Does Age Influence Gastrointestinal Status Responses to Exertional-heat Stress?

This meta-data exploration aimed to determine the impact of exertional-heat stress (EHS) on gastrointestinal status of masters age and young adult endurance athletes. Sixteen MASTERS (mean: 44y) and twenty-one YOUNG (26y) recreational endurance athletes completed 2 h of running at 60% ˙V O2max in 35˚C ambient conditions. Blood samples were collected pre-, immediately and 1 h post-EHS, and analyzed for markers of exercise-induced gastrointestinal syndrome (EIGS). Thermo-physiological measures and gastrointestinal symptoms (GIS) were recorded every 10-20 min during EHS. Peak Δ pre- to post-EHS did not substantially differ (p>0.05) between MASTERS and YOUNG for intestinal epithelial injury [I-FABP: 1652pg/ml vs. 1524pg/ml, respectively], bacterial endotoxic translocation [sCD14: -0.09µg/mL vs. 0.84µg/mL, respectively], lipopolysaccharide-binding protein [LBP: 0.26µg/mL vs. 1.76µg/mL, respectively], and systemic inflammatory response profile (SIR-Profile: 92.0arb.unit vs. 154arb.unit, respectively). A significantly higher peak Δ pre- to post-EHS in endogenous endotoxin anti-body IgM (p=0.042), and pro-inflammatory cytokine IL-1ß (p=0.038), was observed in YOUNG compared to MASTERS. No difference was observed between incidence (81% and 80%, respectively) and severity (summative accumulation: 21 and 30, respectively) of reported GIS during EHS between MASTERS and YOUNG. Pathophysiology of EIGS in response to EHS does not substantially differ with age progression, since masters and younger adult endurance athletes responded comparably.

Influence of acute heat mitigation strategies on core temperature, heart rate and aerobic performance in females: A systematic literature review.

This review examined the effect of acute heat mitigation strategies on physiological strain and exercise performance in females exercising in the heat. Three databases were searched for original research with an acute heat mitigation (intervention) and control strategy in active females and reporting core temperature, heart rate and/or aerobic exercise performance/capacity with ≥ 24°C wet bulb globe temperature. Hedges' g effect sizes were calculated to evaluate outcomes. Thirteen studies (n = 118) were included. Most studies that applied an acute heat mitigation strategy to females did not reduce thermal (9/10) or cardiovascular (6/6) strain or improve exercise performance/capacity (8/10). The most effective strategies for attenuating thermal strain were pre-cooling with ice-slurry (effect size = -2.2 [95% CI, -3.2, -1.1]) and ice-vests (-1.9 [-2.7, -1.1]), and pre- and per-cooling with an ice-vest (-1.8 [-2.9, -0.7]). Only pre-cooling with an ice-vest improved running performance (-1.8 [-2.9, -0.7]; ~0.43 min) whilst sodium hyperhydration improved cycling capacity at 70% V O2peak (0.8 [0.0, 1.6]; ~20.1 min). There is currently limited research on acute heat mitigation strategies in females, so the evidence for the efficacy is scarce. Some studies show beneficial effects with ice-slurry, ice-vests and sodium hyperhydration, which can guide future research to support female exercise performance in the heat.

Auditing the Representation of Females Versus Males in Heat Adaptation Research.

The aim of this audit was to quantify female representation in research on heat adaptation. Using a standardized audit tool, the PubMed database was searched for heat adaptation literature from inception to February 2023. Studies were included if they investigated heat adaptation among female and male adults (≥18-50 years) who were free from noncommunicable diseases, with heat adaptation the primary or secondary outcome of interest. The number and sex of participants, athletic caliber, menstrual status, research theme, journal impact factor, Altmetric score, Field-Weighted Citation Impact, and type of heat exposure were extracted. A total of 477 studies were identified in this audit, including 7,707 participants with ∼13% of these being female. Most studies investigated male-only cohorts (∼74%, n = 5,672 males), with ∼5% (n = 360 females) including female-only cohorts. Of the 126 studies that included females, only 10% provided some evidence of appropriate methodological control to account for ovarian hormone status, with no study meeting best-practice recommendations. Of the included female participants, 40% were able to be classified to an athletic caliber, with 67% of these being allocated to Tier 2 (i.e., trained/developmental) or below. Exercise heat acclimation was the dominant method of heat exposure (437 interventions), with 21 studies investigating sex differences in exercise heat acclimation interventions. We recommend that future research on heat adaptation in female participants use methodological approaches that consider the potential impact of sexual dimorphism on study outcomes to provide evidence-based guidelines for female athletes preparing for exercise or competition in hot conditions.

Plasma measurements of the dual sugar test reveal carbohydrate immediately alleviates intestinal permeability caused by exertional heat stress.

The aim of this set of randomised cross-over studies was to determine the impact of progressive heat exposure and carbohydrate or protein feeding during exertional stress on small intestine permeability using a dual sugar test. In our previous work, and typically in the field, recovery of lactulose and l-rhamnose is measured cumulatively in urine. This follow-up study exploits our novel high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) protocol to accurately quantify the sugars in plasma. Endurance-trained participants completed experimental trial A (ET-A; n = 8), consisting of 2 h running at 60% V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ in temperate, warm and hot ambient conditions, and/or experimental trial B (ET-B; n = 9), consisting of 2 h running at 60% V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ in the heat while consuming water, carbohydrate or protein. Blood samples were collected and plasma lactulose (L) and l-rhamnose (R) appearance, after dual sugar solution ingestion at 90 min of exercise, was quantified by HPAEC-PAD to measure plasma L/R and reveal new information about intestinal permeability immediately post-exercise and during recovery. In ET-A, plasma L/R increased immediately post-exercise in hot compared with temperate and warm conditions, while, in ET-B, carbohydrate alleviated this, and this information was otherwise missed when measuring urine L/R. Consuming carbohydrate or protein before and during exercise attenuated small intestine permeability throughout recovery from exertional heat stress. We recommend using the dual sugar test with quantification of plasma sugars by HPAEC-PAD at intervals to maximise intestinal permeability data collection in exercise gastroenterology research, as this gives additional information compared to urinary measurements. KEY POINTS: Intestinal permeability is typically assessed using a dual sugar test, by administering a drink containing non-metabolisable sugars (e.g. lactulose (L) and l-rhamnose (R)) that can enter the circulation by paracellular translocation when the epithelium is compromised, and are subsequently measured in urine. We demonstrate that our recently developed ion chromatography protocol can be used to accurately quantify the L/R ratio in plasma, and that measuring L/R in plasma collected at intervals during the post-exercise recovery period reveals novel acute response information compared to measuring 5-h cumulative urine L/R. We confirm that exercising in hot ambient conditions increases intestinal epithelial permeability immediately after exercise, while consuming carbohydrate or protein immediately before and during exercise attenuates this. We recommend using our dual sugar absorption test protocol to maximise intestinal epithelial permeability data collection in exercise gastroenterology research and beyond.

A Comparison of Sodium Citrate and Sodium Bicarbonate Ingestion: Blood Alkalosis and Gastrointestinal Symptoms.

This study compared the recommended dose of sodium citrate (SC, 500 mg/kg body mass) and sodium bicarbonate (SB, 300 mg/kg body mass) for blood alkalosis (blood [HCO3-]) and gastrointestinal symptoms (GIS; number and severity). Sixteen healthy individuals ingested the supplements in a randomized, crossover design. Gelatin capsules were ingested over 15 min alongside a carbohydrate-rich meal, after which participants remained seated for forearm venous blood sample collection and completion of GIS questionnaires every 30 min for 300 min. Time-course and session value (i.e., peak and time to peak) comparisons of SC and SB supplementation were performed using linear mixed models. Peak blood [HCO3-] was similar for SC (mean 34.2, 95% confidence intervals [33.4, 35.0] mmol/L) and SB (mean 33.6, 95% confidence intervals [32.8, 34.5] mmol/L, p = .308), as was delta blood [HCO3-] (SC = 7.9 mmol/L; SB = 7.3 mmol/L, p = .478). Blood [HCO3-] was ≥6 mmol/L above baseline from 180 to 240 min postingestion for SC, significantly later than for SB (120-180 min; p < .001). GIS were mostly minor, and peaked 80-90 min postingestion for SC, and 35-50 min postingestion for SB. There were no significant differences for the number or severity of GIS reported (p > .05 for all parameters). In summary, the recommended doses of SC and SB induce similar blood alkalosis and GIS, but with a different time course.

Sex differences among endurance athletes in the pre-race relationships between sleep, and perceived stress and recovery.

This study examined sex differences among endurance athletes in pre-race relationships between sleep, and perceived stress and recovery. Thirty-six athletes completed the Short Recovery and Stress Scale, and had sleep monitored via actigraphy, over four consecutive days prior to an ultra-marathon. Overall, compared with males, females had shorter wake after sleep onset (mean ± SD, 50 ± 23 vs 65 ± 23 min, p = .04) and lower emotional balance (3.9 ± 1.1 vs 4.8 ± 1.1 arbitrary units, p = .001). The day before the race, females scored higher for all stress-related items (p < 0.05). Among females, higher scores for emotional balance (ß = -31 min, p = .01) and negative emotional state (ß = -21 min, p < .001) were associated with reduced sleep duration. Among males, higher scores for overall stress were associated with increased sleep duration (ß = 22 min, p = .01). Across all athletes, longer sleep duration was associated with improved overall recovery (ß = 0.003 arbitrary units, p = .02). Females experienced greater pre-race stress than males, and their sleep duration was associated with emotional factors. The SRSS may help identify female athletes at risk of sleep difficulties prior to competition.

Assessment of Exercise-Associated Gastrointestinal Perturbations in Research and Practical Settings: Methodological Concerns and Recommendations for Best Practice.

Strenuous exercise is synonymous with disturbing gastrointestinal integrity and function, subsequently prompting systemic immune responses and exercise-associated gastrointestinal symptoms, a condition established as "exercise-induced gastrointestinal syndrome." When exercise stress and aligned exacerbation factors (i.e., extrinsic and intrinsic) are of substantial magnitude, these exercise-associated gastrointestinal perturbations can cause performance decrements and health implications of clinical significance. This potentially explains the exponential growth in exploratory, mechanistic, and interventional research in exercise gastroenterology to understand, accurately measure and interpret, and prevent or attenuate the performance debilitating and health consequences of exercise-induced gastrointestinal syndrome. Considering the recent advancement in exercise gastroenterology research, it has been highlighted that published literature in the area is consistently affected by substantial experimental limitations that may affect the accuracy of translating study outcomes into practical application/s and/or design of future research. This perspective methodological review attempts to highlight these concerns and provides guidance to improve the validity, reliability, and robustness of the next generation of exercise gastroenterology research. These methodological concerns include participant screening and description, exertional and exertional heat stress load, dietary control, hydration status, food and fluid provisions, circadian variation, biological sex differences, comprehensive assessment of established markers of exercise-induced gastrointestinal syndrome, validity of gastrointestinal symptoms assessment tool, and data reporting and presentation. Standardized experimental procedures are needed for the accurate interpretation of research findings, avoiding misinterpreted (e.g., pathological relevance of response magnitude) and overstated conclusions (e.g., clinical and practical relevance of intervention research outcomes), which will support more accurate translation into safe practice guidelines.

Factors Influencing Blood Alkalosis and Other Physiological Responses, Gastrointestinal Symptoms, and Exercise Performance Following Sodium Citrate Supplementation: A Review.

This review aimed to identify factors associated with (a) physiological responses, (b) gastrointestinal (GI) symptoms, and (c) exercise performance following sodium citrate supplementation. A literature search identified 33 articles. Observations of physiological responses and GI symptoms were categorized by dose (< 500, 500, and > 500 mg/kg body mass [BM]) and by timing of postingestion measurements (in minutes). Exercise performance following sodium citrate supplementation was compared with placebo using statistical significance, percentage change, and effect size. Performance observations were categorized by exercise duration (very short < 60 s, short ≥ 60 and ≤ 420 s, and longer > 420 s) and intensity (very high > 100% VO2max and high 90-100% VO2max). Ingestion of 500 mg/kg BM sodium citrate induced blood alkalosis more frequently than < 500 mg/kg BM, and with similar frequency to >500 mg/kg BM. The GI symptoms were minimized when a 500 mg/kg BM dose was ingested in capsules rather than in solution. Significant improvements in performance following sodium citrate supplementation were reported in all observations of short-duration and very high-intensity exercise with a 500 mg/kg BM dose. However, the efficacy of supplementation for short-duration, high-intensity exercise is less clear, given that only 25% of observations reported significant improvements in performance following sodium citrate supplementation. Based on the current literature, the authors recommend ingestion of 500 mg/kg BM sodium citrate in capsules to induce alkalosis and minimize GI symptoms. Supplementation was of most benefit to performance of short-duration exercise of very high intensity; further investigation is required to determine the importance of ingestion duration and timing.

The Impact of a Dairy Milk Recovery Beverage on Bacterially Stimulated Neutrophil Function and Gastrointestinal Tolerance in Response to Hypohydration Inducing Exercise Stress.

The study aimed to determine the impact of a dairy milk recovery beverage immediately after endurance exercise on leukocyte trafficking, neutrophil function, and gastrointestinal tolerance markers during recovery. Male runners (N = 11) completed two feeding trials in randomized order, after 2 hr of running at 70% V˙O2max, fluid restricted, in temperate conditions (25 °C, 43% relative humidity). Immediately postexercise, the participants received a chocolate-flavored dairy milk beverage equating to 1.2 g/kg body mass carbohydrate and 0.4 g/kg body mass protein in one trial, and water volume equivalent in another trial. Venous blood and breath samples were collected preexercise, postexercise, and during recovery to determine the leukocyte counts, plasma intestinal fatty acid binding protein, and cortisol concentrations, as well as breath H2. In addition, 1,000 µl of whole blood was incubated with 1 µg/ml Escherichia coli lipopolysaccharide for 1 hr at 37 °C to determine the stimulated plasma elastase concentration. Gastrointestinal symptoms and feeding tolerance markers were measured preexercise, every 15 min during exercise, and hourly postexercise for 3 hr. The postexercise leukocyte (mean [95% confidence interval]: 12.7 [11.6, 14.0] × 109/L [main effect of time, MEOT]; p < .001) and neutrophil (10.2 [9.1, 11.5] × 109/L; p < .001) counts, as well as the plasma intestinal fatty acid binding protein (470 pg/ml; +120%; p = .012) and cortisol (236 nMol/L; +71%; p = .006) concentrations, were similar throughout recovery for both trials. No significant difference in breath H2 and gastrointestinal symptoms was observed between trials. The total (Trial × Time, p = .025) and per cell (Trial × Time, p = .001) bacterially stimulated neutrophil elastase release was greater for the chocolate-flavored dairy milk recovery beverage (+360% and +28%, respectively) in recovery, compared with the water trial (+85% and -38%, respectively). Chocolate-flavored dairy milk recovery beverage consumption immediately after exercise prevents the decrease in neutrophil function during the recovery period, and it does not account for substantial malabsorption or gastrointestinal symptoms over a water volume equivalent.

Test-Retest Reliability of a Modified Visual Analog Scale Assessment Tool for Determining Incidence and Severity of Gastrointestinal Symptoms in Response to Exercise Stress.

Considering the recent growth of exercise gastroenterology research focusing on exercise-induced gastrointestinal syndrome mechanisms, response magnitude, prevention and management strategies, the standardized assessment of gastrointestinal symptoms (GIS) is warranted. The current methodological study aimed to test the reliability of a modified visual analog scale for assessing GIS during exercise, in response to a variety of exertional-stress scenarios, with and without dietary intervention. Recreational endurance runners (n = 31) performed one of the three exercise protocols, which included: 2-hr running at 70% V˙O2max in temperate (24.7 °C) ambient conditions, with fluid restriction; 2-hr running at 60% V˙O2max in hot (35.1 °C) ambient conditions, while consuming chilled water immediately before and every 15 min during exercise; and 2-hr running at 60% V˙O2max in temperate (23.0 °C) ambient conditions, while consuming 30 g/20 min carbohydrate (2∶1 glucose∶fructose, 10% temperate w/v), followed by a 1-hr distance test. GIS was monitored pre-exercise, periodically during exercise, and immediately postexercise. After wash out, participants were retested in mirrored conditions. No significant differences (p > .05) were identified between test-retest using Wilcoxon signed-rank test for all GIS (specific and categorized), within each exercise protocol and the combined protocols. Strong correlations were observed for gut discomfort, total GIS, upper GIS, and nausea (rs = .566 to rs = .686; p < .001), but not for lower GIS (rs = .204; p = .232). Cohen's magnitude of difference was minimal for all GIS (specific δ < 0.14 and categorized δ < 0.08). The modified visual analog scale for assessing GIS during exercise appears to be a reliable tool for identifying incidence and severity of GIS in cohort populations and is sensitive enough to detect exertional and intervention differences.

Ad libitum drinking adequately supports hydration during 2 h of running in different ambient temperatures.

PURPOSE: To examine if ad libitum drinking will adequately support hydration during exertional heat stress. METHODS: Ten endurance-trained runners ran for 2 h at 60% of maximum oxygen uptake under different conditions. Participants drank water ad libitum during separate trials at mean ambient temperatures of 22 °C, 30 °C and 35 °C. Participants also completed three trials at a mean ambient temperature of 35 °C while drinking water ad libitum in all trials, and with consumption of programmed glucose or whey protein hydrolysate solutions to maintain euhydration in two of these trials. Heart rate, oxygen uptake, rectal temperature, perceived effort, and thermal sensation were monitored, and nude body mass, hemoglobin, hematocrit, and plasma osmolality were measured before and after exercise. Water and mass balance equations were used to calculate hydration-related variables. RESULTS: Participants adjusted their ad libitum water intake so that the same decrease in body mass (1.1-1.2 kg) and same decrease in body water (0.8-0.9 kg) were observed across the range of ambient temperatures which yielded significant differences (p < .001) in sweat loss. Overall, water intake and total water gain replaced 57% and 66% of the water loss, respectively. The loss in body mass and body water associated with ad libitum drinking resulted in no alteration in physiological and psychophysiological variables compared with the condition when hydration was nearly fully maintained (0.3 L body water deficit) relative to pre-exercise status from programmed drinking. CONCLUSIONS: Ad libitum drinking is an appropriate strategy for supporting hydration during running for 2 h duration under hot conditions.

The impact of exertional-heat stress on gastrointestinal integrity, gastrointestinal symptoms, systemic endotoxin and cytokine profile.

PURPOSE: The study aimed to determine the effects of exertional-heat stress on gastrointestinal integrity, symptoms, systemic endotoxin and inflammatory responses; and assess the relationship between changes in body temperature and gastrointestinal perturbations. METHODS: Ten endurance runners completed 2 h running at 60% [Formula: see text]O2max in hot (HOT: 35 °C) and temperate (TEMP: 22 °C)-ambient conditions. Rectal temperature (T re) and gastrointestinal symptoms were recorded every 10 min during exercise. Blood samples were collected pre- and post-exercise, and during recovery to determine plasma intestinal fatty acid binding protein (I-FABP), cortisol, bacterial endotoxin and cytokine profile. Calprotectin was determined from pre- and post-exercise faecal samples. Urinary lactulose:L-rhamnose ratio was used to measure intestinal permeability. RESULTS: Compared with TEMP, HOT significantly increased T re (1.4 ± 0.5 vs 2.4 ± 0.8 °C, p < 0.001), cortisol (26 vs 82%, p < 0.001), I-FABP (127 vs 432%, p < 0.001), incidence (70 vs 90%) and severity (58 counts vs 720 counts, p = 0.008) of total gastrointestinal symptoms. Faecal calprotectin and circulating endotoxin increased post-exercise in both trials (mean increase 1.5 ± 2.5 µg/g, p = 0.032, and 6.9 ± 10.3 pg/ml, p = 0.047, respectively), while anti-endotoxin antibodies increased 28% post-exercise in TEMP and decreased 21% in HOT (p = 0.027). However, intestinal permeability did not differ between trials (p = 0.185). Inflammatory cytokines were greater on HOT compared to TEMP (p < 0.05). Increases in T re were positively associated with I-FABP, IL-10, cortisol, nausea and urge to regurgitate (p < 0.05). CONCLUSIONS: Exertional-heat stress induces a thermoregulatory strain that subsequently injures the intestinal epithelium, reduces endotoxin clearance capacity, promotes greater cytokinaemia, and development of gastrointestinal symptoms.

The Impact of Mild Heat Stress During Prolonged Running On Gastrointestinal Integrity, Gastrointestinal Symptoms, Systemic Endotoxin and Cytokine Profiles.

The study aimed to determine the effects of mild exertional heat stress on intestinal injury, permeability, gastrointestinal symptoms, and systemic endotoxin and cytokine responses. Ten endurance runners completed 2 h of running at 60% V̇O2max in warm (WARM: 30°C) and temperate (TEMP: 22°C) ambient conditions. Rectal temperature (Tre) and gastrointestinal symptoms were recorded every 10 min during exercise. Blood samples were collected pre- and post-exercise, and during recovery to determine plasma intestinal fatty acid-binding protein (I-FABP) and cortisol concentrations, and systemic endotoxin and inflammatory cytokine profiles. Urinary lactulose:L-rhamnose ratio (L/R) was used to measure small intestine permeability. Compared with TEMP, WARM significantly increased Tre from 50 min onwards (38.1±0.3°C vs. 38.4±0.5°C, respectively; p<0.01), gastrointestinal symptoms (p=0.017), post-exercise plasma cortisol (26% vs. 59%, respectively; p<0.001) and I-FABP (127% vs. 184%, respectively; p<0.001) concentrations. Circulatory anti-endotoxin antibodies increased post-exercise (p<0.001) on WARM (20%) and TEMP (28%). No differences were observed for plasma endotoxin concentration (6% vs. 5% increase, respectively) or small intestine permeability (L/R 0.026±0.010 and 0.025±0.015, respectively). Both pro- and anti-inflammatory cytokines increased post-exercise, with inflammatory response cytokines TNF-α (p=0.015) and IL-8 (p=0.044), and compensatory anti-inflammatory cytokines IL-10 (p=0.065), and IL-1ra higher on WARM than TEMP. Findings suggest that exposure to warm ambient conditions during prolonged submaximal running induces transient intestinal epithelial injury, increases gastrointestinal symptoms, and promotes greater perturbations to the systemic cytokine profile compared to running in temperate conditions.

Does biological sex impact intestinal epithelial injury, small intestine permeability, gastrointestinal symptoms and systemic cytokine profile in response to exertional-heat stress?

This study aimed to determine the influence of biological sex on intestinal injury, permeability, gastrointestinal symptoms, and systemic cytokine profile in response to exertional-heat stress. Male (n= 13) and eumenorrheic female (n= 11) endurance runners completed 2 h running at 60% V̇O2max in 35°C. Blood samples were collected pre- and post-exercise and during recovery to determine plasma intestinal fatty-acid binding protein (I-FABP) and systemic cytokine profile. Urinary lactulose:L-rhamnose ratio was used to determine small intestine permeability. I-FABP increased 479% pre- to post-exercise (p< 0.001), with no difference between sexes (p= 0.432). No differences between sexes were observed for small intestine permeability (p= 0.808), gut discomfort, total, upper- and lower-gastrointestinal symptoms. However, males reported significantly higher flatulence (p= 0.049) and abdominal stitch (p= 0.025) compared to females. IL-6, IL-8, IL-10 and IL-1ra increased pre- to post-exercise (p< 0.05), with no difference between sexes. However, IL-1ß increased post-exercise in males only, and was higher in males compared to females (p= 0.044). Findings suggest that when females are in the follicular phase of the menstrual cycle, biological sex has no effect on intestinal epithelial injury and permeability, and minimal effect on gastrointestinal symptoms and systemic cytokine profile in response to exertional-heat stress.

The increase in core body temperature in response to exertional-heat stress can predict exercise-induced gastrointestinal syndrome.

Utilizing metadata from existing exertional and exertional-heat stress studies, the study aimed to determine if the exercise-associated increase in core body temperature can predict the change in exercise-induced gastrointestinal syndrome (EIGS) biomarkers and exercise-associated gastrointestinal symptoms (Ex-GIS). Endurance-trained individuals completed 2 h of running exercise in temperate (21.2-30.0°C) to hot (35.0-37.2°C) ambient conditions (n = 132 trials). Blood samples were collected pre- and post-exercise to determine the change in gastrointestinal integrity biomarkers and systemic inflammatory cytokines. Physiological and thermoregulatory strain variables were assessed every 10-15 min during exercise. The strength of the linear relationship between maximal (M-Tre) and change (Δ Tre) in rectal temperature and EIGS variables was determined via Spearman's rank correlation coefficients. While the strength of prediction was determined via simple and multiple linear regression analyses dependent on screened EIGS and Ex-GIS confounding factors. Significant positive correlations between Tre maximum (M-Tre) and change (Δ Tre) with I-FABP (rs = 0.434, p < 0.001; and rs = 0.305, p < 0.001; respectively), sCD14 (rs = 0.358, p < 0.001; and rs = 0.362, p < 0.001), systemic inflammatory response profile (SIR-Profile) (p < 0.001), and total Ex-GIS (p < 0.05) were observed. M-Tre and Δ Tre significantly predicted (adjusted R2) magnitude of change in I-FABP (R2(2,123)=0.164, p < 0.001; and R2(2,119)=0.058, p = 0.011; respectively), sCD14 (R2(2,81)=0.249, p < 0.001; and R2(2,77)=0.214, p < 0.001), SIR-Profile (p < 0.001), and total Ex-GIS (p < 0.05). Strong to weak correlations were observed between M-Tre and Δ Tre with plasma concentrations of I-FABP, sCD14, SIR-Profile, and Ex-GIS in response to exercise. M-Tre and Δ Tre can predict the magnitude of these EIGS variables and Ex-GIS in response to exercise.

Omega-3 long chain polyunsaturated fatty acids as a potential treatment for reducing dysmenorrhoea pain: Systematic literature review and meta-analysis.

AIM: This systematic literature review with meta-analysis aimed to determine the effect of omega-3 long chain polyunsaturated fatty acids on prostaglandin levels and pain severity in women with dysmenorrhoea and identify adverse side effects. METHODS: A literature search was conducted in Embase, Scopus, Web of Science, MEDLINE complete, CINAHL and AMED databases (PROSPERO CRD42022340371). Included studies provided omega-3 long chain polyunsaturated fatty acids compared to a control in women with dysmenorrhoea and reported pain and/or prostaglandin levels. A random effects meta-analysis with Cohen's d effect size (95% confidence interval) was performed in SPPS for studies that reported pain outcomes. Study quality was assessed using the Academy of Nutrition and Dietetics Quality Criteria Checklist. RESULTS: Twelve studies (n = 881 dysmenorrhoeal women) of predominantly neutral quality (83%) were included that provided daily supplementation of 300-1800 mg omega-3 long chain polyunsaturated fatty acids over 2 or 3 months. Meta-analysis (n = 8 studies) showed a large effect of omega-3 long chain polyunsaturated fatty acids (d = -1.020, 95% confidence interval -1.53 to -0.51) at reducing dysmenorrhoea pain. No studies measured prostaglandin levels, 86% of studies measuring analgesic use showed a reduction with omega-3 long chain polyunsaturated fatty acids and few studies reported mild adverse side effects in individual participants. CONCLUSIONS: Findings suggest that daily supplementation of 300-1800 mg omega-3 long chain polyunsaturated fatty acids over 2-3 months are generally well tolerated and reduces pain and analgesic use in women with dysmenorrhoea. However, the neutral quality of research is limited by methodological issues and the mechanism of action remains to be determined.

Total fermentable oligo-, di-, monosaccharides and polyols intake, carbohydrate malabsorption and gastrointestinal symptoms during a 56 km trail ultramarathon event.

AIMS: To explore the relationship between nutritional intake, fermentable oligo-, di, monosaccharides and polyols, and carbohydrate malabsorption, with gastrointestinal symptoms during a 56 km trail ultramarathon event and identify differences in nutritional intake between runners with severe and non-severe gastrointestinal symptoms. METHODS: Forty-four ultramarathoners recorded and self-reported dietary intake 3 days before, morning of, and during the ultramarathon with gastrointestinal symptoms obtained retrospectively and nutrient analysis via FoodWorks. Carbohydrate malabsorption was determined via breath hydrogen content pre- and post-race. Spearman's rank-order and Mann-Whitney U-tests were used to identify relationships and differences between groups. RESULTS: Total fermentable oligo-, di, monosaccharides and polyols intake were not associated with gastrointestinal symptoms, but weak associations were observed for lower energy (rs = -0.302, p = 0.044) and fat intake (rs = -0.340, p = 0.024) 3 days before with upper gastrointestinal symptoms and higher caffeine intake 3 days before with overall gastrointestinal symptoms (rs = 0.314, p = 0.038). Total fermentable oligo-, di-, monosaccharides and polyols intake and breath hydrogen were not different between those with severe versus non-severe symptoms (p > 0.05). Although those with severe symptoms had higher caffeine (p = 0.032), and total polyols intake (p = 0.031) 3 days before, and higher % energy from fat (p = 0.043) and sorbitol intake (p = 0.026) during the race, and slower ultramarathon finish times (p = 0.042). CONCLUSION: Total fermentable oligo-, di-, and monosaccharides intake and carbohydrate malabsorption were not associated with gastrointestinal symptoms. Additional research on the effect of fat, caffeine, and polyol intake on exercise-associated gastrointestinal symptoms is warranted and presents new nutritional areas for consideration when planning nutritional intake for ultramarathoners.

Effects of a Short-Term "Fat Adaptation with Carbohydrate Restoration" Diet on Metabolic Responses and Exercise Performance in Well-Trained Runners.

Periodized carbohydrate availability can enhance exercise capacity, but the effects of short-term fat adaptation carbohydrate restoration (FACR) diets on metabolic responses and exercise performance in endurance athletes have not been conclusively determined. This study aimed to investigate the effect of a FACR diet on measures of resting metabolism, exercise metabolism, and exercise performance. Well-trained male runners (n = 8) completed a FACR dietary intervention (five days' carbohydrate < 20% and fat > 60% energy, plus one-day carbohydrate ≥ 70% energy), and a control high-carbohydrate (HCHO) diet for six days (carbohydrate > 60% energy; fat < 20% energy) in a randomized crossover design. Pre- and post-intervention metabolic measures included resting metabolic rate (RMR), respiratory quotient (RQ), maximum fat oxidation rate during exercise (MFO), and maximum fat oxidation intensity (FATmax). Measures of exercise performance included maximal oxygen uptake (VO2max), running economy (RE), and 5 km running time trial (5 km-TT). In FACR compared with HCHO, there were significant improvements in FATmax (p = 0.006) and RE (p = 0.048). There were no significant differences (p > 0.05) between FACR and HCHO in RMR, RQ, VO2max, or 5 km-TT. Findings suggest that a short-term (six days) FACR diet may facilitate increased fat oxidation and submaximal exercise economy but does not improve 5 km-TT performance.