Physiological Reports最新文献

This study tested the hypothesis that 6 weeks of high-intensity interval training (HIIT) would induce greater physiological adaptations than moderate-intensity continuous training (MICT) in Thoroughbred horses. Seven untrained horses completed two distance-matched treadmill training protocols (three sessions per week) in a randomized crossover design, separated by a three-month washout: MICT (6 min at 70% $\dot{V}{O}_{2\max }$ ) and HIIT (6 × [30 s at 100% $\dot{V}{O}_{2\max }$ with 30 s at 30% $\dot{V}{O}_{2\max }$ ]). Incremental exercise tests were conducted at weeks 0, 3, and 6 to assess exercise performance and physiological responses. Mixed-effects models were used to analyze the effects of time, protocol, and their interaction (p < 0.05). After 6 weeks, HIIT elicited greater improvements than MICT in run distance to exhaustion (+29% vs. +4.5%), speed at $\dot{V}{O}_{2\max }$ (+9.8% vs. +2.4%), and speed at maximal heart rate (+15% vs. +4.3%). Speed at 10 mmol/L of plasma lactate increased only after HIIT (+13% vs. +6.0%). Both protocols similarly improved $\dot{V}{O}_{2\max }$ (+13%) and maximal cardiac output (+7%-8%). In conclusion, despite being matched for total running distance, HIIT induced superior improvements in performance, cardiovascular function, and lactate kinetics compared with MICT, highlighting training intensity as a key determinant of training adaptations in horses.

This study was motivated by the limited high-altitude physiology data available for Asian military aviators, especially in Vietnam. To characterize acute heart rate (HR), blood pressure (BP), and oxygen saturation (SpO₂) responses in healthy Vietnamese pilots during simulated 5000 m hypobaric exposure. Seventy-five healthy male military pilots underwent 30-min exposure in a hypobaric chamber simulating 5000 m altitude. HR, systolic/diastolic BP (SBP/DBP), and SpO₂ were recorded at baseline (0 m), peak altitude, and post-exposure. HR increased from 80.0 ± 9.0 to 91.9 ± 11.0 bpm, SBP/DBP rose by 10.4/6.5 mmHg, and SpO₂ decreased from 98.4 ± 1.0% to 77.7 ± 6.0% (all p < 0.001). All changes were transient, returning to baseline within 5 min after exposure, and no adverse events occurred. Higher baseline HR and older age predicted smaller HR increases. Acute 5000 m hypobaric hypoxia caused transient tachycardia, hypertension, and hypoxemia. Response variability correlated with baseline hemodynamic status and age. This safe, reproducible model can serve as a noninvasive cardiovascular stress test in clinical and aerospace medicine.

This single-case pedagogical tutorial features a respiratory therapist who underwent a physiological shunt study for departmental education. Four formulas were used to estimate the shunt. A standardized 100% oxygen shunt test in a healthy male adult (51 years old, 185 cm, 84 kg) was performed to demonstrate how equation choice and assumptions affected the results. After 20 min breathing FiO₂ = 1.0 at barometric pressure 752 mmHg, routine blood gas variables (PaO₂ 587 mmHg, PaCO₂ 38 mmHg, SaO₂ 0.993, Hb 15.2 g/dL) were used to compute shunt by four approaches: the classic content equation, Chiang's arterial approximation, a P_AO₂-PaO₂ rule-of-thumb, and a simplified saturation method. Across methods, estimates clustered between ~2.8% and 5.2%, illustrating close agreement in health yet revealing how dissolved oxygen, estimation of Sv̄O₂, and assumed arterial-venous content shift results. The protocol and equations are presented as a teaching template for bedside calculation, with reporting of units, devices/supplies, and timing. We emphasize the disclosure of assumptions (RQ, nitrogen washout, capillary saturation), performing at least two methods when venous data are limited, and interpreting shunt results alongside clinical context. This practical, single-case tutorial supports respiratory care/internal medicine education and strengthens confidence in the 100% oxygen shunt test.

Obesity has been increasingly recognized not only as a metabolic disorder but also as a condition that impairs neuromuscular function, including strength relative to body mass. This translational study investigated whether obesity affects both force generation and contraction-relaxation dynamics. In control (CN) and diet-induced obese (OB) male mice, contractile properties of isolated extensor digitorum longus (EDL) and soleus (SOL) muscles were assessed in vitro. In parallel, plantar flexor performance was assessed in 25 normal-weight (CN) and 25 class I obese (OB) sedentary men through maximal voluntary isometric contractions and a dynamic calf raise test. OB mice exhibited lower specific force and slower rates of force development and relaxation in both EDL and SOL (p < 0.05). In men, the lower rate of torque development and prolonged relaxation kinetics of the plantar flexors (p < 0.05), combined with a higher body mass to maximal voluntary isometric torque ratio (p < 0.05), contributed to slower calf raise phases in OB compared to CN men (p < 0.05). These findings reveal that obesity not only has a negative impact on the muscle force generating capacity but also induces slower muscle contractile kinetics.

High-intensity endurance exercise is linked to increased atrial fibrillation (AF) risk. P wave indices are established AF risk markers, but their role in ultramarathon athletes is unexplored. This study aimed to compare P wave indices between ultramarathon athletes and healthy controls. This cross-sectional study enrolled 74 ultramarathon athletes and 38 age- and sex-matched healthy volunteers (2:1 ratio). Athletes had completed ≥1 race of ≥100 km or ≥60 km in the past year. Participants with AF, atrial flutter, cardiovascular diseases, or structural heart abnormalities were excluded. Resting 12-lead ECGs evaluated P wave indices: maximum P wave duration, P wave dispersion, P wave terminal force in lead V1 (PTFV1), and P wave amplitude in lead II (PWAII). The cohort's mean age was 44.8 ± 8.2 years, 70% male. Ultramarathon athletes had significantly higher maximum P wave duration (114.24 ± 7.95 ms vs. 105.76 ± 7.15 ms, p < 0.001), P wave dispersion (18.77 ± 5.75 ms vs. 7.87 ± 2.51 ms, p < 0.001), PTFV1 (5795.66 ± 3212.27 μV·ms vs. 2399.17 ± 1140.19 μV·ms, p < 0.001) and PWAII (0.16 ± 0.05 mV vs. 0.12 ± 0.04 mV). Abnormal P wave duration (>120 ms) and PTFV1 (≥4000 μV·ms) were significantly more prevalent in ultramarathon athletes (25.7% vs. 5.3%, p = 0.010; 63.5% vs. 5.3%, p < 0.001). Similar findings were observed across genders. Ultramarathon runners demonstrate significant atrial electrical remodeling, as evidenced by abnormal P wave indices, may have potential relevance to arrhythmia risk. Further longitudinal studies are warranted to assess clinical outcomes.

Prenatal exercise decreases offspring adiposity, but it is uncertain whether this relationship is present in offspring exposed to obesity in utero. We aimed to determine whether exercise during pregnancy reduces infant cellular and whole-body adiposity in offspring born to women with obesity. This is a sub-analysis of a randomized controlled trial, where women were randomized to supervised exercise or control for ~24 weeks during pregnancy. Exercise FITT-V metrics (frequency, intensity, time, type, and volume) were collected. Infant mesenchymal stem cells (MSCs) (healthy weight [n = 16], obesity [n = 21]) were adipogenically differentiated and stained for lipid content. Infant body composition was measured at 1 month of age via skinfold. Among women randomized to control, maternal BMI influenced infant adiposity; infants exposed to obesity had higher body fat percentage (p = 0.02). Birthweight was negatively correlated with infant body fat; offspring with lower birthweight had higher body fat (R² = 0.38, p = 0.03). Maternal weekly exercise volume trended toward negative association with infant body fat (R² = 0.33, p = 0.06) and lipid content (R² = 0.21, p = 0.06). For infants born to women with obesity, exercise during pregnancy helps reduce adiposity.

Heat tolerance testing (HTT) assesses responses to heat stress with rectal temperature (T_rec) and heart rate (HR) thresholds defining individuals as heat-tolerant (HT) or heat-intolerant (HI). To evaluate classification criteria by acclimation state and sex. Forty participants (19M/21F, mean ± SD, 23 ± 4 years) completed an HTT (120 min, 5 km·h^-1, 2% grade) before (PreHA) and after (PostHA) 5 days of repeated exercise in (40°C, 40% RH) categorized as isothermal (exercise intensity adjusted to maintain T_rec within 38.5°C-39.5°C, 60 min) exercise-heat acclimation (HA). Females had lower body surface area (vs. males) (1.7 ± 0.1 vs. 2.0 ± 0.2 m², p < 0.001), mass (59.5 ± 5.4 vs. 79.5 ± 10.1 kg, p < 0.001), height (164.2 ± 5.7 vs. 179.1 ± 7.6 cm, p < 0.001), maximal oxygen consumption (V̇O₂max, 44.5 ± 5.1 vs. 51.5 ± 5.7 mL·min^-1·kg^-1, p < 0.001), and velocity at V̇O₂max (12.9 ± 1.5 vs. 15.0 ± 1.7 km·h^-1, p < 0.001). PreHA 51.1% (mean % HI classification across criteria) of participants were HI (66.7% F/52.6% M), decreasing (p < 0.001) to 23.6% PostHA (28.6% F/10.5% M), reflected across criteria (p < 0.05). The rate of HI based on plateau in T_rec during the final 60 min (ΔT_{rec (T120-T60)} ≥ 0.45°C) was similar (p = 0.735) PreHA (15% HI) and PostHA (10%), and HA reduced ΔT_{rec (T120-T60)} (0.30 ± 0.19 vs. 0.19 ± 0.20°C, p = 0.001), demonstrating sensitivity to adaptation. HA reduces HI classification rate, but criteria differ in capturing presumed HT and classify more females as HI in naïve and acclimated states.

Asthma diagnosis can be challenging in children. Spirometry is highly effort-dependent and often normal in early disease. Forced oscillation technique (FOT) is an alternative to spirometry and is performed during tidal breathing. We investigated the feasibility of FOT with fewer acquisitions than suggested by technical standards in a pediatric outpatient care setting. We also studied the influence of tidal breathing patterns on FOT indices. Finally, the clinical utility of FOT was compared with spirometry. Ninety-five children aged 3-12 years performed FOT with single-frequency mode of 8 Hz (Resmon Pro, ResTech, Italy) during initial asthma assessment or follow-up. School-aged children (n = 61) also performed spirometry. In preschool age (<6 years), 94% managed one and 74% managed two approved FOT acquisitions, whereas in school-age 100% and 92% managed correspondingly. Reasonable agreement between two device-approved FOT measurements was found. No difference in FOT values was found with spontaneous higher respiratory rates or tidal volumes. Bronchodilation responses measured with FOT, but not spirometry, were associated with ongoing anti-inflammatory asthma medication. FOT with an integrated quality control was highly feasible in children 3-12 years. Reasonable agreement between two device-approved acquisitions was found suggesting one measurement might suffice. Deviations from normal tidal breathing had little influence on FOT results.

We investigated whether including arterial pressure of nitrogen (PaN₂) in a deep-learning analysis of single measurements of arterial blood gases, cardiac output, and indirect calorimetry enables individualized quantification of West's ventilation/perfusion (V/Q) lung model. West's key parameters are shunt (% cardiac output supplying lung units with V/Q = 0), logSD (log standard deviation of unit V/Q ratios), and meanV/Q (mean unit V/Q ratio). By processing randomized combinations of shunt, logSD, meanV/Q, indirect calorimetry, and cardiac output data in a Python computerization of West's model, 2,010,000 blood gases including PaN₂ combined with their input variables completed a simulated monitoring dataset covering broad ranges of oxygenation and acid-base equilibria. Deep-learning applications trained on these data successfully predicted withheld values of shunt, logSD, and meanV/Q from a separate test dataset of 43,915 samples. Linear regression of predicted versus true values produced R² ≥ 0.99 with slopes 0.98-1.00. Kernel density estimates confirmed close agreement. Sensitivity analyses demonstrated high dependence upon PaN₂. Deep-learning analysis of single measurements of arterial blood gases, which include PaN₂, when combined with cardiac output and indirect calorimetry data, can quantify individual lung function with high fidelity in terms of key parameters of West's V/Q model.

Slower oxidative fibers are more resistant to eccentric contraction (ECC)-induced muscle damage than fast-twitch glycolytic fibers, but the mechanisms remain unclear. This study investigated the roles of the exercise-inducible PGC-1α isoform PGC-1α-b and utrophin in protecting against ECC-induced damage. ECCs were induced by supramaximal electrical stimulation of the left triceps surae in C57BL/6N wild-type (WT), PGC-1α-b transgenic (Tg), utrophin knockout (Utrn KO), and PGC-1α-b Tg/Utrn KO mice. Although the proportion of fast-type myosin heavy chain (MyHC) IIb in the gastrocnemius muscle was modestly lower in PGC-1α-b Tg and PGC-1α-b Tg/Utrn KO mice than in WT and Utrn KO mice, MyHC IIb remained the predominant isoform. At 3 days post injury (dpi), WT and Utrn KO mice exhibited reduced maximum isometric torque (MIT), Evans blue dye (EBD) staining in MyHC IIb-positive fibers, and calpain-1 activation. In contrast, PGC-1α-b Tg and PGC-1α-b Tg/Utrn KO mice showed substantial MIT recovery at 1 dpi and minimal EBD uptake and calpain-1 activation at 3 dpi. PGC-1α-b Tg muscles also preserved excitation-contraction coupling proteins and displayed increased mitochondrial markers and integrin α7B expression. Together, our findings suggest that PGC-1α-b confers resistance to ECC-induced muscle damage through a Utrn-independent mechanism.