Journal of applied physiology最新文献

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

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

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

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

{"title":"Cardiac dysfunction is associated with indices of brain atrophy and cognitive impairment in heart failure with reduced ejection fraction.","authors":"Cameron J Morse, Adam M S Luchkanych, Natasha G Boyes, Allen D Champagne, Michael Kelly, Michael D Nelson, Rory A Marshall, Geoffrey Karjala, Alexander Zhai, Haissam Haddad, Darcy D Marciniuk, Corey R Tomczak, T Dylan Olver","doi":"10.1152/japplphysiol.00840.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00840.2024","url":null,"abstract":"<p><p>Cardiac dysfunction in heart failure with reduced ejection fraction (HFrEF) may contribute to brain atrophy and cognitive decline beyond that which is typical of healthy ageing. This study tested the hypothesis that HFrEF would be associated with regionally-unique brain remodelling and impaired cognitive performance independent of age. Further, that cardiac index and clinical markers of HFrEF severity would predict brain remodelling and cognition with age and HFrEF, respectively. Cardiac function and brain morphology were assessed using magnetic resonance imaging in young healthy adults (24±6y), older healthy adults (60±6y) and patients living with HFrEF (59±6y). The Montreal Cognitive Assessment was administered to assess cognition. Gray matter volume (GMV) (young: 492±24, old: 456±24, HFrEF: 433±32cm³, P≤0.05) and cortical thickness (young: 2.44±0.07, old: 2.33±0.08, HFrEF: 2.22±0.10mm, P<0.01) were lower with age and lowered further with HFrEF. Regional analysis revealed a unique pattern of atrophy with HFrEF. Whereas age had little effect on cortical curvature (P=0.60), it was greater in HFrEF (young: 0.127±0.003, old: 0.128±0.003, HFrEF: 0.136±0.005mm^-1, P<0.01). Cardiac index was the best correlate of brain atrophy and cognitive performance with age (R=0.33-0.47; P<0.05). However, EF and end systolic volume index were better correlates of brain atrophy and cognitive performance in HFrEF (R=-0.50-0.49; P≤0.05). These data indicate that lower GMV and cortical thickness in HFrEF are not merely an acceleration of age-related declines but reflect a unique pattern of brain atrophy and remodelling. Additionally, classic markers of HF severity may be better predictors of pathological brain remodelling than reduced cardiac index.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143663425","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 Calf Raise Efficiency in Obesity is Partially Related to Higher Triceps Surae MTU Passive Stiffness, Hysteresis, and Reduced Relative Strength.","authors":"Leonardo Cesanelli, Hans Degens, Cem Rifat Toper, Sigitas Kamandulis, Danguole Satkunskiene","doi":"10.1152/japplphysiol.00702.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00702.2024","url":null,"abstract":"<p><p>The objective of this study was to assess the efficiency of calf raise exercise in individuals with obesity, and to what extent this is related to the structural and mechanical properties of the Triceps Surae muscle-tendon-unit (MTU). In 22 obese (BMI, 32.2 ± 1.5 kg/m²) and 22 non-obese (BMI, 23.3 ± 1.5 kg/²) men we measured anthropometric parameters, gas exchange, heart rate, and rating of perceived exertion in sitting, standing and during a self-paced 30-sec calf raise exercise. Maximal voluntary isometric contraction of the plantar flexor muscles and passive resistive torque of the Triceps Surae MTUs were measured using an isokinetic dynamometer. B-mode ultrasound imaging of plantar flexor muscles and Achilles tendon was also performed. Individuals with obesity exhibited a greater metabolic energy cost during standing and calf raise exercise, and a lower exercise efficiency and ankle mobility (p<0.05). Plantar flexor MTUs stiffness and hysteresis were greater, while gastrocnemius-medialis tendon strain was lower in subjects with obesity compared to controls (p<0.05). There was a negative correlation between calf raise exercise net efficiency, plantar flexor MTUs hysteresis (r=0.38; p<0.05) and the body mass by maximal voluntary isometric torque ratio (r=0.41; p<0.05). These observations indicate that increased musculotendinous stiffness and hysteresis, together with a lower strength to body mass ratio, are among the factors contributing to higher metabolic energy costs, and lower exercise efficiency in individuals with obesity.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143669952","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":"PoWeR elicits intracellular signaling, mitochondrial adaptations, and hypertrophy in multiple muscles consistent with endurance and resistance exercise training.","authors":"Christian J Elliehausen, Szczepan S Olszewski, Dennis M Minton, Audrey L Spiegelhoff, Carolyn G Shult, Wenyuan G Zhu, Troy A Hornberger, Adam R Konopka","doi":"10.1152/japplphysiol.00872.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00872.2024","url":null,"abstract":"<p><p>Physical activity guidelines recommend both endurance and resistance exercise to improve and maintain overall health. Recently, progressive weighted wheel running (PoWeR), a voluntary, progressive, and high-volume exercise paradigm, was posited as a singular prototype of combined endurance and resistance exercise in mice as evident by enhanced capillarization and hypertrophy of select plantar flexor muscles. Despite growing interest in this model, it remains incompletely characterized if PoWeR resembles the acute and chronic responses to resistance and/or endurance exercise in humans. Therefore, the purpose of this study was to assess canonical signaling events, mitochondrial bioenergetics, and cellular adaptations across multiple extensor and flexor muscles of the fore- and hindlimbs that may be conducive for whole-body functional improvements as traditionally observed in humans. 8-weeks of PoWeR (~8km/day) improved glucose metabolism, exercise capacity, body composition, and bone mineral density as well as increased mass, myofiber CSA, and oxidative myofiber type distribution in the soleus, plantaris, and FDL. Using two <i>ex-vivo</i> high-resolution flourorespirometry protocols that model <i>in vivo</i> physiological conditions, PoWeR decreased mitochondrial ADP sensitivity which was accompanied by greater mitochondrial H₂O₂ emissions, respiration, conductance, and protein content in the vastus lateralis, gastrocnemius, and triceps in muscle-specific fashion. Three days of short-term PoWeR stimulated mTORC1 and AMPK signaling in soleus, plantaris and/or FDL in line with the hypertrophic and metabolic adaptations observed with long-term training. Collectively, these data support PoWeR as a suitable paradigm in mice to model the acute signaling and chronic adaptations associated with endurance and resistance exercise in humans.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143657397","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":"Heart rate variability during exercise can quantify cardiorespiratory deconditioning in 55- to 65-year-old men and women exposed to head-down bed rest.","authors":"Jeremy Rabineau, Eric T Hedge, Roxanne Fournier, Carmelo J Mastrandrea, Richard L Hughson","doi":"10.1152/japplphysiol.00017.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00017.2025","url":null,"abstract":"<p><p>The heart rate variability (HRV) features HRV_0.75 and HRV_0.5, obtained by detrended fluctuation analysis during incremental cycle ergometer tests, have been shown to correlate with indices of cardiorespiratory fitness. Here, we evaluate the ability of these features to track individual changes in cardiorespiratory fitness induced by head-down bed rest (HDBR) among late middle-aged adults. Twenty-two healthy participants (55-65 years old, 11 women) were exposed to 14-day HDBR. Eleven participants were assigned to a group performing daily aerobic and resistive exercises during HDBR, while the others were assigned to a control group with no countermeasure intervention. We measured gas exchange and electrocardiography during incremental cycle ergometer tests pre- and post-HDBR. The countermeasure preserved oxygen uptake (V̇O₂) at the two ventilatory thresholds (VT1 and VT2), HRV_0.75 and HRV_0.5. However, these four features decreased in the control group after HDBR. A large and proportional bias was evidenced between V̇O₂ at VT1 and HRV_0.75, which was less the case for V̇O₂ at VT2 versus HRV_0.5. However, the intra-individual changes in the control group were correlated (r_rm = 0.66 for VT1 vs. HRV_0.75 and r_rm = 0.82 for V̇O₂ at VT2 versus HRV_0.5, both p < 0.001). Overall, this study indicated that HRV_0.75 and HRV_0.5 can be used to longitudinally monitor changes in cardiorespiratory fitness in late middle-aged adults with physical deconditioning. Future research can apply these methods to other study populations.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143657381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of Analgesic Doses of Opioids on Cardiorespiratory Responses and Survival to Hemorrhage and Trauma in Rats.","authors":"Stephanie M Lipiec, Kathy L Ryan, Mariam L Calderon, Cassandra M Rodriguez, Brian S Connor, Carmen Hinojosa-Laborde, Harold G Klemcke","doi":"10.1152/japplphysiol.00708.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00708.2024","url":null,"abstract":"<p><p>Opioids are used for analgesia but questions persist about their safety following traumatic hemorrhage. We investigated <i>analgesic</i> doses of three opioids (morphine, fentanyl and sufentanil) on cardiorespiratory responses and survival to moderate or severe (37 and 50% blood volume) hemorrhage after trauma. A conscious hemorrhage model with extremity trauma (fibular fracture + soft tissue injury) was used; mean arterial pressure (MAP) and heart rate (HR) were measured by telemetry while minute volume (MV) was determined by whole body plethysmography. Male rats (n=10/group) received saline, morphine (2 mg/kg), fentanyl (10 µg/kg) or sufentanil (1 µg/kg) after traumatic hemorrhage. Neither survival times (for 37% hemorrhage: P=0.209; for 50% hemorrhage: P=0.88) nor survival percentages (for 37% hemorrhage: P=0.357; for 50% hemorrhage: P=1.0) differed among groups. For 37% hemorrhage, MAP of all opioid groups was higher than the saline-treated group 10 min post-injection. By 75 min post-injection, MAP after sufentanil was higher than saline; MAP for other opioids did not differ from saline. HR did not differ across treatments. Opioid injection decreased MV within 10 min but did not vary by treatment subsequently. For 50% hemorrhage, opioid injection did not immediately alter MAP but morphine and sufentanil were lower than saline at ≥75 min post-injection, with no treatment effects on HR. Fentanyl produced an immediate (5 min) decrease in MV with no treatment effects thereafter. Opioid effects on cardiorespiratory function were therefore modest and did not alter survival during a 4 hr observation period, supporting the judicious use of analgesic doses following traumatic hemorrhage.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143648592","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":"Motor unit discharge behaviour in human muscles throughout force gradation: a systematic-review and meta-analysis with meta-regression.","authors":"J Greig Inglis, Hélio V Cabral, Caterina Cosentino, Alberto Bonardi, Francesco Negro","doi":"10.1152/japplphysiol.00863.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00863.2024","url":null,"abstract":"<p><p>The analysis of motor unit (MU) discharge behaviour provides an effective way of assembling information about the generation and control of movement. In this systematic-review and meta-analysis we identified and summarized the literature investigating MU discharge rate and discharge rate variability (CoV-ISI) during voluntary isometric contractions at various force levels. Databases were searched up to January 7, 2025, and a total of 262 studies were included. The meta-means of MU discharge rate and CoV-ISI were estimated and compared across human muscles. The influence of contraction intensity on MU discharge behaviour was assessed through linear meta-regressions. At low-to-moderate forces (<60% MVC), the <i>first dorsal interosseous, biceps brachii</i> (<i>BB</i>) and <i>forearm extensors</i> (<i>FE</i>) had the highest discharge rate, while the <i>soleus</i> had the lowest. At high force levels (>60% MVC), the <i>tibialis anterior</i> (<i>TA</i>) had the highest mean discharge rate compared to all other muscles, with the <i>soleus</i> maintaining the lowest. Regarding CoV-ISI results at low forces (<30% MVC), the <i>TA</i> had the lowest CoV-ISI values, except in comparison to the <i>vastii</i>. Additionally, the <i>vastii</i> had lower CoV-ISI values than the <i>FE</i>, <i>gastrocnemius medialis</i>, and <i>soleus</i>. Contraction intensity was positively associated with the mean discharge rates in all muscles investigated, although some muscles showed steeper slopes than others. Similar results were observed for CoV-ISI meta-regressions, with muscle-specific differences in slope. These findings suggest potential variations in neural control strategies across muscles during force gradation, such as differences in the relative contribution of rate coding to facilitate increasing force demands.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143648606","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}