Endurance Capacity Research Articles

Impact of VO2 Max Capacity And Application of Training Methods on the Effectiveness of Endurance Ability

This research aims to see the effectiveness of training methods and aerobic capacity (VO2 Max) to increase endurance capacity (aerobic capacity). The method used in this research is an experimental method, with the research sample being Karawang district football players. The independent variables of this research are interval training and vo2 max, while the dependent variable is general endurance (aerobic capacity). In carrying out research, the interval method will be given taking into account the high and low aerobic capacity. The results of the research show that the interval method has a significant influence on increasing endurance (aerobic capacity), and the interval method has an interdependence with the level of aerobic capacity in increasing endurance. Extensive intervals are suitable for athletes who have low aerobic capacity and have not been in the process for long. Intensive interval training is suitable for athletes who have moderate aerobic capacity and have been in the training process for quite a long time. And short intervals are suitable for athletes who have a high aerobic capacity and have been training for a long time. Providing the interval method needs to take into account the high and low levels of aerobic capacity, because the interval method is a fairly heavy training method which needs to take into account the aerobic capacity capital of the athlete who will be trained and whether or not they have been involved in the training process for a long time. Keywords: extensive intervals, intensive and short intervals, VO2 Max, Speed ​​Endurance

Changing Horses in Midstream: Modern Pentathlon After the 2024 Olympic Games.

The decision of the Union Internationale de Pentathlon Moderne to replace horse riding with Obstacle after the 2024 Olympic Games challenges training, testing, and recovery management in Modern Pentathlon. This commentary discusses physiological, technical, and tactical effects of rule changes in the 5 disciplines with a specific focus on the new discipline Obstacle. Modern Pentathlon requires athletes to develop specific endurance capacities relying on both the aerobic and anaerobic systems while simultaneously increasing lower- and upper-body strength capabilities. In addition, movements must be repeatedly executed in an explosive and precise manner. Running and swimming must be fast but economical. Swapping from horse riding to Obstacle will prioritize the explosive strength of the upper extremities and core while keeping high levels of endurance and precision in swimming, fencing, and shooting. Moreover, condensing the Modern Pentathlon competition to a 90-minute television-friendly format enables more competitions in the future. Athletes and coaches will thus also need to develop and maintain effective individual peri-exercise routines (before, during, and after the competition) to successfully meet the resulting tactical and physical challenges of the new format. This commentary aims to stimulate the discussion on the effect of the Union Internationale de Pentathlon Moderne's decisions to replace riding with the new Obstacle discipline and implement a more television-friendly format with a focus on physiological, technical, and tactical aspects.

The effects of chat GPT generated exercise program in healthy overweight young adults

Overweight is an increasing public health issue worldwide. Physical activity may reduce the risks of consequences from overweight. Chat GPT is a potential tool in healthcare projects. This study aimed to evaluate if the chat GPT generated exercise program group (ChatGPT) was effective in overweight persons. This was an intervention study with a randomized controlled fashion. The inclusion criteria were students aged of 18 years or more, male sex, healthy, and had body mass index of 23-24.99 kg/m2. Eligible participants were randomly assigned into two groups by a simple random sampling: control group or ChatGPT group. The intervention was performed for eight weeks and three times/week. The outcomes included weight, cardiovascular endurance, percent fat, percent muscle, flexibility, and lung capacity. There were 9 participants in the study; ChatGPT for 6 persons and control group for 3 persons. At baseline, there was no significant difference of studied variables between both groups. At the end of study, there were three studied variables significantly different between the ChatGPT group and the control group including body mass index, heart rate after standing and knee lifting for three minutes and sit and stand in 30 seconds. The body mass index of the ChatGPT group was significantly lower than the control group (22.99 vs 24.46 kg/m2; p = .020). Chat GPT generated exercise program is feasible for overweight, young adults to lose weight and improve their cardiovascular fitness, muscle fitness, and fat loss. However, further studies are required to confirm the results of this study.

Low physical fitness indicates future injury, mental health, menstrual cycle disruptions and burnout in female emergency service personnel and healthcare providers

Musculoskeletal injury (MSKi), depression, anxiety and burnout place a considerable burden on emergency services personnel and healthcare providers (HCP). Physical fitness is related to both mental and physical health in these populations but females in these are hugely underrepresented in this literature. As female representation in first-responder and HCP roles increases, the need for female specific research is needed. This study examines physical fitness as a short-term indicator of future reproductive health, MSKi, and mental health for females employed as first-responders or HCP. Thirteen first-responders and 29 HCP completed an initial health and demographics questionnaire, a comprehensive physical assessment (e.g., bone mineral density, muscular strength, muscular endurance, muscular power, flexibility, and aerobic capacity), and a health questionnaire 6-7 months after the physical testing. We found that i) bone mineral density, relative upper body strength, and lowerbody power were related to sustaining future MSKi, ii) better lower body endurance and flexibility was related to future menstrual cycle disruptions, and iii) low bone mineral density was related future self-reported burnout and Patient Health Questionnaire score >10. Physical fitness characteristics can be helpful indicators of future MSKi risk, menstrual cycle disruptions, and mental health status in females employed in arduous occupations.

The Effect of Pre-Exercise Caffeine and Glucose Ingestion on Endurance Capacity in Hypoxia: A Double-Blind Crossover Trial

The impact of caffeine and glucose supplementation in a hypoxic environment on endurance exercise performance remains inconclusive. The current study examined the effect of pre-exercise carbohydrate and caffeine supplementation on endurance exercise performance in an acute hypoxic environment. Eight healthy active young males participated in this double-blind, within-subjects crossover study. Participants ingested the test drink 60 min before exercising at 50% Wmax for 90 min on a cycle ergometer (fatiguing preload); there followed an endurance performance test at 85% Wmax until exhaustion in a hypoxic chamber (~15%O2). Participants completed four experimental trials in a randomized order: caffeine (6 mg·kg−1; Caff), glucose (1 g·kg−1; CHO), caffeine (6 mg·kg−1) + glucose (1 g·kg−1; Caff−CHO), and taste- and color-matched placebo with no caffeine or CHO (PLA). Blood samples were collected during fasting, pre-exercise, every 30 min throughout the exercise, and immediately after exhaustion. The caffeine and glucose trials significantly enhanced endurance capacity in hypoxic conditions by Caff, 44% (68.8–31.5%, 95% confidence interval), CHO, 31% (44.7–15.6%), and Caff−CHO, 46% (79.1–13.2%). Plasma-free fatty-acid and glycerol concentrations were higher in Caff and PLA than in CHO and Caff−CHO (p < 0.05). The estimated rate of fat oxidation was higher in Caff and PLA than in CHO and Caff−CHO (p < 0.05). There were no significant differences in ratings of perceived exertion between trials. In conclusion, the ingestion of caffeine, glucose, or caffeine + glucose one hour before exercising in hypoxic conditions significantly improved 85% Wmax endurance performance after prolonged exercise.

Molecular, Histological, and Functional Changes in Acta1-MCM;FLExDUX4/+ Mice

DUX4 is the major gene responsible for facioscapulohumeral dystrophy (FSHD). Several mouse models expressing DUX4 have been developed, the most commonly used by academic laboratories being ACTA1-MCM/FLExDUX4. In this study, molecular and histological modifications in the tibialis anterior and quadriceps muscles were investigated in this model at different time points. We investigated several changes that could be used as markers of therapeutic efficacy. Our results confirm the progressive muscular dystrophy previously described but also highlight biases associated with tamoxifen injections and the complexity of choosing the genes used to calculate a DUX4-pathway gene composite score. We also developed a comprehensive force test that better reflects the movements made in everyday life. This functional force–velocity–endurance model, which describes the force production capacities at all velocity and fatigue levels, was applied on 12–13-week-old animals without tamoxifen. Our data highlight that previously unsuspected muscle properties are also affected by the expression of DUX4, leading to a weaker muscle with a lower initial muscle force but with preserved power and endurance capacity. Importantly, this force–velocity–endurance approach can be used in humans for clinical evaluations.

Application of blood flow restriction training in lower limb rehabilitation

With the popularity of national fitness campaigns, sports injuries, especially lower limb injuries such as anterior cruciate ligament tears and ankle sprains, are increasing year by year. There are limitations in traditional treatment such as muscle atrophy. In recent years, the blood flow restriction training method (BFRT) which simulates high-intensity exercise with low intensity and limits arterial and venous blood flow to promote muscle growth and strength enhancement, has drawn attention as a novel approach to rehabilitation. This article reviews the application of BFRT in the rehabilitation of lower limb injuries, discusses its effects on muscle function, pain management and quality of life, and evaluates its safety and prospects for clinical application. BFRT reduces mechanical stress, relieves pain, improves endurance and aerobic capacity, and improves cardiovascular function. However, there are discomfort and potential risks, such as muscle injury and thrombosis, which require individualised adjustments and standardised training. BFRT has shown positive result(reducing pain &oedema and improving function)s in rehabilitation of ACL reconstruction (ACLR) and chronic ankle instability (CAI). In addition, BFRT has been shown to aid in the functional recovery of the lower extremity in patients with Achilles tendon injuries and strokes. Despite the positive effects of BFRT, relevant studies have problems such as small sample sizes and non-uniform parameters. BFRT is considered a safe training modality, but contraindications should be examined before clinical application. Future research endeavours should investigate the impact of BFRT in many rehabilitation contexts and enhance tailored rehabilitation strategies. In order to maximize the therapeutic benefit, a rehabilitation training program should be developed and refined with a minimum effective dose based on the quantification of the in vivo physiological response to BFRT. The identification of the optimal prognostic approach will help to advance the standardisation of BFR treatment methods.

Loss of atrial natriuretic peptide signaling causes insulin resistance, mitochondrial dysfunction, and low endurance capacity.

Type 2 diabetes (T2D) and obesity are strongly associated with low natriuretic peptide (NP) plasma levels and a down-regulation of NP guanylyl cyclase receptor-A (GCA) in skeletal muscle and adipose tissue. However, no study has so far provided evidence for a causal link between atrial NP (ANP)/GCA deficiency and T2D pathogenesis. Here, we show that both systemic and skeletal muscle ANP/GCA deficiencies in mice promote metabolic disturbances and prediabetes. Skeletal muscle insulin resistance is further associated with altered mitochondrial function and impaired endurance running capacity. ANP/GCA-deficient mice exhibit increased proton leak and reduced content of mitochondrial oxidative phosphorylation proteins. We further show that GCA is related to several metabolic traits in T2D and positively correlates with markers of oxidative capacity in human skeletal muscle. Together, these results indicate that ANP/GCA signaling controls muscle mitochondrial integrity and oxidative capacity in vivo and plays a causal role in the development of prediabetes.

Increased cGMP improves microvascular exercise training adaptations independent of endothelial nitric oxide synthase.

Impaired microvascular function is a hallmark of pre-diabetes. With development of atherosclerosis this impaired microvascular function can result in diminished capacity for ambulation and is a risk factor for Type 2 Diabetes. Dynamic changes in vascular tone are determined, in large part, by the eNOS/NO/cGMP axis. We used gain of function of the eNOS/NO/cGMP axis in diet-induced obese (DIO) mice and reduced function in lean mice to test the hypothesis that functionality of this vascular control mechanism parallels the benefits of an exercise training regimen. DIO mice have lower exercise capacity than lean mice and were used for pharmacological gain of function. The PDE-5a inhibitor - sildenafil - increases cGMP and was administered to DIO mice daily. In sedentary mice, we find that sildenafil does not improve exercise capacity. In contrast, it amplifies the microcirculatory effects of exercise training. Sildenafil synergizes with exercise training to improve performance during an incremental exercise test. Improved exercise performance was accompanied by increased skeletal muscle capillary flow velocity and capillary density measured via intravital microscopy. Loss of function was tested in lean mice hemizygous for endothelial cell (EC) specific eNOS creating an EC-eNOS knockdown (KD). EC-eNOS KD decreases capillary density and exercise tolerance in sedentary mice; however, it did not prevent exercise-training induced improvements in endurance capacity. These data show that 1) increasing cGMP with sildenafil enhances microcirculatory function and exercise work tolerance that results from training; 2) eNOS KD does not prevent the microcirculatory or improvements in exercise tolerance with training. PDE-5a inhibitors combined with physical exercise are a potential mechanism for improving ambulation in patients with circulatory limitations.

Cardiac NAD+ depletion in mice promotes hypertrophic cardiomyopathy and arrhythmias prior to impaired bioenergetics.

Nicotinamide adenine dinucleotide (NAD+) is an essential co-factor in metabolic reactions and co-substrate for signaling enzymes. Failing human hearts display decreased expression of the major NAD+ biosynthetic enzyme nicotinamide phosphoribosyltransferase (Nampt) and lower NAD+ levels, and supplementation with NAD+ precursors is protective in preclinical models. Here we show that Nampt loss in adult cardiomyocytes caused depletion of NAD+ along with marked metabolic derangements, hypertrophic remodeling and sudden cardiac deaths, despite unchanged ejection fraction, endurance and mitochondrial respiratory capacity. These effects were directly attributable to NAD+ loss as all were ameliorated by restoring cardiac NAD+ levels with the NAD+ precursor nicotinamide riboside (NR). Electrocardiograms revealed that loss of myocardial Nampt caused a shortening of QT intervals with spontaneous lethal arrhythmias causing sudden cardiac death. Thus, changes in NAD+ concentration can have a profound influence on cardiac physiology even at levels sufficient to maintain energetics.

The Combined Effects of Endurance and Strength Training on Exercise Tolerance and Quality of Life in Patients with COPD

Chronic Obstructive Pulmonary Disease (COPD) significantly impairs exercise tolerance and quality of life due to respiratory and systemic effects. Exercise training, including endurance and strength modalities, is a cornerstone of pulmonary rehabilitation, yet the combined effects of these training methods remain underexplored. This study aimed to evaluate the combined effects of endurance and strength training on exercise tolerance and quality of life in COPD patients. A randomized controlled trial was conducted involving 100 COPD patients assigned to four groups: Endurance Training, Strength Training, Combined Training, and Control. The interventions were implemented over 12 weeks, with outcomes assessed pre- and post-intervention, including the six-minute walk test (6MWT) for exercise tolerance and the St. George’s Respiratory Questionnaire (SGRQ) for quality of life. Statistical analyses included ANOVA and post-hoc comparisons to determine group differences. The Combined Training group demonstrated the most significant improvement in exercise tolerance, with a mean increase of 72.4 meters in 6MWT distance, compared to 48.7 meters in the Endurance group and 34.2 meters in the Strength group. Quality of life, measured by SGRQ, improved significantly across all intervention groups, with the greatest reduction in total SGRQ scores observed in the Combined Training group (12.6 points), indicating enhanced physical and psychological well-being. Additional improvements in muscle strength and endurance capacity were also most pronounced in the Combined Training group. Combined endurance and strength training provide superior benefits in enhancing exercise tolerance, muscle strength, and quality of life in COPD patients compared to either modality alone. These findings support the integration of multimodal exercise regimens in pulmonary rehabilitation programs to optimize outcomes for COPD patients.

Herbal extract (Cervus elaphus Linnaeus, Angelica gigas Nakai, and Astragalus membranaceus Bunge) ameliorates chronic fatigue: A randomized, placebo-controlled, double-blind trial

BackgroundChronic fatigue syndrome (CFS) reduces the health-related quality of life in the working-age population; however, studies have rarely investigated this group. A mixture of Cervus elaphus Linnaeus, Angelica gigas Nakai, and Astragalus membranaceus Bunge (CAA) may be an effective anti-fatigue supplement. However, few clinical trials have explored the anti-fatigue effects of herbal medicines in human participants. Therefore, this study aimed to investigate the effects of the CAA herbal complex on muscle fatigue and endurance capacity in a randomized, placebo-controlled, double-blind trial. MethodsIn an 8-week trial, 80 patients with chronic fatigue symptoms were randomly assigned to the CAA (43.5 ± 1.2 years) or placebo group (41.8 ± 1.3 years). Fatigue and cardiorespiratory endurance were measured at baseline, interim, and post-intervention. Fatigue-related blood biomarkers were assessed before and at the end of the intervention. ResultsA significant improvement in overall fatigue scores was observed on the fatigue severity scale (p = 0.038), multidimensional fatigue inventory (p = 0.037), and 24-hour visual analog scale (p = 0.002) in the CAA group compared to those in the placebo group. Fatigue improvement was observed in the CAA group, as well as physiological variables, such as increased maximal exercise time to exhaustion (p = 0.003), distance until exhaustion (p = 0.003), and maximum oxygen consumption (p = 0.039). ConclusionCAA positively and significantly affected fatigue and cardiorespiratory endurance in patients with chronic fatigue, suggesting the potential use of herbal supplements for treating chronic fatigue. Trial registrationClinical Research Information Service (CRIS, https://cris.nih.go.kr/): KCT0005613.

Stable isotopes reveal sex- and context-dependent amino acid routing in green anole lizards (Anolis carolinensis).

Allocation of acquired resources to phenotypic traits is affected by resource availability and current selective context. While differential investment in traits is well documented, the mechanisms driving investment at lower levels of biological organization, which are not directly related to fitness, remain poorly understood. We supplemented adult male and female Anolis carolinensis lizards with an isotopically labelled essential amino acid (13C-leucine) to track routing in four tissues (muscle, liver, gonads, and spleen) under different combinations of resource availability (high and low-calorie diets) and exercise training (sprint training and endurance capacity). We predicted sprint training should drive routing to muscle, and endurance training to liver and spleen, and that investment in gonads should be of lower priority in each of the cases of energetic stress. We found complex interactions between training regime, diet, and tissue type in females, and between tissue type and training and tissue type and diet in males, suggesting that males and females adjust their 13C-leucine routing strategies differently in response to similar environmental challenges. Importantly, our data show evidence of increased 13C-leucine routing in training contexts not to muscle as we expected, but to the spleen, which turns over blood cells, and to the liver, which supports metabolism under differing energetic scenarios. Our results reveal the context-specific nature of long-term tradeoffs associated with increased chronic activity. They also illustrate the importance of considering the costs of locomotion in studies of life history strategies.

Effects of physical training on coagulation parameters, interleukin-6, and angiotensin-converting enzyme-2 in COVID-19 survivors

COVID-19 is a highly contagious virus that uses Angiotensin-converting enzyme 2 (ACE2) as a receptor to enter human cells. The virus leads to an increase in inflammatory cytokines (i.e. IL-6) and an impaired coagulation system, which can cause serious complications during and after the disease. Physical exercise has been shown to improve COVID-19 complications through various mechanisms, such as modulation of the immune and coagulation systems. Therefore, this study investigated the effects of 8 weeks of training on inflammatory, coagulation, and physical factors in patients with COVID-19 during the recovery phase. Twenty-seven male and female volunteers (age 20–45 years) who recently recovered from COVID-19 were assigned to the control (n = 13) or the training group (n = 14). Blood samples, aerobic capacity and muscle endurance were collected 24 h before the start of the interventions and 24 h after the final training session in week 4 and 48 h after the final training session in week 8. IL-6, ACE2, fibrinogen, and D-dimer were measured using ELISA. The training group showed a significant increase in muscle endurance (p = 0.004) and aerobic capacity (p = 0.009) compared to the control group. Serum levels of IL-6 and fibrinogen decreased in the training group but this decrease was not statistically significant (p > 0.05). Despite a slight increase in the quality of life and sleep in the training group, no statistically significant difference was observed between the training and the control group. It appears that physical training has beneficial effects on the coagulation system, inflammatory factors, and sleep quality and can facilitate the recovery of COVID-19 patients.

Conceptual design and analysis of a box fan-in-split-wing tiltrotor eVTOL aircraft

PurposeWith the advancements in electric vertical take-off and landing (eVTOL) aircraft technology such as batteries, mechanisms, motors, configurations and so on, designers and engineers are encouraged to create unique and unconventional configurations of eVTOL aircraft to provide better capabilities and higher efficiencies to compete in the market. The box fan-in-split-wing tiltrotor eVTOL aircraft is an innovative design that aims to address the aerodynamic inefficiencies such as propeller effects in cruise and engine mounts drag that existed in traditional eVTOL aircraft designs such as vectored thrust, rotorcraft, lift + cruise and multi-copter configurations. This paper aims to propose a multi-disciplinary design process to conceptually design the box fan-in-split-wing Tiltrotor eVTOL aircraft.Design/methodology/approachAn unconventional methodology was used to design the UAM aircraft, and the following parameters are considered: capable of vertical take-off and landing, highly aerodynamic with a high lift-to-drag ratio, low Cd0 modern and appealing, rechargeable or battery swappable and feature to minimise or negate propeller drag. A heavy emphasis on improving performance and weight based on aerodynamics was enforced during the conceptual design phase. MAPLA and XFOIL were used to identify the aerodynamic properties of the aircraft.FindingsUpon determining the key parameters and the mission requirements and objectives, a list of possible VTOL configurations was derived from theoretical and existing designs. The fan in the wing/split wing was selected, as it could stow the propellers. A tiltrotor configuration was selected because of its ability to reduce the total number of lift props/motors, reducing powerplant weight and improving aerodynamic efficiency. For the propulsion configuration, a battery–motor configuration with a hexa-rotor layout was chosen because of its ability to complement the planform of the aircraft, providing redundant motors in case of failure and because of its reliability, efficiency and lack of emissions. Coupled with the fan-in-wing / split wing concept, the box wing seamlessly combines all chosen configurations.Originality/valueThe box fan-in-split-wing Tiltrotor eVTOL aircraft aims to address the aerodynamic inefficiencies of earlier designs such as propeller effects in cruise and engine mounts drag. The potential benefits of this aircraft, such as increased range, endurance and payload capacity, make it an exciting prospect in the field of Urban Air Mobility.

Impact of Classical Music Listening on Cognitive and Functional Performances in Middle-Aged Women

The purpose of this study was to examine the impact of listening to classical music on functional (upper and lower body strength, functional mobility and aerobic endurance) and cognitive (attentional capacities and working memory (WM)) performances in women aged between 50 and 60 years old. A total of 24 middle-aged women were enrolled to participate in this study. Their functional and cognitive performances were assessed under two-auditory conditions (no-music vs. with music conditions) using the Timed Up and Go (TUG) test for functional mobility, the Arm Curl test and 30 s Chair Stand Tests for the upper and lower body strength, respectively, and the 2 min Step test for aerobic endurance. To assess the attentional capacities and the WM, a simple reaction time (SRT) test and Corsi Block-Tapping Task were used, respectively. As a result, we found that listening to music significantly decreased the scores of the TUG test (p < 0.001) and capacities (p < 0.05), and increased the 2 min Step test values (p < 0.001) compared to the no-music condition. However, no significant changes were found for the upper and lower body strength and WM. We conclude that listening to classical music, i.e., Mozart’s Symphony, is effective in improving functional mobility, aerobic endurance and attentional capacities in middle-aged women. However, these gains were absent for muscle strength and WM, suggesting that the positive effects of music on functional and cognitive performances were dependent on a specific task.

DPHC from Ishige okamurae mitigates oxidative stress-induced myopathy by regulating MuRF-1/MAFbx signaling in C2C12 cells

This study investigated the potential protective effects of diphlorethohydroxycarmalol (DPHC), which was isolated from Ishige okamurae, on oxidative stress-induced myopathy both in vitro and in vivo. DPHC did not exhibit any toxic effects and exerted preventive actions against hydrogen peroxide (H2O2)-induced cell toxicity and scavenged intracellular reactive oxygen species in C2C12 myocytes. Furthermore, the DPHC markedly attenuated H2O2-induced myopathy in C2C12 cells by downregulating MuRF-1/MAFbx, which is a key factor in myopathy. The in vivo study revealed that the DPHC improved the endurance capacity and inhibited oxidative stress induced myopathy through the regulation of MuRF-1/MAFbx protein expressions via the NF-κB and p38 MAPK pathways in muscle tissue based on a H2O2-induced zebrafish model. Further, histological analysis indicated that the DPHC treatment significantly improved H2O2-induced muscle tissue loss and myopathy in vivo. Thus, our findings confirmed the viability of DPHC as a potential candidate for the treatment of oxidative stress-induced myopathy.

Ulk1 phosphorylation at S555 is not required for endurance training-induced improvements in exercise and metabolic capacity in mice.

Endurance exercise training improves exercise capacity as well as skeletal muscle and whole body metabolism, which are hallmarks of high quality-of-life and healthy aging. However, its mechanisms are not yet fully understood. Exercise-induced mitophagy has emerged as an important step in mitochondrial remodeling. Unc-51-like autophagy-activating kinase 1, ULK1, specifically its activation by phosphorylation at serine 555, was discovered as an autophagy driver and to be important for energetic stress-induced mitophagy in skeletal muscle, making it a potential mediator of the beneficial effects of exercise on mitochondrial remodeling. Here, we used CRISPR/Cas9-mediated gene editing and generated knock-in mice with a serine-to-alanine mutation of Ulk1 on serine 555. We now report that these mice displayed normal endurance capacity and cardiac function at baseline with a mild impairment in energy metabolism as indicated by an accelerated increase of respiratory exchange ratio (RER) during acute exercise stress; however, this was completely corrected by 8 wk of voluntary running. Ulk1-S555A mice also retained the exercise-mediated improvements in exercise capacity and metabolic flux. We conclude that Ulk1 phosphorylation at S555 is not required for exercise-mediated improvements of exercise and metabolic capacity in healthy mice.NEW & NOTEWORTHY We have used CRISPR/Cas9-mediated gene editing to generate Ulk1-S555A knock-in mice to show that loss of phosphorylation of Ulk1 at S555 blunted exercise-induced mitophagy and mildly impairs energy metabolism during exercise in healthy mice. However, the knock-in mice retained exercise training-mediated improvements of endurance capacity and energy metabolism during exercise. These findings suggest that exercise-induced mitophagy through Ulk1 activation is not required for the metabolic adaptation and improved exercise capacity in young, healthy mice.

The combined effect of cardiorespiratory and muscular fitness on the incidence of metabolic syndrome before midlife.

Cardiorespiratory fitness (CRF) could reduce the risk of metabolic syndrome (MetS) while the association between muscular endurance capacity (MEC) and incident MetS has rarely been investigated in young adults. A total of 2890 military men and women, aged 18-39years, free of baseline MetS in Taiwan, were followed for incident MetS from baseline (2014) until the end of 2020. All subjects received annual health examinations for assessment of MetS. Physical fitness was assessed by CRF (estimated maximal oxygen uptake, VO2 max [mL/kg/min], in a 3000-m run) and MEC (numbers of 2-min push-ups). MetS was defined according to the International Diabetes Federation (IDF) criteria. Multiple Cox regression analysis was conducted with adjustments for baseline age, sex, substance use status and physical activity to determine the associations of CRF and MEC with incidences of new-onset MetS and related features, for example, central obesity, hypertension, dyslipidaemia and prediabetes or diabetes. To examine the combined effects of CRF and MEC status on incidence of MetS, high and low levels of CRF and MEC were separately defined by over and under the sex-specific median in each exercise test. During a median follow-up of 5.8years, there were 673 (23.3%) new-onset MetS. Higher CRF was associated with a lower incidence of MetS (hazard ratio [HR] and 95% confidence interval: 0.905 [0.877-0.933]), and its components separately, except hypertension. No association was observed between MEC and incident MetS, and its components separately, except hypertension. When evaluating the combined effects of MEC and CRF status on the incidence of MetS, it was observed that compared with the low CRF/low MEC, the high CRF/high MEC (HR: 0.553 [0.439-0.697]) and the high CRF/low MEC (HR: 0.730 [0.580-0.918]) had a lower incidence of new-onset MetS (P value for the intergroup difference=0.04). There was no significant result for the low CRF/high MEC. This study highlights that although the protective effects of MEC to reduce the incidence of MetS and most of its related features were mainly driven by CRF in young adults, there was an addictive effect of greater MEC on CRF to prevent the development of new-onset MetS before midlife.

It's about the long game, not epic workouts: unpacking HIIT for endurance athletes.

High-intensity interval training (HIIT) prescriptions manipulate intensity, duration, and recovery variables in multiple combinations. Researchers often compare different HIIT variable combinations and treat HIIT prescription as a "maximization problem", seeking to identify the prescription(s) that induce the largest acute VO2/HR/RPE response. However, studies connecting the magnitude of specific acute HIIT response variables like work time>90% of VO2max and resulting cellular signalling and/or translation to protein upregulation and performance enhancement are lacking. This is also not how successful endurance athletes train. First, HIIT training cannot be seen in isolation. Successful endurance athletes perform most of their training volume below the first lactate turn point (<LT1), with "threshold training" and HIIT as integrated parts of a synergistic combination of training intensities and durations. Second, molecular signalling research reveals multiple, "overlapping" signalling pathways driving peripheral adaptations, with those pathways most sensitive to work intensity showing substantial feedback inhibition. This makes current training content and longer-term training history critical modulators of HIIT adaptive responses. Third, long term maximization of endurance capacity extends over years. Successful endurance athletes balance low-intensity and high-intensity, low systemic stress, and high systemic stress training sessions over time. The endurance training process is therefore an "optimization problem". Effective HIIT sessions generate both cellular signal and systemic stress that each individual athlete responds to and recovers from over weeks, months, and even years of training. It is not "epic" HIIT sessions but effective integration of intensity, duration, and frequency of all training stimuli over time that drives endurance performance success.