Intestinal epithelial barrier function and tight junction proteins with heat and exercise

A single layer of enterocytes and tight junctions (intercellular multiprotein complexes) form the intestinal epithelial barrier that controls transport of molecules through transcellular and paracellular pathways. A dysfunctional or “leaky” intestinal tight junction barrier allows augmented permeation of luminal antigens, endotoxins, and bacteria into the blood stream. Various substances and conditions have been shown to affect the maintenance of the intestinal epithelial tight junction barrier. The primary focus of the present review is to analyze the effects of exertional or nonexertional (passive hyperthermia) heat stress on tight junction barrier function in in vitro and in vivo (animals and humans) models. Our secondary focus is to review changes in tight junction proteins in response to exercise or hyperthermic conditions. Finally, we discuss some pharmacological or nutritional interventions that may affect the cellular mechanisms involved in maintaining homeostasis of the intestinal epithelial tight junction barrier during heat stress or exercise

Harness Suspension Stress: Physiological and Safety Assessment

Hanging motionless in a full body harness may result in unwanted events, such as acute hypotension and syncope, which has been termed harness suspension stress (HSS). The etiology of HSS has not been explored, and it is unknown if the type of harness influences the HSS response. Objectives: Evaluate hemodynamics, subjective discomfort, and biological markers of muscle damage during 30-minutes suspension; and evaluate differences between harness attachment (frontal or dorsal). Methods: Heart rate, blood pressure, biological markers of muscle damage, and subjective discomfort were measured. Results: Trial time was shorter in the dorsal versus frontal point of attachment. Hemodynamic shift resulted in the dorsal trial which indicated possible perfusion abnormalities. Conclusions: Hemodynamic adjustments contributed to early termination observed in the dorsal trial. A frontal point of attachment may be more suitable for extended harness exposure

Objective and subjective measures of exercise intensity during thermo-neutral and hot yoga.

While hot yoga has gained enormous popularity in recent years due in part to increased environmental challenge associated with exercise in the heat, it is not clear whether hot yoga is more vigorous than thermo-neutral yoga. Therefore, the aim of this study was to determine objective and subjective measures of exercise intensity during constant intensity yoga in a hot and thermo-neutral environment. Using a randomized, cross-over design, 14 participants completed two identical ~20-minute yoga sessions in a hot (35.3 ± 0.8°C; humidity: 20.5 ± 1.4%) and thermo-neutral (22.1 ± 0.2°C; humidity: 27.8 ± 1.6%) environment. Oxygen consumption (VO2) and heart rate (HR) were recorded as objective measures (%VO2max and %HRmax) and rating of perceived exertion (RPE) was recorded as a subjective measure of exercise intensity. There was no difference in exercise intensity based on %VO2max during hot vs. thermo-neutral yoga (30.9 ± 2.3 vs. 30.5 ± 1.8%, p=0.68). However, exercise intensity was significantly higher during hot vs. thermo-neutral yoga based on %HRmax (67.0 ± 2.3 vs. 60.8 ± 1.9%, p=0.01) and RPE (12 ± 1 vs. 11 ± 1, p=0.04). According to established exercise intensities, hot yoga was classified as “light-intensity” based on %VO2 but “moderate-intensity” exercise based on %HRmax and RPE while thermo-neutral yoga was classified as “light-intensity” exercise based on %VO2max, %HRmax, and RPE. Despite the added hemodynamic stress and perception that yoga is more strenuous in a hot environment, we observed similar oxygen consumption during hot vs. thermo-neutral yoga classifying both exercise modalities as “light-intensity” exercise.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Autophagy response to acute high-intensity interval training and moderate-intensity continuous training is dissimilar in skeletal muscle and peripheral blood mononuclear cells and is influenced by sex

Autophagy is an evolutionary conserved cellular degradation system that underlies the positive effects of exercise. Currently, few human data exist investigating the autophagic response to exercise including the response to high-intensity interval training (HIIT), response in divergent tissues, and if sex differences exist. The purpose of this study was to investigate the autophagy response in skeletal muscle and peripheral blood mononuclear cells (PBMCs) following an acute bout of HIIT and moderate-intensity continuous training (MICT) with treadmill running in males and females. Using a crossover design, ten recreationally-active males (n = 5; 25.2 ± 1.1 yrs) and females (n = 5; 21.6 ± 3.6 yrs) performed a bout of MICT (60 min at 55% of max velocity [Vmax]]) and HIIT (12 bouts of 1 min at 100% Vmax and 1 min at 3 miles per hour) in a fasted state separated by ≥ 72 h. Muscle biopsy samples from the vastus lateralis and PBMCs were collected pre- and 3 h post-exercise and analyzed for differences in protein expression of LC3I, LC3II, and p62 via western blot analysis. Expression of LC3II:LC3I was significantly different from pre-exercise 3 h post-exercise in MICT in skeletal muscle (64.3 ± 47.3%; p = 0.024). A significant time effect was found for p62 3 h post-exercise compared to pre-exercise (135.23 ± 84.6%; p = 0.043) in skeletal muscle. No differences in markers of autophagy were observed in PBMCs. When sexes were analyzed separately there was a condition x time x sex interaction in LC3II (p = 0.007) and LC3II:LC3I (p = 0.043) in PBMCs. Post hoc analyses revealed a difference in LC3II pre vs. 3 h post exercise in males, but not females, in both HIIT (144.2 ± 89.7%; p = 0.024) and MICT (61.8 ± 36.1%; p = 0.043). Our findings show that HIIT results in changes in markers of autophagy and that the exercise-induced autophagy response varies in tissues and between sexes