Abdominal symptoms during physical exercise and the role of gastrointestinal ischaemia: a study in 12 symptomatic athletes

Resistance Exercise Increases Gastrointestinal Symptoms, Markers of Gut Permeability, and Damage in Resistance-Trained Adults

PURPOSE

This study aimed to determine the influence of acute resistance exercise (RE) and biological sex on subjective gastrointestinal (GI) symptoms, GI epithelial damage, and GI permeability in resistance-trained males and females.

METHODS

Thirty resistance-trained men ( n = 15) and women ( n = 15) completed an RE bout and a nonexercise control (CON) session in a randomized counterbalanced design. The RE protocol used a load of 70% one-repetition maximum for 4 sets of 10 repetitions with a 90-s rest period length between sets and a 120-s rest period between exercises (squat, seated shoulder press, deadlift, bent-over row, and leg press). Blood samples were collected before exercise (PRE), immediately postexercise (IP), and 15-, 30-, and 60-min postexercise. Participants completed GI symptom questionnaires to assess subjective GI symptoms PRE, IP, and 60-min postexercise. Blood samples were assayed to quantify small intestine damage (I-FABP) and GI permeability (lactulose-rhamnose [L/R] ratio). Data were analyzed via separate repeated-measures ANOVA, and area under the curve (AUC) analyses were completed via one-way ANOVA.

RESULTS

Participants reported greater GI symptoms in RE at IP compared with CON ( P < 0.001) with 70% of participants reporting at least one GI symptom with no differences between sexes. Nausea was the most reported GI symptom (63.3%), followed by vomiting (33.3%). I-FABP and L/R ratio did not exhibit differential responses between conditions. However, L/R ratio AUC was greater in males after RE than male CON ( P = 0.002) and both conditions for females ( P < 0.05). Furthermore, I-FABP AUC in the male RE condition was greater than both female conditions ( P < 0.05).

CONCLUSIONS

Resistance-trained individuals experience GI distress after RE, with males incurring the greatest increases in markers of GI damage and permeability.

Pterostilbene attenuates intestinal epithelial barrier loss induced by high loading intensity of exercise

Mounting evidence suggested that high loading intensity of exercise might be detrimental to human health, especially the gastrointestinal tract. Pterostilbene (PTE), derived from grapes and blueberries, might reach a high concentration of intestinal contents. Our study aimed to evaluate PTE’s ability to prevent the loss of intestinal epithelial barrier in high loading intensity of exercise. The exercise model was established by the forced running of mice. An effective HPLC-UV method was developed to quantify PTE concentration in intestinal content. The mRNA changes were detected by quantitative polymerase chain reaction (qPCR). The structure of intestinal flora was analyzed by 16S rRNA sequencing. The PTE (100 mg/kg/d) could significantly attenuate exercise-induced intestinal epithelial barrier loss. Moreover, the HPLC-UV assay showed that the PTE concentration of intestinal content could last 12 h. Furthermore, the exercise increased the abundance of Alistipes, which was related to lipopolysaccharide (LPS) production but could not be reversed by PTE intervention. Besides, cell experiments showed that PTE could promote the expression of intestinal epithelial tight junction (TJ) molecules in vitro. In conclusion, PTE has a significant interest in preventing exercise-induced intestinal damage.

The Path Towards Progress: A Critical Review to Advance the Science of the Female and Male Athlete Triad and Relative Energy Deficiency in Sport

Energy status plays a key role in the health of athletes and exercising individuals. Energy deficiency/low energy availability (EA), referring to a state in which insufficient energy intake and/or excessive exercise energy expenditure has resulted in compensatory metabolic adaptations to conserve fuel, can affect numerous physiological systems in women and men. The Female Athlete Triad, Male Athlete Triad, and Relative Energy Deficiency in Sport (RED-S) models conceptualize the effects of energy deficiency in athletes, and each model has strengths and limitations. For instance, the Female Athlete Triad model depicts relationships between low EA, reproductive, and bone health, underpinning decades of experimental evidence, but may be perceived as limited in scope, while the more recent RED-S model proposes a wider range of potential health effects of low EA, though many model components require more robust scientific justification. This critical review summarizes current evidence regarding the effects of energy deficiency on athlete health by addressing the quality of the underlying science, the strengths and limitations of each model, and highlighting areas where future research is needed to advance the field. With the health and wellness of athletes and exercising individuals as the overarching priority, we conclude with specific steps that will help focus future research on the Female and Male Athlete Triad and RED-S, and encourage all researchers, clinicians, and practitioners to collaborate to support the common goal of promoting the highest quality science and evidence-based medicine in pursuit of the advancement of athletes' health, well-being, and performance.

Exhaustive Exercise Induces Gastrointestinal Syndrome through Reduced ILC3 and IL-22 in Mouse Model

PURPOSE

This study was to investigate the mechanism of intestinal physical and immune barriers in the occurrence of high-intensive exercise-induced gastrointestinal symptoms.

METHODS

An overtraining model of male C57BL/6 mice was established by running-to-exhaustive exercise. Then, the mice were sacrificed, and a series of evaluation indicators, including the routine blood analysis as well as histological examinations, inflammatory factors, ultrastructure observation, and intestinal permeability of the gut, were measured based on this model. The expressions of inflammatory factors tumor necrosis factor α, interferon-γ, and interleukin (IL)-6 as well as the tight junction and adherence junction proteins ZO-1, Occludin, Claudin-1, and E-cadherin were measured, respectively. Furthermore, the mRNA level of IL-22 and the proportion of ILC3 and IL-22 produced in CD4 T cells in lamina propria lymphocytes (LPL) were analyzed by flow cytometry. Besides, the liver glycogen and the expressions of sirtuins-3 and hypoxia-inducible factor-1a, which were associated with the intestinal metabolism phenotype, were analyzed by Western blotting.

RESULTS

Exhaustive exercise induced a disrupted intestinal barrier integrity, an aggravated intestinal inflammation, increased gut permeability, and the reduced IL-22 mRNA level. Compared with the nonexercise mice, the IL-22 produced in LPL was reduced followed by exhaustive exercise, whereas the proportion of IL-22 produced in CD4 T cells was still unchanged. Significantly, the proportion of ILC3 in the LPL was decreased obviously, including the NCR ILC3. Furthermore, the intestinal metabolism phenotype assessment showed lower liver glycogen and blood glucose as well as higher blood lactic acid and hypoxia-inducible factor-1a, respectively.

CONCLUSIONS

The data indicated that the acute high-intensity running-induced gastrointestinal symptom is closely associated with a reduced percentage of ILC3 and IL-22 level in the LPL, possibly due to the glycogen exhaustion and intestinal mucosa hypoperfusion.

Exercise induces tissue hypoxia and HIF-1α redistribution in the small intestine

BACKGROUND

Exercise induces blood flow redistribution among tissues, leading to splanchnic hypoperfusion. Intestinal epithelial cells are positioned between the anaerobic lumen and the highly metabolic lamina propria with an oxygen gradient. Hypoxia-inducible factor (HIF)-1α is pivotal in the transcriptional response to the oxygen flux.

METHODS

In this study, the pimonidazole hydrochloride staining was applied to observe the tissue hypoxia in different organs, which might be affected by the blood flow redistribution. The HIF-1α luciferase reporter ROSA26 oxygen-dependent degradation domain (ODD)-Luc/⁺ mouse model (ODD domain-Luc; female, n = 3-6/group) was used to detect the HIF-1α expression in the intestine. We used 3 swimming models: moderate exercise for 30 min, heavy-intensity exercise bearing 5% bodyweight for 1.5 h, and long-time exercise for 3 h.

RESULTS

We found that 1 session of swimming at different intensities could induce tissue hypoxia redistribution in the small intestine, colon, liver and kidney, but not in the spleen, heart, and skeletal muscle. Our data showed that exercise exacerbated the extent of physiological hypoxia in the small intestine. Next, using ODD-Luc mice, we found that moderate exercise increased the in vivo HIF-1α level in the small intestine. The post-exercise HIF-1α level was gradually decreased in a time-dependent manner. Interestingly, the redistribution of tissue hypoxia and the increase of HIF-1α expression were not related to the exercise intensity and duration.

CONCLUSION

This study provided evidence that the small intestine is the primary target organ for exercise-induced tissue hypoxia and HIF-1α redistribution, suggesting that HIF-1α may be a potential target for the regulation of gastrointestinal functions after exercise.

Exercise and gut microbiota: clinical implications for the feasibility of Tai Chi. J Integr Med. 2017;15:270-281. [PMID: 28659231 DOI: 10.1016/s2095-4964(17)60342-x]

Recent studies have shown exercise is associated with changes in the gut microbiota in humans as well as in experimental animals. Tai Chi is an exercise that integrates a martial art, deep breathing and mediation, and has various beneficial effects for health. This review summarizes current knowledge and recent literature on the association between exercise and gut microbiota, and explores the feasibility of Tai Chi for improving gut microbiota composition and function. PubMed/MEDLINE was used to search the English literature for the keywords exercise and gut microbiota. Fourteen relevant studies were identified. In humans, exercise increases the gut microbial diversity. However, the evidence for this association is weak, as previous studies were small-scale, non-controlled studies of short duration or cross-sectional design. In animals, exercise alters the composition of gut microbiota, with some studies suggesting exercise increases the Bacteroidetes/Firmicutes ratio. However, these results are controversial, partly because host genetics and physical fitness also influence gut microbiota. Furthermore, the intensity of exercise may play a key role in how exercise affects gut microbiota. Tai Chi is a moderate-intensity exercise that improves immune function and inflammation of the gut. Tai Chi may also affect gut microbiota through vagal modulation and mediating the hypothalamic-pituitary-adrenal axis. However, no studies have investigated the association between Tai Chi and gut microbiota. Well designed studies exploring the effects of Tai Chi on gut microbiota are needed.

Timing of post-resistance exercise nutrient ingestion: effects on gastric emptying and glucose and amino acid responses in humans

This study examined the effects of post-resistance exercise protein ingestion timing on the rate of gastric emptying (GE) and blood glucose (BG) and plasma branched-chain amino acid (BCAA) responses. In all, eleven healthy participants randomly ingested 400 ml of a nutrient-rich drink containing 12 g carbohydrates and 20 g protein at rest (Con), at 5 min (post-exercise (PE)-5) or at 30 min (PE-30) after a single bout of strenuous resistance exercises. The first and second sets comprised ten repetitions at 50 % of each participant's one-repetition maximum (1RM). The third, fourth and fifth sets comprised ten repetitions at 75 % of 1RM, and the sixth set involved repeated repetitions until exhaustion. Following ingestion of the nutrient-rich drink, we assessed the GE rate using 13C-sodium acetate breath test and evaluated two parameters according to the T max-calc (time when the recovery per hour is maximised), which is a standard analytical method, and T 1/2 (time when the total cumulative dose of [13CO2] reaches one-half). T max-calc and T 1/2 were slower for the PE-5 condition than for either the PE-30 or Con condition (T max-calc; Con: 53 (sd 7) min, PE-5: 83 (sd 16) min, PE-30: 62 (sd 9) min, T 1/2; Con: 91 (sd 7) min, PE-5: 113 (sd 21) min, PE-30: 91 (sd 11) min, P<0·05). BG and BCAA responses were also slower for the PE-5 condition than for either the PE-30 or Con condition. Ingesting nutrients immediately after strenuous resistance exercise acutely delayed GE, which affected BG and plasma BCAA levels in blood circulation.

The effect of bovine colostrum supplementation on intestinal injury and circulating intestinal bacterial DNA following exercise in the heat

Purpose

Exercise-induced changes in intestinal permeability are exacerbated in the heat. The aim of this study was to determine the effect of 14 days of bovine colostrum (Col) supplementation on intestinal cell damage (plasma intestinal fatty acid-binding protein, I-FABP) and bacterial translocation (plasma bacterial DNA) following exercise in the heat.

Methods

In a double-blind, placebo-controlled, crossover design, 12 males completed two experimental arms (14 days of 20 g/day supplementation with Col or placebo, Plac) consisting of 60 min treadmill running at 70% maximal aerobic capacity (30 °C, 60% relative humidity). Blood samples were collected pre-exercise (Pre-Ex), post-exercise (Post-Ex) and 1 h post-exercise (1 h Post-Ex) to determine plasma I-FABP concentration, and bacterial DNA (for an abundant gut species, Bacteroides).

Results

Two-way repeated measures ANOVA revealed an arm × time interaction for I-FABP (P = 0.005, with greater Post-Ex increase in Plac than Col, P = 0.01: Plac 407 ± 194% of Pre-Ex vs Col, 311 ± 134%) and 1 h Post-Ex (P = 0.036: Plac 265 ± 80% of Pre-Ex vs Col, 229 ± 56%). There was no interaction (P = 0.904) but there was a main effect of arm (P = 0.046) for plasma Bacteroides/total bacterial DNA, with lower overall levels evident in Col.

Conclusion

This is the first investigation to demonstrate that Col can be effective at reducing intestinal injury following exercise in the heat, but exercise responses (temporal pattern) of bacterial DNA were not influenced by Col (although overall levels may be lower).

Timing of postexercise carbohydrate-protein supplementation: roles of gastrointestinal blood flow and mucosal cell damage on gastric emptying in humans

It is well known that protein ingestion immediately after exercise greatly stimulates muscle protein synthesis during the postexercise recovery phase. However, immediately after strenuous exercise, the gastrointestinal (GI) mucosa is frequently injured by hypoperfusion in the organ/tissue, possibly resulting in impaired GI function (e.g., gastric emptying; GE). The aim of this study was to examine the effect of GI blood flow on the GE rate. Eight healthy young subjects performed an intermittent supramaximal cycling exercise for 30 min, which consisted of a 120% V̇o_2peak for 20 s, followed by 20 W for 40 s. The subjects ingested 300 ml of a nutrient drink containing carbohydrate-protein at either 5 min postexercise in one trial (PE-5) or 30 min postexercise in another trial (PE-30). In the control trial (Con), the subjects ingested the same drink without exercise. The celiac artery blood flow (CABF) and superior mesenteric artery blood flow (SMABF) and GE rate were assessed by ultrasonography. Before drink ingestion in PE-5, CABF significantly decreased from baseline, whereas in PE-30, it returned to baseline. Following drink ingestion in PE-5, CABF did not change from baseline, but it significantly increased in PE-30 and Con. SMABF increased significantly later in PE-5 than in PE-30 and Con. The GE rate was consistently slower in PE-5 than in PE-30 and Con. In conclusion, the CABF response after exercise seems to modulate the subsequent GE rate and SMABF response.NEW & NOTEWORTHY A carbohydrate-protein drink was ingested at either 5 min (i.e., profoundly decreased celiac artery blood flow; CABF) or 30 min (i.e., already recovered CABF) postexercise. In the 5-min postexercise trial, the gastric emptying (GE) rate and superior mesenteric artery blood flow (SMABF) response were slower than those in the 30-min postexercise trial. The GE rate and SMABF response may be altered depending on the postexercise CABF response.

Intestinal fatty acid-binding protein and gut permeability responses to exercise

PURPOSE

Intestinal cell damage due to physiological stressors (e.g. heat, oxidative, hypoperfusion/ischaemic) may contribute to increased intestinal permeability. The aim of this study was to assess changes in plasma intestinal fatty acid-binding protein (I-FABP) in response to exercise (with bovine colostrum supplementation, Col, positive control) and compare this to intestinal barrier integrity/permeability (5 h urinary lactulose/rhamnose ratio, L/R).

METHODS

In a double-blind, placebo-controlled, crossover design, 18 males completed two experimental arms (14 days of 20 g/day supplementation with Col or placebo, Plac). For each arm participants performed two baseline (resting) intestinal permeability assessments (L/R) pre-supplementation and one post-exercise following supplementation. Blood samples were collected pre- and post-exercise to determine I-FABP concentration.

RESULTS

Two-way repeated measures ANOVA revealed an arm × time interaction for L/R and I-FABP (P < 0.001). Post hoc analyses showed urinary L/R increased post-exercise in Plac (273% of pre, P < 0.001) and Col (148% of pre, P < 0.001) with post-exercise values significantly lower with Col (P < 0.001). Plasma I-FABP increased post-exercise in Plac (191% of pre-exercise, P = 0.002) but not in the Col arm (107%, P = 0.862) with post-exercise values significantly lower with Col (P = 0.013). Correlations between the increase in I-FABP and L/R were evident for visit one (P = 0.044) but not visit two (P = 0.200) although overall plots/patterns do appear similar for each.

CONCLUSION

These findings suggest that exercise-induced intestinal cellular damage/injury is partly implicated in changes in permeability but other factors must also contribute.

Effects of a structured exercise programme in sedentary dogs with chronic diarrhoea

The aim of this investigation was to evaluate the effects of a structured exercise programme in sedentary dogs with chronic diarrhoea. Twenty-two dogs were enrolled in the study. All dogs received oral prednisolone (1 mg/kg/day for 14 days, followed by a tapering dosage) for 10 weeks. After four weeks of prednisolone treatment, dogs were assigned to either the exercise or control group (n=11 each). Owners of dogs in the exercise group were instructed to guide their dogs in structured exercise training (low-intensity to moderate-intensity aerobic and resistance exercise three to five days per week). After 10 weeks of prednisolone treatment with concomitant 6 weeks of complementary exercise, the Canine Inflammatory Bowel Disease Activity Index (CIBDAI) score had decreased significantly in the exercise group (from 8.8±1.5 at the start of the exercise programme to 2.4±1.5; P<0.001); no such change was observed in the control group (from 9.2±0.9 to 9.2±1.1). CIBDAI scores differed significantly between the groups at the end of the 10-week study period (P<0.001). The exercise programme affected all six CIBDAI parameters significantly; bodyweight (P<0.001, adjusted r²=0.722) was most affected. A structured exercise programme may have positive effects on clinical symptoms in sedentary dogs with chronic diarrhoea.

Exercise, fitness, and the gut

PURPOSE OF REVIEW

Exercise and gut symptomatology have long been connected. The possibility that regular exercise fosters intestinal health and function has been somewhat overlooked in the scientific literature. In this review, we summarize current knowledge and discuss a selection of recent, relevant, and innovative studies, hypotheses and reviews that elucidate a complex topic.

RECENT FINDINGS

The multiorgan benefits of regular exercise are extensive. When taken in moderation, these benefits transcend improved cardio-respiratory fitness and likely reach the gut in a metabolic, immunological, neural, and microbial manner. This is applicable in both health and disease. However, further work is required to provide safe, effective recommendations on physical activity in specific gastrointestinal conditions.

SUMMARY

Challenging methodology investigating the relationship between exercise and gut health should not deter from exploring exercise in the promotion of gastrointestinal health.

Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations

Gastrointestinal problems are common, especially in endurance athletes, and often impair performance or subsequent recovery. Generally, studies suggest that 30-50% of athletes experience such complaints. Most gastrointestinal symptoms during exercise are mild and of no risk to health, but hemorrhagic gastritis, hematochezia, and ischemic bowel can present serious medical challenges. Three main causes of gastrointestinal symptoms have been identified, and these are either physiological, mechanical, or nutritional in nature. During intense exercise, and especially when hypohydrated, mesenteric blood flow is reduced; this is believed to be one of the main contributors to the development of gastrointestinal symptoms. Reduced splanchnic perfusion could result in compromised gut permeability in athletes. However, although evidence exists that this might occur, this has not yet been definitively linked to the prevalence of gastrointestinal symptoms. Nutritional training and appropriate nutrition choices can reduce the risk of gastrointestinal discomfort during exercise by ensuring rapid gastric emptying and the absorption of water and nutrients, and by maintaining adequate perfusion of the splanchnic vasculature. A number of nutritional manipulations have been proposed to minimize gastrointestinal symptoms, including the use of multiple transportable carbohydrates, and potentially the use of nutrients that stimulate the production of nitric oxide in the intestine and thereby improve splanchnic perfusion. However, at this stage, evidence for beneficial effects of such interventions is lacking, and more research needs to be conducted to obtain a better understanding of the etiology of the problems and to improve the recommendations to athletes.

Perturbed energy balance and hydration status in ultra-endurance runners during a 24 h ultra-marathon

The present study aimed to assess the adequacy of energy, macronutrients and water intakes of ultra-endurance runners (UER) competing in a 24 h ultra-marathon (distance range: 122-208 km). The ad libitum food and fluid intakes of the UER (n 25) were recorded throughout the competition and analysed using dietary analysis software. Body mass (BM), urinary ketone presence, plasma osmolality (POsmol) and volume change were determined at pre- and post-competition time points. Data were analysed using appropriate t tests, with significance set at P <0·05. The total energy intake and expenditure of the UER were 20 (sd 12) and 55 (sd 11) MJ, respectively (control (CON) (n 17): 12 (sd 1) and 14 (sd 5) MJ, respectively). The protein, carbohydrate and fat intakes of the UER were 1·1 (sd 0·4), 11·3 (sd 7·0) and 1·5 (sd 0·7) g/kg BM, respectively. The rate of carbohydrate intake during the competition was 37 (sd 24) g/h. The total water intake of the UER was 9·1 (sd 4·0) litres (CON: 2·1 (sd 1·0) litres), while the rate of water intake was 378 (sd 164) ml/h. Significant BM loss occurred at pre- to post-competition time points (P =0·001) in the UER (1·6 (sd 2·0) %). No significant changes in POsmol values were observed at pre- (285 (sd 11) mOsmol/kg) to post-competition (287 (sd 10) mOsmol/kg) time points in the UER and were lower than those recorded in the CON group (P <0·05). However, plasma volume (PV) increased at post-competition time points in the UER (10·2 (sd 9·7) %; P <0·001). Urinary ketones were evident in the post-competition samples of 90 % of the UER. Energy deficit was observed in all the UER, with only one UER achieving the benchmark recommendations for carbohydrate intake during endurance exercise. Despite the relatively low water intake rates recorded in the UER, hypohydration does not appear to be an issue, considering increases in PV values observed in the majority (80 %) of the UER. Population-specific dietary recommendations may be beneficial and warranted.

Water and sodium intake habits and status of ultra-endurance runners during a multi-stage ultra-marathon conducted in a hot ambient environment: an observational field based study

Background

Anecdotal evidence suggests ultra-runners may not be consuming sufficient water through foods and fluids to maintenance euhydration, and present sub-optimal sodium intakes, throughout multi-stage ultra-marathon (MSUM) competitions in the heat. Subsequently, the aims were primarily to assess water and sodium intake habits of recreational ultra-runners during a five stage 225 km semi self-sufficient MSUM conducted in a hot ambient environment (T_max range: 32°C to 40°C); simultaneously to monitor serum sodium concentration, and hydration status using multiple hydration assessment techniques.

Methods

Total daily, pre-stage, during running, and post-stage water and sodium ingestion of ultra-endurance runners (UER, n = 74) and control (CON, n = 12) through foods and fluids were recorded on Stages 1 to 4 by trained dietetic researchers using dietary recall interview technique, and analysed through dietary analysis software. Body mass (BM), hydration status, and serum sodium concentration were determined pre- and post-Stages 1 to 5.

Results

Water (overall mean (SD): total daily 7.7 (1.5) L/day, during running 732 (183) ml/h) and sodium (total daily 3.9 (1.3) g/day, during running 270 (151) mg/L) ingestion did not differ between stages in UER (p < 0.001 vs. CON). Exercise-induced BM loss was 2.4 (1.2)% (p < 0.001). Pre- to post-stage BM gains were observed in 26% of UER along competition. Pre- and post-stage plasma osmolality remained within normal clinical reference range (280 to 303 mOsmol/kg) in the majority of UER (p > 0.05 vs. CON pre-stage). Asymptomatic hyponatraemia (<135 mmol/L) was evident pre- and post-stage in n = 8 UER, corresponding to 42% of sampled participants. Pre- and post-stage urine colour, urine osmolality and urine/plasma osmolality ratio increased (p < 0.001) as competition progressed in UER, with no change in CON. Plasma volume and extra-cellular water increased (p < 0.001) 22.8% and 9.2%, respectively, from pre-Stage 1 to 5 in UER, with no change in CON.

Conclusion

Water intake habits of ultra-runners during MSUM conducted in hot ambient conditions appear to be sufficient to maintain baseline euhydration levels. However, fluid over-consumption behaviours were evident along competition, irrespective of running speed and gender. Normonatraemia was observed in the majority of ultra-runners throughout MSUM, despite sodium ingestion under benchmark recommendations.