Journal of applied physiology最新文献

{"title":"Cardiac responses to environmental heat exposure in young and older adults.","authors":"Josh Foster, Zachary J McKenna, Satyam Sarma, James P MacNamara, Luke N Belval, Joseph C Watso, Whitley C Atkins, Caitlin P Jarrard, Craig G Crandall","doi":"10.1152/japplphysiol.00917.2024","DOIUrl":"10.1152/japplphysiol.00917.2024","url":null,"abstract":"<p><p>Older individuals are at a greater risk for adverse cardiovascular events during extreme heat exposure. However, detailed characterization of their cardiac responses to environmental heat exposure is lacking. In 20 young (18-39 yr) and 20 older (>65 yr) adults (50% male in both groups), we document the echocardiography-assessed left ventricular responses to a very hot and dry [DRY, 47°C and 15% relative humidity (RH)] and hot humid (HUMID, 41°C and 40% RH) 3-h heat exposure, with intermittent bouts of light physical activity throughout. In both climates and in both age groups, heat stress <i>1</i>) increased cardiac output by ∼0.7 ± 0.8 L/min, <i>2</i>) decreased stroke volume by ∼7 ± 10 mL, and <i>3</i>) augmented diastolic function through increased atrial contribution to filling by 5 ± 5%. In the DRY climate, mitral annular systolic velocity (s') increased to a greater extent in older subjects (Δ 3.3 ± 2.1 vs. Δ 1.5 ± 1.5 cm/s, <i>P</i> = 0.002), with less difference in HUMID (Δ 2.1 ± 1.3 cm/s vs. 1.4 ± 1.3 cm/s, <i>P</i> = 0.096). Despite these adjustments, systolic blood pressure was only maintained in the younger group and fell consistently in older individuals (0 ± 8 mmHg) in DRY (Δ -11 ± 14 mmHg vs. 1 ± 8 mmHg, <i>P</i> = 0.001) and HUMID (Δ -9 ± 15 mmHg vs. -1 ± 8 mmHg, <i>P</i> = 0.030). In summary, older adults rely on a greater augmentation of systolic function during extreme heat exposure, but the magnitude depends on the heat stress severity.<b>NEW & NOTEWORTHY</b> Comparing healthy young and older adults, we assessed left ventricular cardiac function (using echocardiography) during two separate 3-h extreme heat exposures in a very hot and dry or hot humid climate type. Although the augmentation of diastolic function and cardiac output were similar between age groups, older adults showed a greater increase in mitral annular systolic velocity with heat exposure, indicating a stronger reliance on systolic mechanisms to maintain stroke volume.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"616-627"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12362721/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144731086","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elevated LDL-C induces T-cell metabolic dysfunction and increases inflammation and oxidative stress in midlife adults.","authors":"Theodore M DeConne, Arit Ghosh, Catherine Awad, Ibra S Fancher, David G Edwards, Daniel W Trott, Christopher R Martens","doi":"10.1152/japplphysiol.00226.2025","DOIUrl":"10.1152/japplphysiol.00226.2025","url":null,"abstract":"<p><p>T-cells may contribute to chronic, low-grade, sustained inflammation and oxidative stress commonly observed with aging and chronic disease. T-cell metabolic alterations impact T-cell differentiation, inflammation, and oxidative stress in animal models. Low-density lipoprotein cholesterol (LDL-C) has been identified as a novel antigen that activates T-cells via a canonical pathway. However, in humans, little is known about the direct effect of LDL-C on T-cells. Endogenous LDL-C concentration peaks during midlife in humans and may contribute to midlife chronic disease risk by inducing T-cell dysfunction. Thus, this study investigated the effects of exogenous LDL-C exposure on CD4⁺ and CD8⁺ T-cells from midlife adults. Compared with a physiologically \"low\" LDL-C concentration, we hypothesized that exposure to \"borderline high\" LDL-C would induce activation, alter metabolism, and increase mitochondrial reactive oxygen species and inflammatory cytokine production in T-cells from midlife adults. T-cell metabolism was assessed using extracellular flux analysis, and all other outcomes were assessed using flow cytometry. Our findings indicate that exposure to a borderline high concentration of LDL-C induced CD4⁺ and CD8⁺ T-cell activation, impaired mitochondrial respiration, and increased glycolytic metabolism. Further, we observed exogenous LDL-C exposure induced T-cell differentiation toward activated effector memory and effector memory re-expressing CD45RA subpopulations and increased inflammatory cytokine and mitochondrial reactive oxygen species production. These data suggest that borderline high LDL-C induces T-cell dysfunction that may increase the risk for age-related diseases. Future observational and clinical research should investigate the effects of endogenous LDL-C and other blood lipids on in vivo T-cell function and the implications for disease risk.<b>NEW & NOTEWORTHY</b> We evaluated the effect of low-density lipoprotein cholesterol (LDL-C) exposure on human T-cells isolated from midlife adults. T-cells were exposed to physiologically low and borderline high concentrations of LDL-C. We observed that high LDL-C exposure increased intracellular lipids, activated T-cells, and induced metabolic dysfunction. Additionally, high LDL-C exposure induced T-cell differentiation, a senescent-like phenotype, and induced inflammatory cytokine and mitochondrial reactive oxygen species production.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"731-746"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144784298","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":"Vascular function in women with heart failure with preserved ejection fraction: a mismatch beyond diastole.","authors":"Nicholas A Carlini, D Walter Wray, Kerrie L Moreau, Kanokwan Bunsawat","doi":"10.1152/japplphysiol.00467.2025","DOIUrl":"10.1152/japplphysiol.00467.2025","url":null,"abstract":"<p><p>Heart failure with preserved ejection fraction (HFpEF) is a complex multiorgan clinical syndrome representing ∼50% of all heart failure-related cases nationwide. HFpEF is more prevalent in women, yet both men and women with HFpEF present with distinct clinical phenotypes and prognosis that may be attributable, in part, to sex differences in anatomical, physiological, and/or hormonal characteristics. Of particular interest is the role of sex hormones, namely, estrogen, as a contributing factor to sex differences in vascular health in patients with HFpEF. This mini review provides a summary of recent evidence regarding sex differences in coronary microvascular function, peripheral vascular function, and central arterial stiffness in patients with HFpEF. Focus will also be given to potential mechanisms by which age-related loss of estrogen may alter these aspects of physiology in women with HFpEF and provide potential future directions related to implications for women's health in adults with HFpEF.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"747-758"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12419534/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144955469","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cardiovascular challenges of aging in a hotter environment: a narrative review.","authors":"Rachel M Cottle, S Tony Wolf, W Larry Kenney","doi":"10.1152/japplphysiol.00323.2025","DOIUrl":"10.1152/japplphysiol.00323.2025","url":null,"abstract":"<p><p>The increase in duration, severity, and frequency of extreme heat will have a profound detrimental impact on human health, as extreme heat is the deadliest weather-related event around the world. At the same time, the population of older (>65 yr) adults is rapidly expanding. The exaggerated heat, coupled with an aging population, increases the number of people at risk during environmental extremes. During heat waves, cardiovascular events and complications secondary to elevated core temperatures are the leading cause of increased morbidity and mortality among older adults. Seminal work demonstrates an impaired cardiovascular response to elevated core and skin temperatures in older adults, resulting in an attenuated capacity to lose heat coupled with increased cardiac strain, in support of the epidemiological data. Here, we review the impact of heat stress on the aged cardiovascular system and highlight the question: \"In what specific environments does an increased cardiovascular strain begin to occur in older adults?\"</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"832-838"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12481594/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145000682","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Muscle-specific atrophy of the lower limb musculature in response to simulated microgravity exposure in women.","authors":"Kaitlyn R Rogers, Gilhyeon Yoon, Caroline S Vincenty, Scott W Trappe, Todd A Trappe","doi":"10.1152/japplphysiol.00483.2025","DOIUrl":"10.1152/japplphysiol.00483.2025","url":null,"abstract":"<p><p>Despite the increased involvement of women in spaceflight missions, the efforts to understand changes in skeletal muscle health in women with microgravity exposure have been limited. The goal of the current investigation was to expand the limited knowledge on skeletal muscle atrophy responses to microgravity in women. Eight women (34 ± 4 yr) underwent 60 days of simulated microgravity (6° head-down tilt bedrest), and changes in MRI-determined skeletal muscle volume of 17 lower limb muscles were determined after 1 and 2 mo. Muscle volume decreased (<i>P</i> < 0.05) in all 17 muscles of the women after 1 and 2 mo of simulated microgravity. There was nearly a threefold difference between the least (rectus femoris: -10%) and most (soleus: -27%, lateral gastrocnemius: -28%, and medial gastrocnemius: -29%) affected muscles. Muscle-specific atrophy was also evident within muscle groups of the knee extensors (rectus femoris: -10%; vastii: -22%, <i>P</i> < 0.05) and knee flexors (semimembranosus and biceps femoris long head: -20%; gracilis, biceps femoris short head, semitendinosus: -12%, <i>P</i> < 0.05). These findings in women were also compared with data from men (33 ± 7 yr) who previously underwent similar MRI volume determinations of the same 17 muscles after 1 and 2 mo of simulated microgravity exposure. Compared with men, women experienced more pronounced atrophy in 16 of the 17 muscles (<i>P</i> < 0.05), and at least double the atrophy in seven of these muscles. The current findings extend our understanding of the magnitude of muscle- and sex-specific skeletal muscle responses to long-duration microgravity, which should be considered for spaceflight exercise countermeasures program evolution.<b>NEW & NOTEWORTHY</b> This study expands the limited amount of data on skeletal muscle changes with long-duration microgravity exposure in women. Microgravity-induced skeletal muscle atrophy of the lower limbs occurs in a muscle- and sex-specific fashion. This new information should be considered in exercise countermeasures development for astronauts on long-duration spaceflight missions.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"759-765"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144882883","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":"Infant pigs demonstrate motor adaptation across multiple physiologic functions during feeding in response to dynamic changes in milk flow rate.","authors":"Maressa E Kennedy, Elska B Kaczmarek, Ani E Smith, Emily C Volpe, Dylan J Anderson, Skyler M Wallace, Hannah E Shideler, Harlow I Smith, Thomas H Stroud, Christopher J Mayerl","doi":"10.1152/japplphysiol.00552.2025","DOIUrl":"10.1152/japplphysiol.00552.2025","url":null,"abstract":"<p><p>Safe and effective infant feeding requires precise coordination of sucking, swallowing, and breathing, yet disruptions in this coordination affect a significant number of infants. Altering sensory input, such as bottle nipple flow rate, is used to address poor coordination in infants. However, prior studies often compare different nipples used across different feeds, which introduces confounding variables and limits insight into neuromotor responses. To address this, we used infant pigs as a validated animal model to assess real-time neuromotor responses to dynamic changes in flow rate within a single feeding session using a custom, computer-controlled nipple. We collected high-speed biplanar videofluoroscopy, intraoral pressure, and respiratory data to evaluate kinematics, physiology, and coordination patterns. We found that while sucking and breathing rates remained stable, higher flow rates elicited greater tongue, hyoid, and thyroid translations, larger bolus sizes, and lower intraoral pressures. Notably, swallow rate increased, resulting in a shift to suck-swallow-breathe coordination, with swallows occurring earlier in the suck cycle and more frequently per breath. These changes suggest that infants rapidly adapt their motor output to changing sensory conditions. This study demonstrates that real-time flow variation significantly impacts feeding mechanics and coordination, highlighting the potential for sensory-based interventions rooted in motor learning and neuromotor rehabilitation principles. Understanding how infants dynamically adjust to sensory changes offers critical insights into feeding development and provides a framework for developing more effective interventions for infants with feeding disorders.<b>NEW & NOTEWORTHY</b> We developed a novel method to dynamically alter milk flow rate mid-feed in infant pigs to assess real-time neurophysiological responses. Unlike prior studies, our approach avoids confounding variables that would result from providing nipples of different flow rates during separate feeding sessions and reveals how motor output adapts to sensory input in real time, offering new insight into the neuromotor control underlying infant feeding.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"719-730"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12424271/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144882869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The contralateral repeated bout effect is not caused by adaptations in skeletal muscle.","authors":"Nao Tokuda, Koichi Himori, Yuki Ashida, Azuma Naito, Nao Yamauchi, Ayaka Niibori, Takashi Yamada","doi":"10.1152/japplphysiol.00495.2025","DOIUrl":"10.1152/japplphysiol.00495.2025","url":null,"abstract":"<p><p>The repeated bout effect (RBE) refers to the phenomenon whereby the recovery of maximal voluntary contraction, a parameter considered to reflect muscle damage, is enhanced in a subsequent bout of exercise following an initial damaging bout. To investigate whether the ipsilateral RBE (IL-RBE) and contralateral RBE (CL-RBE) involve peripheral skeletal muscle adaptations, we assessed strength recovery following damaging eccentric contractions (ECCs) using supramaximal electrical stimulation to recruit all muscle fibers. Male Wistar rats were randomly assigned to one of the four groups: nondamaging control (CNT), damage (DMG), IL-RBE, and CL-RBE. The plantar flexors were exposed to 100 repeated ECCs with supramaximal electrical stimulation: once in the DMG group and twice at 2-wk intervals in the IL-RBE and CL-RBE groups. In the DMG group, the maximum isometric torque (MIT) at a stimulation frequency of 100 Hz remained 30% lower than the initial value even 4 days after ECCs. This was accompanied by an increased number of Evans Blue Dye-positive fibers, activation of calpain 1, and decreased expression of excitation-contraction coupling proteins. In the IL-RBE group, membrane damage and protein degradation were almost completely prevented and MIT returned to baseline by 1 day after ECCs. Conversely, the CL-RBE group did not show these beneficial effects observed in the IL-RBE group. These findings suggest that protective peripheral muscle adaptations contribute to the IL-RBE, but similar adaptations are unlikely to play a role in the CL-RBE.<b>NEW & NOTEWORTHY</b> When damaging contractions are repeatedly applied to a muscle, voluntary strength recovery is promoted not only in the exercised muscle but also in the contralateral muscle. However, the mechanism underlying this contralateral repeated bout effect (CL-RBE) remains unclear. Our findings show that strength recovery, assessed by electrical stimulation, was promoted only in the exercised muscle, not the contralateral side, suggesting the absence of adaptations within peripheral skeletal muscle in CL-RBE.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"605-615"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144784299","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":"Regional dynamic cerebral autoregulation in acute poikilocapnic hypoxia.","authors":"Alexander T Friend, Michiel Ewalts, Masahiro Horiuchi, Gabriella M K Rossetti, Aamer Sandoo, Jamie H Macdonald, Samuel J Oliver","doi":"10.1152/japplphysiol.00376.2024","DOIUrl":"10.1152/japplphysiol.00376.2024","url":null,"abstract":"<p><p>Dynamic cerebral autoregulation (dCA) of the posterior circulation has been shown to be more pressure-passive compared with the anterior circulation, possibly due to a lower basal vascular tone. In hypoxia, vascular tone and dCA are typically reduced; however, evidence using volumetric assessment is limited to the anterior circulation. We hypothesized that the posterior circulation would have an exacerbated reduction in dCA than the anterior circulation in acute hypoxia. Twenty participants (14 males, 6 females) were exposed to 120 min of normoxia and acute poikilocapnic hypoxia (12.5% fraction of inspired oxygen). dCA was assessed as the rate of regulation (RoR) of vascular conductance to thigh cuff-induced acute hypotension, in the internal carotid artery (ICA) and vertebral artery (VA) by duplex ultrasound, and the middle cerebral artery (MCA) and posterior cerebral artery (PCA) by transcranial Doppler ultrasound, representing anterior (ICA and MCA) and posterior (VA and PCA) circulations. Linear mixed model analysis revealed that ICA RoR [-0.06 (0.22) s^-1, <i>P</i> = 0.279] and VA RoR [-0.05 (0.21) s^-1, <i>P</i> = 0.343] were comparable in normoxia and hypoxia. MCA RoR (<i>P</i> = 0.995) and PCA RoR (<i>P</i> = 0.895) were also comparable between conditions. In males only, hypoxia reduced VA RoR [-0.15 (0.19) s^-1, <i>P</i> = 0.012], but not ICA RoR [-0.07 (0.21) s^-1, <i>P</i> = 0.264]. In addition, hypoxia induced vasodilation of the ICA [+0.30 (0.32) mm, <i>P</i> = 0.009] but not the VA [+0.08 (0.33) mm, <i>P</i> = 0.398] in males. In conclusion, volumetric dCA of the cerebral conduit arteries to acute hypotension in hypoxia was regionally different in males and may not be influenced by changes in vascular tone.<b>NEW & NOTEWORTHY</b> We demonstrate that hypoxia causes regional dynamic cerebral autoregulation (dCA) in males, where volumetric dCA was reduced in the vertebral artery but not the internal carotid artery. In addition, immediately before the dCA assessment, the vertebral artery diameter was unchanged, whereas the internal carotid artery diameter was increased. In combination, these findings challenge the prevailing view that reductions in dCA in hypoxia are due to a reduction in vascular tone.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"709-718"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144821534","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":"In vivo characterization of Achilles subtendon function and morphology within the tendon cross section and along the free tendon.","authors":"Kathryn S Strand, Todd J Hullfish, Josh R Baxter","doi":"10.1152/japplphysiol.00479.2025","DOIUrl":"10.1152/japplphysiol.00479.2025","url":null,"abstract":"<p><p>The Achilles tendon is composed of three distinct fascicle bundles, or subtendons, each originating from the head of one of the three triceps surae muscles. In a healthy tendon, these subtendons slide relative to each other during muscle contractions. This subtendon sliding is reduced in older adults and individuals who suffer from an Achilles tendon injury. However, subtendon sliding is challenging to quantify in low-load scenarios that are critical for monitoring subtendon biomechanics in patients with mechanically compromised tendons, such as following an Achilles tendon rupture and repair. The purpose of this study was to develop a reliable method to characterize subtendon behavior in vivo using combined transverse plane ultrasound imaging and neuromuscular electrical stimulation of individual gastrocnemii. We used a Kanade-Lucas-Tomasi point tracking algorithm to quantify tendon displacement during isolated muscle stimulations. Next, we applied <i>k</i>-means clustering to characterize heterogeneous subtendon behavior within the tendon cross section. The tendon cross section displayed differential displacement patterns depending on the stimulated muscle (<i>P</i> < 0.0001), and these displacements differed along the tendon length during lateral gastrocnemius stimulations (<i>P</i> = 0.004). These results reflect possible differences in load-sharing between adjacent subtendons and differing muscle-tendon dynamics among the triceps surae muscles. Finally, this method confirmed no bilateral differences in subtendon behavior and demonstrated high intersession reliability (intraclass correlation > 0.74). Overall, this study furthers our understanding of the differential muscle-tendon dynamics of individual Achilles subtendons within the tendon cross section and along the tendon length.<b>NEW & NOTEWORTHY</b> Achilles subtendon function and morphology are challenging to characterize in vivo. This study used transverse plane ultrasound imaging and neuromuscular electrical stimulation to characterize the behavior of individual subtendons both within the tendon cross section and along the free tendon. It is the first study to demonstrate functional behavior of the Achilles subtendons using these combined tools. In addition, the lack of bilateral differences in healthy individuals presents this tool's potential to quantify altered subtendon function post injury.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"812-822"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12427142/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144873353","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterization of the effects of sex, speed, and incline on metabolic rate during partial gravity ambulation.","authors":"Logan Kluis, Callie Wynn, Deanna Kennedy, Ana Diaz-Artiles","doi":"10.1152/japplphysiol.00627.2024","DOIUrl":"10.1152/japplphysiol.00627.2024","url":null,"abstract":"<p><p>With the Artemis missions returning humans to the Moon, characterizing ambulation and metabolic rate in partial gravity environments is critical for spacesuit design, mission planning, and architecture. To date, no study has assessed the combined effects of sex, speed, and incline on metabolic rate across a broad range of partial gravity levels. In this study, 12 subjects ambulated on a treadmill under 16 conditions combining speeds (3 mph and 4 mph), gravity levels (0.25 g, 0.5 g, 0.75 g, and 1 g), and inclines (0% and 10%). A novel body weight support system, the Portable Offloading for Walking, Exercise, and Running (POWER) device, was used to simulate partial gravity. Metabolic rate was measured with a COSMED K5 system. Dose-response curves were constructed using a generalized linear mixed-effects model, revealing significant increases in metabolic rate with speed (<i>P</i> < 0.001), gravity level (<i>P</i> < 0.001), incline (<i>P</i> < 0.001), and significant interactions between speed and gravity level (<i>P</i> = 0.022) and between gravity level and incline (<i>P</i> < 0.001). Each partial gravity level differed significantly from the 1-g baseline in all ambulation conditions. Sex differences were statistically significant only at 4 mph, 10% incline, and 1 g (<i>P</i> = 0.002), the most challenging condition. These results advance understanding of energy expenditure during ambulation in reduced gravity and provide valuable data to support astronaut training and spacesuit development for future planetary exploration.<b>NEW & NOTEWORTHY</b> We characterized the effects of sex, speed, and incline on metabolic rate in 12 subjects (6 females) across partial gravity levels (0.25-1 g). Model results showed significant increases in metabolic rate with speed, gravity, incline, and interactions between speed and gravity, and gravity and incline. Sex differences appeared only in the most demanding condition (4 mph, 10% incline, 1 g). This framework quantifies key variables of partial gravity ambulation relevant to planetary exploration.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"787-796"},"PeriodicalIF":3.3,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144955348","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}