Elite Cyclists with Type 1 Diabetes Show Acceptable Glycemic Excursions During a Time-Trial Performance Under High-Definition Transcranial Direct Current Stimulation.

OBJECTIVE: To evaluate the effects of bilateral dorsolateral prefrontal cortex high-definition transcranial direct current stimulation (HD-tDCS) on glycemic excursions during a time-trial performance in elite cyclists with type 1 diabetes (T1D). METHODS: In a double-blind, randomized crossover order, 9 elite cyclists with T1D (no complications) underwent either HD-tDCS (F3 and F4) or control (SHAM) and completed a constant-load trial at 75% of the second ventilatory threshold plus a 15-km cycling time trial. RESULTS: Real-time continuous glucose monitoring revealed similar glycemic variability between the 2 conditions, showing a significant effect of time but no interaction (stimulation × time) or stimulation effect. CONCLUSION: Because glycemic control is crucial for both health and performance, these findings suggest that HD-tDCS could be safely used to enhance performance in athletes with T1D and potentially in a broader active T1D population.

Heart Rate Variability in Professional and Semiprofessional Soccer: A Scoping Review.

In modern soccer, fitness and fatigue monitoring tools tend to be focused on noninvasive, time-efficient and player-friendly measures. Heart rate variability (HRV) has been suggested as an effective method for monitoring training response and readiness to perform. However, there is still a lack of consensus on HRV monitoring when it comes to soccer. Thus, this scoping review aims to map existing evidence on HRV in professional and semiprofessional soccer settings, and to identify knowledge gaps to inform future research directions. A search of databases (PubMed, Scopus, Web of Science, Google Scholar) according to the PRISMA-ScR statement was employed. Studies were screened for eligibility on inclusion criteria: (1) HRV was among the topics discussed in the article; (2) adult professional or semiprofessional soccer players were involved in the study; (3) both male and female participants; (4) no geographical area exclusion; (5) articles published in English; and (6) article full text available. The search of the selected databases revealed 8456 records. The titles and abstracts of all articles were retrieved for screening of eligibility, leaving 30 articles for further consideration. Following screening against set criteria, a total of 25 studies were included in this review, the sample size of which ranged from 6 to 124 participants. The participants in the included studies were professional and semiprofessional soccer players, interviewed clubs staff, and practitioners. Along with other monitoring strategies, morning vagally mediated HRV analysis via (ultra)short-term orthostatic measurements may be an efficient way to assess training adaptations and readiness to perform in professional and semiprofessional soccer players. Further research is required to make definitive recommendations.

Power output at the moderate-to-heavy intensity transition decreases in a non-linear fashion during prolonged exercise.

PURPOSE: The aims of this study were to: (i) describe the time course of the decrease in power output at the moderate-to-heavy intensity transition during prolonged exercise; (ii) investigate the association between durability of the moderate-to-heavy intensity transition and exercise capacity; and (iii) explore physiological correlates of durability of the moderate-to-heavy intensity transition. METHODS: Twelve trained cyclists (age: 40 ± 8 y, V ˙ O2peak: 52.3 ± 5.2 mL·min-1·kg-1) performed an exhaustive cycling protocol involving alternating incremental exercise tests to determine power output at the moderate-to-heavy intensity transition via the first ventilatory threshold (VT1), and 30-min bouts at 90% of the power output at the previously estimated VT1 in the rested state. The individual time course of VT1 was modelled using linear and second-order polynomial functions, and time to a 5% decrease in VT1 (Δ5%VT1) was estimated using the best-fitting model. RESULTS: Power output at VT1 decreased according to a second-order polynomial function in 11 of 12 participants. Time-to-task failure (234 ± 66 min) was correlated with Δ5%VT1 (139 ± 78 min, rs = 0.676, p = 0.016), and these were strongly correlated with absolute and relative rates of fat oxidation at specific exercise intensities measured during the incremental test performed in the rested state. CONCLUSIONS: These data: (i) identify a non-linear time course of decreases in the moderate-to-heavy intensity transition during prolonged exercise; (ii) support the importance of durability of the moderate-to-heavy intensity transition in prolonged exercise capacity; and (iii) suggest durability of the moderate-to-heavy intensity transition is related to fat oxidation rates.

Muscle-UCP3 in the regulation of energy metabolism.

Uncoupling protein-3 (UCP3) is a mitochondria-regulatory protein with potential energy- homeostatic functions. This study explores the role of UCP3 in the regulation of muscle- and energy metabolism. UCP3 is critical for tuning substrate utilization, favoring lipid oxidation, particularly in conditions of high-fat availability. While UCP3 is non-essential for lipid oxidation during energy excess, it proves vital during fasting, indicating an energy-homeostatic trait. Preliminary evidence indicates UCP3' promotion of glucose uptake and oxidation, at least in conditions of high glucose/low fat availability. However, the dynamics of how fats and glucose differentially influence UCP3 remain undefined. UCP3 exhibits inducible proton transport and uncoupling activity, operating in a dual manner: a resting state with no/low activity and an activated state in the presence of activators. Uncoupling may enhance thermogenesis in specific conditions and in the presence of activators such as fatty acids, thyroid hormones, and catecholamines. This energy-dissipative activity adapts to varying energy availability, balancing energy dissipation with fatty acid oxidation to optimize whole-body energy homeostasis: fasting triggers UCP3 upregulation, enhancing lipid utilization while suppressing uncoupling. Additionally, UCP3 upregulation induces glucose and lipid disposal from the bloodstream and decreases tri-/diglyceride storage in muscle. This process improves mitochondrial functionality and insulin signaling, leading to enhanced systemicgluco-metabolic balance and protection from metabolic conditions. Reviewed evidence suggests that UCP3 plays a crucial role in adapting the system to changing energy conditions. However, the precise role of UCP3 in regulating metabolism requires further elucidation.

Corrigendum: Fat oxidation rates and cardiorespiratory responses during exercise in different subject populations with post-acute sequelae of SARS-CoV-2 infection: a comparison with normative percentile values.

[This corrects the article DOI: 10.3389/fphys.2023.1310319.].

The Day-by-Day Periodization Strategies of a Giro d'Italia Podium Finisher.

PURPOSE: The aim of this study was to describe the day-by-day training and racing characteristics in preparation for the Giro d'Italia of 1 world-class road cyclist who achieved a place on the podium in the final general classification of the Giro d'Italia. METHODS: Day-by-day power meter training and racing data of 1 study subject (road cyclist; age 25 y; relative maximum oxygen consumption 81 mL·min-1·kg-1; relative 20-min record power output 6.6 W·kg-1) covering the 152 days leading up to the podium in the Giro d'Italia final general classification were retrospectively analyzed. Daily load, daily volume, and intensity distribution were considered. RESULTS: During training a pattern alternating "hard days" versus "easy days" was observed, as significant amounts of medium or high intensity, or load, were not performed for more than 2 consecutive days This pattern was achieved combining high volume (>4 h) with a significant amount of medium and high intensity within the same training sessions. During training, when training load and intensity increased, the density of "easy days" augmented. In 1-week stage races and the Giro d'Italia, 3 to 8 consecutive days with significant amounts of medium and high intensity were performed. A high number of training sessions with small amounts of medium- and high-intensity volume was observed: 38 days accumulating 3 to 10 minutes at medium intensity and 29 days spending 1 to 9 minutes at high intensity. CONCLUSION: These data provide novel insights about the day-by-day periodization strategies leading to a top 3 in the Giro d'Italia general classification.

Is change of direction influenced by motor competencies? A possible response from a MOBAK-based study in Italian schoolchildren.

BACKGROUND: Change of direction (COD) ability requires higher motor control capacity and helps children improve individual motor skills. Likewise, basic motor competencies (BMC) are relevant during child maturation and may interleave with COD ability. This study aimed to investigate the possible individual determinants between the COD ability and the BMC, cognitive skills, and anthropometrics characteristics in Italian primary school children aged 6 to 11. METHODS: Children of both sexes (N.=221) were recruited from primary schools (grade 1 to 5) of Northwestern Italy. COD was assessed by 10×5 m Shuttle Run Test; motor coordination by the Motor Coordination (Motorische Basiskompetenzen, MOBAK) 1-6 test battery, whereas Trail Making Test was used to assess cognitive performance. RESULTS: A stepwise linear regression indicated that motor competencies level - assessed by the MOBAK Test - is the most fitting dimension describing COD performance for girls, with the highest R2 in Grade 5 (SEE=0.56); and the lowest SEE in Grade 5 (SEE=1.44); moreover, for boys the highest in Grade 3 (SEE=0.52) and the lowest SEE in Grade 4 (SEE=1.30). CONCLUSIONS: This study confirms the biunivocal relationship between COD and BMC, and the need for physical education teachers and trainers to stimulate both, during growth.

Fat oxidation rates and cardiorespiratory responses during exercise in different subject populations with post-acute sequelae of SARS-CoV-2 infection: a comparison with normative percentile values.

Introduction: Post-acute sequelae of SARS-CoV-2 infection (PASC) presents a spectrum of symptoms following acute COVID-19, with exercise intolerance being a prevalent manifestation likely linked to disrupted oxygen metabolism and mitochondrial function. This study aims to assess maximal fat oxidation (MFO) and exercise intensity at MFO (FATmax) in distinct PASC subject groups and compare these findings with normative data. Methods: Eight male subjects with PASC were involved in this study. The participants were divided into two groups: "endurance-trained" subjects (V˙O2max > 55 mL/min/kg) and "recreationally active" subjects (V˙O2max < 55 mL/min/kg). Each subject performed a graded exercise test until maximal oxygen consumption (V˙O2max) to measure fat oxidation. Subsequently, MFO was assessed, and FATmax was calculated as the ratio between V˙O2 at MFO and V˙O2 max. Results: The MFO and FATmax of "endurance-trained" subjects were 0.85, 0.89, 0.71, and 0.42 and 68%, 69%, 64%, and 53%, respectively. Three out of four subjects showed both MFO and FATmax values placed over the 80th percentile of normative data. The MFO and FATmax of "recreationally active" subjects were 0.34, 0.27, 0.35, and 0.38 and 47%, 39%, 43%, and 41%, respectively. All MFO and FATmax values of those subjects placed below the 20th percentile or between the 20th and 40th percentile. Discussion: Significant differences in MFO and FATmax values between 'endurance-trained' and "recreationally active" subjects suggest that specific endurance training, rather than simply an active lifestyle, may provide protective effects against alterations in mitochondrial function during exercise in subjects with PASC.

Cardiorespiratory and metabolic consequences of detraining in endurance athletes.

Background: A training program can stimulate physiological, anatomical, and performance adaptations, but these improvements can be partially or entirely reversed due to the cessation of habitual physical activity resulting from illness, injury, or other influencing factors. Purpose: To investigate the effects of detraining on cardiorespiratory, metabolic, hormonal, muscular adaptations, as well as short-term and long-term performance changes in endurance athletes. Methods: Eligible studies were sourced from databases and the library up until July 2023. Included studies considered endurance athletes as subjects and reported on detraining duration. Results: Total cessation of training leads to a decrease in VO2max due to reductions in both blood and plasma volume. Cardiac changes include decreases in left ventricular mass, size, and thickness, along with an increase in heart rate and blood pressure, ultimately resulting in reduced cardiac output and impaired performance. Metabolically, there are declines in lactate threshold and muscle glycogen, increased body weight, altered respiratory exchange ratio, and changes in power parameters. In the short term, there is a decrease in insulin sensitivity, while glucagon, growth hormone, and cortisol levels remain unchanged. Skeletal muscle experiences reductions in arterial-venous oxygen difference and glucose transporter-4. Implementing a partial reduction in training may help mitigate drastic losses in physiological and performance parameters, a consideration when transitioning between training seasons. Conclusion: There is a dearth of data investigating the detraining effects of training reduction/cessation among endurance athletes. Delving deeper into this topic may be useful for professionals and researchers to identify the optimal strategies to minimize these effects.