Journal of applied physiology最新文献

{"title":"Acute contractile activity induces the activation of the mitochondrial integrated stress response and the transcription factor ATF4.","authors":"Victoria C Sanfrancesco, David A Hood","doi":"10.1152/japplphysiol.00307.2024","DOIUrl":"10.1152/japplphysiol.00307.2024","url":null,"abstract":"<p><p>Skeletal muscle relies on mitochondria to produce energy and support its metabolic flexibility. The function of the mitochondrial pool is regulated by quality control (MQC) processes. The integrated stress response (ISR), a MQC pathway, is activated in response to various cellular stressors. The transcription factor ATF4, the main effector of the ISR, ameliorates cellular stress by upregulating protective genes, such as CHOP and ATF5. Recent literature has shown that the ISR is activated upon mitochondrial stress; however, whether this includes acute exercise-induced stress is poorly defined. To investigate this, a mouse in situ hindlimb protocol was utilized to acutely stimulate muscles at 0.25, 0.5, and 1 tetanic contraction/s for 9 min, followed by a 1-h recovery period. CAMKIIα and JNK2 were robustly activated sixfold immediately after the protocol. ISR activation, denoted as the ratio of phosphorylated to total eIF2α protein levels, was also elevated after recovery. Downstream, contractile activity induced an increase in the nuclear localization of ATF4. Robust twofold increases in the mRNA expression of ATF4 and CHOP were also observed after the recovery period. Changes in ATF4 mRNA were independent of transcriptional activation, as assessed with an ATF4 promoter-reporter plasmid. Instead, mRNA decay assays revealed an increase in ATF4 mRNA stability post contractile activity, as a result of enhanced stabilization by the RNA binding protein HuR. Thus, acute contractile activity is sufficient to induce mitochondrial stress and activate the ISR, corresponding to the induction of ATF4 with potential consequences for mitochondrial phenotype adaptations in response to repeated exercise.<b>NEW & NOTEWORTHY</b> The integrated stress response (ISR) is a mitohormetic stress response critical for the maintenance of mitochondrial homeostasis. However, its role in mediating mitochondrial adaptations with exercise-induced stress is not well established. This research demonstrates that acute contractile activity can elicit mitochondrial stress and activate the ISR to maintain mitochondrial homeostasis via the enhancement of the functioning of ATF4, illustrating an early response to exercise that promotes mitochondrial health and adaptations.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"857-871"},"PeriodicalIF":3.3,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142466231","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":"Transfer of balance performance depends on the specificity of balance training.","authors":"Alex Rizzato, Sara Faggian, Antonio Paoli, Giuseppe Marcolin","doi":"10.1152/japplphysiol.00695.2024","DOIUrl":"10.1152/japplphysiol.00695.2024","url":null,"abstract":"<p><p>This study investigated whether a 4-wk training on an easy-level (EL) unstable board could induce a transfer of balance performance in a hard-level (HL) unstable board and in an unexpected perturbation-based task. Nonlinear 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, <i>N</i> = 17) group and a control (CTRL, <i>N</i> = 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 (<i>P</i> < 0.001), FiB (<i>P</i> < 0.05), and GB (<i>P</i> < 0.01) on EL and HL boards. In the perturbation-based task, the earliest CoP response consequent to perturbation improved after training (<i>P</i> < 0.01). SampEn and SDA revealed increased automaticity (<i>P</i> < 0.05) and efficiency (<i>P</i> < 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.<b>NEW & NOTEWORTHY</b> Our study showed that improvement in balance performance is task-specific, with transfer depending on functional similarities between the trained and the untrained tasks. Computational nonlinear methods highlighted that training could extend the improved efficiency and automaticity of balance control of the trained task to a similar untrained task. Therefore, the benefits of balance training may not generalize to all balance challenges, highlighting the importance of targeted testing and training approaches.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"761-773"},"PeriodicalIF":3.3,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143491552","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":"Effect of condensed heat acclimation on thermophysiological adaptations, hypoxic cross-tolerance, exercise performance, and deacclimation.","authors":"Charlotte E Stevens, Joseph T Costello, Michael J Tipton, Ella F Walker, Alex A M Gould, John S Young, Ben J Lee, Thomas B Williams, Fiona A Myers, Jo Corbett","doi":"10.1152/japplphysiol.00775.2024","DOIUrl":"10.1152/japplphysiol.00775.2024","url":null,"abstract":"<p><p>Short duration heat acclimation (HA) (≤5 daily heat exposures) elicits incomplete adaptation compared with longer interventions, possibly due to the lower accumulated thermal \"dose.\" It is unknown if matching thermal \"dose\" over a shorter timescale elicits comparable adaptation to a longer intervention. Using a parallel-groups design, we compared: <i>1)</i> \"condensed\" HA (CHA; <i>n</i> = 17 males) consisting of 4 × 75 min·day^-1 heat exposures [target rectal temperature (<i>T</i>_rec) <i>=</i> 38.5 °C] for two consecutive days, with <i>2)</i> \"traditional\" HA (THA; <i>n</i> = 15 males) consisting of 1 × 75 min·day^-1 heat exposure (target <i>T</i>_rec = 38.5°C) for eight consecutive days. Physiological responses to exercise heat stress, hypoxia, and normoxic exercise performance were evaluated pre- and postintervention. Thermal (<i>T</i>_rec over final 45 min: CHA = 38.45 ± 0.17°C, THA = 38.53 ± 0.13°C, <i>P</i> = 0.126) and cardiovascular strain were not different during interventions, indicating similar thermal \"dose,\" although CHA had lower sweating rate, higher starting <i>T</i>_rec, and greater inflammation, gastrointestinal permeability, and renal stress (<i>P</i> < 0.05). However, CHA elicited an array of thermophysiological adaptations that did not differ from THA [reduced indices of peak thermal (e.g., Δ peak <i>T</i>_rec CHA = -0.28 ± 0.26°C, THA = -0.36 ± 0.17°C, <i>P</i> = 0.303) and cardiovascular strain, inflammation, and renal stress; blood and plasma volume expansion; improved perceptual indices], although improvements in resting thermal strain (e.g., Δ resting <i>T</i>_rec CHA = -0.14 ± 0.21°C, THA = -0.35 ± 0.29°C, <i>P</i> = 0.027) and sweating rate were less with CHA. Both interventions improved aspects of hypoxic tolerance, but effects on temperate normoxic exercise indices were limited. The diminished thermal strain was well-maintained over a 22-day decay period. In conclusion, CHA could represent a viable acclimation option for time-restricted young healthy males preparing for a hot, and possibly high-altitude, environment.<b>NEW & NOTEWORTHY</b> This study has shown, for the first time, that a novel condensed heat acclimation program can elicit an array of thermophysiological adaptations, many of which do not differ from traditional heat acclimation. These findings suggest that accumulated thermal \"dose\" is an important factor contributing to the adaptive responses to heat stress and that condensed heat acclimation may represent a viable option for time-restricted individuals (e.g., military personnel, firefighters, and athletes) preparing to enter a hot environment.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"634-650"},"PeriodicalIF":3.3,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143006000","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":"Manuscript writing for dummies: like sands through the hourglass.","authors":"W Larry Kenney","doi":"10.1152/japplphysiol.00842.2024","DOIUrl":"10.1152/japplphysiol.00842.2024","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"718-719"},"PeriodicalIF":3.3,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143006011","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":"Low-intensity activity breaks combined with alternate day interval training mitigate cardiovascular effects of sedentary behavior.","authors":"Courtney R Chang, Angelo Sabag, Monique E Francois","doi":"10.1152/japplphysiol.00484.2024","DOIUrl":"10.1152/japplphysiol.00484.2024","url":null,"abstract":"<p><p>This study aimed to determine whether interrupting prolonged sitting with brief bouts of light-intensity activity (ISIT), undertaking structured high-intensity interval training (HIIT), or the combination of both interventions would elicit greater cardiometabolic benefits. Seventeen healthy adults (22-50 yr) were recruited to undertake three 2-wk interventions in a random order: <i>1</i>) HIIT (6 HIIT sessions + <5,000 steps following the session and on the next day), <i>2</i>) ISIT (2.5-min light-intensity walking every hour for 12 h/day on weekdays), and <i>3</i>) HIIT + ISIT. Participants underwent a 6-day lead-in phase prior to each condition (<i>days 1-3</i>: normal activity, <i>days 4-6</i> sedentary: <5,000 steps/day). Pre- and postassessments included glycemic control (2-h postprandial glucose), endothelial function via flow-mediated dilation (FMD), cardiorespiratory fitness, and body composition. Changes in primary and secondary outcomes were assessed via repeated measures ANOVA. Eleven participants completed all conditions (8 female, 33 ± 5 yr, 23 ± 4 kg/m², habitual activity 7,156 ± 2,272 steps/day). FMD significantly improved following HIIT + ISIT when compared with ISIT (+1.04 ± 1.20%, <i>P</i> = 0.02), but there were no differences when ISIT was directly compared with HIIT. Cardiorespiratory fitness improved significantly following HIIT + ISIT when compared with ISIT (+1.88 ± 2.03 mL/kg/min, <i>P</i> = 0.01), but there were no differences when ISIT alone was compared with HIIT. There were no significant differences between groups for outcomes related to glucose control or body composition. HIIT + ISIT elicits greater improvements in cardiovascular outcomes when compared with ISIT but not HIIT. The benefits of structured exercise, such as HIIT, may go beyond those achieved by limiting sedentary behavior alone.<b>NEW & NOTEWORTHY</b> Although the adverse health effects of sedentary behavior are well-recognized, effective strategies for interrupting such behavior remain unclear. This study demonstrates that combining light-intensity activity breaks throughout the day with structured high-intensity exercise every other day can mitigate some of the cardiovascular consequences associated with prolonged sedentary periods in healthy young adults. Furthermore, our findings also suggest that merely incorporating regular breaks of light-intensity activity may not suffice. These results underscore the importance of regular exercise for cardiovascular health amid sedentary lifestyles.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"799-809"},"PeriodicalIF":3.3,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143065882","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":"Chain of survival for a severe exertional heat stroke casualty.","authors":"David W DeGroot, Aaron C Litchfield, Cora A Blodgett, Blair B Rhodehouse, Kevin P Hudson","doi":"10.1152/japplphysiol.01006.2024","DOIUrl":"10.1152/japplphysiol.01006.2024","url":null,"abstract":"<p><p>Exertional heat stroke is characterized by profound central nervous system dysfunction and core (rectal) temperature typically >40°C. With prompt recognition and response, the probability of survival is excellent; however, there are limited cases with T_c >43.3°C associated with good outcomes. A 23-yr-old male soldier was conducting land navigation training and was found unresponsive by a nonmedical cadre. Emergency medical services personnel obtained a rectal temperature of 44.3°C, which is the highest-ever body core temperature recorded in a patient with exertional heat stroke who survived without significant sequelae. In this case, we report numerous key decisions that contributed to the good outcome. Among those were the use of a GPS-enabled tracking device that enabled the location of the patient on the land navigation course, and the rapid recognition and response by nonmedical personnel at the point of injury. In addition, prioritizing airway, breathing, and circulation over the choice of cooling modality was important in the setting of a patient in acute respiratory distress. Finally, the careful selection of pharmaceutical agents in the Emergency Department minimized additional stress, primarily on the liver and kidneys, which were already significantly stressed. After transfer to a higher level of care due to developing heat-induced disseminated intravascular coagulation and liver failure, the patient was transferred to inpatient rehabilitation 3 wk postinjury. He recovered by 14 mo postinjury, has been medically cleared to return to active duty without limitations, and is continuing his military service.<b>NEW & NOTEWORTHY</b> We present the details surrounding an exertional heat stroke casualty who had the highest-ever body core temperature, 44.3°C, and survived without significant sequelae. Critical decisions that contributed to this outcome, from the point of injury through the first 24 h, are detailed. Treatment considerations included rapid cooling, maintaining the patient's airway, and hemodynamic stability, and minimizing further physiological strain due to the choice of pharmaceutical agents.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"699-705"},"PeriodicalIF":3.3,"publicationDate":"2025-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143391006","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 pharyngo-esophageal 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":"https://doi.org/10.1152/japplphysiol.00516.2024","url":null,"abstract":"<p><strong>Background: </strong>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.</p><p><strong>Methods: </strong>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.</p><p><strong>Key results: </strong>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.</p><p><strong>Conclusions: </strong>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.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-02-19","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":"Polycystic ovary syndrome potentiates blood pressure and vascular responses to the cold pressor test.","authors":"Danielle E Berbrier, Yasmine Coovadia, Divine Malenda, Charlotte W Usselman","doi":"10.1152/japplphysiol.00697.2024","DOIUrl":"10.1152/japplphysiol.00697.2024","url":null,"abstract":"<p><p>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 [<i>n</i> = 10; age: 22 ± 3 yr, body mass index (BMI): 23.9 ± 3 kg/m²] and healthy controls (CTRL; <i>n</i> = 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; <i>P</i> = 0.25), nor was systolic BP (SBP; 109 ± 9 vs. 106 ± 7 mmHg; <i>P</i> = 0.42). Across the CPT, MAP and SBP were higher in PCOS than CTRL (main effects of group, both <i>P</i> < 0.05). Peak CPT induced increases in MAP (+12 ± 5 vs. +7 ± 4 mmHg; <i>P</i> = 0.04) and corresponding changes in SBP (+13 ± 7 vs. +7 ± 3 mmHg; <i>P</i> = 0.04) and FVR (+0.17 ± 0.08 vs. +0.02 ± 0.13 mmHg/mL/min; <i>P</i> = 0.01) were larger in PCOS than CTRL. Within-group regressions indicated that FAI was positively associated with relative increases in peak MAP (<i>R</i>² = 0.72, <i>P</i> < 0.01) and corresponding changes in FVR (<i>R</i>² = 0.83, <i>P</i> < 0.01) in females with PCOS but not in CTRL (MAP: <i>R</i>² = 0.03, <i>P</i> = 0.62; FVR: <i>R</i>² = 0.12, <i>P</i> = 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.<b>NEW & NOTEWORTHY</b> 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.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"404-414"},"PeriodicalIF":3.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142807178","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":"Shear wave elastography reveals passive and active mechanics of triceps surae muscles in vivo: from shear modulus-ankle angle to stress-strain characteristics.","authors":"Manuela Zimmer, Louis Fabian Straub, Filiz Ateş","doi":"10.1152/japplphysiol.00459.2024","DOIUrl":"10.1152/japplphysiol.00459.2024","url":null,"abstract":"<p><p>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 (<i>P</i> < 0.001 for all). At 15° DF, the passive shear modulus of the SOL was 76% lower than that of the GM (<i>P</i> < 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, <i>P</i> = 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 (<i>P</i> < 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.<b>NEW & NOTEWORTHY</b> 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.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"577-591"},"PeriodicalIF":3.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143046731","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":"A case report of the female world record holder from 1,500 m to the marathon in the 75+ age category.","authors":"Bas Van Hooren, Zoi Balamouti, Michele Zanini","doi":"10.1152/japplphysiol.00974.2024","DOIUrl":"10.1152/japplphysiol.00974.2024","url":null,"abstract":"<p><p>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.<b>NEW & NOTEWORTHY</b> 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.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"603-611"},"PeriodicalIF":3.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143039000","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}