Journal of applied physiology最新文献

{"title":"Heart rate variability during exercise can quantify cardiorespiratory deconditioning in 55- to 65-yr-old men and women exposed to head-down bed rest.","authors":"Jeremy Rabineau, Eric T Hedge, Roxanne Fournier, Carmelo J Mastrandrea, Richard L Hughson","doi":"10.1152/japplphysiol.00017.2025","DOIUrl":"10.1152/japplphysiol.00017.2025","url":null,"abstract":"<p><p>The heart rate variability (HRV) features HRV_0.75 and HRV_0.5, obtained by detrended fluctuation analysis during incremental cycle ergometer tests, have been shown to correlate with indices of cardiorespiratory fitness. Here, we evaluate the ability of these features to track individual changes in cardiorespiratory fitness induced by head-down bed rest (HDBR) among late middle-aged adults. Twenty-two healthy participants (55-65 yr old, 11 women) were exposed to 14-day HDBR. Eleven participants were assigned to a group performing daily aerobic and resistive exercises during HDBR, whereas the others were assigned to a control group with no countermeasure intervention. We measured gas exchange and electrocardiography during incremental cycle ergometer tests pre- and post-HDBR. The countermeasure preserved oxygen uptake (V̇o₂) at the two ventilatory thresholds (VT1 and VT2), HRV_0.75 and HRV_0.5. However, these four features decreased in the control group after HDBR. A large and proportional bias was evidenced between V̇o₂ at VT1 and HRV_0.75, which was less the case for V̇o₂ at VT2 versus HRV_0.5. However, the intraindividual changes in the control group were correlated (<i>r</i>_rm = 0.66 for VT1 vs. HRV_0.75 and <i>r</i>_rm = 0.82 for V̇o₂ at VT2 vs. HRV_0.5, both <i>P</i> < 0.001). Overall, this study indicated that HRV_0.75 and HRV_0.5 can be used to longitudinally monitor changes in cardiorespiratory fitness in late middle-aged adults with physical deconditioning. Future research can apply these methods to other study populations.<b>NEW & NOTEWORTHY</b> We report the applicability of two heart rate variability features (HRV_0.75, HRV_0.5) computed during exercise to assess changes in cardiorespiratory fitness. Although previous cross-sectional studies suggested that these features were highly correlated to the ventilatory thresholds, we highlight the fact that they should not be considered as equivalent. More easily obtained than ventilatory thresholds, HRV_0.75 and HRV_0.5 could be used as fitness markers along a continuum of the physiological response between rest and maximal exercise.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1002-1010"},"PeriodicalIF":3.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143657381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sexually dimorphic mechanisms of H₂O₂-mediated dilation in porcine coronary arterioles with ischemia and endurance exercise training.","authors":"Kalen Johnson, Jeff F Bray, Cristine L Heaps","doi":"10.1152/japplphysiol.00761.2024","DOIUrl":"10.1152/japplphysiol.00761.2024","url":null,"abstract":"<p><p>We determined the impact of sex on H₂O₂-mediated dilation in coronary arterioles and the contribution of K⁺ channels after exercise training in ischemic heart disease. We hypothesized that arterioles from male and female swine would similarly display impaired H₂O₂-induced dilation after chronic occlusion that would be corrected by exercise training. Yucatan miniswine were surgically instrumented with an ameroid constrictor around the proximal left circumflex artery, gradually inducing occlusion and a collateral-dependent myocardium. Arterioles from the left anterior descending artery myocardial region served as nonoccluded controls. Eight weeks postoperatively, swine of each sex were separated into sedentary and exercise-trained (progressive treadmill regimen; 5 days/wk for 14 wk) groups. Collateral-dependent arterioles of sedentary female pigs displayed impaired sensitivity to H₂O₂ that was reversed with exercise training. In contrast, male pigs exhibited enhanced sensitivity to H₂O₂ in collateral-dependent versus nonoccluded arterioles in both sedentary and exercise-trained groups. Large-conductance, calcium-dependent K⁺ (BKCa) and 4-aminopyridine (AP)-sensitive voltage-gated K⁺ (Kv) channels contributed to H₂O₂-mediated dilation in nonoccluded and collateral-dependent arterioles of exercise-trained females, but not in arterioles of sedentary female or sedentary or exercise-trained male swine. BKCa channel, protein kinase A (PKA), and protein kinase G (PKG) protein levels were not significantly different between groups, nor were kinase enzymatic activities. Taken together, our studies suggest that in female swine, exercise training stimulates the coupling of H₂O₂ signaling with BKCa and 4-AP-sensitive Kv channels, compensating for impaired dilation in collateral-dependent arterioles. Interestingly, coronary arterioles from neither sedentary female or male swine, regardless of training status, depended upon BKCa or 4-AP-sensitive Kv channels for H₂O₂-mediated dilation.<b>NEW & NOTEWORTHY</b> The current studies reveal sexually dimorphic adaptations to H₂O₂-mediated dilation, and unique contributions of K⁺ channels, in coronary arterioles from swine subjected to chronic ischemia and exercise training; findings important for development of therapeutic strategies. In female swine, chronic ischemia attenuates dilation, which is reversed by exercise training via BKCa and Kv channel stimulation. In male swine, ischemia enhances dilation to H₂O₂, which is further augmented by exercise training and independent of BKCa and Kv channels.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"950-963"},"PeriodicalIF":3.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143584862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Short bouts of hypoxia improve insulin sensitivity in adults with type 2 diabetes.","authors":"Jiahui Zhao, Sahar D Massoudian, Sten Stray-Gundersen, Frank Wojan, Sophie Lalande","doi":"10.1152/japplphysiol.00932.2024","DOIUrl":"10.1152/japplphysiol.00932.2024","url":null,"abstract":"<p><p>Hypoxia stimulates glucose uptake independently from the action of insulin. The purpose of this study was to determine the effect of intermittent hypoxia, consisting of alternating short bouts of breathing hypoxic and room air, on glucose concentration, insulin concentration, and insulin sensitivity during an oral glucose tolerance test in adults with type 2 diabetes and adults with normal glycemic control. Nine adults with type 2 diabetes (2 women, HbA1c: 7.3 ± 1.5%, age: 52 ± 13 yr) and nine adults with normal glycemic control (4 women, HbA1c: 5.4 ± 0.1%, age: 24 ± 4 yr) performed a 2-h oral glucose tolerance test on two separate visits to the laboratory. Following ingestion of the glucose drink, participants were exposed to either an intermittent hypoxia protocol, consisting of eight 4-min hypoxic cycles at a targeted oxygen saturation of 80% interspersed with breathing room air to resaturation, or a sham protocol consisting of eight 4-min normoxic cycles interspersed with breathing room air. Intermittent hypoxia did not attenuate the increase in glucose concentration but attenuated the increase in insulin concentration in response to an oral glucose tolerance test in comparison with the sham protocol in adults with type 2 diabetes. Insulin sensitivity was greater during intermittent hypoxia in comparison with the sham protocol in adults with type 2 diabetes (0.043 ± 0.036 vs. 0.032 ± 0.046 μmol/kg/min/pmol, <i>P</i> = 0.01), but did not change in the control group (0.122 ± 0.015 vs. 0.128 ± 0.008 μmol/kg/min/pmol, <i>P</i> = 0.12). In conclusion, intermittent hypoxia improved insulin sensitivity in adults with type 2 diabetes.<b>NEW & NOTEWORTHY</b> The aim of this study was to determine the effect of short bouts of hypoxia, which stimulates glucose uptake, on glucose concentration, insulin concentration, and insulin sensitivity during an oral glucose tolerance test in adults with type 2 diabetes and adults with normal glycemic control. Intermittent hypoxia acutely improved insulin sensitivity in adults with type 2 diabetes.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"873-880"},"PeriodicalIF":3.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143515809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Leg stiffness adjustment during hopping by dynamic interaction between the muscle and tendon of the medial gastrocnemius.","authors":"Kazuki Kuriyama, Daisuke Takeshita","doi":"10.1152/japplphysiol.00375.2024","DOIUrl":"10.1152/japplphysiol.00375.2024","url":null,"abstract":"<p><p>The biomechanics underlying bouncing exercises are characterized by the spring-like behavior of the human leg. This study investigated a specific form of hopping-performed with an extended knee and minimal ground contact duration-to examine how muscle dynamics contribute to leg stiffness adjustment. This constrained hopping pattern allows us to isolate the role of ankle joint, especially plantar flexor muscle-tendon complex (MTC). To quantitatively analyze changes in the MTC of the medial gastrocnemius (MG) muscle, we utilized an MTC model comprising an active spring and a passive spring connected in series, representing a contractile component (CC) and series elastic component (SEC), respectively. We hypothesized that an increase in CC stiffness would coincide with the increase in leg stiffness, thereby enabling hopping at higher frequencies. Joints and MG fascicle dynamics were collected across different hop frequencies. The results showed that the stiffness of the MTC increased with hop frequency and exhibited a strong correlation with the leg stiffness. In addition, with increasing frequency, the fascicle contractions shifted from isometric to concentric. Consequently, a negative CC stiffness was observed, thereby increasing the overall MTC stiffness. Although this result appears to diverge from our initial hypothesis, the effect of negative CC stiffness on MTC stiffness can be understood, from the perspective of two springs in series, as an extension of the very high stiffness effect. This quantitative understanding of the dynamic interaction between the fascicle and tendon provides deeper insight into the adjustment mechanisms underlying bouncing gaits.<b>NEW & NOTEWORTHY</b> The mechanistic understanding of how humans adjust leg stiffness in bouncing exercises remains unclear. An MTC model comprising two springs, contractile and series elastic components, was used to analyze the medial gastrocnemius muscle dynamics during hopping with different hop frequencies. The contractile component showed negative stiffness at high hop frequency due to shortening against increasing load, achieving high MTC stiffness and leg stiffness required for high-frequency hopping.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"899-908"},"PeriodicalIF":3.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143542048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Pharyngeal electrical stimulation favorably modifies healthy human pharyngoesophageal function: a randomized trial using high-resolution manometry impedance.","authors":"Marthe Everaert, Shaheen Hamdy, Ann Goeleven, Jan Tack, Tim Vanuytsel, Nathalie Rommel","doi":"10.1152/japplphysiol.00516.2024","DOIUrl":"10.1152/japplphysiol.00516.2024","url":null,"abstract":"<p><p>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. As part of a prospective randomized controlled trial (RCT), 20 asymptomatic volunteers were randomly assigned to 3 days of PES or SHAM treatment. HRMI assessments were conducted at baseline (during which pharyngeal length measurements were acquired) and repeated at 1-2 h, and at 24-72 h following PES or SHAM treatment. Twenty healthy adults [10 males, median age: 28.0 (interquartile range, IQR 23.8-45.0) yr, age range: 20-65 yr] 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 with the SHAM group, the PES group scored better on multiple pharyngeal and esophageal metrics resulting in improved global swallow function values 1-2 h after treatment (<i>P</i> = 0.029). One day later, most of these beneficial effects were no longer present. 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.<b>NEW & NOTEWORTHY</b> Pharyngeal electrical stimulation (PES) positively influences clinical swallow-outcomes in patients with neurogenic dysphagia. Its effect on the underlying swallowing physiology remains unknown. Our study evaluated this effect of PES in healthy individuals using high-resolution manometry impedance. PES showed short-term improved pharyngeal contractility, upper esophageal sphincter relaxation, proximal esophageal contractility and bolus flow, resulting in improved swallowing. One day later, most of these beneficial effects were no longer present as expected in already intact swallow systems.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"988-1001"},"PeriodicalIF":3.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143458023","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Whole genome transcriptomic profiling reveals distinct sex-specific responses to heat stroke.","authors":"Abderrezak Bouchama, Maria Gomez, Mashan L Abdullah, Saeed Al Mahri, Shuja Shafi Malik, Saber Yezli, Sameer Mohammad, Cynthia Lehe, Bisher Abuyassin, Robert Hoehndorf","doi":"10.1152/japplphysiol.00001.2025","DOIUrl":"10.1152/japplphysiol.00001.2025","url":null,"abstract":"<p><p>Heat-related mortality remains health challenges exacerbated by climate change, with sex-based differences in outcomes, yet underlying mechanisms remain poorly understood. This study examined transcriptomic responses to heat exposure in peripheral blood mononuclear cells from 19 patients with heat stroke (HS; 8 males, mean age 64.8 ± 6.6 yr; 11 females, mean age 49.7 ± 11 yr) and 19 controls (11 males, mean age 48.9 ± 9.6 yr; 8 females, mean age 44.9 ± 11.8 yr). At admission, gene expression revealed upregulation of heat shock protein genes, and pathway analysis demonstrated activation of heat shock and unfolded protein responses across both sexes consistent with proteotoxic stress. However, distinct metabolic, oxidative stress, cell cycle control, and immune responses were observed within each sex. Females displayed inhibition of protein synthesis, oxidative phosphorylation, and metabolic pathways, including glucose metabolism, indicative of a hypometabolic state. Males maintained metabolic activity precooling and enhanced adenosine triphosphate production postcooling. Females activated nuclear factor erythroid 2-related factor 2 (NRF2)-mediated oxidative stress responses and inhibited DNA replication and mitosis, potentially mitigating genomic instability, whereas these pathways showed limited regulation in males. Females promoted innate immunity via interleukin (IL)-6, inflammasome, and triggering receptor expressed on myeloid cells 1 (TREM1) signaling, whereas males showed suppression of both innate and adaptive immunity, including IL-12, Th1, and T-cell receptor pathways. Upstream analysis identified over 100 transcription factors in both sexes. Males primarily relied on transcriptional mechanisms, whereas females also exhibited translational regulation via La ribonucleoprotein 1 (LARP1), fragile X messenger ribonucleoprotein 1 (FMR1), insulin-like growth factor 2 mRNA binding protein 1 (IGF2BP1), and eukaryotic translation initiation factor 6 (EIF6). These findings suggest distinct, sex-specific molecular adaptations to heat stroke, underscoring the need for targeted therapeutic strategies to mitigate heat-induced morbidity and mortality.<b>NEW & NOTEWORTHY</b> Heat-related mortality continues to rise with climate change. Our transcriptomic analysis reveals distinct sex-specific metabolic strategies to heat stroke: females enter a hypometabolic state, an evolutionary adaptation that conserves energy, whereas males sustain metabolic activity. Transcription factors and a subset of translation regulators in females modulate proteostasis and bioenergetics, driving these sex-specific pathways. These novel findings highlight the critical need to consider sex-specific differences in heat-related illnesses and inform carefully targeted interventions to improve patient outcomes.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"964-978"},"PeriodicalIF":3.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143604951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Home-based heat therapy lowers blood pressure and improves endothelial function in older adults.","authors":"Ysabella I Ruiz-Pick, Heidi L Cope, Rauchelle E Richey, Amy M Moore, Tyson C Garfield, Albert H Olivencia-Yurvati, Steven A Romero","doi":"10.1152/japplphysiol.00977.2024","DOIUrl":"10.1152/japplphysiol.00977.2024","url":null,"abstract":"<p><p>Advancing age is associated with vascular dysfunction and hypertension, both of which increase cardiovascular event risk. Heat therapy has emerged as a novel intervention to improve cardiovascular health in various populations. Therefore, we tested the hypothesis that home-based lower body heat therapy would reduce blood pressure and improve endothelium-dependent vasodilation in older adults. Ambulatory blood pressure monitoring was performed in 19 older adults (67 ± 7 yr) before and after 8 wk of a sham intervention or heat therapy. Endothelium-dependent vasodilation of the superficial femoral artery was assessed via flow-mediated dilation. Participants were provided with a pair of tube-lined pants connected to a portable water circulator to perform the home-based sessions. Water temperature was set to 31°C for sham and 51°C for heat therapy, resulting in target skin temperatures of ∼33°C and ∼40°C, respectively. Participants were instructed to wear the pants 4 days/wk for 60 min each session. Adherence was 100% for both groups. Heat therapy reduced ambulatory daytime systolic blood pressure by Δ -5 ± 8 mmHg, but was unchanged for the sham group (Δ 1 ± 6 mmHg; <i>P</i> = 0.04). Likewise, heat therapy increased flow-mediated dilation (<i>P</i> = 0.02), whereas there was no change across time for the sham group (<i>P</i> = 0.5). These results combined with a strong adherence rate suggest that home-based lower body heat therapy could be an alternative nonpharmacological intervention to reduce blood pressure and improve vascular function, ultimately reducing long-term cardiovascular event risk in older adults.<b>NEW & NOTEWORTHY</b> Advancing age is associated with vascular dysfunction and hypertension, both of which increase cardiovascular event risk. This study determined that 8 wk of home-based lower body heat therapy reduced ambulatory daytime systolic blood pressure and increased flow-mediated dilation of the superficial femoral artery, outcomes not observed in the sham group. These improvements, coupled with 100% adherence among participants, suggest that home-based heat therapy is a pragmatic and effective strategy for improving cardiovascular health in older adults.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"979-987"},"PeriodicalIF":3.3,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143585846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Determining operating lung volumes during a CO₂ rebreathing test: Does the inspiratory capacity maneuver influence the hypercapnic ventilatory response?","authors":"Parsa Shekarloo, Christine A Darko, Ghazal Adibmoradi, Parsa Jamal-Zadeh, Tania J Pereira, Heather Edgell, Devin B Phillips","doi":"10.1152/japplphysiol.00938.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00938.2024","url":null,"abstract":"<p><p>Previous studies using the modified Duffin CO₂ rebreathing test have not accounted for changes in operating lung volumes, which may affect the hypercapnic ventilatory response (HCVR). Importantly, determining operating lung volumes requires the performance of an inspiratory capacity maneuver (IC), which could influence the HCVR. Therefore, the purpose of this study was to determine if serial IC measurements during a modified Duffin CO₂ rebreathing test influenced HCVR. Thirty young healthy participants (15 male:15 female) completed two modified Duffin CO₂ rebreathing tests on separate days (order randomized). Serial IC maneuvers were completed at 2-minute intervals throughout rebreathing (IC condition only) and expired-gas data were acquired to determine ventilation (⩒_E) and the partial pressure of end-tidal CO₂ (P_ETCO₂). Basal ⩒_E, the ⩒_E recruitment for threshold for CO₂ (VRTCO₂), and the ⩒_E:CO₂ slope (⩒_ES) were determined and expired-gas and sensory data were compared between-conditions at standardized time points. There were no between-condition (IC vs no-IC trial) differences in basal ⩒_E, VRTCO₂, and ⩒_ES (all p>0.05). Repeated measure analysis revealed no betweencondition differences in ⩒_E or P_ETCO₂ as a function of rebreathing time (all p>0.05). Intraclass correlation coefficient values for basal ⩒_E, VRTCO₂, and ⩒_ES were 0.745, 0.692, and 0.828, indicating good between test agreement. The HCVR during a standardized CO₂ rebreathing protocol was unaffected when including serial measurements of IC. The findings from the current study support inclusion of IC measurements to determine operating lung volumes in healthy young adults, which in turn will improve characterization of the HCVR.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730113","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Redefining muscular action: Human \"adductor\" magnus is designed to act primarily for hip \"extension\" rather than adduction in living young individuals.","authors":"Katsuki Takahashi, Hironoshin Tozawa, Raki Kawama, Taku Wakahara","doi":"10.1152/japplphysiol.00600.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00600.2024","url":null,"abstract":"<p><p>Human leg muscles are uniquely enlarged for upright bipedalism, and the adductor magnus is one of the largest muscles. While this muscle is recognized as a hip adductor, hip adduction torque is not greatly required during human locomotion such as walking and running. The functional role of this giant muscle remains unclear. Here, we tested the hypothesis that the human adductor magnus acts primarily for hip extension rather than adduction in living young individuals. Utilizing diffusion tensor imaging, we reconstructed fascicles over the entire muscle in fifteen young adults at the hip neutral position. We divided the muscle into three portions based on fascicle insertion and examined their 3D architectures. The posterior and anterior-distal portions comprised over 80% of the whole muscle volume and physiological cross-sectional area. These portions demonstrated a longer moment arm for hip extension than adduction. Consequently, the potential torque (maximal torque-generating capacity) of the whole muscle was over two-fold greater for hip extension than adduction. The hip extension potential torque was correlated with the maximal hip extension torque measured with a dynamometer. These results highlight the architectural design of the adductor magnus favoring hip extension over adduction, providing novel insights into its functional role beyond the frontal plane in human locomotor mechanics.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Directional sensitivity analysis of the cerebral pressure-flow relationship during normothermia and moderate hyperthermia.","authors":"Mahmoudreza Taghizadeh, R Matthew Brothers, Lawrence Labrecque, Marc-Antoine Roy, Daniel Gagnon, Jonathan D Smirl, Craig G Crandall, Patrice Brassard","doi":"10.1152/japplphysiol.00712.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00712.2024","url":null,"abstract":"<p><p>Dynamic cerebral autoregulation (dCA) reacts differently when mean arterial pressure (MAP) increases versus decreases (i.e. directional sensitivity). While heat stress alters dCA, its influence on directional sensitivity remains unclear. This analysis investigated the impact of moderate hyperthermia on the directional sensitivity in the cerebral pressure-flow relationship. Ten healthy participants (7 males; age: 37 ± 12 yrs.; body mass: 75 ± 9 kg) underwent 6 min of oscillatory lower body negative pressure (OLBNP) to induce large MAP fluctuations, at 0.03 and 0.10 Hz under normothermic and moderately hyperthermic conditions (+1.0°C increase in core temperature) induced via a water-perfused suit. We calculated changes in middle cerebral artery mean blood velocity (MCAv) per alterations to MAP to compute absolute and relative ratios adjusted for time intervals during each OLBNP-induced MAP increases (ΔMCAv_T/ΔMAP_T^INC; %MCAvT/%MAPT INC) and decreases (ΔMCAv_T/ΔMAP_T^DEC; %MCAvT/%MAPT DEC). Therea􀅌er, we compared average absolute and relative ratios. There was no main effect of MAP direction on ΔMCAv_T/ΔMAPT or %MCAvT/%MAPT during either 0.03 Hz (P=0.291, P=0.281) or 0.10 Hz (P=0.295, P=0.178) OLBNP. Regardless of MAP direction, ΔMCAv_T/ΔMAP_T^INC (0.65 ± 0.17 vs 0.84 ± 0.22 cm. s^-1/mmHg), ΔMCAv_T/ΔMAP_T^DEC (0.70 ± 0.15 vs 0.85 ± 0.18 cm. s^-1/mmHg) (thermal state: P=0.009), %MCAvT/%MAPT INC (0.92 ± 0.22 vs 1.33 ± 0.60), and %MCAvT/%MAPT DEC (1.01 ± 0.27 vs 1.30 ± 0.51) (thermal state: P=0.001) were lower in hyperthermia at 0.03 Hz OLBNP. Regardless of thermal states, these findings suggest an absence of dCA directional sensitivity. Reduced directional sensitivity metrics during hyperthermia may indicate more efficient dCA at very low frequency.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143730165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}