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Mechanistic influence of the torque cadence relationship on power output during exhaustive all-out field tests in professional cyclists
(Taylor & Francis, 2025-03-15) Leo, Peter; Martinez-Gonzalez, Borja; Mujika, Iñigo; Giorgi, Andrea
Understanding the torque-cadence-power relationship can be important in assessing a cyclist’s performance potential. This study explored these relationships in elite male cyclists (N = 17; age: 24.1 ± 3.8 years; body mass: 66.0 ± 4.8 kg, critical power (CP): 5.5 ± 0.3 W.kg−1) through sprint, torque, and CP tests conducted in fresh and after accumulated work. Testing protocols, performed during a pre-season training camp, included maximal efforts across varied gear ratios and durations (15 s, 3 min, and 12 min), under stable environmental conditions (15–20°C). Results revealed reduced power output, torque, and cadence after accumulated work compared to fresh conditions (p ≤ .001). Sprint-derived maximum torque (Tmax) was strongly correlated with torque intercepts for CP fresh (r = .558, p = .020) and after accumulated work (r = .556, p = .020). The cadence relationships demonstrated a large negative correlation between maximum cadence (Cmax) and optimum cadence (Copt) from the sprint test and the 15 s, 3 min and 12 min cadence recorded during CP after accumulated work (r = -0.541 to −0.634, p = 0.006 to 0.025). These findings highlight that accumulated work-induced reductions in work capacity (W’) and CP values were accompanied by lower cadences across all effort durations.
What Is “Zone 2 Training”?: Experts’ Viewpoint on Definition, Training Methods, and Expected Adaptations
(Human Kinetics, Inc., 2025-02-26) Sitko, Sebastian; Artetxe, Xabier; Bonnevie-Svendsen, Martin; Galán-Rioja, Miguel Ángel; Gallo, Gabriele; Grappe, Frédéric; Leo, Peter; Mateo, Manuel; Mujika, Iñigo; Sanders, Dajo; Seiler, Stephen; Zabala, Mikel; Valenzuela, Pedro L.; Viribay, Aitor
The role of high-volume low-intensity training for enhancing endurance performance has gained growing interest in recent years. Specifically, so-called “zone 2 training” is currently receiving much attention, and many propose that this is the target intensity at which a large proportion of total endurance training should be performed. However, despite the popularity of this concept, there is no clear consensus among coaches, athletes, and scientists regarding the definition of zone 2 training. Purpose: This commentary summarizes the perspectives, experience, and knowledge of an expert panel of 14 applied sport scientists and professional coaches with the aim of providing insight and a basis for definitional consensus on zone 2 training. Moreover, potential training strategies at this intensity are proposed, and the expected physiological adaptations when exercising at this intensity and related research gaps are also discussed. Results: Experts reached consensus that zone 2 training should preferably be performed at intensities located immediately below the first lactate or ventilatory threshold through continuous, variable, or interval-type sessions. Furthermore, experts expected a broad range of central and peripheral adaptations from zone 2 training. These expected adaptations might not be unique to zone 2 and could also be induced with sessions performed at slightly higher and lower intensities. Conclusions: This commentary provides practical insight and unified criteria regarding the preferred intensity, duration, and session type for the optimization of zone 2 training based on the perspectives of acknowledged sport scientists and professional coaches.
Current Periodization, Testing, and Monitoring Practices of Strength and Conditioning Coaches
(Human Kinetics, Inc., 2025) Washif, Jad Adrian; James, Carl; Pagaduan, Jeffrey; Lim, Julian; Lum, Danny; Raja Azidin, Raja Mohammed Firhad; Mujika, Iñigo; Beaven, Chistopher Martyn
This study investigated the periodization, testing, and monitoring practices of strength and conditioning practitioners across different levels of coaching experience and sports. Methods: An online survey was completed by 58 practitioners (25 sports/events) from 9 Southeast and East Asian countries. The survey focused on periodization models, programming frameworks, unloading strategies, fitness assessments, and pretraining readiness monitoring. Frequency analysis and chi-square tests were used to assess data distribution and differences. Results: Hybrid (multiple) periodization was favored over a single model for different training objectives (39%–45%), including very short-term training (≤4 wk). Emerging approaches, including flexible programming, were similarly adopted (43%). Program adjustment was primarily driven by athlete feedback (90%), self-observation (78%), and technical execution (74%). Major programming challenges identified were managing fatigue (72%), optimizing training stimuli (53%), specificity (50%), and adherence (47%). Deloading practices (95%) and tapering applications (91%) were common. Physical performance changes were primarily identified from testing (90%) but also athlete/coach feedback (76%), monitoring (71%), training data (67%), and performance data/statistics (62%). Strength assessments were conducted 2 to 4 times yearly (67%) using 1 to 4 exercises (76%). Pretraining readiness was monitored via conversations (71%), wellness tools (46%), and performance devices (31%). Practitioners also utilized monitoring technology, force plates (21%), and velocity-tracking devices (23%). Training load was commonly quantified using volume load (81%) and session RPE (72%). None of the comparisons differed across experience levels and sports types (P > .05). Conclusion: Practitioners adopted multiple periodization models, incorporating flexible approaches. Unloading strategies were commonly applied alongside various assessment methods. Technologies were used for monitoring, but conversational/subjective methods remained more widespread.
What It Takes to Win: Examining Predicted Versus Actual Swimming Performances at the Paris 2024 Olympic Games, and What Comes Next
(Human Kinetics, Inc., 2025-02-13) Powell, Cormac; Pyne, David B.; Crowley, Emmet; Mujika, Iñigo
Predictions of performances should be evaluated to confirm their accuracy. Work by this group has resulted in 3 sets of predictions being generated for swimming events at the Paris 2024 Olympic Games, using the same statistical approach for each set. Purpose: To examine the accuracy of swimming predictions for the Paris 2024 Olympic Games and generate updated predictions for both the Singapore 2025 World Aquatics Championships and Los Angeles 2028 Olympic Games. Methods: A linear regression and forecasting function was used to generate predictions for the Paris 2024 Olympic Games across 3 performance categories (rank 1st–3rd, 4th–8th, and 9th–16th). Mean absolute error was used to assess the accuracy of the predicted versus actual Paris 2024 Olympic Games times for all events across the 3 performance categories. New predictions for the 2028 Olympic cycle were subsequently generated using results from the World Championships and Olympic Games between 2011 and 2024. Results: Across all events, a mean absolute error value of 0.84% was observed between the Paris 2024 Olympic Games predicted and actual times. Predicted times were highly correlated with actual times (r2 = .99). Across the 3 sets of predictions (created in 2022, 2023, and 2024), the 2023 set of predictions had the lowest overall mean absolute error value (0.55%). Conclusions: The methods used to create predictions for swimming performances at the Paris 2024 Olympic Games were deemed accurate. These methods enable national swimming federations to create a series of predictions for a given major championship, inform athlete identification and development pathways, and allocate appropriate resources, including sport-science provision.
Hematological adaptations to altitude training in female water polo players: a case report of a world championships medal-winning team
(MDPI, 2025-01-31) Mujika, Iñigo; Mara, Jocelyn; Zelenkova, Irina; Rodrigo, Zacca; Pyne, David B.
Background: The effective monitoring of athletes’ adaptation is crucial to optimize the outcomes of altitude camps and minimize the risk of maladaptation to the hypoxic stress and intensive training. This case report assessed the hematological adaptations in 22 world-class female water polo players during a 16-day ‘live high-train high’ (LHTH) altitude camp (2320 m) and evaluated the differences between selected (n = 13) and non-selected (n = 9) players and between playing positions. Methods: Hematological parameters, including total hemoglobin mass (tHBmass) and blood volume, were measured before and after the camp. Resting heart rate, peripheral oxygen saturation, body mass, fatigue, and sleep were monitored daily. Results: Relative tHbmass increased PRE to POST (5.4 ± 5.1%, range −3.9–20.2), but blood volume did not change (p = 0.797). Erythrocyte count, hemoglobin concentration, hematocrit, and red cell distribution width increased PRE–POST (p < 0.001, ES = 1.21–2.69), while mean corpuscular volume and hemoglobin decreased (p < 0.001, ES = 0.51 and 0.72, respectively). No substantial differences were observed in the hematological parameters between selected and non-selected players. There was a large difference in the change in relative blood volume between centers (n = 4, PRE 74.1 ± 5.4, POST 69.7 ± 5.9 mL/kg; mean ± SD) and field players (n = 15, PRE 80.8 ± 10.6, POST 82.8 ± 6.8 mL/kg; adj p = 0.046, ES = 1.15) and between centers and goalkeepers (n = 3, PRE 89.7 ± 9.6, POST 82.0 ± 7.1 mL/kg; adj p = 0.046, ES = 1.62). Conclusions: A 16-day LHTH camp can induce favorable hematological adaptations in world-class women’s water polo players, without substantial differences between selected and non-selected players, and larger increases in field players.
Writing High-Quality Case Studies in Sport Science
(Human Kinetics, Inc., 2025-04-08) Mujika, Iñigo; Yamashita, Daichi; Solli, Guro Strøm
Sport-physiology and -performance research often relies on group designs that compare experimental and control groups and/or preintervention and postintervention results. This commentary highlights the key elements of a high-quality case study and provides clear guidelines for readers and authors of the International Journal of Sports Physiology and Performance. We propose 4 essential components. First, case studies should offer relevant and original insights by tackling novel issues and defining a clear purpose. Second, they must employ rigorous methodology, encompassing careful participant selection, comprehensive data collection from diverse sources (eg, interviews, surveys, physiological tests, training diaries, competition data), and deliberate data analysis that explicitly addresses factors influencing performance changes. Third, they should be well structured and engagingly presented to reach both academic and practical audiences. Finally, bridging the science–practice gap is vital, requiring and strengthening collaboration between researchers and practitioners to enable data-driven decision making and spark new hypotheses. Conclusions: Although case studies traditionally rank low in the research evidence hierarchy, high-quality examples can significantly bridge the gap between research and practice. By working closely with the sporting community and strategically sharing findings, case studies can enhance evidence-based training strategies and amplify the real-world impact of sport science.
PhD Programs in Sport Science: Impact Beyond Academia and Scientific Publishing
(Human Kinetics, Inc., 2025-06-03) Mujika, Iñigo; Abbiss, Chris R.
The PhD is an important academic qualification that not only supports innovative and impactful research but also provides structure and standards for the development of researchers. Given that fewer than 50% of PhD graduates are likely to be employed in an academic institution, the focus of the degree is not solely on the development of university-employed academics or researchers. Indeed, PhD programs develop an individual’s research skills and advance learning and/or professional practice that can be applied across a range of sectors. Sport-science PhD graduates, for instance, often work in Olympic or professional sport, private practice, health, government agencies, or other industries. Industry-focused PhD programs will typically occur through cosupervision and codesign of the research among university and nonuniversity organizations. A tension in the management of such programs can be the complex balance between rapidly addressing important industry-relevant research questions or needs and the slower long-term process of developing the researcher. While these objectives can be achieved simultaneously, embedding transferable skills, industry-relevant learning, and end-user engagement into academic curricula within the PhD has its challenges.
Leveraging shared variation among traits for the discovery of genetic variants in complex phenotypes such as obesity
(Wiley; The Obesity Society, 2025-06-01) Fernández-Verdejo, Rodrigo; Hughes, David; Ravussin, Eric
Identifying genetic variants associated with obesity is critical forunderstanding the role of genetics and its interaction with the envi-ronment in the regulation of body weight. Hundreds of genetic vari-ants have been identified so far, mostly associated with body massindex (BMI). Nevertheless, given the complex pathogenesis andthe evolving definition and diagnosis of obesity, exploring traitsbeyond BMI becomes crucial to advancing the field. Obesityresults from a prolonged positive energy balance, during which energyintake exceeds energy expenditure. Therefore, identifying geneticvariants associated with energy balance-related traits should provideadditional insight into the genetic basis of obesity.
Baseline body fat percentage is associated to weight and fat mass gain from high-fat overfeeding over 8 weeks
(Oxford University Press; Endocrine Society, 2025-04-21) Galgani, Jose E.; Fernández-Verdejo, Rodrigo; Bray, George A.; Smith, Steven R.; Ghosh, Sujoy; Javvadi, Pravalika; Ravussin, Eric
Background & aims: Epidemiological data suggest that participants with lower vs. higher body mass index (BMI) resist exposure to the obesogenic environment. To test this, we analyzed the relationship between overfeeding-induced weight and fat mass gains with baseline BMI and body fat percentage. Methods: In this controlled intervention study, 34 men (age: 26±5 y old; BMI: 25.5±2.4 kg/m2, body fat [DXA]: 19.3±5.1%) consumed for 8 weeks 40% more energy than needed at weight maintenance. The energy costs of weight and fat mass gain were calculated as the 8-week excess energy consumed divided by weight or fat mass gain. Energy expenditure (baseline and after overfeeding) was determined using a metabolic chamber and doubly labeled water. Transcriptomic analysis was conducted from abdominal subcutaneous adipose tissue samples. Results: Body weight increased 7.2±2.1 kg and fat mass 4.0±1.4 kg. There was no statistical association between baseline BMI and weight and fat mass gains. However, baseline body fat percentage was significantly associated with weight (r=0.57) and fat mass (r=0.59) gains. Body fat percentage was also statistically associated with energy cost of weight (r=-0.38) and fat mass (r=-0.40) gains. Metabolic adaptation in energy expenditure (adaptive thermogenesis) was unrelated to the energy cost of weight and fat mass gains. Transcriptomics analysis showed that high energy cost of weight gain was associated with up-regulation of inflammation-related pathways. Conclusion: Body fat percentage at baseline was inversely associated with overfeeding-induced weight and fat gain resistance. The underlying compensatory response appears unrelated to changes in energy expenditure.
Estimation of ventilatory thresholds during exercise using respiratory wearable sensors
(Springer Nature, 2024) Contreras-Briceño, Felipe; Cancino, Jorge; Espinoza-Ramírez, Maximiliano; Fernández, Gonzalo; Johnson, Vader; Hurtado, Daniel
Ventilatory thresholds (VTs) are key physiological parameters used to evaluate physical performance and determine aerobic and anaerobic transitions during exercise. Current assessment of these parameters requires ergospirometry, limiting evaluation to laboratory or clinical settings. In this work, we introduce a wearable respiratory system that continuously tracks breathing during exercise and estimates VTs during ramp tests. We validate the respiratory rate and VTs predictions in 17 healthy adults using ergospirometry analysis. In addition, we use the wearable system to evaluate VTs in 107 recreational athletes during ramp tests outside the laboratory and show that the mean population values agree with physiological variables traditionally used to exercise prescription. We envision that respiratory wearables can be useful in determining aerobic and anaerobic parameters with promising applications in health telemonitoring and human performance.
Study protocol and rationale of "the UP project": evaluating the effectiveness of active breaks on health indicators in desk-based workers
(Frontiers Media S.A., 2024) Cristi-Montero, Carlos; Martínez-Flores, Ricardo; Espinoza-Puelles, Juan Pablo; Favero-Ramirez, Laura; Zurita-Corvalan, Natalia; Castillo Cañete, Ignacio; Leppe, Jaime; Ferrari, Gerson; Sadarangani, Kabir P.; Cancino, Jorge; Hernandez-Jaña, Sam; Yuing Farias, Tuillang; Batista Lemes, Vanilson; Rodríguez-Rodríguez, Fernando; Brand, Caroline
Background: Excessive sedentary time has been negatively associated with several health outcomes, and physical activity alone does not seem to fully counteract these consequences. This panorama emphasizes the essential of sedentary time interruption programs. “The Up Project” seeks to assess the effectiveness of two interventions, one incorporating active breaks led by a professional and the other utilizing a computer application (self-led), of both equivalent duration and intensity. These interventions will be compared with a control group to evaluate their impact on physical activity levels, sedentary time, stress perception, occupational pain, and cardiometabolic risk factors among office workers. Methods: This quasi-experimental study includes 60 desk-based workers from universities and educational institutes in Valparaiso, Chile, assigned to three groups: (a) booster breaks led by professionals, (b) computer prompts that are unled, and (c) a control group. The intervention protocol for both experimental groups will last 12 weeks (only weekdays). The following measurements will be performed at baseline and post-intervention: cardiometabolic risk based on body composition (fat mass, fat-free mass, and bone mass evaluated by DXA), waist circumference, blood pressure, resting heart rate, and handgrip strength. Physical activity and sedentary time will be self-reported and device-based assessed using accelerometry. Questionnaires will be used to determine the perception of stress and occupational pain. Discussion: Governments worldwide are addressing health issues associated with sedentary behavior, particularly concerning individuals highly exposed to it, such as desk-based workers. Despite implementing certain strategies, there remains a noticeable gap in comprehensive research comparing diverse protocols. For instance, studies that contrast the outcomes of interventions led by professionals with those prompted by computers are scarce. This ongoing project is expected to contribute to evidence-based interventions targeting reduced perceived stress levels and enhancing desk-based employees’ mental and physical well-being. The implications of these findings could have the capacity to lay the groundwork for future public health initiatives and government-funded programs.
Early exercise through telerehabilitation after bariatric surgery: is it feasible?
(Springer, 2024) Pino Zúñiga, Johanna; Olivares, Mariela; Muñoz, Giselle; Boza, Camilo; Duque, Camilo; Cancino, Jorge
Purpose: The feasibility of early telerehabilitation after bariatric surgery is unknown. The objective of this study was to assess the feasibility and perception of engaging in the online exercise protocol in patients during the first month after bariatric surgery. Material and methods: A total of 67 patients, enrolled in a telerehabilitation program following bariatric surgery, completed a survey assessing their perception of the intensity, discomfort, and safety during exercise sessions. Results: Forty percent of participants began exercising between 5 and 10 days after surgery. Seventy-one percent of patients did not experience discomfort during the first month of exercise, and those who reported discomfort mainly mentioned dizziness and abdominal pain. No significant differences were found in the presence of discomfort among different types of surgeries performed. There was a significant difference in the presence of discomfort between patients who started exercising before and after 15 days of surgery, with less discomfort reported in the group that started after 15 days. Ninety-eight percent of patients felt safe during online exercise sessions. Most participants perceived the intensity of the sessions as moderate. The most frequently mentioned benefits of exercise were increased energy, mood, and feeling more active. Conclusion: Telerehabilitation conducted during the first month after bariatric surgery was feasible and well tolerated by patients, providing a safe alternative for those patients who face difficulties with in-person interventions.
The effects of maca (lepidium meyenii walp) on cellular oxidative stress: a systematic review and meta-analysis
(MDPI, 2024-08-28) Huerta Ojeda, Álvaro; Rodríguez Rojas, Javiera; Cuevas Guíñez, Jorge; Ciriza Velásquez, Stephanie; Cancino, Jorge; Barahona Fuentes, Guillermo; Yeomans Cabrera, María Mercedes; Pavez, Leonardo; Jorquera Aguilera, Carlos
Lepidium meyenii Walp (LmW) or Maca, including its bioactive components such as macamides, among others, has demonstrated antioxidant effects. However, the effect size (ES) of LmW on oxidative stress has not been qualitatively described and calculated. The primary objective of this systematic review and meta-analysis was to review and qualitatively describe the studies published up to 2023 that supplemented LmW to control cellular oxidative stress; the secondary objective was to calculate the ES of the different interventions. The search was designed following the PRISMA® guidelines for systematic reviews and meta-analyses and performed in the Web of Science, Scopus, SPORTDiscus, PubMed, and MEDLINE until 2023. The selection of studies included randomized controlled trials, with tests and post-tests, both in vitro and in vivo in animals and humans. The methodological quality and risk of bias were evaluated with the CAMARADES tool. The main variables were reduced glutathione, glutathione peroxidase, superoxide dismutase, and malondialdehyde. The analysis was conducted with a pooled standardized mean difference (SMD) through Hedges’ g test (95% CI). Eleven studies were included in the systematic review and eight in the meta-analysis. They revealed a small effect for reduced glutathione (SMD = 0.89), a large effect for glutathione peroxidase (SMD = 0.96), a moderate effect for superoxide dismutase (SMD = 0.68), and a moderate effect for malondialdehyde (SMD = −0.53). According to the results, the phytochemical compounds of LmW effectively controlled cellular oxidative stress, mainly macamides. It was also determined that a higher dose of LmW generated a greater antioxidant effect. However, information concerning humans is scarce.
Creatine supplementation prior to strength exercise training is not superior in preventing muscle mass loss compared with standard nutritional recommendations in females after bariatric surgery: a pilot study
(Springer Nature, 2024) Díaz Pizarro, Marcelo; Pino Zúñiga, Johanna; Olivares Gálvez , Mariela; Rendón Vesga , Carolina; Luengas Tello, Rafael; Duque Seguro, Juan Camilo; Cancino, Jorge
Background: This study examines whether creatine supplementation combined with strength training mitigates muscle mass loss in women during early rehabilitation post-bariatric surgery, as its effectiveness remains untested in this context. Methods: Fifteen women (37.8 ± 9.6 years; BMI, 38.8 ± 5.6 kg/m2) completed the intervention (creatine group = 7; placebo group = 8). Both groups followed a strength training program three times a week for 8 weeks. The dosage for both the creatine and placebo was 8 g prior to each exercise session. Body weight, skeletal muscle mass, fat mass, handgrip strength, and physical activity levels were measured before and after the intervention. Results: The creatine group showed a reduction of 9.5 ± 1.5 kg in body weight, with a 0.72 ± 0.6 kg decrease in muscle mass and an 8.64 ± 1.2 kg reduction in fat mass. The placebo group had a reduction of 9.6 ± 3.5 kg in body weight, with a 0.6 ± 1.2 kg decrease in muscle mass and an 8.88 ± 3.2 kg reduction in fat mass, without significant differences between groups (p > 0.05). Conclusion: The pre-session strength exercise training creatine supplementation is not superior to placebo regarding body weight and fat mass losses and the attenuation of muscle mass loss during the first weeks of rehabilitation following bariatric surgery.
A single bout of resistance exercise triggers mitophagy, potentially involving the ejection of mitochondria in human skeletal muscle
(Wiley, 2024-09-24) Díaz-Castro, Francisco; Tuñón-Suárez, Mauro; Rivera, Patricia; Botella, Javier; Cancino, Jorge; Figueroa, Ana María; Gutiérrez, Juan; Cantin, Claudette; Deldicque, Louise; Zbinden-Foncea, Hermann; Nielsen, Joachim; Henríquez-Olguín, Carlos; Morselli, Eugenia; Castro-Sepulveda, Mauricio
Aim The present study aimed to investigate the effects of a single bout of resistance exercise on mitophagy in human skeletal muscle (SkM). Methods Eight healthy men were recruited to complete an acute bout of one-leg resistance exercise. SkM biopsies were obtained one hour after exercise in the resting leg (Rest-leg) and the contracting leg (Ex-leg). Mitophagy was assessed using protein-related abundance, transmission electron microscopy (TEM), and fluorescence microscopy. Results Our results show that acute resistance exercise increased pro-fission protein phosphorylation (DRP1Ser616) and decreased mitophagy markers such as PARKIN and BNIP3L/NIX protein abundance in the Ex-leg. Additionally, mitochondrial complex IV decreased in the Ex-leg when compared to the Rest-leg. In the Ex-leg, TEM and immunofluorescence images showed mitochondrial cristae abnormalities, a mitochondrial fission phenotype, and increased mitophagosome-like structures in both subsarcolemmal and intermyofibrillar mitochondria. We also observed increased mitophagosome-like structures on the subsarcolemmal cleft and mitochondria in the extracellular space of SkM in the Ex-leg. We stimulated human primary myotubes with CCCP, which mimics mitophagy induction in the Ex-leg, and found that BNIP3L/NIX protein abundance decreased independently of lysosomal degradation. Finally, in another human cohort, we found a negative association between BNIP3L/NIX protein abundance with both mitophagosome-like structures and mitochondrial cristae density in the SkM. Conclusion The findings suggest that a single bout of resistance exercise can initiate mitophagy, potentially involving mitochondrial ejection, in human skeletal muscle. BNIP3L/NIX is proposed as a sensitive marker for assessing mitophagy flux in SkM.
BMAL1 and CLOCK proteins exhibit differential association with mitochondrial dynamics, protein synthesis pathways and muscle strength in human muscle
(The Physiological Society, 2024-06-26) Figueroa-Toledo, A. M.; Gutiérrez-Pino, J.; Carriel-Nesvara, A.; Marchese-Bittencourt, M.; Zbinden-Foncea, Hermann; Castro-Sepulveda, Mauricio
Murine models lacking CLOCK/BMAL1 proteins in skeletal muscle (SkM) present muscle deterioration and mitochondria abnormalities. It is unclear whether humans with lower levels of these proteins in the SkM have similar alterations. Here we evaluated the association between BMAL1 and CLOCK protein mass with mitochondrial dynamics parameters and molecular and functional SkM quality markers in males. SkM biopsies were taken from the vastus lateralis of 16 male (non-athletes, non-obese and non-diabetic) subjects (8–9 a.m.). The morphology of mitochondria and their interaction with the sarcoplasmic reticulum (mitochondria-SR) were determined using transmission electron microscopy images. Additionally, protein abundance of the OXPHOS complex, mitochondria fusion/fission regulators, mitophagy and signalling proteins related to muscle protein synthesis were measured. To evaluate the quality of SkM, the cross-sectional area and maximal SkM strength were also measured. The results showed that BMAL1 protein mass was positively associated with mitochondria-SR distance, mitochondria size, mitochondria cristae density and mTOR protein mass. On the other hand, CLOCK protein mass was negatively associated with mitochondria-SR interaction, but positively associated with mitochondria complex III, OPA1 and DRP1 protein mass. Furthermore, CLOCK protein mass was positively associated with the protein synthesis signalling pathway (total mTOR, AKT and P70S6K protein mass) and SkM strength. These findings suggest that the BMAL1 and CLOCK proteins play different roles in regulating mitochondrial dynamics and SkM function in males, and that modulation of these proteins could be a potential therapeutic target for treating muscle diseases.
Detraining’s effects on cardiorespiratory fitness and maximal and explosive strength in army soldiers: does age matter?
(MDPI, 2024-07-01) Arce-Álvarez, Alexis; Zaio, Ángelo; Salazar-Ardiles, Camila; Álvarez, Cristian; Merino-Muñoz, Pablo; Vasquez-Muñoz, Manuel; Izquierdo, Mikel; Castro-Sepulveda, Mauricio; Andrade, David C.
Purpose: This study investigated the impact of four weeks of age-dependent detraining on army soldiers’ cardiorespiratory fitness and maximal and explosive strength. Methods: Fourteen volunteer tactical athletes participated, divided into two age groups (20 to 29 and 30 to 40 years). Before and after the detraining period, we assessed their anthropometric measurements (weight, height, body mass index, fat mass, and fat-free mass), cardiorespiratory fitness (maximal oxygen uptake [VO2max] and ventilatory thresholds [VT1 and VT2]), and kinematic properties during a single-leg counter-moving jump (CMJ) test for both the dominant and non-dominant legs. Two-way ANOVA followed by the Holm–Sidak post hoc test was used. Results: The anthropometric and cardiovascular variables did not show significant differences between the groups. However, both groups exhibited a significantly reduced maximum time and speed at the VO2max. Furthermore, the flight time and maximum height during the CMJ significantly decreased in the non-dominant leg for both age groups. Notably, the dominant leg’s concentric impulse (CI) significantly reduced during the CMJ, but this effect was observed only in the 30–40 age group. There were significant differences between the two age groups. Conclusions: Our findings suggest that four weeks of detraining negatively impacts aerobic fitness and muscular strength, independently of age. However, the dominant leg may be more susceptible to detraining effects in army soldiers aged 30–40. Furthermore, as a perspective, our results strongly suggest that a detraining period could affect successful missions (aerobic performance deterioration), as well as promote a muscle imbalance between the legs, which could encourage muscle injuries and endanger combat missions.
Effects of an antioxidants cocktail on glucose metabolism at rest, during exercise, and during a glucose load in healthy young subjects
(Sociedad Chilena de Nutrición, Bromatología y Toxicología, 2023-12-15) Rodríguez, Ivan; Paez Espinosa, Enma Verónica; Zbinden-Foncea, Hermann; Echeverria, Francisca; Castro-Sepulveda, Mauricio
Background: Reactive oxygen species (ROS) regulate glucose metabolism (GM) in skeletal muscle by improving the translocation of GLUT4. Antioxidant supplementation could block this physiological effect, altering glucose signaling during exercise. However, there is limited evidence in humans on whether antioxidant intake affects GM. Therefore, we aimed to determine the effect of an antioxidant cocktail (AOC) on GM at rest and during metabolic challenges. Methods: Ten healthy male subjects received AOC supplementation (1000 mg of Vitamin C, 600 IU of Vitamin E, and 600 mg of α-lipoic acid) or placebo (2.000 mg of talc) before two trials conducted 7 days apart. Trial 1: AOC 120 and 90 minutes before an endurance exercise (EEX) bout at 60 % of maximal oxygen uptake (VO2max); Trial 2: AOC 120 and 90 minutes before an oral glucose tolerance test (OGTT; 75 g glucose). Measurements of gas exchange and capillary blood samples were collected every 15 minutes during both trials. Results: AOC supplementation increased resting glucose levels (p<0.05). During Trial 1 (EEX), the AOC increased carbohydrate oxidation (CHOox) (p= 0.03), without effect in glucose blood levels. During Trial 2 (OGTT), the AOC supplementation had no significant effect on GM parameters. Conclusion: Acute supplementation with AOC increased resting glucose levels and CHOox during EEX in healthy subjects, with no effect on GM during the OGTT.
Regulation of mitochondrial morphology and cristae architecture by the TLR4 pathway in human skeletal muscle
(Frontiers Media S.A., 2023-06-25) Castro-Sepulveda, Mauricio; Tuñón-Suárez, Mauro; Rosales-Soto, Giovanni; Vargas-Foitzick, Ronald; Deldicque, Louise; Zbinden-Foncea, Hermann
In skeletal muscle (SkM), a reduced mitochondrial elongate phenotype is associated with several metabolic disorders like type 2 diabetes mellitus (T2DM). However, the mechanisms contributing to this reduction in mitochondrial elongate phenotype in SkM have not been fully elucidated. It has recently been shown in a SkM cell line that toll-like receptor 4 (TLR4) contributes to the regulation of mitochondrial morphology. However, this has not been investigated in human SkM. Here we found that in human SkM biopsies, TLR4 protein correlated negatively with Opa1 (pro-mitochondrial fusion protein). Moreover, the incubation of human myotubes with LPS reduced mitochondrial size and elongation and induced abnormal mitochondrial cristae, which was prevented with the co-incubation of LPS with TAK242. Finally, T2DM myotubes were found to have reduced mitochondrial elongation and mitochondrial cristae density. Mitochondrial morphology, membrane structure, and insulin-stimulated glucose uptake were restored to healthy levels in T2DM myotubes treated with TAK242. In conclusion, mitochondrial morphology and mitochondrial cristae seem to be regulated by the TLR4 pathway in human SkM. Those mitochondrial alterations might potentially contribute to insulin resistance in the SkM of patients with T2DM.
Mitochondria-SR interaction and mitochondrial fusion/fission in the regulation of skeletal muscle metabolism
(Elsevier, 2023-07-01) Castro-Sepulveda, Mauricio; Fernández-Verdejo, Rodrigo; Zbinden-Foncea, Hermann; Rieusset, Jennifer
Mitochondria-endoplasmic/sarcoplasmic reticulum (ER/SR) interaction and mitochondrial fusion/fission are critical processes that influence substrate oxidation. This narrative review summarizes the evidence on the effects of substrate availability on mitochondrial-SR interaction and mitochondria fusion/fission dynamics to modulate substrate oxidation in human skeletal muscle. Evidence shows that an increase in mitochondria-SR interaction and mitochondrial fusion are associated with elevated fatty acid oxidation. In contrast, a decrease in mitochondria-SR interaction and an increase in mitochondrial fission are associated with an elevated glycolytic activity. Based on the evidence reviewed, we postulate two hypotheses for the link between mitochondrial dynamics and insulin resistance in human skeletal muscle. First, glucose and fatty acid availability modifies mitochondria-SR interaction and mitochondrial fusion/fission to help the cell to adapt substrate oxidation appropriately. Individuals with an impaired response to these substrate challenges will accumulate lipid species and develop insulin resistance in skeletal muscle. Second, a chronically elevated substrate availability (e.g. overfeeding) increases mitochondrial production of reactive oxygen species and induced mitochondrial fission. This decreases fatty acid oxidation, thus leading to the accumulation of lipid species and insulin resistance in skeletal muscle. Altogether, we propose mitochondrial dynamics as a potential target for disturbances associated with low fatty acid oxidation.

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