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Cannabidiol (CBD) is widely used in sports for recovery, pain management, and sleep improvement, yet its effects on muscle are not well understood. This study aimed to determine the transcriptional response of murine skeletal muscle myotubes to broad‐spectrum CBD and synthetic CBD (sCBD). Differentiated C2C12 myotubes were treated with 10 μM CBD, sCBD, or vehicle control (DMSO) for 24 h before RNA extraction. Poly‐A tail‐enriched mRNA libraries were constructed and sequenced using 2 × 50 bp paired‐end sequencing. CBD and sCBD treatment induced 4489 and 1979 differentially expressed genes (DEGs; p < 0.001, FDR step‐up <0.05), respectively, with common upregulation of 857 genes and common downregulation of 648 genes. Common upregulated DEGs were associated with "response to unfolded protein," "cell redox homeostasis," "endoplasmic reticulum stress," "oxidative stress," and "cellular response to hypoxia." Common downregulated DEGs were linked to "sarcomere organization," "skeletal muscle tissue development," "regulation of muscle contraction," and "muscle contraction." CBD treatment induced unique DEGs compared to sCBD. The data indicate CBD may induce mild cellular stress, activating pathways associated with altered redox balance, unfolded protein response, and endoplasmic reticulum stress. We hypothesize that CBD interacts with muscle and may elicit a "mitohormetic" effect that warrants further investigation. [ABSTRACT FROM AUTHOR]

Microcycles are fundamental structures for training prescription and load management, helping to optimise training effects and performance. This study quantified external and internal loads of Italian Serie A youth soccer players across competitive weeks and their periodisation within microcycles. Data were collected from 90 players belonging to four age groups (under-19, -17, -16, -15) across a season. Methods of monitoring external [duration and global navigation satellite systems (GNSS)] and internal load [heart rate (HR) and rating of perceived exertion (RPE)] were employed. Linear mixed models determined differences in training loads across age groups, training days and player positions. Under-19 and under-17 players trained five times per week, while younger players trained four times. Late-stage academy players (under-19 and -17) demonstrated higher weekly accumulated external and sRPE training load compared to their younger counterparts (p < 0.05 between groups). Weekly accumulated HR internal loads were higher in under-15 players (p < 0.05 between groups). Marked fluctuations of daily load were observed across microcycles in under-19 and under-17 groups (p < 0.05 between days). These findings highlight progressive increases in training load throughout the development pathway, with late-stage academy players training with higher frequency, volume and marked periodisation compared to younger players. [ABSTRACT FROM AUTHOR]

The field of exercise physiology has undergone significant technological advancements since the pioneering works of exercise physiologists in the early to mid‐20th century. Historically, the ability to detect metabolites in biofluids from exercising participants was limited to single‐metabolite analyses. However, the rise of metabolomics, a discipline focused on the comprehensive analysis of metabolites within a biological system, has facilitated a more intricate understanding of metabolic pathways and networks in exercise. This review explores some of the pivotal technological and bioinformatic advancements that have propelled metabolomics to the forefront of exercise physiology research. Metabolomics offers a unique 'fingerprint' of cellular activity, offering a broader spectrum than traditional single‐metabolite assays. Techniques, including mass spectrometry and nuclear magnetic resonance spectroscopy, have significantly improved the speed and sensitivity of metabolite analysis. Nonetheless, challenges persist, including study design and data interpretation issues. This review aims to serve as a guide for exercise physiologists to facilitate better research design, data analysis and interpretation within metabolomics. The potential of metabolomics in bridging the gap between genotype and phenotype is emphasised, underscoring the critical importance of careful study design and the selection of appropriate metabolomics techniques. Furthermore, the paper highlights the need to deeply understand the broader scientific context to discern meaningful metabolic changes. The emerging field of fluxomics, which seeks to quantify metabolic reaction rates, is also introduced as a promising avenue for future research. What is the topic of this review?The integration of metabolomics in exercise physiology.What advances does it highlight?Technolgical advances in the study of metabolites, with particular relevance to exercise. [ABSTRACT FROM AUTHOR]

Cannabidiol (CBD) is a non‐intoxicating phytocannabinoid which has been proposed to possess anti‐inflammatory and analgesic properties. Given the potential for perceptions of pain to limit exercise performance, the aim of the present study was to investigate if 3 weeks of daily CBD supplementation (150 mg day−1) improved performance in a 10‐min performance‐trial on a cycle ergometer. In a randomized, double‐blind and placebo‐controlled study, 22 healthy participants (n = 11 male and n = 11 female) completed two 10‐min performance trials on a WattBike cycle ergometer interspersed with a 3‐week supplementation period. Supplementation involved either 150 mg day−1 oral CBD or 150 mg day−1 of a visually identical placebo (PLA). During trials, ratings of perceived exertion (RPE [6–20]), heart rate (HR) and blood lactate (BLa) were collected every 2 min. Mean power (W) was also taken throughout the exercise at each time point. All data were analyzed using two‐way ANOVAs. There were no significant differences (P > 0.05) between CBD or PLA groups for mean power (W) during the 10‐min performance trial. There were also no significant differences (P > 0.05) in any of the physiological or perceptual parameters (HR, BLa and RPE) between conditions. Three weeks supplementation of a broad‐spectrum CBD supplement did not improve performance via any change in RPE during a 10‐min time trial on a cycle ergometer, and as such, this evidence does not support the claim that broad‐spectrum CBD supplements could be performance‐enhancing in this exercise modality. Highlights: 3 weeks supplementation of 150 mg/day broad‐spectrum cannabidiol (CBD) does not influence perceived exertion during a 10‐min aerobic performance trial.3 weeks supplementation of 150 mg/day broad CBD does not improve physical performance in a 10‐min aerobic performance trialAthletes should continue abstinence of "Off‐the‐shelf" CBD supplements to avoid anti‐doping rule violations from The World Anti‐Doping Agency. [ABSTRACT FROM AUTHOR]

Inducing a heat-acclimated phenotype via repeated heat stress improves exercise capacity and reduces athletes̓ risk of hyperthermia and heat illness. Given the increased number of international sporting events hosted in countries with warmer climates, heat acclimation strategies are increasingly popular among endurance athletes to optimize performance in hot environments. At the tissue level, completing endurance exercise under heat stress may augment endurance training adaptation, including mitochondrial and cardiovascular remodeling due to increased perturbations to cellular homeostasis as a consequence of metabolic and cardiovascular load, and this may improve endurance training adaptation and subsequent performance. This review provides an up-to-date overview of the metabolic impact of heat stress during endurance exercise, including proposed underlying mechanisms of altered substrate utilization. Against this metabolic backdrop, the current literature highlighting the role of heat stress in augmenting training adaptation and subsequent endurance performance will be presented with practical implications and opportunities for future research. [ABSTRACT FROM AUTHOR]

Flow cytometry is routinely used in the assessment of skeletal muscle progenitor cell (myoblast) populations. However, a full gating strategy, inclusive of difficult to interpret forward and side scatter data, which documents cytometric analysis of differentiated myoblasts (myotubes) has not been reported. Beyond changes in size and shape, there are substantial metabolic and protein changes in myotubes allowing for their potential identification within heterogenous cell suspensions. To establish the utility of flow cytometry for determination of myoblasts and myotubes, C2C12 murine cell populations were assessed for cell morphology and metabolic reprogramming. Laser scatter, both forward (FSC; size) and side (SSC; granularity), measured cell morphology, while mitochondrial mass, reactive oxygen species (ROS) generation and DNA content were quantified using the fluorescent probes, MitoTracker green, CM‐H2DCFDA and Vybrant DyeCycle, respectively. Immunophenotyping for myosin heavy chain (MyHC) was utilized to confirm myotube differentiation. Cellular viability was determined using Annexin V/propidium iodide dual labelling. Fluorescent microscopy was employed to visualize fluorescence and morphology. Myotube and myoblast populations were resolvable through non‐intuitive interpretation of laser scatter‐based morphology assessment and mitochondrial mass and activity assessment. Myotubes appeared to have similar sizes to the myoblasts based on laser scatter but exhibited greater mitochondrial mass (159%, p < 0.0001), ROS production (303%, p < 0.0001), DNA content (18%, p < 0.001) and expression of MyHC (147%, p < 0.001) compared to myoblasts. Myotube sub‐populations contained a larger viable cluster of cells which were unable to be fractionated from myoblast populations and a smaller population cluster which likely contains apoptotic bodies. Imaging of differentiated myoblasts that had transited through the flow cytometer revealed the presence of intact, 'rolled‐up' myotubes, which would alter laser scatter properties and potential transit through the laser beam. Our results indicate that myotubes can be analyzed successfully using flow cytometry. Increased mitochondrial mass, ROS and DNA content are key features that correlate with MyHC expression but due to myotubes 'rolling up' during flow cytometric analysis, laser scatter determination of size is not positively correlated; a phenomenon observed with some size determination particles and related to surface properties of said particles. We also note a greater heterogeneity of myotubes compared to myoblasts as evidenced by the 2 distinct sub‐populations. We suggest that acoustic focussing may prove effective in identifying myotube sub populations compared to traditional hydrodynamic focussing. [ABSTRACT FROM AUTHOR]

Purpose: Carbohydrate (CHO) intake periodization via the sleep low train low (SL‐TL) diet–exercise model increases fat oxidation during exercise and may enhance endurance‐training adaptation and performance. Conversely, training under environmental heat stress increases CHO oxidation, but the potential of combined SL‐TL and heat stress to enhance metabolic and performance outcomes is unknown. Methods: Twenty‐three endurance‐trained males were randomly assigned to either control (n = 7, CON), SL‐TL (n = 8, SLTemp) or SL‐TL + heat stress (n = 8, SLHeat) groups and prescribed identical 2‐week cycling training interventions. CON and SLTemp completed all sessions at 20°C, but SLHeat at 35°C. All groups consumed matched CHO intake (6 g·kg−1·day−1) but timed differently to promote low CHO availability overnight and during morning exercise in both SL groups. Submaximal substrate utilization was assessed (at 20°C), and 30‐min performance tests (at 20 and 35°C) were performed Pre‐, Post‐, and 1‐week post‐intervention (Post+1). Results: SLTemp improved fat oxidation rates at 60% MAP (~66% VO2peak) at Post+1 compared with CON (p < 0.01). Compared with SLTemp, fat oxidation rates were significantly lower in SLHeat at Post (p = 0.02) and Post+1 (p < 0.05). Compared with CON, performance was improved at Post in SLTemp in temperate conditions. Performance was not different between any groups or time points in hot conditions. Conclusion: SL‐TL enhanced metabolic adaptation and performance compared with CON and combined SL‐TL and heat stress. Additional environmental heat stress may impair positive adaptations associated with SL‐TL. [ABSTRACT FROM AUTHOR]

Exercise-induced muscle damage (EIMD) is characterized by symptoms that present both immediately and for up to 14 days after the initial exercise bout. The main consequence of EIMD for the athlete is the loss of skeletal muscle function and soreness. As such, numerous nutrients and functional foods have been examined for their potential to ameliorate the effects of EIMD and accelerate recovery, which is the purpose of many nutritional strategies for the athlete. However, the trade-off between recovery and adaptation is rarely considered. For example, many nutritional interventions described in this review target oxidative stress and inflammation, both thought to contribute to EIMD but are also crucial for the recovery and adaptation process. This calls into question whether long term administration of supplements and functional foods used to target EIMD is indeed best practice. This rapidly growing area of sports nutrition will benefit from careful consideration of the potential hormetic effect of long term use of nutritional aids that ameliorate muscle damage. This review provides a concise overview of what EIMD is, its causes and consequences and critically evaluates potential nutritional strategies to ameliorate EIMD. We present a pragmatic practical summary that can be adopted by practitioners and direct future research, with the purpose of pushing the field to better consider the fine balance between recovery and adaptation and the potential that nutritional interventions have in modulating this balance. [ABSTRACT FROM AUTHOR]