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Mitochondrial Function and Health - NED Infobite
BANT's scientific NED InfoBites are designed to provide key elements of the latest research using plain language. They provide quick overviews on particular health issues and nutrition topics for a speedy introduction to the science. Visually attractive and easily shareable with clients and social media followers.
2024
Abstract
The function of cellular mitochondria has far reaching effects on human health. This NED Infobite looks at different dietary types and specific antioxidants and their interplay with mitochondrial function, in particular in the relation to metabolic dysregulation and optimal physical performance.
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Effects of a Raisin Supplement on Cognitive Performance, Quality of Life, and Functional Activities in Healthy Older Adults-Randomized Clinical Trial.
Rodrigo-Gonzalo, MJ, González-Manzano, S, Pablos-Hernández, MC, Méndez-Sánchez, R, Ayuda Duran, B, González-Sánchez, J, Barbero-Iglesias, F, González-Paramás, AM, Recio-Rodríguez, JI
Nutrients. 2023;15(12)
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The regular intake of foods rich in polyphenols shows many biological activities, such as antioxidant, cardioprotective, anti-inflammation and anti-aging properties. This diversity of compounds found in grapes, especially red grapes, makes it a candidate for testing the role of dietary polyphenols to health. The objective of this single blinded randomised controlled clinical trial was to evaluate the effects of consuming 50g of Málaga muscatel raisins which are dried grapes on cognitive performance, quality of life, and functional activities in healthy adults over 70 years. According to the researchers this is the first study looking at the effect of raisins on cognitive performance. A group of 80 participants were split into two groups with one group adding 50g of raisins a day to their usual diet for six months and a control group of 40 patients receiving no raisins. Cognitive performance was measured by various tests which are summarised in the full text article. The results of this study showed that the supplement of 50 g of raisins slightly improved cognitive performance including spatial orientation, memory and comprehension, reading, writing, and drawing. In addition to a slight improvement in quality of life and functional activities. This shows promising results and that the addition of raisins to the diet along with a variety of foods rich in polyphenols can confer positive health benefits that can prevent age related cognitive decline. More research is needed to know exactly the mechanism of action of polyphenols on cognitive performance.
Abstract
The objective of this study was to evaluate the effects of consuming 50 g of raisins on cognitive performance, quality of life, and functional activities in healthy older adults. This is a parallel randomized controlled clinical trial, in which 80 subjects over 70 years of age participated. For 6 months, the intervention group (IG; n = 40) consumed 50 g of raisins per day added to their usual diet, whereas the control group (CG; n = 40) received no supplement. All variables were measured at baseline and at 6 months. Cognitive performance assessed with the Montreal Cognitive Assessment (MOCA) test shows a difference of 3.27 points (95% CI 1.59 to 4.96), p ≤ 0.001, favorable to the IG, after the intervention. Among the cognitive performances, an improvement is observed in the IG in orientation, assessed both with the MOCA test 0.49 (95% CI 0.10 to 0.87), p = 0.014, and with the Mini-Mental State Examination (MMSE) test, 0.36 (95% CI 0.02 to 0.70), p = 0.038. In visuospatial/executive capacity and in language, improvements were also observed in the IG, 1.36 (95% CI 0.77 to 1.95), p = 0.001, and 0.54 points (95% CI 0.12 to 0.96), p = 0.014, respectively. Immediate and delayed recall, assessed with the Rey Auditory Verbal Learning Test, improved in the IG. In addition, the IG showed a better quality of life and greater autonomy in instrumental activities of daily living after 6 months. No significant changes were observed in the rest of the variables analyzed. Therefore, the consumption of 50 g of raisins produces a slight improvement in cognitive performance, quality of life, and functional activities in the elderly.
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Manipulation of Dietary Intake on Changes in Circulating Testosterone Concentrations.
Zamir, A, Ben-Zeev, T, Hoffman, JR
Nutrients. 2021;13(10)
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Androgens, like testosterone, are steroid hormones commonly associated with reproduction. However, they also govern metabolic functions, body composition and growth. Higher levels of circulating androgens enhance athletic performance by supporting metabolic activities such as protein production, regeneration and growth and by inhibiting breakdown processes. Manipulating testosterone to enhance athletic performance without the use of anabolic steroids hormones has been of much interest. As macro-and micronutrients can influence androgen hormones, this review examined whether specific energy and nutrient intake can ‘naturally’ manipulate testosterone levels. The authors describe the metabolic functions of testosterone before exploring the current evidence on selected plant extracts and nutrients and their impact on aromatase activity. Inhibiting aromatase can prevent androgens from being converted into oestrogen and thus may help to raise circulating androgens. Discussed are a range of plant-derived compounds, flavonoids, macronutrients and micronutrients (Vitamin D, Zinc and Magnesium) and their impact on testosterone levels. The authors conclude that the nutrients discussed have some supportive evidence, yet overall findings are inconclusive due to limited studies. Regarding macronutrients more research is available, and the evidence supports that low energy intake negatively impacts testosterone levels and performance. Whereby supplementation of vitamins crucial to testosterone production seems to provide value in cases of deficiency further research is required. This article yields an overview of plant compounds, macro-and micronutrients and their potential impact on circulating testosterone levels. While low energy intake and nutrient deficiencies appears to be unfavourable, the absence of clear evidence on other compounds would warrant further case-specific investigations.
Abstract
Elevations in the circulating concentration of androgens are thought to have a positive effect on the anabolic processes leading to improved athletic performance. Anabolic-androgenic steroids have often been used by competitive athletes to augment this effect. Although there has been concerted effort on examining how manipulating training variables (e.g., intensity and volume of training) can influence the androgen response to exercise, there has been much less effort directed at understanding how changes in both macronutrient and micronutrient intake can impact the androgen response. Thus, the focus of this review is to examine the effect that manipulating energy and nutrient intake has on circulating concentrations of testosterone and what the potential mechanism is governing these changes.
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Development of Maximal Dynamic Strength During Concurrent Resistance and Endurance Training in Untrained, Moderately Trained, and Trained Individuals: A Systematic Review and Meta-analysis.
Petré, H, Hemmingsson, E, Rosdahl, H, Psilander, N
Sports medicine (Auckland, N.Z.). 2021;51(5):991-1010
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Athletes often require a combination of both strength and endurance in their chosen sport. As a result, a training programme which has both endurance and strength exercises within the same training period has become popular and is known as concurrent training. However, there are conflicting studies on the effectiveness of this way of training for athletic performance. This systematic review of 27 studies aimed to determine the overall effect of concurrent training on athletic performance based on the results of several studies and whether the time between training types could influence the effect. The results showed that leg press and squat exercises were negatively affected in trained individuals, but only if they were performed within the same training session. This was not evident in untrained and moderately trained individuals. It was concluded that in trained athletes, the performance of endurance and strength training within the same session can have a detrimental effect on lower body strength development. This study could be used by professionals to recommend that trained individuals separate endurance and strength training when increased strength is the goal.
Abstract
BACKGROUND The effect of concurrent training on the development of maximal strength is unclear, especially in individuals with different training statuses. OBJECTIVE The aim of this systematic review and meta-analysis study was to compare the effect of concurrent resistance and endurance training with that of resistance training only on the development of maximal dynamic strength in untrained, moderately trained, and trained individuals. METHODS On the basis of the predetermined criteria, 27 studies that compared effects between concurrent and resistance training only on lower-body 1-repetition maximum (1RM) strength were included. The effect size (ES), calculated as the standardised difference in mean, was extracted from each study, pooled, and analysed with a random-effects model. RESULTS The 1RM for leg press and squat exercises was negatively affected by concurrent training in trained individuals (ES = - 0.35, p < 0.01), but not in moderately trained ( - 0.20, p = 0.08) or untrained individuals (ES = 0.03, p = 0.87) as compared to resistance training only. A subgroup analysis revealed that the negative effect observed in trained individuals occurred only when resistance and endurance training were conducted within the same training session (ES same session = - 0.66, p < 0.01 vs. ES different sessions = - 0.10, p = 0.55). CONCLUSION This study demonstrated the novel and quantifiable effects of training status on lower-body strength development and shows that the addition of endurance training to a resistance training programme may have a negative impact on lower-body strength development in trained, but not in moderately trained or untrained individuals. This impairment seems to be more pronounced when training is performed within the same session than in different sessions. Trained individuals should therefore consider separating endurance from resistance training during periods where the development of dynamic maximal strength is prioritised.
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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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Combined Effects of Citrulline Plus Nitrate-Rich Beetroot Extract Co-Supplementation on Maximal and Endurance-Strength and Aerobic Power in Trained Male Triathletes: A Randomized Double-Blind, Placebo-Controlled Trial.
Burgos, J, Viribay, A, Fernández-Lázaro, D, Calleja-González, J, González-Santos, J, Mielgo-Ayuso, J
Nutrients. 2021;14(1)
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Triathletes often resort to taking ergogenic supplements to boost their performance as diet alone may not be sufficient to meet their physical demands. Previous studies have shown the ergogenic effects of L-citrulline (CIT) and beetroot extract (BR) in improving aerobic and anaerobic metabolism and boosting sports performance. In addition, both BR and CIT contain nitric oxide, which is known to enhance athletic performance, neuromuscular strength and endurance. This randomised, double-blinded, placebo-controlled trial for nine weeks on thirty-two male trained triathletes evaluated the effect of oral co-supplementation of 3g/day of CIT with 2.1g/day of BR on sports performance. The researchers found that oral co-supplementation of CIT plus BR for nine weeks improved maximal strength, endurance strength and performance among amateur trained male triathletes. Long-term, extensive, robust studies are required to further explore the effects of co-supplementation. Nevertheless, Healthcare and nutrition practitioners can use the findings of this study to understand the ergogenic effects of CIT and BR co-supplementation and consider co-supplementation during phases of intensive practice to boost athletic performance.
Abstract
Citrulline (CIT) and nitrate-rich beetroot extract (BR) are ergogenic aids and nitric oxide (NO) precursors. In addition, both supplements seem to have other actions at the level of muscle metabolism that can benefit strength and aerobic power performance. Both supplements have been studied in numerous investigations in isolation. However, scientific evidence combining both supplements is scarce, and to the best of the authors' knowledge, there is no current study of endurance athletes. Therefore, the main purpose of this study was to determine the effect of 9 weeks of CIT plus BR supplementation on maximal and endurance-strength performance and aerobic power in male triathletes. This study was a randomized double-blind, placebo-controlled trial where participants (n = 32) were randomized into four different groups: placebo group (PLG; n = 8), CIT plus BR group (CIT- BRG; 3 g/kg/day of CIT plus 3 mg/kg/day of nitrates (NO3-); n = 8), CIT group (CITG; 3 g/kg/day; n = 8) and BR group (BRG; 3 mg/kg/day of NO3-; n = 8). Before (T1) and after 9 weeks (T2), four physical condition tests were carried out in order to assess sport performance: the horizontal jump test (HJUMP), handgrip dynamometer test, 1-min abdominal tests (1-MAT) and finally, the Cooper test. Although, no significant interactions (time × supplementation groups) were found for the strength tests (p > 0.05), the CIT- BRG supplementation presented a trend on HJUMP and 1-MAT tests confirmed by significant increase between two study moments in CIT-BRG. Likewise, CIT-BRG presented significant interactions in the aerobic power test confirmed by this group's improve estimated VO2max during the study with respect to the other study groups (p = 0.002; η2p = 0.418). In summary, supplementing with 3 g/day of CIT and 2.1 g/day of BR (300 mg/day of NO3-) for 9 weeks could increase maximal and endurance strength. Furthermore, when compared to CIT or BR supplementation alone, this combination improved performance in tests related to aerobic power.
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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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The effects of different doses of caffeine on maximal strength and strength-endurance in women habituated to caffeine.
Filip-Stachnik, A, Wilk, M, Krzysztofik, M, Lulińska, E, Tufano, JJ, Zajac, A, Stastny, P, Del Coso, J
Journal of the International Society of Sports Nutrition. 2021;18(1):25
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Athletes commonly consume caffeinated drinks or supplements containing caffeine due to its ergogenic effect on performance. However, very few studies have investigated the effect of acute intake of caffeine on muscular performance in strength-trained women. This randomised, double-blinded, crossover trial examines the effect of acute intake of caffeine on maximal strength and local strength-endurance during the bench press exercise in women habituated to acute intake of caffeine. In this study, twenty-one healthy and strength-trained women were randomised to take 3 and 6 mg/kg/body mass acute caffeine intake. While both doses showed positive effects, this study also observed a dose-dependent (6 mg/kg body mass) significant increase in the response of acute intake of caffeine on maximal strength in women habituated to caffeine. The acute intake of caffeine at 6 mg/kg/body mass also increased the number of repetitions and time under tension during the bench press. The results of the study must be interpreted with caution due to a wide variation in caffeine habituation, resistance training levels, and strength exercise practices across the general population. Future robust studies are required to investigate this further. This study may help healthcare practitioners better understand the ergogenic effects of caffeine consumption in strength-trained habituated women.
Abstract
PURPOSE The main goal of this study was to assess the acute effects of 3 and 6 mg of caffeine intake per kg of body mass (b.m.) on maximal strength and strength-endurance in women habituated to caffeine. METHODS Twenty-one healthy resistance-trained female students (23.0 ± 0.9 years, body mass: 59.0 ± 6.6 kg), with a daily caffeine intake of 5.8 ± 2.6 mg/kg/b.m. participated in a randomized, crossover, double-blind design. Each participant performed three experimental sessions after ingesting either a placebo (PLAC) or 3 mg/kg/b.m. (CAF-3) and 6 mg/kg/b.m. (CAF-6) of caffeine. In each experimental session, the participants underwent a 1RM test and a strength-endurance test at 50 %1RM in the bench press exercise. Maximal load was measured in the 1RM test and the time under tension, number of preformed repetitions, power output and bar velocity were registered in the strength-endurance test. RESULTS The one-way ANOVA showed a main effect of caffeine on 1RM bench press performance (F = 14.74; p < 0.01). In comparison to the PLAC (40.48 ± 9.21 kg), CAF-3 (41.68 ± 8.98 kg; p = 0.01) and CAF-6 (42.98 ± 8.79 kg; p < 0.01) increased 1RM bench press test results. There was also a significant increase in 1RM for CAF-6 when compared to CAF-3 (p < 0.01). There was a main effect of caffeine on time under tension during the strength-endurance test (F = 13.09; p < 0.01). In comparison to the PLAC (53.52 ± 11.44 s), CAF-6 (61.76 ± 15.39 s; p < 0.01) significantly increased the time under tension during the maximal strength-endurance test. CONCLUSION An acute dose of 3-to-6 mg/kg/b.m. of caffeine improves maximum strength. However, these doses of caffeine had minimal ergogenic effect on strength-endurance performance in women habituated to caffeine.
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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.