randomized, placebo-controlled study examined the effects of NO3- supplementation on isokinetic peak power, maximal voluntary isometric contraction (MVIC) force, muscular endurance (time-to-task failure; TTF), and recovery from fatigue in young females (n=12) and males (n=14). Participants consumed ~13mmol NO3- (BRJ), or an identical NO3--depleted beverage (PL), for ~3 days and 2 hours before testing visits. Plasma nitrate and nitrite were elevated in the BRJ condition (p ≤ 0.05). Peak power (W·kg-1) showed a sex effect (p ≤ 0.05) at all angular velocities and a sex-by-treatment effect at 270 and 360°/sec (p ≤ 0.05). Post hoc analysis revealed no significant differences between treatments (p > 0.05). Estimated maximal knee extension power (Pmax) and maximal knee extension velocity (Vmax) demonstrated no sex, treatment, or sex-by-treatment effect (p > 0.05). There were no significant effects for TTF (F: PL; 269±161 vs BRJ; 277±158s and M: PL; 228±171 vs BRJ; 194±100s; p > 0.05). Cohen's d effect sizes for peak power showed moderate to large effect sizes at 270 (d=0.92) and 360 deg/sec (d=0.81), showing a possible differentiated effect of dietary nitrate in females and males. The present data indicate that NO3- supplementation does not significantly affect knee extensor maximal power, maximal contraction velocity, and muscular endurance in either sex. The sex-dependent response to dietary nitrate supplementation requires further investigation as data on females is scarce.

The Effects of Inorganic Nitrate Supplementation on Muscular Power and Endurance Across the Menstrual Cycle.

Oral inorganic nitrate (NO3-) supplementation increases nitric oxide (NO) bioavailability and may improve muscular power in males and females, although data in females is limited. Estrogen increases NO bioavailability and fluctuates throughout the menstrual cycle (MC), with low levels in the early follicular (EF) phase and peaking during the late follicular (LF) phase. The purpose of the present study was to examine the effects of NO3- supplementation on isokinetic peak power, maximal voluntary isometric contraction (MVIC) force, muscular endurance, and recovery from fatigue in healthy young females during the EF and LF phases of the MC. Ten eumenorrheic females were tested in a double-blinded, randomized, placebo-controlled design. Participants consumed ~13mmol NO3-, in the form of 140ml beetroot juice (BRJ), or an identical NO3--depleted placebo (PL), for ~5 days prior to visits and 2 hours prior to testing. Plasma estradiol was elevated in the LF phase, and plasma nitrite and nitrate were elevated in the BRJ condition (p < 0.05). While isokinetic peak power was unchanged, calculated maximal power (Pmax) and maximal velocity (Vmax) was significantly worsened in the BRJ treatment independent of the MC phase (p = 0.02 and 0.03, respectively). Muscular endurance, MVIC, and fatigue recovery were unaltered by BRJ or the MC. These data indicate that NO3- supplementation decreased maximal power and velocity in females and suggest that the benefits of NO3- supplementation previously found in males may not extend to young females.

Testing Green Tea Extract and Ammonium Salts as Stimulants of Physical Performance in a Forced Swimming Rat Experimental Model.

The study of drugs of natural origin that increase endurance and/or accelerate recovery is an integral part of sports medicine and physiology. In this paper, decaffeinated green tea extract (GTE) and two ammonium salts-chloride (ACL) and carbonate (ACR)-were tested individually and in combination with GTE as stimulants of physical performance in a forced swimming rat experimental model. The determined parameters can be divided into seven blocks: functional (swimming duration); biochemistry of blood plasma; biochemistry of erythrocytes; hematology; immunology; gene expression of slow- and fast-twitch muscles (m. soleus, SOL, and m. extensor digitorum longus, EDL, respectively); and morphometric indicators of slow- and fast-twitch muscles. Regarding the negative control (intact animals), the maximum number of changes in all blocks of indicators was recorded in the GTE + ACR group, whose animals showed the maximum functional result and minimum lactate values on the last day of the experiment. Next, in terms of the number of changes, were the groups ACR, ACL, GTE + ACL, GTE and NaCl (positive control). In general, the number of identified adaptive changes was proportional to the functional state of the animals of the corresponding groups, in terms of the duration of the swimming load in the last four days of the experiment. However, not only the total number but also the qualitative composition of the identified changes is of interest. The results of a comparative analysis suggest that, in the model of forced swimming we developed, GTE promotes restoration of the body and moderate mobilization of the immune system, while small doses of ammonium salts, especially ammonium carbonate, contribute to an increase in physical performance, which is associated with satisfactory restoration of skeletal muscles and the entire body. The combined use of GTE with ammonium salts does not give a clearly positive effect.

Effect of Endurance Exercise Training on Gut Microbiota and ER Stress.

Regular exercise as part of one's lifestyle is well-recognized for its beneficial effect on several diseases such as cardiovascular disease and obesity; however, many questions remain unanswered regarding the effects of exercise on the gut environment. This study aimed to investigate the impact of long-term endurance exercise on modulating inflammation and endoplasmic reticulum (ER) stress. Fifteen-week-old male Sprague-Dawley (SD) rats were subjected to six months of endurance treadmill training, while age-matched controls remained sedentary. Results showed that IL-6 mRNA levels in colon tissues were significantly higher in the exercise group compared to the sedentary group. Exercise activated a significant ER stress-induced survival pathway by increasing BiP and phosphorylation of eIF2α (p-eIF2α) expressions in the liver and colon, while decreasing CHOP in the liver. Gene expressions of MUC2, Occludin, and Claudin-2 were increased in the colon of the exercise group, indicating enhanced intestinal integrity. Furthermore, the data showed a positive correlation between microbiota α-diversity and BiP (r = 0.464~0.677, p < 0.05). Populations of Desulfovibrio C21 c20 were significantly greater in the exercise group than the sedentary group. Additionally, predicted functions of the gut microbial community in terms of enzymes and pathways supported the enhancement of fatty-acid-related processes by exercise. These findings suggest that prolonged endurance exercise can affect the colon environment, which is likely related to changes in inflammation, ER stress, mucin layers and tight junctions, associated with modifications in the gut microbiome.

Submaximal force-velocity relationships during mountain ultramarathon: Data from the field.

This study presents a novel method for evaluating the submaximal velocity-force (V(F)) relationship in mountain ultramarathon races using crowdsourced data from Strava.com. The dataset includes positional data from 408 participants of the 171-km UTMB® 2023 race (9,850-m D+). The race was divided into 100-m segments. The mean net propulsive force and velocity were computed for each segment to describe the submaximal V(F) relationship as a rational function of three parameters. F1: propulsive force at 1 m · s-1; V0: theoretical maximum velocity on flat terrain; C: curvature parameter (the lower C, the more linear the V(F) relationship). The V(F) profile parameters were found to be F1 = 1.80 ± 0.33 N · kg-1, V0 = 2.36 ± 0.42 m · s-1, and C = 0.66 ± 1.81, with good independence between the parameters within a group of homogeneous performance. The best athletes had the highest F1, V0, and C values. V(F) parameters were affected by fatigue during the race, with decreases of 20.9%, 32.0%, and 59.8% between the first and second parts of the race respectively. These findings suggest that the V(F) relationship is an interesting original approach for studying performance and fatigability during mountain ultra-endurance races.

Acute ergogenic effects of repetitive maximal breath-holding maneuvers on hematological and physiological responses: a graded exercise test investigation.

PURPOSE: Repetitive maximal breath-holds (BHs or apneas) have been noted to induce advantageous hematological and blood buffering changes. Building on this, the hypothesis was formulated that the execution of repeated maximal BH efforts might lead to subsequent enhancements in performance during a time-to-exhaustion test. METHODS: This study investigated the acute effects of five static maximal breath-holding maneuvers conducted with face immersion in cold water (10 °C) on subsequent graded exercise test (GET) performance. Seventeen well-trained participants completed a GET on a motorized treadmill under two randomized cross-over conditions: baseline measurement (CON) and after five repeated maximal breath-holding efforts (EXP). RESULTS: The GET protocol consists of incremental increases in speed until exhaustion. After the fifth breath-hold, participants in the EXP condition exhibited significant (P < 0.05) increases in hematocrit, hemoglobin concentration, red blood cell count, and muscle deoxygenation, accompanied by a reduction in blood lactate concentration (4.09 ± 2.21%, 3.9 ± 1.76%, 3.96 ± 2.1%, 81.48 ± 23.83%, and 15.22 ± 17.64%, respectively), compared to CON. During GET, the EXP condition showed a significantly (P < 0.05) delayed onset time of the second ventilatory threshold (3.14 ± 5.85%) and (P < 0.05) increased time to exhaustion (0.75 ± 1.02%). CONCLUSION: This evidence suggests that repeated maximal static breath-holding maneuvers enhance the oxygen delivery system by increasing the circulation of reserve red blood cells, heightened muscle oxygen deoxygenation, enhanced aerobic metabolism utilization, and postponing the transition from aerobic to anaerobic metabolism, implying a potential ergogenic effect. While pre-exercise breath-holding shows promise for improving time-to-exhaustion and optimizing subsequent distance running performance, further in-depth investigation is essential to fully elucidate the underlying mechanistic factors.

Dysfunctional eating attitudes and behaviors among French elite athletes: the impact of psychological characteristics and the sporting calendar.

Background: Research on sport psychology suggests that athletes are at risk of developing dysfunctional eating attitudes and behaviors (DEAB), however the origins of these behaviors remain largely unexplored. The present study aims to identify factors (i.e., personality traits, anxiety levels, eating attitudes and behaviors, the internalization of sport thinness norms, and resilience) associated with the development of DEAB among female endurance athletes, in training and competition. Method: A longitudinal follow-up study was conducted among 14 elite female athletes who were tested daily, weekly, and quarterly over 12 months in 2022, for a total of 545 measures. Participants completed questionnaires assessing personality traits, anxiety levels, eating attitudes and behaviors, the internalization of sport thinness norms, and resilience. Descriptive statistics were calculated for all study data, and odds ratios were conducted to compare the variance of psychological factors and sporting factors depending on the level of DEAB and the sport period. Significance was set at p < 0.05. Results: Overall, 28% of our sample of athletes were identified with DEAB. Among those with DEAB, scores for agreeableness, anxiety, and competitive anxiety were significantly higher, while scores for resilience were significantly lower than those without DEAB. During the competitive season, scores for self-regulatory eating attitudes and the internalization of thinness norms were significantly higher than during the training period. Conclusion: Our results suggest a greater probability of DEAB among athletes who exhibit the trait of agreeableness, experience anxiety during competition, and lack resilience. The competitive season was also identified as a period conducive for developing DEAB compared with the training period. Based on these results our study suggests preventive measures that can be implemented with athletes displaying these traits, with a particular emphasis during the competitive phase.