Journal of applied physiology最新文献

This study investigated whether a four-week training on an easy-level unstable board (EL) could induce a transfer of balance performance in a hard-level unstable board (HL) and in an unexpected perturbation-based task. Non-linear center of pressure (CoP) analysis investigated whether training could induce postural control adaptations in trained and untrained tasks. Thirty-four subjects were divided into a training (TR, N=17) and a control (CTRL, N=17) group. Balance was assessed before (T₀) and after (T₁) a balance training under static and dynamic conditions (EL, HL, and perturbation-based task). A force platform allowed the calculation of CoP displacement while balance performance based on the angular displacement of the unstable boards was assessed with an inertial sensor. From the angular displacement, we calculated three parameters of balance performance: Full Balance (FB), Fine Balance (FiB), and Gross Balance (GB). Stabilogram diffusion analysis (SDA) and sample entropy (SampEn) indirectly assessed neuromuscular control mechanisms. Results showed improvements in the TR from T₀ to T₁ in balance performance for FB (p<0.001), FiB (p<0.05), and GB (p<0.01) on EL and HL boards. In the perturbation-based task, the earliest CoP response consequent to perturbation improved after training (p<0.01). SampEn and SDA revealed increased automaticity (p<0.05) and efficiency (p<0.05) of balance control in the EL and HL tasks after training. Balance training led to highly task-specific adaptations and improvements that can be transferred between functionally similar balance tasks. Postural strategies learned during training seemed barely transferable to a different balance task, as the unexpected perturbation of the base of support.

Background: Despite positive clinical evidence for the effects of Pharyngeal Electrical Stimulation (PES) on swallowing performance in disease, it remains unknown which specific swallow characteristics improve. Using High Resolution Manometry Impedance (HRMI) with Pressure Flow Analysis (PFA), we aimed to assess the effects of PES on normal swallow function and to evaluate the impact of pharyngeal length variability on electrode placement.

Methods: As part of a prospective RCT, 20 asymptomatic volunteers were randomly assigned to three days of PES or SHAM treatment. HRMI assessments were conducted at baseline (during which pharyngeal length measurements were acquired) and repeated at 1-2 hours, and at 24-72 hours following PES or SHAM treatment.

Key results: Twenty healthy adults (10 male, median age: 28.0 (IQR 23.8-45.0) years, age range: 20-65 years) participated in this RCT. We developed an objective, standardized method of catheter placement based on pharyngeal length measurements. Over 3 days, the median stimulation intensity of PES was 11 mA. When compared to the SHAM group, the PES group scored better on multiple pharyngeal and esophageal metrics resulting in improved global swallow function values 1-2 hours after treatment (p=0.029). One day later, most of these beneficial effects were no longer present.

Conclusions: This study suggests that PES can temporarily alter swallow function in healthy individuals. Functional reserve in healthy individuals may be further enhanced by PES. In the majority of volunteers, electrode position needed to be adjusted 1-3 cm to account for variations in pharyngeal length.

At high-altitude, periodic breathing (PB) can occur during sleep in healthy individuals. PB is characterized by a cyclical ventilatory pattern that alternates between central sleep apnea and brief episodes of hyperventilation. The aim of this study was to evaluate the effect of periodic breathing on sleep S_pO₂. 36 healthy males subjects (median-age:26[24-28]years old, median BMI:22.7[21.1-23.8]Kg/m²) underwent a polysomnography at a simulated altitude of 3,500 meters(FiO₂:13%). Correlations were sought between the Apnea-Hypopnea Index(AHI), Oxygen Desaturation Index(ODI), percentage of total sleep time spent in PB, and mean S_pO₂ throughout the entire sleep period by calculating the Spearman's rank correlation test. We identified 20 participants who had experienced at least 3 minutes of PB adjacent to at least 3 minutes of regular breathing(RB). We compared the mean S_pO₂ between the two respiratory patterns using Wilcoxon signed-rank test. At simulated-altitude, the subjects spent a median-IQR of 43.9[12.5-79.1]% of sleep in PB and the median-AHI was 77.3[31.4-127.5]/h. Median awake and asleep S_pO₂ were 75.4[24-28]% and 68.5[66.4-72.5]% respectively. We found no within subject difference in S_pO₂ between RB and PB periods (median-IQR RB vs PB: 67.2%{63.8-74.8%} vs 67.5%{64.5-73.9%},p=0.43). No significant correlation was found between the mean sleep S_pO₂ and AHI(n=36,rs=-0.19,p=0.26), ODI(n=36,rs=-0.23,p=0.18) or PB(n=36,rs=-0.07,p=0.67). Awake S_pO₂ was correlated with mean S_pO₂ during sleep(n=36,rs=0.55;p=0.001). PB per se does not have a detrimental effect on mean S_pO₂ in young healthy males. Correlation between awake and sleep S_pO₂, suggests that sleep S_pO₂ at high-altitude is primarily determined by baseline oxygen saturation rather than the respiratory pattern developed during sleep.

Rapid cardiovascular and autonomic adaptations occur during early pregnancy to accommodate augmented cardiac output and placental circulation, with inadequate adaptation associated with hypertensive pregnancy complications. Habitual physical activity (PA) and limiting time in sedentary behaviors (SED) may improve pregnancy-related vascular and autonomic function. The objective of this study was to examine the magnitude of the predicted associations between device-measured PA and SED with cardiovascular and autonomic biomarkers including aortic stiffness, blood pressure variability (BPV) and baroreflex sensitivity (BRS) in the first trimester of pregnancy. Pregnant women (N=92, 21-44 years of age) free from cardiovascular disease were assessed between 10⁰-12⁶ weeks gestation. Participants wore a thigh-mounted activPAL device for seven days to assess PA (light intensity and moderate-to-vigorous intensity) and SED. Aortic stiffness was measured by non-invasive applanation tonometry and expressed as carotid-femoral pulse wave velocity (cfPWV). Beat-to-beat blood pressure and R-R interval were synchronously recorded for 10 minutes via finger plethysmography and ECG to derive beat-to-beat BPV and spontaneous cardiovagal BRS (sequence method). In the entire group, neither PA or SED were related to cfPWV, BPV or BRS and this finding was similar in nulliparous and parous pregnant women. In stratified analyses, the association between moderate-to-vigorous-intensity PA and cfPWV differed by gestational age, such that this inverse association was only present in the 12^th week of gestation (β = -0.365, P=0.015). The present study indicates that PA and SED are not associated with aortic stiffness or autonomic function in the first trimester.

Understanding changes to gut microbiota composition in response to hormonal birth control (HBC) may provide insight into the microbial mechanisms underlying the metabolic effects of HBC, for example, altered short-chain fatty acid (SCFA) production. Athletes' unique physiological demands may interact with these microbial mechanisms in distinct ways; however, there is limited research on HBC and gut microbiota diversity and composition across different menstrual cycle phases in physically active females. A pilot cohort of physically active females using HBC (oral contraceptives, hormone-based intrauterine devices, or arm implants) and a control group not using HBC (n=12 per group; 22±2yrs, 24±4kg/m² vs. 22±4yrs, 23±4kg/m²; Ps≥0.496) provided fecal samples alongside self-reported menstrual phase and circulating sex hormones. Alpha diversity (microbial richness and evenness) was assessed using Shannon Index while beta-diversity (microbial composition differences) was analyzed using PERMANOVA based on Bray-Curtis dissimilarity. Circulating estrogen and luteinizing hormone increased from early (days 1-5) to mid-cycle (days 12-17) in both groups (time effect Ps≤0.01), with greater changes in Control (Ps≤0.046) than HBC (Ps≥0.231). While no menstrual phase effect was observed on either diversity measure (Ps≥0.473), beta-diversity differed between Control and HBC groups (P=0.015), reflecting distinct gut microbiota profiles irrespective of menstrual phase. Seven taxa linked to SCFA production were less abundant in the HBC group (unadjusted Ps≤0.046), though significance was lost after adjusting for multiple comparisons. These findings suggest that in physically active females, hormonal contraception influences gut microbial composition, which may have downstream effects on metabolism and performance.

The Acute Respiratory Distress Syndrome (ARDS) is a critical condition that necessitates mechanical ventilation (MV) to ensure sufficient ventilation and oxygenation for patients. Intensivists employ various therapeutic tools such as adjusting Positive End Expiratory Pressure (PEEP) levels or positioning the patient prone. However, practitioners encounter several challenges when dealing with ARDS: High variability among patients, Limited understanding of underlying mechanisms As a result, decision-making by physicians largely relies on experience. Yet, having the ability to estimate the likelihood of a patient responding to different therapeutic approaches would hold significant clinical value. Moreover, gaining a deeper understanding of the biomechanical and physiological phenomena underlying patient responses could inform the development of new MV strategies for ARDS management. To address these challenges, a coupled physio-mechanical computational framework based on patient CT-scan data was conceived and implemented. Simulations were conducted for prone positioning and PEEP-increment scenarios. The model results qualitatively align with both literature data and clinical measurements. However, some results diverge quantitatively from clinical measurements, emphasizing the necessity for thorough model calibration. Nonetheless, this serves as a proof of concept that the developed framework could be valuable in supporting intensivists' decision-making processes.

Introduction: Non-invasive assessments of lung volume distribution often require inhaled contrast and are limited by low regional resolution. We aimed to examine a non-contrast imaging method of spatial lung volume displacement, adapted to assess changes with non-invasive positive pressure ventilation (NIPPV) Methods: This study evaluated regional lung volume displacement in nine healthy volunteers (6 males, 3 females; ages 29 - 55 years; BMI 20.2 - 31.3 kg/m²) using X-ray velocimetry (XV). Participants were assessed during tidal breathing and, also with 15 cm H₂O inspiratory and 5 cm H₂O expiratory pressures in a supine position. Regional specific ventilation (SV) was measured during tidal breathing and NIPPV. Mean specific ventilation (MSV, mL/mL), low volume region (LVR; % < 0.1 mL/mL), and high-volume region (HVR; % > 0.3 mL/mL) were calculated as output variables. Images were segmented into lobar as well as central and peripheral zones. Two-way ANOVA and paired t-tests were used to determine regional differences within individuals and the effect of NIPPV.

Results: NIPPV increased MSV in both peripheral (p=0.01) and central (p=0.02) lung regions compared to tidal breathing. High volume regions increased in both peripheral (p=0.04) and central regions (p=0.04) during NIPPV.

Discussion: This study demonstrates that non-contrast imaging techniques can assess regional lung ventilation and redistribution of lung volumes on NIPPV. Heterogeneous responses to NIPPV may be associated with distinct distribution of ventilation, and further work is needed to ascertain differential response to NIPPV due to lung pathology among those with respiratory disease.

Polycystic ovary syndrome (PCOS) predisposes women to cardiovascular diseases. Blood pressure (BP) responses to the cold pressor test (CPT) predict future cardiovascular risk but have yet to be characterized in PCOS. Therefore, we compared BP responses to the CPT between females with PCOS [n = 10; age: 22 ± 3 yr, body mass index (BMI): 23.9 ± 3 kg/m²] and healthy controls (CTRL; n = 10; age: 22 ± 2 yr, BMI: 22.1 ± 2 kg/m²). BP (finger photoplethysmography calibrated to manual sphygmomanometry-derived values), femoral blood flow (duplex ultrasound), and vascular resistance [FVR; mean arterial pressure (MAP)/blood flow] were measured continuously at baseline and across a 3-min hand CPT. Venous blood samples were used to quantify the free androgen index (FAI; total testosterone/sex hormone binding globulin × 100). Baseline MAP was not different between PCOS and CTRL (87 ± 7 vs. 82 ± 11 mmHg, respectively; P = 0.25), nor was systolic BP (SBP; 109 ± 9 vs. 106 ± 7 mmHg; P = 0.42). Across the CPT, MAP and SBP were higher in PCOS than CTRL (main effects of group, both P < 0.05). Peak CPT induced increases in MAP (+12 ± 5 vs. +7 ± 4 mmHg; P = 0.04) and corresponding changes in SBP (+13 ± 7 vs. +7 ± 3 mmHg; P = 0.04) and FVR (+0.17 ± 0.08 vs. +0.02 ± 0.13 mmHg/mL/min; P = 0.01) were larger in PCOS than CTRL. Within-group regressions indicated that FAI was positively associated with relative increases in peak MAP (R² = 0.72, P < 0.01) and corresponding changes in FVR (R² = 0.83, P < 0.01) in females with PCOS but not in CTRL (MAP: R² = 0.03, P = 0.62; FVR: R² = 0.12, P = 0.41). Young, lean females with PCOS demonstrate exaggerated BP and vascular responses to the CPT that may be indicative of elevated cardiovascular risk mediated in part by the detrimental effects of elevated androgens.NEW & NOTEWORTHY Young, lean, and otherwise healthy females with polycystic ovary syndrome (PCOS) demonstrated exaggerated blood pressure responses to the cold pressor test (CPT) relative to controls. CPT responses were associated with bioavailable androgens, suggesting that hyperandrogenism contributes to exaggerated responses to the CPT in PCOS. Given associations between CPT responsiveness and the subsequent development of hypertension, these findings add to mounting evidence for increased cardiovascular risk even in lean females with PCOS.

Characterizing individual muscle behavior is crucial for understanding joint function and adaptations to exercise, diseases, or aging. Shear wave elastography (SWE) is a promising tool for measuring the intrinsic material properties of muscle. This study assessed the passive and active shear modulus of the triceps surae muscles in 14 volunteers (7 females, 25.9 ± 2.5 yr) using SWE. Ankle moment, surface electromyography, and SWE of the gastrocnemius medialis (GM), gastrocnemius lateralis (GL), and soleus (SOL) muscles were measured from 30° plantar flexion (PF) to 15° dorsiflexion (DF) ankle angles during passive and isometric contractions at 25%, 50%, and 75% of maximum voluntary contraction (MVC). Muscle length, passive and active ankle moment, and passive shear modulus increased from PF to DF (P < 0.001 for all). At 15° DF, the passive shear modulus of the SOL was 76% lower than that of the GM (P < 0.001), suggesting that the SOL operates within a lower strain range. The active shear modulus decreased from PF to DF (e.g., by 36.8% at 75% MVC, P = 0.009) and was lowest in SOL. The decreasing active shear modulus suggests that the muscles operate at shorter-than-optimal to optimal lengths. Contraction intensity also affected the shear modulus (P < 0.001), indicating distinct force-sharing strategies, with GL possibly playing a crucial role at higher-intensity contractions and longer lengths. This study demonstrated SWE's potential to characterize muscle mechanics in vivo. If validated, predictions from SWE could facilitate studying muscle behavior and force-sharing strategies, serving as a diagnostic or monitoring tool for muscle function and performance.NEW & NOTEWORTHY This study assessed the length- and activation-dependent shear moduli of the triceps surae muscles using shear wave elastography. By combining joint moment, muscle fascicle geometry, and electromyography data, we characterize the muscles' in vivo passive and active mechanical behaviors. Our results indicate that the muscles operate at shorter-than-optimal to optimal lengths with soleus force production being least impacted by joint position. We observed muscle-specific shear modulus characteristics, providing insights into stress-strain behavior and force-sharing strategies.

This study assessed the cardiorespiratory fitness, running biomechanics, muscle architecture, and training characteristics of a 76-yr-old female runner who currently holds the world record 1,500 m to marathon in the women's 75-79 yr age category. Maximum oxygen uptake (V̇o_2max), running economy (RE), lactate threshold (LT), lactate turnpoint (LTP), maximal heart rate (HR_max), and running biomechanics were measured during a discontinuous treadmill protocol followed by a maximal incremental test. Muscle architecture was assessed using ultrasound. The testing was done in close proximity to her world record marathon performance in 2024. V̇o_2max was 47.9 mL·kg^-1·min^-1, and HR_max was 180 beats·min^-1. At marathon speed (11.9 km·h^-1) her RE was 210 mL·kg^-1·km^-1 and her fractional utilization was 88% of V̇o_2max. Fractional utilization at LT (11.1 km·h^-1) and LTP (12.5 km·h^-1) were 83% and 92% of V̇o_2max, respectively. Average weekly distance was 115 and 84 km·wk^-1 in the 6 wk prior to the marathon world record, and 2024 World Masters Athletics Championships (where she achieved 6 gold medals out of 6 events), respectively, with on average 90%, 9%, and 1% of training time performed in the moderate, heavy, and severe intensity domain, respectively. The 76-yr-old female world-record holder 1,500 m to marathon showed the highest V̇o_2max ever recorded for a female >75 yr old, a very high fractional utilization of V̇o_2max at LT, LTP, and marathon pace, while RE was found to be modest compared with other world-class master and younger elite runners.NEW & NOTEWORTHY This case study investigates the physiological determinants of exceptional performance in a 76-yr-old female world-record holder across distances from 1,500 m to the marathon. It reveals the highest V̇o_2max ever recorded in females aged >75 yr and exceptional fractional utilization at metabolic thresholds and marathon speed, comparable to younger world-class distance runners. The modest running economy found can be partially explained by biomechanical and training data.