Journal of applied physiology最新文献

{"title":"Sex differences in upper-body strength, lean mass, and bone density across the adult lifespan: insights into musculoskeletal aging and strength preservation.","authors":"William J Kraemer, Noor F Chaudhry, Jillian H Graham, Matthew J Stauder, James A Onate, Maren S Fragala, Jeff S Volek, Scott M Hayes","doi":"10.1152/japplphysiol.00544.2025","DOIUrl":"10.1152/japplphysiol.00544.2025","url":null,"abstract":"<p><p>Aging is associated with declines in upper-body strength, lean mass, and bone mineral density (BMD), yet sex-specific patterns of musculoskeletal aging remain unclear. This study examined the relationships between upper-body strength, lean mass, and arm BMD across the adult lifespan in male and female participants. Upper-body strength [free-weight bench press one-repetition maximum (1RM)], arm BMD [g/cm² via dual-energy X-ray absorptiometry (DXA)], and lean body mass (kg via DXA) were assessed in 174 adults (105 females, 69 males; mean age = 53.5 ± 17.4 yr). Hierarchical linear regression models examined associations between strength, BMD, and lean mass. Age was associated with lower bench press 1RM (β = -0.32, <i>P</i> < 0.001) and arm BMD (β = -0.27, <i>P</i> < 0.001) and was marginally significant with lean mass (β = -0.13, <i>P</i> = 0.08). Male participants exhibited a stronger negative association between age and strength (β = -0.19, <i>P</i> < 0.05). Female participants exhibited a marginally stronger negative association between age and arm BMD (β = 0.22, <i>P</i> = 0.061). Upper-body strength was positively associated with arm BMD (β = 0.34, <i>P</i> < 0.001), and the strength of this relationship increased with age (β = 0.11, <i>P</i> < 0.05) and was stronger in female participants (β = -0.56, <i>P</i> < 0.001). Upper-body lean mass was associated with strength (β = 0.62, <i>P</i> < 0.001) and BMD (β = 0.43, <i>P</i> < 0.001), but the strength-mass association weakened with age (β = -0.15, <i>P</i> < 0.001) and was stronger in males (β = 0.39, <i>P</i> < 0.001). These findings highlight the sex-specific differences in musculoskeletal aging, emphasizing the importance of strength preservation, particularly in female participants, for mitigating bone loss and osteoporosis risk.<b>NEW & NOTEWORTHY</b> This study reveals that upper-body strength declines more rapidly in males than females with age, whereas trending results suggest that bone mineral density may show a stronger decline in female participants. We found that upper-body strength and lean mass predict arm bone mineral density, and these relationships strengthen with age. These findings highlight the importance of maintaining upper-body strength for skeletal health, particularly in female participants, to mitigate osteoporosis risk.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1000-1009"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144955479","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":"Systemic and regional hemodynamic and (de)oxygenation responses across repeated breath-holds.","authors":"Antonis Elia, Mikael Gennser, Ola Eiken, Michail E Keramidas","doi":"10.1152/japplphysiol.00508.2025","DOIUrl":"10.1152/japplphysiol.00508.2025","url":null,"abstract":"<p><p>Regional cerebral and peripheral tissue (de)oxygenation responses to breath-holding (apnea) have predominantly been examined during isolated attempts. How these responses evolve across repeated efforts remains unclear, as previous studies either averaged data across bouts or focused solely on the final repetition. Accordingly, this study mapped the (de)oxygenation dynamics across successive breath-holds. Fifteen nondivers performed three repeated maximal static breath-holds, separated by 2-min rest intervals. Systemic cardiovascular variables, gas exchange, and cerebral frontal cortex and forearm muscle (de)oxygenation were assessed. At each breath-hold onset, a transient fall in cerebral oxygenated hemoglobin (cO₂Hb) and arterial pressure occurred, coinciding with tachycardia. A cardiovascular steady state followed, which persisted until the onset of involuntary breathing movements (IBMs). At IBM onset, cO₂Hb increased only during the first attempt (Δ8 ± 5 µM, <i>P</i> < 0.001), with smaller changes in subsequent breath-holds (apnea-2, Δ3 ± 6 µM; apnea-3, Δ3 ± 5 µM, <i>P</i> ≤ 0.014). Cerebral deoxygenated hemoglobin (cHHb) increased progressively across breath-holds (apnea-1, Δ3 ± 4 µM; apnea-2, Δ5 ± 4 µM; apnea-3, Δ7 ± 5 µM, <i>P</i> ≤ 0.001), whereas arterial pressure increases were of similar magnitude (<i>P</i> ≥ 0.064). Forearm (de)oxygenation profiles were comparable across attempts (<i>P</i> ≥ 0.085). In nine subjects, a triphasic peripheral response emerged: initial rapid decline in O₂Hb and rise in HHb at breath-holding onset, a transient intermediate plateau, and further divergence near IBM onset. Breath-holds were terminated at successively lower cO₂Hb, cerebral tissue oxygen index, and end-tidal oxygen, and higher cHHb (<i>P</i> ≤ 0.034), but similar end-tidal carbon dioxide levels (<i>P</i> > 0.912). The magnitude and timing of regional (de)oxygenation responses vary greatly over repeated breath-holds. Cerebral oxygenation showed a pronounced increase during the first attempt but progressively smaller changes across subsequent bouts. In contrast, peripheral tissue oxygenation demonstrated a time-dependent decline across successive attempts.<b>NEW & NOTEWORTHY</b> In nondivers, regional cerebral (de)oxygenation responses varied greatly across repeated breath-holds, whereas peripheral tissue responses were comparable. At IBM onset, cerebral oxygenation increased significantly during the first breath-hold but showed progressively smaller changes in subsequent attempts. In the periphery, a triphasic (de)oxygenation pattern was identified. Its final phase-characterized by a further oxygenation decline-coincided with increased cerebral oxygenation, supporting the concept of sympathetically mediated vasoconstriction and selective blood redistribution toward vital organs.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1019-1028"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145130928","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":"Reduced sleep irregularity does not impact peripheral vascular function before or following total sleep deprivation.","authors":"Gabriel Narvaez, Joaquin U Gonzales","doi":"10.1152/japplphysiol.00392.2025","DOIUrl":"10.1152/japplphysiol.00392.2025","url":null,"abstract":"<p><p>Consistent sleep patterns are associated with better cardiovascular health, whereas sleep loss is known to impair vascular function. This study examined whether consistent sleep could improve vascular function and mitigate the negative effect of 25-h total sleep deprivation. Sixteen healthy adults [10 females, 6 males; 34 ± 9 yr; body mass index (BMI): 25 ± 3 kg/m²] completed a randomized crossover study involving two 12-night sleep conditions, habitual sleep, and a consistent sleep/wake schedule that were separated by a 1- to 2-wk washout. Sleep was tracked via wrist actigraphy. Vascular assessments were conducted after each sleep condition at baseline and after one night of total sleep deprivation. Forearm reactive hyperemia (RH) was measured using venous occlusion plethysmography. Blood pressure responses to static handgrip exercise and postexercise ischemia (PEI) were assessed using finger photoplethysmography. Consistent sleep reduced sleep irregularity (sleep duration standard deviation) as compared with habitual sleep (0.96 ± 0.24 to 0.51 ± 0.24 h, <i>P</i> < 0.0001). Peak RH was unaltered by consistent sleep (main effect for condition: 27 ± 9 to 28 ± 5 mL/100 mL/min, <i>P</i> = 0.53) and sleep deprivation reduced peak RH (main effect for time: 28 ± 7 to 25 ± 8 mL/100 mL/min, <i>P</i> = 0.004) with no interaction present between sleep conditions (<i>P</i> = 0.69). Resting blood pressure and blood pressure reactivity to handgrip exercise and PEI were unchanged by consistent sleep or total sleep deprivation (<i>P</i> > 0.05). These results find that a short-term reduction in sleep irregularity does not improve resting peripheral vascular function or diminish the decrease in peripheral vasodilation following total sleep deprivation.<b>NEW & NOTEWORTHY</b> We examined the effect of a short-term reduction in sleep duration irregularity on peripheral vascular function. Maintaining a consistent sleep schedule reduced sleep duration standard deviation (SD) but had no effect on peak reactive hyperemia in the forearm or blood pressure reactivity to sympathetic stimuli. One night of total sleep deprivation decreased peak reactive hyperemia in the forearm, an impairment that was not mitigated by consistent sleep behavior.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"909-917"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145029986","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":"Concerns Regarding the Standard Deviation of Individual Responses for Assessing Treatment Response Heterogeneity.","authors":"Aaron R Caldwell, David B Allison, Andrew W Brown, Gary L Gadbury, Thirupathi Reddy Mokalla, R Drew Sayer, Andrew D Vigotsky","doi":"10.1152/japplphysiol.00485.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00485.2025","url":null,"abstract":"<p><p>The estimation of treatment response heterogeneity (TRH) is increasingly important as medicine moves toward personalized approaches. While various statistical methods have been proposed to quantify TRH in parallel-group trials, the standard deviation of individual responses (SD_IR) has gained prominence within physiological research. This method is intended to quantify individual response variation by comparing standard deviations of change scores between intervention and control groups. We acknowledge that SD_IR represents an improvement over many other flawed approaches that often involve responder counting. However, SD_IR has critical limitations: 1) it cannot overcome the fundamental problem of causal inference because the correlation between potential outcomes remains unidentifiable, 2) it is incorrectly predicated on the assumption that TRH is present only when treatment group variance exceeds control group variance, and 3) it is statistically inefficient. We present an alternative framework, which involves assessing heteroskedasticity and estimating the bounds for the standard deviation of treatment effects (SD_D). The presence of heteroskedasticity between treatment groups is a sufficient but not necessary condition for the presence of TRH. Further, SD_D makes fewer assumptions than SD_IR and, therefore, paints a more complete picture of potential TRH. Using data from a published exercise physiology study, we demonstrate how SD_D can better characterize uncertainty in TRH estimation. We recommend researchers probe TRH by assessing heteroskedasticity, providing bounds for SD_D, and estimating outcome distributions and probabilities while carefully crafting the theoretical rationale for the presence of TRH.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145199414","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":"Sex-specific survival but not tissue wasting in the KPP mouse model of pancreatic cancer-induced cachexia.","authors":"Natalia M Weinzierl, Jayarani Putri, Kathryn M Spitler, Erin E Talbert","doi":"10.1152/japplphysiol.00706.2025","DOIUrl":"10.1152/japplphysiol.00706.2025","url":null,"abstract":"<p><p>Cancer cachexia, a multifactorial condition resulting in muscle and adipose tissue wasting, reduces the quality of life of many people with cancer. Cachexia is highly prevalent in people with pancreatic ductal adenocarcinoma (PDAC), and many animal models of pancreatic cancer are used to understand mechanisms underlying cachexia. One such model is the <i>Kras_LSL-G12D</i>, <i>Ptf1a^Cre-ER/+</i>, <i>Pten^flox/flox</i> (KPP) model, which utilizes an inducible Cre recombinase to initiate tumor development by tamoxifen administration. In our previous work, tumors were induced in KPP mice at 4 weeks of age. However, mice are rapidly growing at this age, and a portion of the body weight differences seen between control and KPP mice is likely due to slowed growth of KPP mice. In our current study, pancreatic tumors were induced to develop with tamoxifen in KPP mice after rapid postnatal growth has slowed at 10 weeks of age (KPP10). Given the expanding evidence of sexual dimorphisms in cancer cachexia, we utilized both male and female mice to assess potential sex differences. Similar to our previous findings, KPP10 mice had lower body, muscle, and adipose tissue weights compared to non-tumor mice, and these differences were similar between male and female mice. However, male mice experienced greater relative weight loss. Unexpectedly, we identified that survival was significantly shorter in female KPP10 mice compared to KPP10 males. Greater body weight at tumor induction was associated with longer survival, suggesting that the sex difference in survival may be related to differences in body weight between male and female mice.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145199558","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":"Sex differences in performance fatigability after a maximal intermittent fatiguing protocol with a flywheel device.","authors":"Jorge Salse-Batán, Michel Marina, Priscila Torrado","doi":"10.1152/japplphysiol.00307.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00307.2025","url":null,"abstract":"<p><p>This study aimed to determine whether sex influences neuromuscular modulation following a maximal intermittent fatiguing protocol (IFP_max) using a flywheel device (FD; moment of inertia: 0.13 kgꞏm²). A secondary objective was to assess the recovery of force and electromyographic signals. Thirty-six young adults (20 females) completed 10 sets of 10 half-squats with 3-min rest intervals. Knee extension force was assessed during maximal voluntary isometric contraction (MVC) at pre-fatigue (PRE), following the IFP_max (POST), and after a recovery of 10-min (P10). Additionally, femoral nerve stimulation, such as doublets at 100 Hz (Db₁₀₀) and 10 Hz (Db₁₀) and single twitches (Tw) were applied to obtain electrically-evoked mechanical and electromyographic responses, voluntary activation (VA), H-reflex, and superimposed and resting M-wave variables at the three time points. Although males demonstrated higher pre-fatigue MVC values, they experienced a larger decline at POST (-42% vs -31%; P = 0.032). Electrically-evoked forces remained reduced at P10 compared to PRE (P < 0.001). Males showed greater declines in peak Tw (-63% vs -51%; P = 0.049), Db₁₀ (-70% vs -58%; P = 0.021) and Db_10:100 ratio (-39% vs -30%; P = 0.041). Overall, M-wave variables showed similar decrements in both sexes. Irrespective of sex, VA and H-reflex decreased at POST (P ≤ 0.037). The IFP_max performed using a FD induced a pronounced peripheral fatigue, with contractile mechanisms being more impaired in males. In contrast, central adjustments were similar between sexes. Future research is warranted to determine the most effective strength training strategies tailored to sex-specific responses.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145199473","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":"Sex-specific protective effects of angiotensin II type 1 receptor knockdown on disuse muscle atrophy in the rat soleus muscle.","authors":"Toshinori Yoshihara, Mizuki Takaragawa, Shohei Dobashi, Hisashi Naito","doi":"10.1152/japplphysiol.00731.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00731.2025","url":null,"abstract":"<p><p>Skeletal muscle disuse leads to atrophy. Accumulating evidence suggests that angiotensin II type 1 receptor (AT1R) contributes to sex-dependent catabolic signaling. However, the direct role of AT1R in skeletal muscle is unclear. This study investigated whether selective suppression of AT1R expression in the rat soleus muscle via adeno-associated virus serotype 9 (AAV9)-mediated short hairpin RNA (shRNA) delivery could mitigate hindlimb unloading (HU)-induced muscle atrophy, and whether this effect differed between male and female rats. Male and female rats received intramuscular injections of AAV9 vectors encoding AT1R-targeted shRNA into the soleus muscle. After 7 d of HU, <i>AT1R</i> gene copy number (digital PCR), receptor abundance (ligand binding assay), muscle fiber cross-sectional area (CSA), and downstream molecular markers (including phosphorylated Smad2/3 and Smad1/5/8, HDAC4 expression, and the atrogenes, <i>Fbxo32</i> and <i>Trim63</i>) were assessed. Female rats exhibited substantially higher <i>AT1R</i> gene copy numbers, which were selectively reduced by AAV9-shRNA. Ligand binding confirmed reduced receptor abundance in both sexes. CSA loss attenuation was observed exclusively in females, particularly in type I fibers. In female animals, AT1R knockdown substantially increased Smad1/5/8 phosphorylation and decreased HDAC4 expression. The AT1R copy number was positively correlated with <i>Fbxo32</i> and <i>Trim63</i> expression, independent of AAV dose. AT1R plays a sex-specific role in disuse-induced muscle atrophy, as muscle-specific AT1R knockdown conferred selective protection in female rats. The effect appears to be mediated via Smad1/5/8-HDAC4 signaling rather than oxidative stress or autophagy. This study provides mechanistic support for sex-informed therapeutic strategies targeting the muscle-localized renin-angiotensin system.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145181993","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":"Multidimensional Modeling to Maximize Adaptations to eXercise: The M³AX Trial Rationale and Study Design.","authors":"Zachary A Graham, Matthew P Bubak, Christiana J Raymond-Pope, Gary R Cutter, Jeremy S McAdam, S Craig Tuggle, Jacob A Siedlik, Luis G O de Sousa, Ed J Chappe, Kana Meece, Amritpal Kaur, Benny S R Ruiz, Sophia C Bamman, Katherine M Vanselow, Trevor W Perry, Jorge S Acosta-Arreguin, Natalie J Bohmke, Greg J Addison, J Michelle Bowers, Rachel L Wright, Lena D Fuentes, Jennifer E Smith, Karyn A Esser, Benjamin F Miller, Sue C Bodine, Marcas M Bamman","doi":"10.1152/japplphysiol.00486.2025","DOIUrl":"10.1152/japplphysiol.00486.2025","url":null,"abstract":"<p><p>Age-related functional declines are thought to be caused by hallmark biological processes that manifest in physical, mental, and metabolic impairments compromising intrinsic capacity, healthspan and quality-of-life. Exercise is a multipotent treatment with promise to mitigate most aging hallmarks, but there is substantial variability in individual exercise responsiveness. This inter-individual response heterogeneity (IRH) was first extensively interrogated by Bouchard and colleagues in the context of endurance training. Our group has interrogated IRH in response to resistance training and combined training, and we have conducted trials in older adults examining dose titration and adjuvant treatments in attempts to boost response rates. Despite the work of many groups, the mechanisms underpinning IRH and effective mitigation strategies largely remain elusive. The National Institute on Aging (NIA) hosted a focused workshop in 2022 titled \"Understanding heterogeneity of responses to, and optimizing clinical efficacy of, exercise training in old adults\". This workshop spurred a dedicated NIA request for applications (RFA) with the major goal \"to better understand factors underlying response variability to exercise training in older adults.\" We developed a two-phase Sequential Multiple Assignment Randomized Trial (SMART) in response to the RFA that will allow us to classify individual responsiveness to combined endurance and resistance training and interrogate potential mechanistic underpinnings (Phase I), followed by an approach to boost responsiveness (Phase II). Using deep in vivo, ex vivo, and molecular phenotyping, we will establish multidimensional biocircuitry of responsiveness and build predictive models, providing a basis for personalized exercise prescriptions.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145182006","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":"The medial gastrocnemius fascicle shortening and tendon lengthening in static standing are associated with age-related postural instability in older adults.","authors":"Taku Miyazawa, Hiroki Hanawa, Keisuke Kubota, Keisuke Hirata, Tsutomu Fujino, Naohiko Kanemura","doi":"10.1152/japplphysiol.00431.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00431.2025","url":null,"abstract":"<p><p>Muscle-tendon unit (MTU) dynamics are involved in small body movements, including static standing. However, the effect of age-related reductions in tendon stiffness on static standing stability remains unclear. In this study, Achilles tendon stiffness was assessed in young and older adults, and muscle fascicle length and tendon length were measured during static standing with eyes open (EO) and eyes closed (EC) using ultrasonography. To isolate muscle-controlled activity, we analyzed intervals around the peak center of pressure (COP) velocity points. Fascicle length change (ΔL_fas) and tendon length change (ΔL_TS) during these intervals were calculated, compared by age group, and examined for their relationship to COP sway. COP was decomposed into rambling and trembling components, representing supraspinal and spinal-peripheral control processes, respectively. Results showed significantly reduced Achilles tendon stiffness and increased COP velocity and trembling in older adults (P=0.02, <0.001, and <0.001, respectively). Both age groups demonstrated fascicle shortening and tendon lengthening around peak COP velocity points, but changes were more pronounced in older adults, showing greater fascicle shortening and tendon elongation (age effect: P=0.012 and 0.031, respectively). ΔL_fas amplitude positively correlated with COP velocity (EO: Young r=0.39, Older r=0.55; EC: Young r=0.71, Older r=0.44, all P<0.05) and trembling velocity (EO: Young r=0.49, Older r=0.56; EC: Young r=0.82, Older r=0.45, all P<0.001). These parameters, known to increase with age, are linked to co-contraction. This study demonstrates that excessive fascicle shortening, resulting from reduced tendon stiffness, contributes to increased postural sway in older adults.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145130963","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":"Acute cardiovascular and cerebral blood flow responses to high frequency, low amplitude vibration on the neck.","authors":"Viet Q Dinh, Malinda Hansen, K Austin Davis, Lindsey Peralez, Caroline A Rickards","doi":"10.1152/japplphysiol.00328.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00328.2025","url":null,"abstract":"<p><p>Local muscle vibration (LMV) is a potential therapeutic approach to treat symptoms related to stroke by improving muscle function and blood flow. In this study, we assessed the acute cardiovascular and cerebral blood flow responses to LMV when applied to the anterior neck muscles in young and healthy participants. We hypothesized that LMV would elicit minimal acute cardiovascular responses. Ten human participants (5 male, 5 female) underwent LMV on both sides of their neck for 5-min each. Arterial pressure, middle cerebral artery blood velocity (MCAv), and common carotid artery (CCA) blood flow were measured continuously. There was no effect of LMV on <b>mean arterial pressure</b> (RIGHT, Baseline: 96.9±4.9 mmHg vs. LMV: 97.8±5.7 mmHg vs. Recovery: 98.2±4.6 mmHg, P=0.25; LEFT, Baseline: 96.0±7.8 mmHg vs. LMV: 97.0±7.7 mmHg vs. Recovery: 97.9±7.5 mmHg; P=0.23) or <b>MCAv</b> (RIGHT, Baseline: 61.4±10.5 cm/s vs. LMV: 62.0±10.7 cm/s vs. Recovery: 59.3±9.7 cm/s; P=0.15; LEFT, Baseline: 59.9±10.2 cm/s vs. LMV: 60.6±10.8 cm/s vs. Recovery: 58.4±10.2 cm/s; P=0.20). <b>CCA diameter</b> increased slightly with LMV on both sides of the neck (RIGHT, Baseline: 6.2±0.6 mm vs. LMV: 6.3±0.7 mm, P=0.03; LEFT, Baseline: 6.4±0.5 mm vs. LMV: 6.5±0.5 mm, P=0.03). However, this did not affect <b>CCA blood flow</b> (RIGHT, Baseline: 330.7±68.5 ml/min vs. LMV: 324.7±57.6 ml/min, P=0.59; LEFT, Baseline: 358.1±67.5 vs. LMV: 344.2±78.3 ml/min, P=0.30). These data provide evidence that a single acute session of LMV does not affect key cardiovascular parameters in young and healthy participants.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145130918","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}