Experimental Physiology最新文献

Exercise in hot climates increases the risk of gastrointestinal (GI) disruption and respiratory illness. We investigated the effects of a 42 day prebiotic intervention on markers of intestinal epithelial injury, GI discomfort and immunity following football specific exercise in the heat and daily upper respiratory illness. Twenty-six team-sport male athletes were randomized to receive 3.65 (2.75 active galactooligosaccharide) g day^-1 of either Bimuno galactooligosaccharide (Bimuno^® GOS; n = 13) or a maltodextrin placebo (Placebo; n = 13) for 42 days in a double-blind parallel group design. At days 0 and 42 of each intervention, participants completed the football specific intermittent treadmill protocol in 33°C and 50% relative humidity. Blood, saliva and GI symptoms were collected at days 0 and 42 for the assessment of plasma intestinal fatty acid binding protein, lipopolysaccharide binding protein, salivary immunoglobulin A (sIgA) and GI discomfort. Participants also completed questionnaires for self-reported upper respiratory and gastrointestinal symptoms (daily and weekly, respectively), over the 42 days. At day 42, there was a reduction in pre-full-time change in plasma intestinal fatty acid binding protein and severity of GI discomfort in the Bimuno^® GOS group compared with Placebo, but no change in lipopolysaccharide binding protein. The day 0-42 change in sIgA secretion rate after the football specific intermittent treadmill protocol was higher in the Bimuno^® GOS than the Placebo group, and during the 42 days there was a reduction in upper respiratory symptom duration and severity in the Bimuno^® GOS group compared with Placebo. In team-sport athletes, 42 days of supplementation with prebiotic Bimuno^® GOS can alleviate GI disruption and better maintain sIgA secretion rate in response to football specific activity in the heat, whilst also reducing the duration and severity of upper respiratory symptoms.

The effects of high-load (HL) versus high-volume (HV) resistance training (RT) on various molecular outcomes are similar. However, mitochondrial responses remain understudied. Therefore, the purpose of this study was to interrogate mitochondrial mRNA and protein responses to acute and chronic HL versus HV RT. Vastus lateralis biopsies from resistance trained males in two prior studies were assessed. In Study 1, 11 college-aged men completed an acute bout of either HL or HV RT exercises to failure. Biopsies were collected at PRE, 3-h post-, and 6-h post-exercise. In Study 2, 15 college-aged men participated in 6 weeks of supervised unilateral RT where each leg was assigned to either HL or HV RT. Biopsies were collected from both legs prior to and 72 h following last training bout of the intervention. Biopsies from both studies were used to assess mitochondrial mRNAs, and Study 2 biopsies were assayed for mitochondrial proteins and citrate synthase (CS) activity. Results from both studies revealed several significant main effects of time but no significant interactions. Additionally, CS activity, a surrogate of mitochondrial content, decreased following chronic RT (P = 0.016) but no interaction was observed between the HV and the HL leg over time (P = 0.882). In conclusion, while RT resulted in both acute mitochondrial mRNA and chronic CS activity and mitochondrial protein responses, there were no differences in the HL versus HV paradigms on these outcomes.

Control of frontal plane mechanics requires active integration of sensory feedback to regulate stability in response to gait perturbations, such as split-belt walking (SBW). In comparison to sagittal plane mechanics, mediolateral (ML) kinematic and kinetic adaptations to split-belt perturbations are less extensively reported. Moreover, the associated metabolic cost of ML adaptations and the retention of previously learned adaptations, defined as motor savings, have not been examined concurrently. We investigated bilateral adaptations in step width and peak ML ground reaction forces to an initial SBW and metabolic cost. We also examined the retention of these adaptations during a subsequent SBW (adapt 2). Given evidence that priming the nervous system with acute intermittent hypoxia (AIH) enhances motor adaptation, we compared the magnitude of these adaptations after AIH. Legs on the fast and slow belt increased step width during initial SBW, but the magnitude of width reduced during adapt 2. Distinct kinetic modulation patterns emerged between legs as the initial increase in ML ground reaction forces was attenuated for the slow leg during the braking impulse phase and for the fast leg during the propulsive impulse phase. Metabolic cost reductions were positively associated with adaptations in ML force but not step width. During adapt 2, individuals who received AIH demonstrated greater reductions in step width and ML ground reaction forces during propulsion, suggesting enhanced motor savings. These asymmetrical ML kinetic adaptations contribute to stability and reduced metabolic cost during SBW. These insights might inform the design of training approaches to improve stability in clinical populations.

Horizontal bed rest (HBR) and head-down tilt (HDT) are models of physical inactivity. In this systematic review and meta-analysis, we aimed to quantify changes in cardiometabolic outcomes during HBR and HDT in healthy adults. Following the PRISMA guidelines, we searched PubMed, Scopus, Web of Science and Cochrane Library until 1 October 2025. Included studies recruited healthy adults (≥18 years of age) undergoing ≥2 days of HBR or HDT. A meta-analysis with mean differences (MD) and 95% confidence intervals (CI), using random-effects modelling was conducted. Forty-four studies were included. HBR (≤14 days) reduced fasting glucose (MD, -0.15 mmol/L, P = 0.00033). HBR (≤14 days) and HDT (≤60 days) increased insulin (HBR: MD, 7.07 pmol/L; HDT: MD, 9.65 pmol/L; P < 0.0001). The homeostatic model assessment for insulin resistance was increased under both models (HBR ≤30 days: MD, 0.10, P = 0.0004; HDT ≤60 days: MD, 0.24, P < 0.0001). HDT lowered total cholesterol (MD: -13.89 mg/dL, P = 0.000467); HBR raised triglycerides (MD, 18.96 mg/dL, P < 0.0001), and high-density lipoprotein cholesterol was decreased in both models (HBR ≤14 days: MD, -4.53 mg/dL, P = 0.000608; HDT ≤60 days: MD, -6.89; P < 0.0001). C-Reactive protein was elevated in HBR (MD, 1.57; P < 0.0001), and tumour necrosis factor alpha was elevated in both (HBR ≤14 days: MD, 1.33, P < 0.0001; HDT ≤21 days: MD, 0.40; P = 0.00643). In conclusion, HBR and HDT induce model- and duration-specific changes in glucose metabolism and lipid profiles. Interventions that could mitigate these effects may be warranted.

The purpose of this study was to perform a novel exploration of sex-based differences in various single- and paired-pulse transcranial magnetic stimulation (TMS)-based measures of corticospinal excitability and inhibition. Thirty participants (15 females) attended one laboratory visit where responses evoked by single- and paired-pulse TMS were recorded using electromyography from the first dorsal interosseous muscle. Excitability was assessed via the motor-evoked potential (MEP) and intracortical facilitation (ICF). Inhibition was assessed via the cortical silent period (CSP), short-interval intracortical inhibition (SICI), and long-interval intracortical inhibition (LICI). Each measure was compared between sexes. Overall, males and females did not significantly differ in excitability (MEP: P = 0.070; ICF: P = 0.194). Males displayed significantly greater inhibition compared to females for the SICI (P = 0.016) and LICI (P = 0.003) measures but not CSP (P = 0.612). These findings suggest that sex may be an important consideration for some (SICI and LICI), but not all TMS-based measures of corticospinal excitability and inhibition.

Restriction of fetal substrate supply has an adverse effect on surfactant maturation in the lung and thus affects the transition from in utero placental oxygenation to pulmonary ventilation ex utero. However, the consequences of reduced fetal substrate supply are dependent on the timing of gestation, severity and duration. We hypothesise that maternal nutrient restriction (MNR) from early pregnancy negatively impacts fetal lung maturation. Female baboons of similar age and weight were randomly assigned to either a control diet (n = 3F, 5M offspring) or MNR (n = 4F, 4M offspring). On a weight-adjusted basis, MNR animals were fed 70% of the feed consumed by controls. Fetal lung tissue was collected at 0.9 gestation (term = 184 days). qRT-PCR and immunohistochemistry were utilised to measure expression of key molecules involved in surfactant maturation, reabsorption of lung liquid, vascularisation and immune cells. MNR decreased type II alveolar epithelial cell density and the mRNA expression of PCYT1A, the gene for choline-phosphate cytidylyltransferase A, the enzyme required for de novo surfactant phospholipid synthesis. However, MNR had no effect on the expression of surfactant proteins in the fetal lung. There was a reduced number of α-smooth muscle actin-stained vessels and presence of CD45⁺ immune cells within the lung of fetuses exposed to MNR. These data indicate that MNR from early pregnancy increases risk of neonatal respiratory complications at birth by impairing the capacity for surfactant maturation, reducing vascularisation within the fetal lung and impairing innate lung immunity.

In this study, we compared acute metabolic responses and barbell velocity loss (VL) during cluster set (CS) versus traditional set (TS) resistance exercise. Six strength-trained individuals completed two randomized crossover sessions of back squats. The CS protocol included 30 s intra-set rest intervals after the second and fourth repetitions, whereas the TS protocol used continuous repetitions. Barbell velocity, oxygen uptake and blood lactate concentrations were measured to derive model-based indices of energy system engagement. CS were associated with better preservation of barbell velocity and lower blood lactate concentrations compared with TS. Model-based indices suggested distinct metabolic patterns between set structures, with CS being associated with a higher alactic and lower lactic component than TS. Inter-individual responses were consistent across most participants. These findings indicate that acute metabolic and mechanical responses differ between CS and TS configurations. CS were associated with reduced indices of metabolic stress alongside improved velocity preservation, highlighting that set structure can influence the acute physiological-performance profile of resistance exercise.