The effect of oral glutamine supplementation on gut permeability and heat shock protein regulation in runners with a history of gastrointestinal distress

Gastrointestinal (GI) permeability increases during high intensity exercise leading to endotoxin leakage, and a pro-inflammatory immune response. The purpose of this study are to assess whether oral glutamine supplementation (1) reduces exercise induced permeability through up-regulation of the heat shock response resulting in occludin stabilization, and (2) depresses the exercise induced inflammatory response. Methods. Eight human subjects (n=8) participated in baseline (PRE) testing, a glutamine (GLN), and placebo (PLA) supplementation trial in a double blind design. After PRE measurements, subjects ingested .9g/kg fat free mass of glutamine per day or a sugar free lemon placebo drink for seven days with a one-month washout period between trials. A 60-min treadmill run at 70% of maximal oxygen consumption was performed at 30°C in an environmental chamber at the end of each supplementation period. Intestinal permeability was assessed at rest and during each trial through urine concentrations of lactulose and rhamnose. Plasma glutamine, plasma endotoxin, and peripheral blood mononuclear cell levels of heat shock protein 70 (HSP70), and nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκB-α) were measured pre-exercise, post-exercise, 2hr post-exercise, and 4hr post-exercise. Cultured caco-2 human intestinal epithelial cells supplemented with three concentrations of GLN (0, 4, and 6mmol/L) were exposed to heat stress (41\xbaC) to simulate exercise and control (37\xbaC) conditions. HSP70, heat shock factor 1 (HSF-1), and occludin were measured from each culture. Results: Core temperature was not different between exercise trials (39.40 ± .39 vs. 39.54 ± .22 for PLA vs. GLN, respectively, p\u3e0.05). Resting plasma glutamine levels were significantly higher in the GLN trial versus PLA (1.893 ± 0.245mmol.L vs. 0.8285 ± 0.078 mmol.L, p\u3c0.05). Permeability as the ratio of lactulose to rhamnose was significantly higher in the PLA trial when compared to PRE (.0604 ± .0470 vs. .0218 ±.0084, respectively, p\u3c0.05). Permeability was not statistically different between GLN trial and PRE (.0272 ± .0074 vs. .0218 ± .0084, respectively, p\u3e0.05). PBMC expression of IκB-α and HSP70 were higher at the 4hr post-exercise time point in the GLN trial when compared to the 4hr mark in the PLA (.9839 ± .1587 vs. 1.520 ±.2294 and 2.083 ± .6712 vs. 2.895 ± .8444, p\u3c0.05 for IKB-α and HSP70, respectively). Plasma endotoxin was higher compared to pre-exercise at the 2hr post-exercise in the PLA trial (2.883 ± 0.4310 pg.ml vs. 4.550 ± 0.3350 pg.ml, p\u3c0.05 respectively) and significantly higher when compared to the 2hr post-exercise mark in GLN trial (4.550 ± 0.3350 pg/ml vs. 2.883 ± .4314 pg/ml, p\u3c0.05). Results of cell culture: HSP70 expression in Caco-2 cells was higher in the 6mmol 41\xbaC trial when compared to the 0mmol 41\xbaC trial (1.973 ± 0.163 vs. 1.133 ± 0.064, p\u3c0.05, respectively). HSF-1 was higher in the 4mmol 41 \xbaC and the 6mmol 41\xbaC trials when compared to the 0mmol 41\xbaC (1.649 ± 0.185, 1.785 ± 0.185 vs. 0.6681 ± 0.145, p\u3c0.05). Occludin levels were statistically lower in the 0mmol 41\xbaC when compared to 0mmol 37\xbaC representing de-stabilization of the TJ protein in response to heat stress (0.7434 ± 0.015 ± 1.0000 ± 0.000, p\u3c0.05, respectively). Occludin levels during both 4mmol 41\xbaC and 6mmol 41\xbaC trials were statistically higher when compared to 0mmol 41\xbaC (1.236 ± 0.143 and 1.849 ± 0.143 vs. 0.7434 ± 0.015, p=0.032, p\u3c0.001, respectively) Conclusion: Seven days of oral glutamine supplementation prevents exercise induced intestinal permeability and endotoxin leakage possibly through HSF-1 and HSP70 activation leading to occludin stabilization at the tight junction. In addition, glutamine suppressed the inflammatory response to high intensity exercise through activation of HSP70, reduced IKB-α degradation and possible NFκ-B inhibition

Targeted exercise therapy to enhance neural activation

Various types of exercise therapies, have been implemented into treatment for those suffering from psychological disorders and traumatic brain injury. The prefrontal cortex (PFC), which houses key cognitive constructs is responsive to exercise, and is commonly measured using functional near infrared spectroscopy (fNIRS). Evidence suggests that exercise mediates neural adaptation through increased blood flow and neurogenesis, which enhances neural activation leading to improved cognitive performance. However, the intensity of exercise that has the most robust impact on brain blood flow is currently unknown. Purpose. Therefore, the primary aim of the study is to compare PFC activation during cognitive tasks performed after low-intensity, high intensity, and yoga exercises. Methods. Eight subjects (4=M, 4=F), aged 35±5 years completed a control, high intensity, low intensity, and yoga exercise trial followed by administration of a cognitive task (NIH Toolbox Fluid Cognition). Left and right PFC oxygenation were measured during the post-exercise cognitive assessment using fNIRS technology. Results. Oxygenation during the cognitive task was higher in the left PFC region after low intensity exercise compared to all other trials (control, high intensity, yoga). Regression model analysis showed that a 10% increase in %HRmax up to 70% intensity predicts an increase in left PFC oxygenation by 2.11 umol. Conclusion. Acute exercise below 70% aerobic intensity increased brain blood flow during a post-exercise cognitive task. Therefore, it may be beneficial for those who engage in any cognitive related activity to perform a brief bout of low-intensity exercise prior to the task (e.g. academic-based testing or motor training)

Oral Glutamine Supplement Reduces Subjective Fatigue Ratings during Repeated Bouts of Firefighting Simulations

Wildland firefighting requires repetitive (e.g., consecutive work shifts) physical work in dangerous conditions (e.g., heat and pollution). Workers commonly enter these environments in a nonacclimated state, leading to fatigue and heightened injury risk. Strategies to improve tolerance to these stressors are lacking. Purpose: To determine if glutamine ingestion prior to and after consecutive days of firefighting simulations in the heat attenuates subjective ratings of fatigue, and evaluate if results were supported by glutamine-induced upregulation of biological stress responses. Methods: Participants (5 male, 3 female) ingested glutamine (0.15 g/kg/day) or a placebo before and after two consecutive days (separated by 24 h) of firefighter simulations in a heated chamber (35 degrees C, 35% humidity). Perceived fatigue and biological stress were measured pre-, post-, and 4 h postexercise in each trial. Results: Subjective fatigue was reduced pre-exercise on Day 2 in the glutamine group (p \u3c 0.05). Peripheral mononuclear cell expression of heat shock protein 70 (HSP70) and serum antioxidants were elevated at 4 h postexercise on Day 1 in the glutamine trial (p \u3c 0.05). Conclusions: Ingestion of glutamine before and after repeated firefighter simulations in the heat resulted in reduced subjective fatigue on Day 2, which may be a result of the upregulation of biological stress systems (antioxidants, HSPs). This response may support recovery and improve work performance

Evidence for the Invalidity of the Wingate Test for the Assessment of Peak Power, Power Decrement and Muscular Fatigue

We hypothesized that the protocol-induced initial cadence of the WAnT is too high to allow high muscle force production and peak power generation. Twenty endurance, strength or power trained subjects (9 male, 11 female) completed two 30 s maximal exertion stationary cycle ergometer tests involving the traditional peak cadence start (TRAD) vs. a stationary start (STAT). Inertia corrected mechanical power, cadence, EMG from the vastus lateralis, and applied force to the pedals were measured continuously throughout both tests. Peak power was higher during TRAD; 11.32 ±1.41 vs. 10.40 ±1.35 Watts/kg (p < 0.0001), as was peak cadence; 171.4 ±16.3 vs. 120.9 ±15.1 rev/min (p < 0.0001). However, during TRAD EMG root mean squared (rms) increased continuously throughout the test, force applied to the pedals increased from 1 to 3 s (0.73 ±0.27 vs. 0.90 ±0.39 N/kg; p = 0.02) and thereafter remained relatively stable. EMG mean frequency also increased from 1 to 3 s, but then decreased throughout the remainder of the test. During TRAD, mechanical power decreased near immediately despite increasing EMG rms, EMGmean frequency and force application to the pedals. The initial 10 s of data from the WAnT is invalid. We recommend that intense cycle ergometer testing should commence with a stationary start

The Effect of Self-Selected Exercise Workloads on Perceived Enjoyment and Self-Efficacy in Sedentary Adults

Self-selected workloads are shown to be more enjoyable than researcher-selected workloads. In addition, it is unclear if sedentary adults find aerobic interval or continuous exercise more pleasant. Therefore, the primary purpose of this study was to determine the effects of two acute bouts (interval vs. continuous) of self-selected moderate-intensity treadmill exercises on perceived enjoyment and self-efficacy towards exercise in a sedentary cohort. Methods: Sixteen sedentary adults completed two 30 min bouts of moderate-intensity treadmill activity, one interval and one continuous. Participants blindly (could not see speed, grade, and heart rate) selected their own treadmill workload with guidance from the Borg RPE 6–20 scale. Post-exercise self-efficacy and perceived enjoyment were assessed using the Self-Efficacy for Exercise Scale and the Physical Activity Enjoyment Scale, respectively. Exercise workloads using treadmill speed and grade and exercise heart rate were compared between trials. Results: No significant differences were found between conditions for self-selected workloads (p = 0.62), self-efficacy (p = 0.58), perceived enjoyment (p = 0.41), and heart rate (p = 0.12). Discussion: Sedentary individuals reported no difference in self-efficacy or perceived exercise enjoyment. Participants were, however, adequate in self-selecting their own intensities with RPE guidance as there were no differences in the workloads across conditions. These results suggest that when able to self-select moderate-intensity exercise workloads, sedentary individuals equally enjoy both interval and continuous exercise

Exercise Prescription and Progression Practices among US Cardiac Rehabilitation Clinics

Background: Little is known about exercise prescription practices in cardiac rehabilitation (CR). Therefore, the purpose of this study was to understand how initial exercise is prescribed and how exercise intensity is progressed among cardiac patients enrolled in United States CR programs. Methods: A 22-question survey was sent out to US CR clinics. Results: Ninety-three clinics responded to the survey. RPE was the most commonly reported exercise intensity indicator used for prescribing exercise, followed by resting HR + 20–30 bpm. Exercise progression practices were also based on patient sustained RPE values. Conclusions. Exercise prescription practice has become reliant on subjective indicators of exercise intensity. This may limit patient outcomes, such as improvement in functional measures

The Influence of Exercise Workload Progression Across 36 Sessions of Cardiac Rehabilitation on Functional Capacity

Defining time frames throughout cardiac rehabilitation (CR) to progress exercise workloads may lead to improve functional capacity outcomes. The purpose of this study was to investigate the role of exercise progression on functional capacity among cardiac patients enrolled in CR. This was a retrospective database analysis study. Extracted data included: Demographic, functional capacity (in METs), and exercise intensity during exercise sessions 2, 12, 24, and 36 of CR from 150 patients who completed a 36-session program. Progression of exercise was determined by calculating percent change in treadmill exercise workload within predefined time frames of CR. The time frames were percent change from exercise session 2 to 12 (“%ΔS2–S12), 12 to 24 (%ΔS12–S24), and 24 to 36 (%ΔS24–S36). A multiple linear regression model was developed to predict change in functional capacity (ΔMETs). A significant proportion (21%) of total variation in ΔMETs was predicted by %ΔS2–12, %ΔS12–24, %ΔS24–36, age, sex, and body mass index (BMI). Percent changes between sessions 12 to 24 (%ΔS12–24; β = 0.17, p = 0.03) and 24 to 36 (%ΔS24–36; β = 0.23, p < 0.01) were significant predictors. Progressing patients between sessions 12 to 24 and 24 to 36 predicted significant changes in functional capacity and reinforced the importance of exercise progression across all 36 sessions of CR

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

Cardiac rehabilitation utilization, barriers, and outcomes among patients with heart failure

Exercise-based cardiac rehabilitation (CR) is effective for improving both primary (i.e., mortality and hospitalizations) and secondary (i.e., functional capacity and quality of life among) clinical outcomes among patients with heart failure (HF). The mechanisms that explain these benefits are complex and are linked to exercise adaptations such as central and peripheral hemodynamics combined with improved overall medical management. Despite the benefits of CR, utilization rates are low among CR eligible patients. Clinician-, patient-, and health system-related barriers have been identified as primary factors contributing to the lack of CR utilization among HF patients. These include patient referrals (clinician-related), psychosocial factors (patient-related), and patient access to CR services (health system-related). The aims of this review are to detail the components of each barrier as well as identify evidence-based strategies to improve CR utilization and adherence among HF. The improvements in primary and secondary outcomes along with the mechanisms that are linked to these changes will also be examined

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