Lifestyle intervention is critical for young adults with early-stage hypertension. A Western diet has negative effects on kidney function and blood pressure; however, time-of-day effects are understudied. We hypothesized...Lifestyle intervention is critical for young adults with early-stage hypertension. A Western diet has negative effects on kidney function and blood pressure; however, time-of-day effects are understudied. We hypothesized that consumption of a Western-style meal that is misaligned with the endogenous circadian rhythm would have adverse effects on blood pressure, kidney function, and vascular function. Ten young adults with elevated blood pressure or stage 1 hypertension (means ± SD: 26 ± 8 yr, 50% female) underwent a randomized crossover, isocaloric controlled feeding intervention. Participants were allocated to receive a Western-style meal high in sodium, sugar, and saturated fat in the morning (MMC) or the evening (EMC). Participants completed 24-h urine collection and simultaneous 24-h ambulatory blood pressure monitoring. Daytime fractional excretion of sodium was greater after MMC compared with EMC (MMC vs. EMC: 0.84 ± 0.28 vs. 0.35 ± 0.13%, = 0.008). However, nighttime sodium excretion was not elevated after EMC (0.48 ± 0.24 vs. 0.39 ± 0.30%, = 0.314), suggestive of overnight sodium retention. There were increased systolic (126 ± 6 vs. 121 ± 6 mmHg, = 0.028), diastolic (80 ± 4 vs. 77 ± 6.4 mmHg, = 0.028), and mean arterial (95 ± 5 vs. 91 ± 6 mmHg, = 0.028) blood pressures during waking hours of MMC. Following consumption of the EMC, nocturnal blood pressure elevation was mitigated, presumably through protective sodium storage mechanisms (systolic pressure dipping: 15 ± 5 vs. 12 ± 5%, = 0.249). Resting systolic blood pressure was increased the morning following EMC (119 ± 8 vs.121.8 ± 9 mmHg, = 0.018). The findings suggest that in young adults with early-stage hypertension, a misaligned Western-style meal consumed late at night results in extended sodium retention and nocturnal blood pressure control was uncoupled from renal-mediated mechanisms. Using a controlled feeding intervention, we investigated the time-of-day impact of Western-style meal consumption on acute blood pressure and renal responses in young adults with early-stage hypertension. Our pilot results translate preclinical work demonstrating that endogenous diurnal kidney function does not acutely respond to food as a time cue. Therefore, timing of a high sodium meal that was misaligned with the endogenous kidney function rhythm extended sodium retention, and blood pressure regulation was potentially uncoupled from renal-mediated mechanisms.
Exertional dyspnea is the main symptom of chronic obstructive pulmonary disease (COPD). Based on the positive relationship between the levels of dyspnea (Borg score) and the electrical activity of respiratory muscles [el...Exertional dyspnea is the main symptom of chronic obstructive pulmonary disease (COPD). Based on the positive relationship between the levels of dyspnea (Borg score) and the electrical activity of respiratory muscles [electromyogram (EMG)] during an incremental cardiopulmonary exercise test, it has been suggested that respiratory EMG can provide a physiological biomarker for dyspnea. This study aimed to characterize the relationship between dyspnea and EMG during exercises simulating daily activities. Surface EMG was measured at two locations on the chest of 28 patients with COPD while they were performing constant-work rate cycling tests and walking/cycling exercises that were part of their rehabilitation program. Simultaneously, the level of dyspnea was assessed using the Borg score at several timepoints throughout the exercise sessions, along with respiration rate (RR), heart rate (HR), and transcutaneous oxygen saturation ([Formula: see text]). Patients completed each up to 10 such study visits during their 8-wk stay at the rehabilitation center (CIRO, the Netherlands). In total, 1981 Borg scores with associated EMG measurements were recorded during 263 study visits. A linear-mixed model was used to assess the relation of the Borg score with EMG while controlling for RR, HR, (type of) exercise, [Formula: see text], age, and sex. Random effects for patient and visit were included to account for correlation in the measurements. EMG had a highly significant association with the Borg score ( < 0.0001). Respiratory EMG and Borg score showed consistent positive correlations, of which the magnitude varied between patients. These results indicate that respiratory EMG can provide a physiological biomarker for dyspnea during activities of daily living in patients with COPD. This study demonstrates that, even after controlling several physiological variables, electromyography (EMG) of the respiratory muscles is significantly associated with dyspnea, as assessed by the Borg scale in patients with chronic obstructive pulmonary disease (COPD) during daily activities. This finding suggests that respiratory EMG may serve as a physiological biomarker for dyspnea. Surface EMG measured on the chest offers valuable insights for assessing dyspnea, providing an additional, objective tool to capture the intensity of dyspnea during daily living.
Autonomic cardiovascular control is often disrupted following a spinal cord injury (SCI), resulting in impaired autonomic cardiac regulation and hemodynamic instability. A systematic preregistered review following existi...Autonomic cardiovascular control is often disrupted following a spinal cord injury (SCI), resulting in impaired autonomic cardiac regulation and hemodynamic instability. A systematic preregistered review following existing guidelines was undertaken to evaluate the effect of exercise training on noninvasive measures of autonomic cardiovascular control, including orthostatic intolerance, blood pressure variability (BPV), baroreflex function, and heart rate variability (HRV) in adults with SCI. Seven databases were searched from inception to October 2025. Experimental studies (randomized controlled trials, nonrandomized controlled trials, or pre-post studies) consisting of exercise interventions of ≥2 wk evaluating measures of orthostatic tolerance, BPV, baroreflex function, and/or HRV in adults (≥18 yr old) with SCI were included. Risk of bias and study quality were assessed. Of 1,208 unique records identified, 16 studies (329 participants) were included: 8 randomized controlled trials, 3 nonrandomized controlled trials, and 5 pre-post studies. Five of seven studies reported no change in orthostatic intolerance following exercise training, whereas three of five studies found no changes in power spectral analysis of BPV. Conversely, all five studies reporting baroreflex outcomes found improved function, with enhanced cardiovagal baroreflex sensitivity or effectiveness index after training. The 13 studies assessing autonomic cardiac control through HRV reported mixed results, irrespective of whether time- or frequency-domain analyses were used. This review provides preliminary evidence that exercise training can improve baroreflex function in adults with SCI. However, current evidence remains inconclusive regarding whether exercise training can improve HRV, BPV, and the ability to tolerate postural stress and thus prevent orthostatic hypotension.
Muscle protein metabolism is thought to regulate muscle mass. High-intensity muscle contraction (HiMC) increases muscle protein synthesis (MPS), resulting in muscle hypertrophy. Inhibiting the mechanistic target of rapam...Muscle protein metabolism is thought to regulate muscle mass. High-intensity muscle contraction (HiMC) increases muscle protein synthesis (MPS), resulting in muscle hypertrophy. Inhibiting the mechanistic target of rapamycin complex 1 (mTORC1) using rapamycin leads to partially inhibited mTORC1 activation, along with increased MPS, and muscle hypertrophy after HiMC. Therefore, we hypothesized that rapamycin-sensitive mTORC1 regulates myofibrillar protein translation, and the purpose of this study was to investigate this possibility. The right gastrocnemius muscle of male Sprague Dawley rats was contracted isometrically via percutaneous electrical stimulation, and the left gastrocnemius muscle served as control. Vehicle or rapamycin was intraperitoneally injected 1 h before HiMC. Gastrocnemius muscles were collected at 6 h after a bout of HiMC and 48 h after chronic muscle contractions for 4 wk (3 HiMC per week). Rapamycin completely inhibited HiMC-induced activation of 70 kDa ribosomal protein S6 kinase, which is a rapamycin-sensitive mTORC1 substrate. However, rapamycin completely inhibited HiMC-induced dissociation of eukaryotic translation initiation factor 4E (eIF4E):eukaryotic translation initiation factor 4E (eIF4E)-binding protein (4E-BP1) and the interaction of eIF4E:eIF4G, despite the HiMC-induced phosphorylation of 4E-BP1 (Thr37/46, Thr70, and Ser65) being unaffected by rapamycin. Importantly, HiMC-induced myofibrillar protein synthesis was not influenced by rapamycin. Changes in myosin and actin levels relative to muscle mass induced by chronic muscle contraction remained constant even under rapamycin administration. These results indicated that rapamycin-sensitive mTORC1 signaling is not fully responsible for contraction-induced increases in myofibrillar protein synthesis. Muscle contraction activates mTOR signaling, resulting in increased protein synthesis and muscle hypertrophy. Rapamycin-sensitive mTORC1 is important for cap-dependent translation, but the effects of suppressing mTORC1 function using rapamycin on myofibrillar protein synthesis caused by contraction remains unclear. We observed that the eIF4F complex is a translation initiator induced by contraction dependently on rapamycin-sensitive mTORC1. Myofibrillar protein translation increased by muscle contraction was insensitive to rapamycin.
Conceição M, Vechin FC, Telles G
… +10 more, Lixandrão M, Ribeiro N, Riani Costa LA, Hevia-Larraín V, Scarpelli MC, Damas F, Libardi CA, Camera DM, Hawley JA, Ugrinowitsch C
Concurrent training is commonly associated with blunted muscle hypertrophy compared with resistance training alone, but the underlying physiological mechanisms remain unclear. This study aimed to investigate the acute an...Concurrent training is commonly associated with blunted muscle hypertrophy compared with resistance training alone, but the underlying physiological mechanisms remain unclear. This study aimed to investigate the acute and chronic effects of concurrent versus resistance training on muscle protein synthesis, satellite cell dynamics, myonuclear content, myogenic regulatory factor expression, muscle fiber hypertrophy, strength, and aerobic capacity. Nineteen previously untrained young men were randomly assigned to either concurrent or resistance training for 16 wk. Muscle biopsies were collected before and 48 h after a standardized exercise session at and . Samples were analyzed for myofibrillar protein synthesis via deuterium oxide incorporation, satellite cell content, myonuclear number, and gene expression. Strength, aerobic capacity, and muscle fiber cross-sectional area were measured at baseline and postintervention. Muscle protein synthesis increased 48 h postexercise at both and ( = 0.0105), with no group differences. Satellite cell content increased over time in type II fibers only ( = 0.0021). Myonuclear number increased in both fiber types (type I: = 0.0301 and type II: = 0.0009), with higher values in type I fibers in the concurrent training group ( = 0.0027). MYF5 and MYF6 expression increased over time ( = 0.0141 and = 0.034, respectively), and MYOD1 was elevated postexercise only in concurrent training ( = 0.0009). Type II fiber size increased ( = 0.016). Strength gains were greater in resistance training ( = 0.016), whereas aerobic capacity improved only in concurrent training ( < 0.001). Sixteen weeks of concurrent training did not inhibit molecular mechanisms associated with muscle hypertrophy in previously untrained individuals. Sixteen weeks of concurrent training with long-interval HIIT preserved key molecular adaptations related to muscle hypertrophy, including protein synthesis, satellite cell activity, and gene expression. Both concurrent and resistance training increased type II fiber cross-sectional area, but only concurrent training improved V̇o. Although strength gains were lower with concurrent training, molecular and cellular remodeling remained intact, supporting it as an effective strategy to enhance both muscle growth and aerobic fitness simultaneously.
Older adults walk with reduced ankle and greater hip mechanical output compared to young adults. This "distal-to-proximal redistribution" likely contributes to the greater metabolic energy expenditure during walking in o...Older adults walk with reduced ankle and greater hip mechanical output compared to young adults. This "distal-to-proximal redistribution" likely contributes to the greater metabolic energy expenditure during walking in older versus young adults. Because of the inverse relationship between ankle and hip use, functional electrical stimulation (FES) of the ankle extensors may increase ankle mechanical work and indirectly decrease hip mechanical work. Although FES increases stimulated muscle metabolism, bilateral soleus stimulation may restore more youthful walking kinetics without a detectable change in whole body metabolism because ankle extension requires less metabolic energy than hip extension. Ten young adults and 10 older adults walked on a treadmill at 1.25 m/s with and without FES bilaterally applied over the respective leg's soleus when the anterior-posterior ground reaction force exceeded +10% body weight. FES use altered walking mechanics and metabolic power similarly across age groups (all FES condition and age group interactions ≥ 0.214). Across age groups, FES increased ankle mechanical power ( = 0.041) and redistributed mechanical work production to occur relatively more at the ankle and less at the hip ( = 0.010). The lower limb joint redistribution ratio of older adults walking with FES was not different from that of young adults during baseline ( = 0.785). Moreover, walking with FES increased metabolic power by 2% ( = 0.037). FES attenuated older adult distal-to-proximal redistribution and modestly increased whole body metabolic rate. Overall, FES applied to soleus muscles during walking affects users similarly across the lifespan, indicating that FES interventions ought to consider a person's functional needs, regardless of age. Functional electrical stimulation (FES) attenuates the distal-to-proximal redistribution in older adult joint mechanics with a small increase in whole body metabolic rate. Furthermore, FES affects young and older adults similarly, suggesting that such stimulation paradigms can be prescribed based on user needs, independent of age.
Valenčič T, Maeo S, Kluzek S
… +3 more, Holobar A, Škarabot J, Folland JP
J Appl Physiol (1985)
· 2026 Jan · PMID 41363660
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This study examined the effect of the knee-joint angle on motor unit (MU) discharge properties of the vastii muscles and their modulation with contraction level. Twelve young adults performed unilateral isometric knee-ex...This study examined the effect of the knee-joint angle on motor unit (MU) discharge properties of the vastii muscles and their modulation with contraction level. Twelve young adults performed unilateral isometric knee-extension contractions during three experimental sessions at either 25°, 55°, and 85° of knee flexion (full extension: 0°) in a randomized order. Each session involved maximal voluntary contractions (MVCs) followed by submaximal trapezoidal and triangular contractions at different levels relative to maximal voluntary torque (MVT). High-density surface electromyograms were recorded from vastus lateralis and medialis muscles and, subsequently, decomposed to obtain discharge timings of individual MUs. MVT was the greatest, whereas MU discharge rate (DR) during MVCs and submaximal contraction levels (≥30% MVT) was the lowest at the intermediate joint angle (55°). The highest DR during MVCs and high-level contractions (70% MVT), however, was at the most flexed knee position (85°), which was due to a greater DR increase 50%-70% MVT compared with 25° and 55°. The onset-offset DR hysteresis (Δ), an estimate of persistent inward current contribution to motoneuron discharge, decreased with knee flexion and increased with contraction level, whereas the degree of motoneuron input-output nonlinearity (brace height) did not vary with joint angle but decreased with contraction level. At 85°, Δ increased more and brace height decreased less with contraction level compared with 25° and 55°. These findings indicate that vastii MU DR and its modulation with contraction level vary with knee-joint angle, which could be partly explained by the modulation of motoneuron intrinsic electrical properties. This study explored the relationship between motoneuron output to the vastii muscles at different knee-joint angles (quadriceps lengths) and isometric contraction levels. We showed that the motor unit discharge rate was lowest at the angle of the greatest absolute torque capacity, whereas the contraction-level-induced increases in discharge rate and motoneuron excitability were the greatest in the flexed position. These findings suggest that joint-angle-dependent adjustments in sensory feedback modulate motor control of the knee-extensor muscles.
Although some studies report attenuated net muscle glycogenolysis with carbohydrate ingestion, others show no effect, possibly due to small sample sizes or methodological differences. Objective of this study is to determ...Although some studies report attenuated net muscle glycogenolysis with carbohydrate ingestion, others show no effect, possibly due to small sample sizes or methodological differences. Objective of this study is to determine whether carbohydrate ingestion during endurance exercise reduces net skeletal muscle glycogen use and to identify potential moderating factors. A meta-analysis was conducted using data from 31 studies, which included 48 unique effect sizes derived from crossover trials comparing carbohydrate versus placebo ingestion during prolonged endurance exercise. Standardized mean differences (SMDs) in net muscle glycogen use were calculated. A multilevel random-effects model accounted for repeated estimates within studies. Subgroup and meta-regression analyses tested potential moderators. Sensitivity analyses were conducted using a range of plausible pre-/postcorrelation values. Carbohydrate ingestion was associated with a small but statistically significant muscle glycogen-sparing effect [SMD = -0.16, 95% confidence interval (CI): -0.30 to -0.02, = 0.021]. Subgroup and moderator analyses revealed no significant effects of exercise mode, carbohydrate type, ingestion rate, or preexercise glycogen on the observed effect. Translating the standardized effect into absolute units, carbohydrate ingestion was estimated to spare ∼24 mmol·kg dry wt (95% CI: 4-45 mmol·kg) of muscle glycogen, relative to placebo, during ∼100 min of exercise. Carbohydrate ingestion during endurance exercise leads to a small but statistically significant reduction in net skeletal muscle glycogen utilization. Although no consistent moderating variables were identified, the direction of effect was consistent across studies, and the absolute magnitude of sparing may be physiologically meaningful during prolonged or repeated efforts.
Lair B, Le Roux E, de Glisezinski I
… +9 more, Larrouy D, Harant I, Bareille MP, Treffel L, Gauquelin-Koch G, Moro C, Simon C, Laurens C, Bergouignan A
Even brief periods of physical inactivity can induce metabolic disruptions; however, the underlying cellular and molecular mechanisms initiating these alterations remain unclear. We investigated whole-body and skeletal m...Even brief periods of physical inactivity can induce metabolic disruptions; however, the underlying cellular and molecular mechanisms initiating these alterations remain unclear. We investigated whole-body and skeletal muscle-specific metabolic responses to short-term inactivity induced by dry immersion (DI), a model of rapid physical deconditioning. Eighteen healthy men (age = 33.6 [SD 5.5] years, body mass index (BMI) = 23.3 [1.8] kg/m) underwent five days of DI in a longitudinal within-subject design, with each participant serving as his own control. DI-induced inactivity reduced V̇o (-7.4%, = 0.003), fat mass [dual energy X-ray absorptiometry (DXA), -2.6%, = 0.002], fat-free mass (DXA, -2.6%, < 0.001), and quadriceps cross-sectional area (MRI, -2.8%, < 0.001). Fat content increased in the liver (MRI, +21%, < 0.001), but not in the muscles (MRI, +0.1%, = 0.218). Urinary nitrogen excretion rose (+28%, < 0.001), indicating increased whole-body protein catabolism. Fasting insulin (+46%, = 0.009) and triglycerides (+14%, = 0.013), as well as postprandial incremental glucose (+49%, = 0.002) and insulin (+90%, < 0.001) concentrations following a carbohydrate-rich meal were increased. Fasting and postprandial total lipid and carbohydrate oxidation measured by indirect calorimetry and adjusted for body composition remained unchanged ( > 0.05 for all). In differentiated myotubes isolated from vastus lateralis biopsies, insulin-stimulated Akt Thr308 phosphorylation ( = 0.03), in vitro glycogen synthesis assessed from U-C glucose ( < 0.01), and the ability to suppress in vitro palmitate oxidation (1-Cpalmitate) following incremental glucose concentrations were impaired ( = 0.02). The ability to increase palmitate oxidation when palmitate availability rises was not significantly altered. These results suggest that early intrinsic skeletal muscle cell changes may contribute to the onset of whole-body metabolic disorders induced by physical inactivity. Five days of dry immersion led to reduced cardiovascular fitness, muscle atrophy, hepatic fat accumulation, and lower glucose tolerance. These alterations occur despite no detectable changes in whole body fat and carbohydrate oxidation following a carbohydrate-rich meal. In cultured primary myotubes, insulin action and metabolic flexibility (fuel switching) are impaired. Early alterations in intrinsic muscle cell metabolism likely reflect rapid epigenetic imprinting of satellite cells and may contribute to systemic metabolic disturbances induced by physical inactivity.
Transspinal evoked potentials (TEPs) elicited by transcutaneous spinal cord stimulation (tSCS) share some neurophysiological similarities with the H-reflex evoked by peripheral nerve stimulation (PNS). The purpose of thi...Transspinal evoked potentials (TEPs) elicited by transcutaneous spinal cord stimulation (tSCS) share some neurophysiological similarities with the H-reflex evoked by peripheral nerve stimulation (PNS). The purpose of this study was to further compare these two responses during and/or following different external interventions, known to activate Ia afferents. Fourteen volunteers took part in two experimental sessions, where PNS and tSCS promoted the same afferent solicitation of soleus muscle (target muscle). During the first experimental session, modulations of H-reflex and TEP were examined after 20 s of neuromuscular electrical stimulation delivered both at low and high frequency. During the second experimental session, changes in both responses during and following local vibration and passive stretching were evaluated. Results showed no differential modulation between the two soleus responses across the four tested interventions (all > 0.25). Both H-reflex and TEP significantly decreased following low-frequency electrical stimulation ( = 0.001), whereas no significant modulation was observed after high-frequency stimulation ( = 0.08). Similar amplitude reductions between the two responses were also observed during local vibration and passive stretching ( < 0.001). In addition to the similar modulation of soleus responses, modulations of tSCS-evoked responses in synergist muscles during the low-frequency train, as well as in both synergist and antagonist muscles during local vibration and passive stretching, have also been observed. These results provide further evidence of the similarities between H-reflex and TEP, while highlighting the potential of tSCS to concomitantly assess multiple muscles modulations. This study provides evidence that soleus H-reflex, induced by peripheral nerve stimulation and soleus transspinal evoked potential, elicited by tSCS, exhibit similar modulations during and after interventions known to vary afferent input to spinal motoneurons. It further reveals the impact of these interventions on multiple lower limb muscles, highlighting the significant advantage of using tSCS-evoked responses as a powerful tool to assess modulations of the neuromuscular system.
Riem L, Pinette M, DuCharme O
… +16 more, Pabon V, Morris J, Coggins A, Harold L, Costanzo KE, Cousins M, Hein R, Rhodes M, Lievens E, Shah R, Feng X, Benusa S, Breeding T, Nelson MD, Derave W, Blemker SS
Body sizes and shapes vary widely, even among healthy adults, resulting in diverse muscle sizes, strengths, and performance capacities. This study developed an artificially intelligent (AI) algorithm to segment individua...Body sizes and shapes vary widely, even among healthy adults, resulting in diverse muscle sizes, strengths, and performance capacities. This study developed an artificially intelligent (AI) algorithm to segment individual muscles and bones from whole body MRI scans of 102 healthy adults (49 males, 53 females) aged 18-50 yr, generating three-dimensional (3-D) segmentations of 70 muscles and 13 bones spanning the upper limbs, trunk, and lower limbs. We quantified muscle volume, asymmetry, and fat fraction at whole body, regional, and individual-muscle levels, and examined how these properties correlate with body size and skeletal dimensions. Fat fraction and asymmetry varied across muscles and were generally similar between sexes; however, the distribution of muscle volume across the body differed between females and males. Across all predictors tested, total bone volume showed the strongest correlation with total muscle volume ( = 0.85), followed by femur volume, height × mass, mass, height, and BMI. At the individual muscle level, the associated bone volume consistently explained more variance in muscle size than anthropometric predictors. Correlations between muscle volume and body-size parameters were significantly different between males and females, whereas bone-volume correlations showed no significant sex differences. These results suggest that skeletal dimensions-reflecting an individual's "frame size"-are stronger determinants of muscularity than body size metrics and explain the observed sex differences in muscle sizes. This work presents a comprehensive in vivo muscle-level dataset to date, introduces a novel framework for analyzing muscle-bone correlations, and provides reference data for applications from clinical diagnostics to athletic performance and musculoskeletal modeling. This study presents the most comprehensive in vivo dataset of full-body muscle and bone volumes in healthy adults, showing that skeletal dimensions are the strongest predictors of muscularity, with height × mass emerging as the second-best predictor.