Journal of applied physiology最新文献

{"title":"The influence of sex on the effects of inorganic nitrate supplementation on muscular power and endurance.","authors":"Joaquin Ortiz de Zevallos, Austin C Hogwood, Ka'eo Kruse, Jeison De Guzman, Meredith Buckley, Alexandra F DeJong Lempke, Arthur Weltman, Jason D Allen","doi":"10.1152/japplphysiol.00321.2024","DOIUrl":"10.1152/japplphysiol.00321.2024","url":null,"abstract":"<p><p>Inorganic nitrate ([Formula: see text]) supplementation increases nitric oxide (NO) bioavailability and may improve muscular power and endurance, although most studies are in males. Therefore, the present double-blind, randomized, placebo-controlled study examined the effects of [Formula: see text] supplementation on isokinetic peak power, maximal voluntary isometric contraction (MVIC) force, muscular endurance (time-to-task failure; TTF), and recovery from fatigue in young females (<i>n</i> = 12) and males (<i>n</i> = 14). Participants consumed ∼13 mmol [Formula: see text] [beetroot juice (BRJ)], or an identical [Formula: see text]-depleted beverage placebo (PL), for ∼3 days and 2 h before testing visits. Plasma nitrate and nitrite were elevated in the BRJ condition (<i>P</i> ≤ 0.05). Peak power (W·kg^-1) showed a sex effect (<i>P</i> ≤ 0.05) at all angular velocities and a sex-by-treatment effect at 270 and 360°/s (<i>P</i> ≤ 0.05). Post hoc analysis revealed no significant differences between treatments (<i>P</i> > 0.05). Estimated maximal knee extension power (<i>P</i>_max) and maximal knee extension velocity (<i>V</i>_max) demonstrated no sex, treatment, or sex-by-treatment effect (<i>P</i> > 0.05). There were no significant effects for TTF (F: PL; 269 ± 161 vs. BRJ; 277 ± 158 s and M: PL; 228 ± 171 vs. BRJ; 194 ± 100 s; <i>P</i> > 0.05). Cohen's <i>d</i> effect sizes for peak power showed moderate to large effect sizes at 270 (<i>d</i> = 0.92) and 360°/s (<i>d</i> = 0.81), showing a possible differentiated effect of dietary nitrate in females and males. The present data indicate that [Formula: see text] supplementation does not significantly affect knee extensor maximal power, maximal contraction velocity, and muscular endurance in either sex. The sex-dependent response to dietary nitrate supplementation requires further investigation as data on females is scarce.<b>NEW & NOTEWORTHY</b> Recent data have suggested that inorganic nitrate ([Formula: see text]) supplementation may benefit males; however, females may experience worsened endurance capacity. This study revealed a potential differentiated effect of [Formula: see text] supplementation on outcomes of muscle contractile function between healthy, young males and females. The specific responses of [Formula: see text] supplementation in females and across sexes remain understudied and require further investigation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1649-1658"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142466241","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":"Training volume and total energy expenditure of an Olympic and Ironman world champion: approaching the upper limits of human capabilities.","authors":"Marcus S Dasa, Olav Aleksander Bu, Øyvind Sandbakk, Bent R Rønnestad, Guy Plasqui, Hilde Gundersen, Morten Kristoffersen","doi":"10.1152/japplphysiol.00706.2024","DOIUrl":"10.1152/japplphysiol.00706.2024","url":null,"abstract":"<p><p>Research on world-class athletes in endurance events, such as cycling Grand Tours, has reported extreme levels of total energy expenditure. However, it has been argued that over extended periods, such as months, sustained energy expenditure is capped at approximately 2.5 times the basal metabolic rate. Triathlon is particularly notable for its high energetic demands due to its multimodal nature, requiring athletes to maintain high training volumes. In this case study, we analyzed the total energy expenditure of world-class triathlete Kristian Blummenfelt using doubly labeled water over two specific periods, along with 3 yr of training data. Total energy expenditure ranged from 7,019 to 8,506 kcal/day. Reported energy intake ranged from 4,899 to 6,360 kcal/day. The annual training volumes for the years 2020-2022 were 1,480, 1,350, and 1,308 h, respectively, following a pyramidal intensity distribution. Approximately 53% of the entire three-year period matched with the doubly labeled water measurement periods in terms of training volume, indicating that the recorded total energy expenditure is representative of the majority of the observed data. Hence, the greater part of the 3-yr period likely exceeds the proposed metabolic ceiling for sustained total energy expenditure. This not only questions the validity of the current metabolic limits but also suggests a new perspective on what is physiologically achievable in world-class athletes.<b>NEW & NOTEWORTHY</b> The current paper presents unprecedented data on the training volume and intensity distribution of a world-class triathlete. Furthermore, using doubly labeled water measurements and training data, we argue that our findings challenge the proposed alimentary limit for sustained energy expenditure, thereby raising the upper boundary of what is physiologically possible in humans.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1535-1540"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142545679","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":"Running for two (or three!): the journey of an ultramarathoner across two pregnancies.","authors":"Gyan Bains, Sophie Carter, Melanie J Hayman, Margie H Davenport","doi":"10.1152/japplphysiol.00488.2024","DOIUrl":"10.1152/japplphysiol.00488.2024","url":null,"abstract":"<p><p>There is a lack of evidence regarding the safety of long-duration and vigorous-intensity physical activity during pregnancy, such as that required during an ultramarathon. This case study is the first to examine the training, performance, health, and delivery outcomes for an ultramarathoner across two successive pregnancies (one twin and one singleton) that were delivered when the athlete was 41 and 43 yr, respectively. During her twin pregnancy, she ran an average of 91.72 ± 23.17 km across 9.06 ± 2.38 h/wk. Both twins were normal for gestational age and delivered at 37 wk. <i>Twin 2</i> experienced mild hypoxic-ischemic encephalopathy but made a full recovery following treatment. Twin pregnancy increases the risk of this complication, and there is no evidence to suggest that it is associated with vigorous-intensity endurance activity. During her singleton pregnancy, the participant's distance and pace increased, running on average 157.80 ± 14.69 km across 14.08 ± 1.60 h/wk. She also competed in five races including three ultramarathons and ranked well, with no adverse events during or following each of the races. She delivered prematurely (36 wk and 6 days), but her baby was normal for gestational age.<b>NEW & NOTEWORTHY</b> This study provides the first description of a pregnant female ultramarathoner's training patterns, performance outcomes, and health and birthing outcomes across two pregnancies.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1659-1665"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142500987","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":"Comparison of awake respiratory control versus sleep obstructive sleep apnea endotypes.","authors":"David Wang, Rodrigo T Martins, Luke Rowsell, Keith K Wong, Brendon J Yee, Ronald R Grunstein, Danny J Eckert","doi":"10.1152/japplphysiol.00138.2024","DOIUrl":"10.1152/japplphysiol.00138.2024","url":null,"abstract":"<p><p>Most approaches to advance simplified physiology-based precision medicine strategies for obstructive sleep apnea (OSA) focus on sleep parameters (i.e., OSA endotypes). However, wakefulness physiology measures can also provide prediction insight for certain OSA therapies, yet their relationship with sleep parameters has not been extensively investigated. This study aimed to investigate potential relationships between awake ventilatory control parameters and sleep OSA endotypes and their potential to predict changes in OSA severity with morphine. Data were acquired from a randomized, crossover trial that investigated the effects of morphine versus placebo on OSA severity and underlying mechanisms. Here, awake ventilatory chemoreflex testing before overnight polysomnography was compared with direct measures of sleep respiratory control (e.g., hypercapnic ventilatory responses and loop gain) and OSA endotypes during a separate overnight physiology study [pharyngeal critical closure pressure (Pcrit), muscle responsiveness via genioglossus intramuscular electromyography, and arousal threshold via epiglottic pressure catheter to transient continuous positive airway pressure reductions]. Twenty-one men with OSA completed both study arms. During placebo, <i>1</i>) awake chemosensitivity correlated with Pcrit (<i>r</i> = 0.726, <i>P</i> = 0.001), <i>2</i>) arousal threshold correlated with awake CO₂ ventilatory response threshold (<i>r</i> = -0.467, <i>P</i> = 0.047) and basal ventilation (<i>r</i> = -0.500, <i>P</i> = 0.029). Awake chemosensitivity and Pcrit also correlated with the apnea-hypopnea index (<i>P</i> < 0.001) during placebo. Awake chemosensitivity was predictive of changes in OSA severity with morphine (<i>r</i> = -0.535, <i>P</i> = 0.013). In conclusion, awake measures of respiratory control are related to physiological endotypes, such as airway collapsibility and arousal threshold during sleep and OSA severity. Awake ventilatory chemosensitivity has the best potential to predict changes in OSA severity with morphine.<b>NEW & NOTEWORTHY</b> Both awake ventilatory control measures and OSA endotypes measured during sleep have reported potentials in endotyping/phenotyping OSA, although no randomized, controlled trial has compared/linked between the two techniques. From a double-blind, randomized placebo-controlled crossover trial, we found that awake measures of respiratory control are related to physiological endotypes such as airway collapsibility and arousal threshold during sleep and OSA severity. Awake ventilatory chemosensitivity has the best potential to predict changes in OSA severity with morphine.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1524-1534"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142400371","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":"GDF15 associates with, but is not responsible for, exercise-induced increases in corticosterone and indices of lipid utilization in mice.","authors":"Meagan Arbeau, Bradley J Baranowski, Stewart Jeromson, Annalaura Bellucci, Michael Akcan, Serena Trang, Katelyn Eisner, Kyle D Medak, David C Wright","doi":"10.1152/japplphysiol.00519.2024","DOIUrl":"10.1152/japplphysiol.00519.2024","url":null,"abstract":"<p><p>Growth differentiation factor 15 (GDF15) is a stress-induced cytokine that increases with exercise and is thought to increase corticosterone and lipid utilization. How postexercise nutrient availability impacts GDF15 and the physiological role that GDF15 plays during and/or in the recovery from exercise has not been elucidated. The purpose of this investigation was to examine how postexercise nutrient availability impacts GDF15 and to use this as a model to explore associations between GDF15, corticosterone, and indices of lipid and carbohydrate metabolism. In addition, we explored the causality of these relationships using GDF15-deficient mice. Male and female C57BL/6J mice ran for 2 hours on a treadmill and were euthanized immediately or 3 hours after exercise with or without access to a chow diet. In both sexes, circulating concentrations of GDF15, corticosterone, nonesterified fatty acids (NEFA), and beta-hydroxybutyrate (BHB) were higher immediately postexercise and remained elevated when food was withheld during the recovery period. While serum GDF15 was positively associated with corticosterone, BHB, and NEFA, increases in these factors were similar in wild-type and GDF15^-/- mice following exercise. The lack of a genotype effect was not explained by differences in insulin, glucagon, or epinephrine after exercise. Our findings provide evidence that while GDF15 is associated with increases in corticosterone and indices of lipid utilization this is not a causal relationship.<b>NEW & NOTEWORTHY</b> Circulating growth differentiation factor 15 (GDF15) increases during exercise, but the physiological role that it plays has not been elucidated. Recent data suggest that GDF15 regulates corticosterone and lipid utilization. Here we demonstrate that postexercise nutrient availability influences GDF15 in the recovery from exercise and GDF15 is associated with corticosterone and indices of lipid utilization. However, the associations were not causal as exercise-induced increases in fatty acids, beta-hydroxybutyrate, and corticosterone were intact in GDF15^-/- mice.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1512-1523"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142545676","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":"Carbon monoxide inhalation for performance: dancing with the devil?","authors":"Christopher T Minson, Michael J Joyner","doi":"10.1152/japplphysiol.00767.2024","DOIUrl":"10.1152/japplphysiol.00767.2024","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1563-1565"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142545674","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 heterogeneity of cerebral blood flow immediately after the onset of ventricular pacing in anesthetized rats.","authors":"Kei Ishii, Hidehiko Komine","doi":"10.1152/japplphysiol.00436.2024","DOIUrl":"10.1152/japplphysiol.00436.2024","url":null,"abstract":"<p><p>Selective distribution of cerebral blood flow (CBF) to vital brain regions likely occurs during rapid severe hypotension caused by tachyarrhythmia but has not yet been demonstrated. In this study, we aimed to test the hypothesis that CBF is differentially preserved between brain regions depending on the degree of hypotension. In anesthetized rats, CBF was measured in the motor cortex (MC), medial prefrontal cortex, amygdala, thalamus, dorsal hypothalamus, hippocampus, ventral tegmental area, dorsolateral periaqueductal gray (dlPAG), and parabrachial nucleus (PB) by using laser-Doppler flowmetry. Ventricular pacing was performed for 30 s at 550-800 beats/min. The cerebrovascular CO₂ response time and reactivity were evaluated during 5% CO₂ exposure. During 1-4 s of ventricular pacing, mean arterial pressure (MAP) rapidly decreased, with minor changes in central venous and intracranial pressures. CBF was relatively well maintained in brain regions other than the MC (<i>P</i>s ≤ 0.012) when moderate hypotension occurred (-34 mmHg ≤ ΔMAP ≤ -15 mmHg), whereas severe hypotension (-54 mmHg ≤ ΔMAP ≤ -35 mmHg) induced selective CBF distribution to regions other than the MC, thalamus, and dlPAG. The cerebrovascular CO₂ response time/reactivity was rapid or high in the thalamus, dlPAG, and PB, which almost completely differed from the brain regions in which CBF was relatively maintained during pacing-induced severe hypotension. These results suggest that regional heterogeneity of CBF arises depending on the degree of tachyarrhythmia-induced hypotension. Clarifying the mechanisms and functions of CBF maintenance would be beneficial to syncope and cerebral ischemia management in patients with arrhythmia.<b>NEW & NOTEWORTHY</b> When lethal tachyarrhythmia occurs, survival is prioritized by counterregulating the cardiovascular system, which is driven by vital brain regions. However, whether limited cerebral blood flow is selectively distributed to vital brain regions is unknown. We demonstrated the preferential maintenance of cerebral blood flow in vital brain regions, depending on the degree of hypotension caused by ventricular pacing, in anesthetized rats. Our data may have clinical implications for syncope and cerebral ischemia management in patients with arrhythmia.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1580-1591"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142545678","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":"Does running speed affect the performance improvements experienced by elite distance runners wearing advanced footwear technology spikes?","authors":"Bradley J Needles, Alena M Grabowski","doi":"10.1152/japplphysiol.00610.2024","DOIUrl":"10.1152/japplphysiol.00610.2024","url":null,"abstract":"<p><p>Elite distance runners have exhibited race time improvements since the 2020 introduction of advanced footwear technology (AFT) for track and field, also known as \"super\" spikes. The observed performance improvements may be due to changes in midsole compliance, which could affect leg stiffness while wearing AFT spikes. Since increased leg stiffness has been associated with running speeds greater than 6 m/s, race time improvements for elite distance runners wearing AFT spikes may be reduced at faster running speeds. To investigate the relationship between the use of AFT spikes, running speed, and race performance, we conducted a statistical analysis of the race times from the top 100 male and female elite runners for 800-m to 10,000-m events from 2001 to 2023. We calculated race performance improvement (RPI) as the percentage difference between the pre-AFT spike (2001-2019) regression equation predicted average race times from the top 100 athletes and actual average race times from the top 100 athletes for 2021, 2022, and 2023. Overall, RPI after the introduction of AFT spikes was 0.89 ± 0.58% (range: 0.22-2.03%; <i>P</i> < 0.001) or roughly 1.2 s faster per kilometer than predicted by the regression equations. In addition, average running speed is faster as race distance decreases and we found that RPI was negatively associated with running speed from 10,000-m to 800-m (<i>P</i> < 0.001). Although overall race performances have improved since the introduction of AFT spikes, the use of AFT spikes may disproportionately improve race performance based on running speed.<b>NEW & NOTEWORTHY</b> After accounting for historical race time trends, average race times from the top 100 elite male and female athletes competing in the 800-m to 10,000-m events have improved since the introduction of advanced footwear technology spikes. However, the percentage performance improvement is smaller at faster average running speeds. Thus, future research is warranted to determine the interaction of footwear compliance, running speed, and performance for elite runners.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1690-1698"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142667977","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":"Lower maximal skin wettedness in both warm-humid and hot-dry environments with advanced age (PSU HEAT project).","authors":"Kat G Fisher, Daniel J Vecellio, Rachel M Cottle, Olivia K Leach, S Tony Wolf, W Larry Kenney","doi":"10.1152/japplphysiol.00758.2024","DOIUrl":"10.1152/japplphysiol.00758.2024","url":null,"abstract":"<p><p>Maximum skin wettedness (ω_max) is the proportion of the body covered in sweat at the upper limit of compensable heat stress. It has yet to be determined how ω_max changes with aging. We examined variability in ω_max at the upper limit of compensable heat stress in warm-humid (WH) and hot-dry (HD) environments in young (Y, 18-29 yr), middle-aged (MA, 40-60 yr), and older (O, 65-89 yr) adults during minimal activity (MinAct; ∼1.8 METS) and in O subjects at rest. ω_max was calculated using partitional calorimetry for 27 Y (13 F), 27 MA (16 F), and 32 O (18 F) at the previously determined upper limits of compensable heat stress in WH and HD environments. In WH environments, ω_max was greater in Y (0.69 ± 0.12) and MA (0.64 ± 0.20) compared with O (0.47 ± 0.14; both <i>P</i> < 0.05), but not different between Y and MA (<i>P</i> = 0.85). In HD environments, ω_max was greater in Y (0.52 ± 0.05) compared with O adults (0.40 ± 0.07; <i>P</i> < 0.05), but not different between MA (0.48 ± 0.10) and Y or O (both <i>P</i> ≥ 0.15). In O participants at rest, ω_max was lower than MinAct in WH (<i>P</i> < 0.001) but not HD environments. These findings indicate that <i>1</i>) ω_max is lower with advanced age across environments and <i>2</i>) is lower at rest than during light activity in O in humid conditions. ω_max established herein for unacclimated adults during activities of daily living and older adults at rest may be used to model heat stress responses for these populations and environments.<b>NEW & NOTEWORTHY</b> This study is the first to identify <i>1</i>) maximal skin wettedness values for unacclimated adults across the adult age span of 18 to 89 yr at a metabolic rate representative of minimal activities of daily living and <i>2</i>) establish specific ω_max values for older adults during rest and activities of daily living. These findings provide empirical data for the modeling of physiological responses to heat stress across the adult age span.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1549-1553"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142604665","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 Achilles tendon stiffness in aging associates with higher metabolic cost of walking.","authors":"Aubrey J Gray, Rebecca L Krupenevich, John A Batsis, Gregory S Sawicki, Jason R Franz","doi":"10.1152/japplphysiol.00377.2024","DOIUrl":"10.1152/japplphysiol.00377.2024","url":null,"abstract":"<p><p>The mechanisms responsible for increased metabolic cost of walking in older adults are poorly understood. We recently proposed a theoretical premise by which age-related reductions in Achilles tendon stiffness (k_AT) can disrupt the neuromechanics of calf muscle force production and contribute to faster rates of oxygen consumption during walking. The purpose of this study was to objectively evaluate this premise. We quantified k_AT at a range of matched relative activations prescribed using electromyographic biofeedback and walking metabolic cost and ankle joint biomechanics in a group of 15 younger (age: 23 ± 4 yr) and 15 older (age: 72 ± 5 yr) adults. Older adults averaged 44% lower k_AT than younger adults at matched triceps surae activations during isokinetic dorsiflexion tasks on a dynamometer (<i>P</i> = 0.046). Older adults also walked with a 17% higher net metabolic power (<i>P</i> = 0.017) but indistinguishable peak Achilles tendon forces than younger adults. Thus, data implicate altered tendon length-tension relations with age more than differences in the operating region of those length-tension relations between younger and older adults. In addition, we discovered empirical evidence that lesser k_AT-likely due to the shorter muscle lengths and thus higher relative activations it imposes-was positively correlated with higher net metabolic power during walking (<i>r</i> = -0.365, <i>P</i> = 0.048). These results pave the way for interventions focused on restoring ankle muscle-tendon unit structural stiffness to improve walking energetics in aging.<b>NEW & NOTEWORTHY</b> This study provides the first empirical evidence to our knowledge that age-related decreases in k_AT exact a potentially significant metabolic penalty during walking. These results pave the way for interventions focused on restoring ankle muscle-tendon unit structural stiffness to improve walking energetics in aging.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1541-1548"},"PeriodicalIF":3.3,"publicationDate":"2024-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142604674","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}