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The Effect of a Ketogenic Low-Carbohydrate, High-Fat Diet on Aerobic Capacity and Exercise Performance in Endurance Athletes: A Systematic Review and Meta-Analysis.
Cao, J, Lei, S, Wang, X, Cheng, S
Nutrients. 2021;13(8)
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A low-carbohydrate diet has been shown at the cellular level to be of benefit to endurance athletes, however how this effects performance remains controversial. Ketogenic diets have recently become popular and is a special type of low-carbohydrate, high-fat diet with 5% or less energy from carbohydrates. This systematic review and meta-analysis aimed to determine the effects of a ketogenic low-carbohydrate, high-fat diet (K-LCHF) on aerobic capacity and exercise performance in endurance athletes. The results showed that 10 studies were found and that K-LCHF diets had no effect on aerobic capacity and exercise performance of endurance athletes. It was concluded that K-LCHF diet is unlikely to be of benefit to endurance athletes. This study could be used by healthcare professionals to understand that modifying fat and carbohydrate ratios may have little effect on endurance and that alternative dietary modifications should be researched.
Abstract
A low-carbohydrate, high-fat (LCHF) diet has been proposed to enhance the fat utilization of muscle and the aerobic capacity of endurance athletes, thereby improving their exercise performance. However, it remains uncertain how the macronutrient intake shift from carbohydrate to fat affects endurance exercise training and performance. This study performed a systematic review and meta-analysis to explore the effects of a ketogenic low-carbohydrate, high-fat (K-LCHF) diet on aerobic capacity and exercise performance among endurance athletes. Searches were carried out in five electronic databases, and we followed the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. The search included studies using an LCHF diet as an intervention protocol and compared data on factors such as maximum oxygen uptake (VO2max) and rating of perceived exertion (RPE) from the graded exercise test. In this case, 10 studies met the criteria and were included in the meta-analysis. We did not find a significant effect of K-LCHF diet interventions on VO2max, time to exhaustion, HRmax or RPE. However, a significant overall effect in the substrate oxidation response to respiratory exchange rate was observed. The meta-analysis showed that K-LCHF diets did not affect aerobic capacity and exercise performance. Therefore, high-quality interventions of a K-LCHF diet are needed to illustrate its effect on various endurance training programs.
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Effect of food sources of nitrate, polyphenols, L-arginine and L-citrulline on endurance exercise performance: a systematic review and meta-analysis of randomised controlled trials.
d'Unienville, NMA, Blake, HT, Coates, AM, Hill, AM, Nelson, MJ, Buckley, JD
Journal of the International Society of Sports Nutrition. 2021;18(1):76
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Nitric oxide (NO) is a molecule that is found in some foods and is involved in muscle function and repair. Given this fact, increased dietary NO intake to improve endurance exercise performance has become popular. The aim of this systematic review and meta-analysis was to determine the effect of consuming foods rich in precursors to NO synthesis on endurance exercise performance. 118 studies were found, with the majority looking at polyphenols, which are micronutrients found in plants, and nitrates. A small number of studies were found on L-citrulline, which is a natural compound mainly found in watermelon. Diets rich in L-citrulline showed little effect on endurance exercise performance and those rich in polyphenols and nitrates had a small effect on exercise performance. Different foods were shown to have different effects with nitrate-rich foods such as beetroot showing a small benefit, but not red spinach, Swiss chard, or rhubarb. Amongst polyphenol rich foods, a small benefit was seen with grape, beetroot, French maritime pine, Montmorency cherry and pomegranate, whilst no benefits were evident for New Zealand blackcurrant, cocoa, ginseng, green tea, or raisins. Well-trained males showed benefits from polyphenols but not nitrate rich foods. It was concluded that foods rich in polyphenols and nitrates may have a small benefit on endurance exercise performance, but this effect may be food specific. Highly trained males may only find a benefit from a polyphenol rich diet. This study could be used by healthcare professionals to understand that foods rich in precursors involved in the production of NO may have a limited effect on endurance exercise performance and that it may be dependent upon the food given and the level of fitness.
Abstract
BACKGROUND Increasing nitric oxide bioavailability may induce physiological effects that enhance endurance exercise performance. This review sought to evaluate the performance effects of consuming foods containing compounds that may promote nitric oxide bioavailability. METHODS Scopus, Web of Science, Ovid Medline, EMBASE and SportDiscus were searched, with included studies assessing endurance performance following consumption of foods containing nitrate, L-arginine, L-citrulline or polyphenols. Random effects meta-analysis was conducted, with subgroup analyses performed based on food sources, sex, fitness, performance test type and supplementation protocol (e.g. duration). RESULTS One hundred and eighteen studies were included in the meta-analysis, which encompassed 59 polyphenol studies, 56 nitrate studies and three L-citrulline studies. No effect on exercise performance following consumption of foods rich in L-citrulline was identified (SMD=-0.03, p=0.24). Trivial but significant benefits were demonstrated for consumption of nitrate and polyphenol-rich foods (SMD=0.15 and 0.17, respectively, p<0.001), including performance in time-trial, time-to-exhaustion and intermittent-type tests, and following both acute and multiple-day supplementation, but no effect of nitrate or polyphenol consumption was found in females. Among nitrate-rich foods, beneficial effects were seen for beetroot, but not red spinach or Swiss chard and rhubarb. For polyphenol-rich foods, benefits were found for grape, (nitrate-depleted) beetroot, French maritime pine, Montmorency cherry and pomegranate, while no significant effects were evident for New Zealand blackcurrant, cocoa, ginseng, green tea or raisins. Considerable heterogeneity between polyphenol studies may reflect food-specific effects or differences in study designs and subject characteristics. Well-trained males (V̇O2max ≥65 ml.kg.min-1) exhibited small, significant benefits following polyphenol, but not nitrate consumption. CONCLUSION Foods rich in polyphenols and nitrate provide trivial benefits for endurance exercise performance, although these effects may be food dependent. Highly trained endurance athletes do not appear to benefit from consuming nitrate-rich foods but may benefit from polyphenol consumption. Further research into food sources, dosage and supplementation duration to optimise the ergogenic response to polyphenol consumption is warranted. Further studies should evaluate whether differential sex-based responses to nitrate and polyphenol consumption are attributable to physiological differences or sample size limitations. OTHER The review protocol was registered on the Open Science Framework ( https://osf.io/u7nsj ) and no funding was provided.
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The effects of phosphocreatine disodium salts plus blueberry extract supplementation on muscular strength, power, and endurance.
Anders, JPV, Neltner, TJ, Smith, RW, Keller, JL, Housh, TJ, Daugherty, FJ, Tempesta, MS, Dash, AK, Munt, DJ, Schmidt, RJ, et al
Journal of the International Society of Sports Nutrition. 2021;18(1):60
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The effects of polyphenols and phosphocreatine supplementation on exercise performance, muscular strength, power, and endurance are largely unknown. This randomised, double-blinded, placebo-controlled, parallel-design trial aimed to differentiate the effects of a blend of 5 grams of phosphocreatine disodium salts plus 200 mg blueberry extract (PCDSB), 3 grams of Creatinine monohydrate (CM), and placebo on measures of muscular strength, power, and endurance. PCDSB contained 60 grams of phenols and 2.5 grams of pure creatine, and CM contained 2.4 grams of pure creatin. During this trial, thirty-three men took random supplements for 28 days and kept up their regular exercise regimen. In both PCDSB and CM, Peak torque (PT) and Average power (AP) increased after 28 days of supplementation with no effect on fatigue-induced PT% and AP% or body mass. Additionally, a greater proportion of participants showed a meaningful increase in muscular strength to PCDSB than to CM. To evaluate the additive effects of ingredients in the PCDSB supplement, longer-term studies are needed with larger supplementation doses. The study provides insight into the ergogenic effects of PCDSB and CM for healthcare practitioners.
Abstract
BACKGROUND Numerous studies have demonstrated the efficacy of creatine supplementation for improvements in exercise performance. Few studies, however, have examined the effects of phosphocreatine supplementation on exercise performance. Furthermore, while polyphenols have antioxidant and anti-inflammatory properties, little is known regarding the influence of polyphenol supplementation on muscular strength, power, and endurance. Thus, the purpose of the present study was to compare the effects of 28 days of supplementation with phosphocreatine disodium salts plus blueberry extract (PCDSB), creatine monohydrate (CM), and placebo on measures of muscular strength, power, and endurance. METHODS Thirty-three men were randomly assigned to consume either PCDSB, CM, or placebo for 28 days. Peak torque (PT), average power (AP), and percent decline for peak torque (PT%) and average power (AP%) were assessed from a fatigue test consisting of 50 maximal, unilateral, isokinetic leg extensions at 180°·s- 1 before and after the 28 days of supplementation. Individual responses were assessed to examine the proportion of subjects that exceeded a minimal important difference (MID). RESULTS The results demonstrated significant (p < 0.05) improvements in PT for the PCDSB and CM groups from pre- (99.90 ± 22.47 N·m and 99.95 ± 22.50 N·m, respectively) to post-supplementation (119.22 ± 29.87 N·m and 111.97 ± 24.50 N·m, respectively), but no significant (p = 0.112) change for the placebo group. The PCDSB and CM groups also exhibited significant improvements in AP from pre- (140.18 ± 32.08 W and 143.42 ± 33.84 W, respectively) to post-supplementation (170.12 ± 42.68 W and 159.78 ± 31.20 W, respectively), but no significant (p = 0.279) change for the placebo group. A significantly (p < 0.05) greater proportion of subjects in the PCDSB group exceeded the MID for PT compared to the placebo group, but there were no significant (p > 0.05) differences in the proportion of subjects exceeding the MID between the CM and placebo groups or between the CM and PCDSB groups. CONCLUSIONS These findings indicated that for the group mean responses, 28 days of supplementation with both PCDSB and CM resulted in increases in PT and AP. The PCDSB, however, may have an advantage over CM when compared to the placebo group for the proportion of individuals that respond favorably to supplementation with meaningful increases in muscular strength.
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Acute effect of high-definition and conventional tDCS on exercise performance and psychophysiological responses in endurance athletes: a randomized controlled trial.
da Silva Machado, DG, Bikson, M, Datta, A, Caparelli-Dáquer, E, Unal, G, Baptista, AF, Cyrino, ES, Li, LM, Morya, E, Moreira, A, et al
Scientific reports. 2021;11(1):13911
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Exercise-induced fatigue can be associated with a limited descending command from the central nervous system to the muscle which may affect muscle contraction and its ability to generate force. Transcranial direct current stimulation (tDCS) is the application of weak electrical current to stimulate different areas of the brain to influence exercise performance and perception. High-definition transcranial direct current stimulation (HD-tDCS) is a modification of conventional tDCS to increase the focality, precision, long-lasting effects and greater neuronal excitability change. This single-centre, randomised, crossover, single-blinded, sham-controlled trial compared the effects of HD-tDCS and conventional tDCS on exercise performance and psychophysiological responses in healthy young male endurance athletes. The study found no effect of HD-tDCS or conventional tDCS on exercise performance and psychophysiological responses to exhaustive exercise. Further robust studies are required to evaluate the effects of both forms of tDCS in athletes compared to non-athletes and its effects when tDCS is applied to other areas of the central nervous system. Healthcare professionals can use the results of this study to understand that there is no evidence currently to support the utilisation of tDCS in improving exercise performance in athletes.
Abstract
Transcranial direct current stimulation (tDCS) has been used aiming to boost exercise performance and inconsistent findings have been reported. One possible explanation is related to the limitations of the so-called "conventional" tDCS, which uses large rectangular electrodes, resulting in a diffuse electric field. A new tDCS technique called high-definition tDCS (HD-tDCS) has been recently developed. HD-tDCS uses small ring electrodes and produces improved focality and greater magnitude of its aftereffects. This study tested whether HD-tDCS would improve exercise performance to a greater extent than conventional tDCS. Twelve endurance athletes (29.4 ± 7.3 years; 60.15 ± 5.09 ml kg-1 min-1) were enrolled in this single-center, randomized, crossover, and sham-controlled trial. To test reliability, participants performed two time to exhaustion (TTE) tests (control conditions) on a cycle simulator with 80% of peak power until volitional exhaustion. Next, they randomly received HD-tDCS (2.4 mA), conventional (2.0 mA), or active sham tDCS (2.0 mA) over the motor cortex for 20-min before performing the TTE test. TTE, heart rate (HR), associative thoughts, peripheral (lower limbs), and whole-body ratings of perceived exertion (RPE) were recorded every minute. Outcome measures were reliable. There was no difference in TTE between HD-tDCS (853.1 ± 288.6 s), simulated conventional (827.8 ± 278.7 s), sham (794.3 ± 271.2 s), or control conditions (TTE1 = 751.1 ± 261.6 s or TTE2 = 770.8 ± 250.6 s) [F(1.95; 21.4) = 1.537; P = 0.24; η2p = 0.123]. There was no effect on peripheral or whole-body RPE and associative thoughts (P > 0.05). No serious adverse effect was reported. A single session of neither HD-tDCS nor conventional tDCS changed exercise performance and psychophysiological responses in athletes, suggesting that a ceiling effect may exist.
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Relationship between energy availability, energy conservation and cognitive restraint with performance measures in male endurance athletes.
Jurov, I, Keay, N, Hadžić, V, Spudić, D, Rauter, S
Journal of the International Society of Sports Nutrition. 2021;18(1):24
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Athletes who do endurance exercise sometimes experience low energy availability which can affect their performance. Low energy availability may lead to a syndrome called Relative energy deficiency in sports. This cross-sectional controlled study assessed the pre-race energy availability in twelve lean, healthy endurance athletes without pre-existing signs of relative energy deficiency. Results showed that two-thirds of the participants had low mean energy availability. Lower energy availability was associated with higher energy expenditure. Participants in the study deliberately restricted their energy intake to achieve an optimal body composition. This may have led to energy conservation in participants. However, the study failed to show any associations between energy conservation and energy availability. There is a need for more robust studies to determine the true cut-off value of energy availability in male endurance athletes. Healthcare professionals can use the results of this study to understand the need for eating behaviour screening to reduce disordered eating in endurance athletes and the clinical applicability of energy conservation assessment.
Abstract
BACKGROUND Low energy availability in male athletes has gained a lot of attention in recent years, but direct evidence of its effects on health and performance is lacking. The aim of this research was to objectively measure energy availability (EA) in healthy male endurance athletes without pre-existing relative energy deficiency signs during pre-race season. METHODS Twelve trained endurance athletes (performance level 3, 4, and 5) participated in the cross-sectional controlled laboratory study. Fat-free mass, exercise energy expenditure, and energy intake were measured to calculate EA. Resting energy expenditure was measured and estimated to assess energy conservation. Three specific performance tests were used to assess endurance, agility, and explosive strength performance. For psychological evaluation, the Three Factor Eating Questionnaire and a short Well-being questionnaire were completed. RESULTS Mean EA was 29.5 kcal/kg FFM/day. The majority (66.6%) had EA under the threshold for low EA in females. Critical cognitive restraint (≥13) was reported by 75% of participants. There were no differences in performance, blood values, or psychological evaluation when subjects were divided into two groups divided by EA = 30 kcal/kg FFM/day. Cognitive restraint was negatively associated with measured resting energy expenditure and energy conservation (r = -.578, p = .025 and r = -.549, p = .032, respectively). CONCLUSIONS The mean EA measured in this study supports the theory that the threshold for low EA in endurance male athletes might be under the threshold for females. In addition, we confirmed cognitive restraint could be useful for early detection of energy conservation. The high cognitive restraint as measured in our sample stressed the need of eating behavior screening in endurance athletes in order to reduce risk of any disordered eating patterns.
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Metabolic, hormonal and performance effects of isomaltulose ingestion before prolonged aerobic exercise: a double-blind, randomised, cross-over trial.
Notbohm, HL, Feuerbacher, JF, Papendorf, F, Friese, N, Jacobs, MW, Predel, HG, Zacher, J, Bloch, W, Schumann, M
Journal of the International Society of Sports Nutrition. 2021;18(1):38
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Isomaltulose is a low-glycaemic index carbohydrate that lowers insulin and glucose levels postprandially. The benefits of taking Isomaltulose in an exercise setting are not well studied. This double-blinded, randomised, crossover study evaluated the effects of Isomaltulose intake on metabolic responses, hormonal responses, exercise performance and gastrointestinal disturbances in runners. Twenty-one male recreational endurance runners took part in four separate experimental sessions to compare Isomaltulose to maltodextrin and glucose. Fat and carbohydrate oxidation rates were not different among groups. This might be because the lower dose of Isomaltulose (50g) was used in this trial. Compared to glucose and maltodextrin, isomaltulose lowered metabolic and hormonal responses to exercise. In the study, Isomaltulose, glucose, and maltodextrin did not differ in exercise performance or gastrointestinal disturbances. A higher dose may be needed in order to demonstrate exercise performance, but caution should be exercised since a higher dose may cause gastrointestinal upset. A robust investigation of Isomalulose dose and its effects on glucose, insulin, and glucose-dependent insulinotropic polypeptides is required to determine if exercise leads to hypoglycaemia in the clinical population. Healthcare practitioners can use the findings of this study to understand the advantageous effects of 50g Isomaltulose in regulating glucose, insulin and glucose-dependent insulinotropic polypeptide during aerobic exercise.
Abstract
BACKGROUND Isomaltulose has been discussed as a low glycaemic carbohydrate but evidence concerning performance benefits and physiological responses has produced varying results. Therefore, we primarily aimed to investigate the effects of isomaltulose ingestion compared to glucose and maltodextrin on fat and carbohydrate oxidation rates, blood glucose levels and serum hormone concentrations of insulin and glucose-dependent insulinotropic polypeptide (GIP). As secondary aims, we assessed running performance and gastrointestinal discomfort. METHODS Twenty-one male recreational endurance runners performed a 70-min constant load trial at 70% maximal running speed (Vmax), followed by a time to exhaustion (TTE) test at 85% Vmax after ingesting either 50 g isomaltulose, maltodextrin or glucose. Fat and carbohydrate oxidation rates were calculated from spiroergometric data. Venous blood samples for measurement of GIP and insulin were drawn before, after the constant load trial and after the TTE. Capillary blood samples for glucose concentrations and subjective feeling of gastrointestinal discomfort were collected every 10 min during the constant load trial. RESULTS No between-condition differences were observed in the area under the curve analysis of fat (p = 0.576) and carbohydrate oxidation rates (p = 0.887). Isomaltulose ingestion led to lower baseline postprandial concentrations of blood glucose compared to maltodextrin (percent change [95% confidence interval], - 16.7% [- 21.8,-11.6], p < 0.001) and glucose (- 11.5% [- 17.3,-5.7], p = 0.001). Similarly, insulin and GIP concentrations were also lower following isomaltulose ingestion compared to maltodextrin (- 40.3% [- 50.5,-30.0], p = 0.001 and - 69.1% [- 74.3,-63.8], p < 0.001, respectively) and glucose (- 32.6% [- 43.9,-21.2], p = 0.012 and - 55.8% [- 70.7,-40.9], p < 0.001, respectively). Furthermore, glucose fluctuation was lower after isomaltulose ingestion compared to maltodextrin (- 26.0% [- 34.2,-17.8], p < 0.001) and glucose (- 17.4% [- 29.1,-5.6], p < 0.001). However, during and after exercise, no between-condition differences for glucose (p = 0.872), insulin (p = 0.503) and GIP (p = 0.244) were observed. No between-condition differences were found for TTE (p = 0.876) or gastrointestinal discomfort (p = 0.119). CONCLUSION Isomaltulose ingestion led to lower baseline postprandial concentrations of glucose, insulin and GIP compared to maltodextrin and glucose. Consequently, blood glucose fluctuations were lower during treadmill running after isomaltulose ingestion, while no between-condition differences were observed for CHO and fat oxidation rates, treadmill running performance and gastrointestinal discomfort. Further research is required to provide specific guidelines on supplementing isomaltulose in performance and health settings.
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The Effect of Kefir Supplementation on Improving Human Endurance Exercise Performance and Antifatigue.
Lee, MC, Jhang, WL, Lee, CC, Kan, NW, Hsu, YJ, Ho, CS, Chang, CH, Cheng, YC, Lin, JS, Huang, CC
Metabolites. 2021;11(3)
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Compared to sedentary people, athletes exhibit a much more abundant and diverse composition of gut bacteria. Hence the relationship between gut microbes and energy usage and exercise performance has attracted much attention in recent years. Probiotics and prebiotic-related products have demonstrated the potential to enhance metabolic pathways and influence energy levels, energy consumption and exercise performance. And previous studies demonstrated positive effects on exercise endurance associated with the consumption of kefir, a fermented dairy product containing Lactobacilli species as part of the microbial symbiosis. This study investigated whether kefir can promote changes in the gut microbiota, improve exercise endurance performance, and influences fatigue during and after exercise. The study enrolled sixteen, untrained 20–30-year-old for a double-blind crossover design study, supplementing with SYNKEFIR™ for 28 days whilst observing changes in metabolic markers, body composition, exercise endurance and faecal gut bacteria. In summary, supplementation with SYNKEFIR™ significantly improved exercise performance and reduced the production of lactic acid after exercise. In addition, kefir supplementation seemed to reduce fatigue and accelerated the recovery from fatigue after exercise, with a marked reduction in lactic acid production after exercise. Though kefir supplementation had no significant effect on other post-exercise fatigue biochemical indicators nor did it induce notable changes in gut bacteria composition. As SYNKEFIR™ is a starter culture isolated from traditional kefir it could be expected that other traditional kefir products would have similar effects. Kefir as a food product is suited to a wide range of people, and it could be considered part of a healthy diet plan for untrained individuals wishing to support their exercise performance.
Abstract
Kefir is an acidic, carbonated, and fermented dairy product produced by fermenting milk with kefir grains. The Lactobacillus species constitutes an important part of kefir grains. In a previous animal study, kefir effectively improved exercise performance and had anti-fatigue effects. The purpose of this research was to explore the benefits of applying kefir to improve exercise performance, reduce fatigue, and improve physiological adaptability in humans. The test used a double-blind crossover design and supplementation for 28 days. Sixteen 20-30 year-old subjects were divided into two groups in a balanced order according to each individual's initial maximal oxygen uptake and were assigned to receive a placebo (equal flavor, equal calories, 20 g/day) or SYNKEFIR™ (20 g/day) every morning. After the intervention, there were 28 days of wash-out, during which time the subjects did not receive further interventions. After supplementation with SYNKEFIR™, the exercise time to exhaustion was significantly greater than that before ingestion (p = 0.0001) and higher than that in the Placebo group by 1.29-fold (p = 0.0004). In addition, compared with the Placebo group, the SYNKEFIR™ administration group had significantly lower lactate levels in the exercise and recovery (p < 0.05). However, no significant difference was observed in the changes in the gut microbiota. Although no significant changes in body composition were found, SYNKEFIR™ did not cause adverse reactions or harm to the participants' bodies. In summary, 28 days of supplementation with SYNKEFIR™ significantly improved exercise performance, reduced the production of lactic acid after exercise, and accelerated recovery while also not causing any adverse reactions.
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The Effects of Exercise on Indirect Markers of Gut Damage and Permeability: A Systematic Review and Meta-analysis.
Chantler, S, Griffiths, A, Matu, J, Davison, G, Jones, B, Deighton, K
Sports medicine (Auckland, N.Z.). 2021;51(1):113-124
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Gut permeability and intestinal cell damage are often observed in various gastrointestinal and metabolic conditions. Based on recent findings, exercise appears to cause damage to intestinal cells, leading to an increase in gut permeability. The aim of this review was to determine the effect of an acute bout of exercise on gut damage and permeability and explore the plausible mechanisms underlying these effects. This review analysed 34 studies that evaluated biomarkers of gut permeability and cell damage in response to exercise compared to resting controls. These findings revealed a significant impact of exercise on gut damage and permeability, and the markers were exacerbated when exercise was performed in hot conditions. The duration of exercise did not have any impact on cell damage or permeability. Based on these results, the authors conclude a single bout of exercise increases gut damage and permeability and they encourage further investigation into nutritional strategies to prevent adverse effects during the post-exercise period. Future research should consider the efficacy nutritional interventions to minimize these negative effects to optimise athletic health and performance.
Abstract
AIM: Exercise appears to cause damage to the endothelial lining of the human gastrointestinal tract and elicit a significant increase in gut permeability. OBJECTIVE The aim of this review was to determine the effect of an acute bout of exercise on gut damage and permeability outcomes in healthy populations using a meta-analysis. METHODS PubMed, The Cochrane Library as well as MEDLINE, SPORTDiscus and CINHAL, via EBSCOhost were searched through February 2019. Studies were selected that evaluated urinary (ratio of disaccharide/monosaccharide excretion) or plasma markers [intestinal Fatty Acid Binding Protein (i-FABP)] of gut permeability and gut cell damage in response to a single bout of exercise. RESULTS A total of 34 studies were included. A random-effects meta-analysis was performed, and showed a large and moderate effect size for markers of gut damage (i-FABP) (ES 0.81; 95% CI 0.63-0.98; n = 26; p < 0.001) and gut permeability (Disaccharide Sugar/Monosaccharide Sugar) (ES 0.70; 95% CI 0.29-1.11; n = 17; p < 0.001), respectively. Exercise performed in hot conditions (> 23 °C) further increased markers of gut damage compared with thermoneutral conditions [ES 1.06 (95% CI 0.88-1.23) vs. 0.66 (95% CI 0.43-0.89); p < 0.001]. Exercise duration did not have any significant effect on gut damage or permeability outcomes. CONCLUSIONS These findings demonstrate that a single bout of exercise increases gut damage and gut permeability in healthy participants, with gut damage being exacerbated in hot environments. Further investigation into nutritional strategies to minimise gut damage and permeability after exercise is required. PROSPERO database number (CRD42018086339).
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Is a vegan diet detrimental to endurance and muscle strength?
Boutros, GH, Landry-Duval, MA, Garzon, M, Karelis, AD
European journal of clinical nutrition. 2020;74(11):1550-1555
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There is a common belief amongst the general population that a vegan diet leads to lower exercise performance due to the potential lack of dietary protein and nutrients. However, previous research that compared aerobic capacity and muscle strength between different diet groups only showed marginal variance, if any at all. But it is criticized that these studies did not always distinguish between the multiple subtypes of vegetarian or veganism. Hence this study sought to focus specifically on the comparison of strict plant-based eaters with omnivores. The participants involved were 56 active women, around their mid-twenties, with an average Body Mass Index of 22. Assessed were estimated VO2 max (an indicator of aerobic fitness), submaximal endurance performance and upper and lower body muscle strength. The 3-day food diaries of each participant was analysed and showed a similar intake of energy and fats in both groups. Vegans had higher carbohydrate, fibre, vitamin C, iron, and magnesium consumption and lower intake of protein, leucine, alanine, saturated fat, vitamin D, and vitamin B12, when compared to omnivores. Whilst upper body strength appeared to be marginally lower in the vegan group, higher levels of estimated VO2 max and significantly higher submaximal endurance levels were observed. The results contradict the common belief, demonstrating that a vegan diet appears to have no detrimental impact on endurance and muscle strength in healthy, young and lean women. In fact, the findings suggest that a vegan diet can be advantageous on endurance performance compared to omnivores. The authors propose that the higher intake of carbohydrates amongst vegans could be linked to better endurance performance and that such a plant-based diet can have favourable effects on oxidative stress and inflammatory profiles. The outcomes of this study may be of interest to those supporting the sports performance of strict plant-based eaters.
Abstract
BACKGROUND/OBJECTIVES In the general population, there is a popular belief that a vegan diet may be associated with a lower exercise performance due to the lack of certain nutrients in vegan individuals. Thus, the purpose of the present study was to examine endurance and muscle strength differences between vegan and omnivore participants. SUBJECTS/METHODS We studied 56 healthy young lean physically active women (age: 25.6 ± 4.1 years; body mass index: 22 ± 1.9 kg/m2). Participants were classified as vegan (n = 28) or omnivore (n = 28) based on their eating habits. All volunteers followed either a vegan or an omnivore diet for at least 2 years. Anthropometric measurements, body composition, estimated maximal oxygen consumption (VO2 max), a submaximal endurance test (70% of VO2 max), muscle strength (leg and chest press), and dietary factors were measured. RESULTS Both groups were comparable for physical activity levels, body mass index, percent body fat, lean body mass, and muscle strength. However, vegans had a significantly higher estimated VO2 max (44.5 ± 5.2 vs. 41.6 ± 4.6 ml/kg/min; p = 0.03, respectively) and submaximal endurance time to exhaustion (12.2 ± 5.7 vs. 8.8 ± 3.0 min; p = 0.007, respectively) compared with omnivores. CONCLUSIONS The results suggest that a vegan diet does not seem to be detrimental to endurance and muscle strength in healthy young lean women. In fact, our study showed that submaximal endurance might be better in vegans compared with omnivores. Therefore, these findings contradict the popular belief of the general population.
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Ketone ester supplementation blunts overreaching symptoms during endurance training overload.
Poffé, C, Ramaekers, M, Van Thienen, R, Hespel, P
The Journal of physiology. 2019;597(12):3009-3027
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Overload training is often used by endurance athletes to improve endurance performance. Overload training, however, can result in muscle protein breakdown, a catabolic state, and a decrease in muscle performance. Therefore, this randomised, double-blinded, placebo-controlled study examined the protective effects of ketone ester supplementation in reducing the detrimental effects of endurance training-induced overreaching. When compared to the control group, the subjects taking oral ketone ester supplements showed a 15% increase in sustained training load and power output and maintained energy balance. Supplementation with ketones ester inhibited the night-time increase in neurotransmitter noradrenaline and hormone adrenaline and maintained heart rate, suggesting a blunting of cardiovascular, sympathetic and hormonal symptoms caused by the endurance training overload. Growth differentiation factor 15 (GDF15) increased by training overload was negated by ketone ester intake. Further studies should be conducted to establish the long-term effects of ketone esters in training and recovery. These results can help healthcare professionals better understand how elevated blood ketones can enhance exercise performance and reduce the detrimental effects of exercise overload.
Abstract
KEY POINTS Overload training is required for sustained performance gain in athletes (functional overreaching). However, excess overload may result in a catabolic state which causes performance decrements for weeks (non-functional overreaching) up to months (overtraining). Blood ketone bodies can attenuate training- or fasting-induced catabolic events. Therefore, we investigated whether increasing blood ketone levels by oral ketone ester (KE) intake can protect against endurance training-induced overreaching. We show for the first time that KE intake following exercise markedly blunts the development of physiological symptoms indicating overreaching, and at the same time significantly enhances endurance exercise performance. We provide preliminary data to indicate that growth differentiation factor 15 (GDF15) may be a relevant hormonal marker to diagnose the development of overtraining. Collectively, our data indicate that ketone ester intake is a potent nutritional strategy to prevent the development of non-functional overreaching and to stimulate endurance exercise performance. ABSTRACT It is well known that elevated blood ketones attenuate net muscle protein breakdown, as well as negate catabolic events, during energy deficit. Therefore, we hypothesized that oral ketones can blunt endurance training-induced overreaching. Fit male subjects participated in two daily training sessions (3 weeks, 6 days/week) while receiving either a ketone ester (KE, n = 9) or a control drink (CON, n = 9) following each session. Sustainable training load in week 3 as well as power output in the final 30 min of a 2-h standardized endurance session were 15% higher in KE than in CON (both P < 0.05). KE inhibited the training-induced increase in nocturnal adrenaline (P < 0.01) and noradrenaline (P < 0.01) excretion, as well as blunted the decrease in resting (CON: -6 ± 2 bpm; KE: +2 ± 3 bpm, P < 0.05), submaximal (CON: -15 ± 3 bpm; KE: -7 ± 2 bpm, P < 0.05) and maximal (CON: -17 ± 2 bpm; KE: -10 ± 2 bpm, P < 0.01) heart rate. Energy balance during the training period spontaneously turned negative in CON (-2135 kJ/day), but not in KE (+198 kJ/day). The training consistently increased growth differentiation factor 15 (GDF15), but ∼2-fold more in CON than in KE (P < 0.05). In addition, delta GDF15 correlated with the training-induced drop in maximal heart rate (r = 0.60, P < 0.001) and decrease in osteocalcin (r = 0.61, P < 0.01). Other measurements such as blood ACTH, cortisol, IL-6, leptin, ghrelin and lymphocyte count, and muscle glycogen content did not differentiate KE from CON. In conclusion, KE during strenuous endurance training attenuates the development of overreaching. We also identify GDF15 as a possible marker of overtraining.