Enhance Exercise Performance Research Articles

No Influence of Low-, Medium-, or High-Dose Tyrosine on Exercise in a Warm Environment.

Tyrosine administration may counter exercise fatigue in a warm environment, but the typical dose is inconclusive, with little known about higher doses. We explored how three tyrosine doses influenced the circulating ratio of tyrosine/amino acids competing for brain uptake and hypothesized that a medium and high dose would enhance exercise performance in a warm environment. Eight recreationally trained, non-heat-acclimated male individuals (mean ± SD age, 23 ± 4 yr; stature, 181 ± 7 cm; body mass, 76.1 ± 5.9 kg; peak oxygen uptake, 4.1 ± 0.5 L·min) performed a peak oxygen uptake test, two familiarization trials, then four experimental trials in a randomized order separated by 7 d. Before exercise, subjects drank 2 × 300 mL sugar-free drinks delivering 0 (PLA), 150 (LOW), 300 (MED), or 400 (HIGH) mg·kg body mass tyrosine in a double-blind fashion. Subjects performed a 60-min constant intensity cycling then a simulated time trial in 30°C and 60% relative humidity. Time trial performance (P = 0.579) was not influenced by tyrosine ingestion. The plasma ratio of tyrosine/∑(free-tryptophan, leucine, isoleucine, valine, phenylalanine, methionine), a key determinant of brain tyrosine influx, increased relative to PLA (P < 0.001). The increase was similar (P > 0.05) in MED (7.7-fold) and HIGH (8.2-fold), and greater than that in LOW (5.3-fold; P < 0.05). No differences existed between trials in core and skin temperature, heart rate, RPE, or thermal sensation (P > 0.05). Exercise performance in a warm environment was not influenced by tyrosine availability in recreationally trained male individuals. The results provide novel data informing future studies, on the tyrosine dose maximizing the circulating ratio of tyrosine/amino acids competing for brain uptake.

Ischemic Preconditioning: Improved Cycling Performance Despite Nocebo Expectation.

Ischemic preconditioning (IPC) through purposeful circulatory occlusion may enhance exercise performance. The value of IPC for improving performance is controversial owing to challenges with employing effective placebo controls. This study examines the efficacy of IPC versus a deceptive sham protocol for improving performance to determine whether benefits of IPC are attributable to true physiological effects. It was hypothesized that IPC would favorably alter performance more than a sham treatment and that physiological responses to exercise would be affected only after IPC treatment. In a randomized order, 16 participants performed incremental exercise to exhaustion on a cycle ergometer in control conditions and after sham and IPC treatments. Participants rated their belief as to the efficacy of each treatment compared with control. Time to exhaustion was greatest after IPC (control = 1331 [270]s, IPC = 1429 [300]s, sham = 1343 [255]s, P = .02), despite negative performance expectations after IPC and positive expectation after sham. Maximal aerobic power remained unchanged after both SHAM and IPC (control = 42.0 [5.2], IPC = 41.7 [5.5], sham = 41.6 [5.5]mL·kg-1·min-1, P = .7), as did submaximal lactate concentration (control = 8.9 [2.6], sham = 8.0 [1.9], IPC = 7.7 [2.1]mmol, P = .1) and oxygen uptake (control = 37.8 [4.8], sham = 37.5 [5.3], IPC = 37.5 [5.5]mL·kg-1·min-1, P = .6). IPC before cycling exercise provides an ergogenic benefit that is not attributable to a placebo effect from positive expectation and that was not explained by traditionally suggested mechanisms.

Nitrate uptake and metabolism in human skeletal muscle cell cultures

Several studies show that dietary nitrate enhances exercise performance, presumably by increasing muscle blood flow and improving oxygen utilization. These effects are likely mediated by nitrate metabolites, including nitrite and nitric oxide (NO). However, the mechanisms of nitrate production, storage, and metabolism to nitrite and NO in skeletal muscle cells are still unclear. We hypothesized that exogenous nitrate can be taken up and metabolized to nitrite/NO inside the skeletal muscle. We found rapid uptake of exogeneous nitrate in both myoblasts and myotubes, increasing nitrite levels in myotubes, but not myoblasts. During differentiation we found increased expression of molybdenum containing proteins, such as xanthine oxidoreductase (XOR) and the mitochondrial amidoxime-reducing component (MARC); nitrate and nitrite reductases. Sialin, a known nitrate transporter, was detected in myoblasts; nitrate uptake decreased after sialin knockdown. Inhibition of chloride channel 1 (CLC1) also led to significantly decreased uptake of nitrate. Addition of exogenous nitrite, which resulted in higher intracellular nitrite levels, increased intracellular cGMP levels in myotubes. In summary, our results demonstrate for the first time the presence of the nitrate/nitrite/NO pathway in skeletal muscle cells, namely the existence of strong uptake of exogenous nitrate into cells and conversion of intracellular nitrate to nitrite and NO. Our results further support our previously formulated hypothesis about the importance of the nitrate to nitrite to NO intrinsic reduction pathways in skeletal muscles, which likely contributes to improved exercise tolerance after nitrate ingestion.

The Efficacy of Administering Fruit-Derived Polyphenols to Improve Health Biomarkers, Exercise Performance and Related Physiological Responses.

Polyphenols are secondary metabolites involved in a myriad of critical processes in plants. Over recent decades, special attention has been paid to the anti-oxidative role of fruit-derived polyphenols in the human diet, with evidence supporting the contribution of polyphenols in the prevention of numerous non-communicable disease outcomes. However, due to the low concentration in biological fluids in vivo, the antioxidant properties of polyphenols seem to be related to an enhanced endogenous antioxidant capacity induced via signaling through the nuclear respiratory factor 2 pathway. Polyphenols also seem to possess anti-inflammatory and antioxidant properties and have been shown to enhance vascular function via nitric oxide mediated mechanisms. Consequently, there is rationale to support fruit-derived polyphenol supplementation to enhance exercise performance, possibly via improved muscle perfusion. Fruit-derived polyphenol supplementation in exercise studies have included a variety of fruits, e.g., New Zealand blackcurrant, pomegranate, and cherry, in the form of extracts (multicomponent or purified), juices and infusions to varying degrees of benefit. For example, research has yet to link the health-related benefits of black elderberry (Sambucus nigra L.) ingestion to exercise performance in spite of the purported health benefits associated with black elderberry provision in vitro and in vivo models, which has been attributed to their high antioxidant capacity and polyphenol content. This review summarizes the existing evidence supporting a beneficial effect of fruit-derived polyphenols on various biological processes and outlines the potential for black elderberry ingestion to improve nitric oxide production, exercise performance, and the associated physiological responses before-, during- and post-exercise.

Seven-day ischaemic preconditioning improves muscle efficiency during cycling

ABSTRACTIschaemic preconditioning (IPC) has emerged as a potential non-invasive ergogenic aid to enhance exercise performance. Repeated application of IPC has demonstrated clinical efficacy, therefore our aims were to investigate its effect on endurance cycling performance and muscle efficiency. Twenty participants undertook 7-d repeated bilateral lower limb occlusion (4 x 5-min) of IPC (220 mmHg) or sham (20 mmHg). Prior to and 72-h following the intervention, participants performed submaximal cycling at 70, 80 and 90% of ventilatory threshold (VT) followed by an incremental exercise test. IPC had no effect on O2max (P = 0.110); however, time to exhaustion increased by ~ 9% and Wmax by ~ 5 % (IPC pre 307 ± 45 to post 323 ± 51 W) relative to sham (P = 0.002). There were no changes in gross efficiency (GE) (P > 0.05); however, delta efficiency (DE) increased by 3.1% following IPC (P = 0.011). Deoxyhaemoglobin (HHb) was reduced following IPC ~ 30% (P = 0.017) with no change in total haemoglobin (tHb). Repeated IPC over 7-d enhanced muscle efficiency and extended cycling performance. The physiological effects of repeated IPC on skeletal muscle efficiency explains the notable improvements in endurance performance.

The Influence of Compression Socks During a Marathon on Exercise-Associated Muscle Damage.

Compression socks have become increasingly popular with athletes due to perceived enhancement of exercise performance and recovery. However, research examining the efficacy of compression socks to reduce exercise-associated muscle damage has been equivocal, with few direct measurements of markers of muscle damage. To examine the influence of compression socks worn during a marathon on creatine kinase (CK) levels. A randomized controlled trial. 2013 Hartford Marathon, Hartford, CT. Adults (n = 20) randomized to control (CONTROL; n = 10) or compression sock (SOCK; n = 10) groups. Blood samples were collected 24 hours before, immediately after, and 24 hours following the marathon for the analysis of CK, a marker of muscle damage. Baseline CK levels did not differ between CONTROL (89.3 [41.2]U/L) and SOCK (100.0 [56.2]U/L) (P = .63). Immediately following the marathon (≤1h), CK increased 273% from baseline (P < .001 for time), with no difference in exercise-induced changes in CK from baseline between CONTROL (+293.9 [278.2]U/L) and SOCK (+233.1 [225.3]U/L; P = .60 for time × group). The day following the marathon (≤24h), CK further increased 1094% from baseline (P < .001 for time), with no difference in changes in CK from baseline between CONTROL (+ 1191.9 [1194.8]U/L) and SOCK (+889.1 [760.2]U/L; P = .53 for time × group). These similar trends persisted despite controlling for potential covariates such as age, body mass index, and race finishing time (Ps > .29). Compression socks worn during a marathon do not appear to mitigate objectively measured markers of muscle damage immediately following and 24 hours after a marathon.

Cooling during exercise enhances performances, but the cooled body areas matter: A systematic review with meta-analyses.

Hyperthermia during exercise induces central and peripheral fatigue and impairs physical performance. To facilitate heat loss and optimize performance, athletes can hasten body cooling prior (pre-cooling) or during (per-cooling) exercise. However, it is unclear whether per-cooling effect is the same on 'aerobic' and 'anaerobic' types of exercise (duration <75 and >76seconds, respectively, according to Gastin [Sports Med 2001;31:725-741]) and whether the body area that is cooled makes a difference. A literature search led to the identification of 1582 potential studies. Included studies had to include physical exercise with sufficient details on the type, duration, intensity, and provide valid performance measures and a cooling intervention administered during exercise with sufficient details on the type and site of application. Forty-five studies were included. Per-cooling provides a performance benefit during 'aerobic' (standardized mean difference (SMD) of0.60, P<.001)and 'anaerobic' exercises (SMD=0.27, P<.02).The effects were greater during aerobic compared to anaerobic exercises (P<.01). Internal cooling (cold fluid ingestion such as cold water and ice slurry/menthol beverage) and external cooling (face, neck, and torso) provide the greatest performance benefit for 'aerobic' performance with a moderate to large effect (0.46<SMD<1.24). For 'anaerobic' exercises, wearing a whole-body cooling garment is the best way to enhance exercise performance (SMD=0.39, P<.01). Per-cooling improves 'aerobic' and 'anaerobic' exercise performance with a greater benefit for 'aerobic' exercise. The magnitude of the effect depends on the type and site of the cooling application.

The ethanol extract from the rhodophyta Gloiopeltis furcata and its active ingredient docosahexaenoic acid improve exercise performance in mice

The effectiveness of natural bioresources at enhancing exercise performance is of interest to those in sports and health care. The use of 29 common seaweed species as supplements to enhance exercise performance and the recovery from physical fatigue was evaluated. The ethanol extract of the red seaweed Gloiopeltis furcata (GFE) had the greatest effect on forelimb grip strength and swimming endurance in mice. The optimal daily dose of GFE was 0.1mg per 10μl per g of body weight. GFE significantly increased muscle mass but had little effect on body weight and fatty deposits. The extract also significantly raised the blood superoxide dismutase and high-density lipoprotein cholesterol levels, while reducing the lactate and urea levels (p<0.05). Docosahexaenoic acid (DHA) from GFE made the greatest contribution to improving physical exercise performance. These results support the use of GFE and DHA in health food products for enhancing physical performance. PRACTICAL APPLICATIONS: The study shows the exercise enhancement and anti-fatigue activities of GFE using the forelimb grip strength test, forced swimming endurance test, muscle mass measurement, and blood biochemical parameters. These results support the use of GFE and its active constituent DHA in functional foods or nutraceuticals for enhancing physical performance.

The influence of transcranial direct current stimulation on pain affect and endurance exercise

IntroductionTranscranial direct current stimulation (tDCS) is a non-invasive form of electrical brain stimulation that has been offered as a novel method to enhance endurance exercise performance. While the underlying mechanisms for these performance enhancing effects remain unclear, one explanation relates to a reduction in pain experienced during exercise. Research examining this explanation however, has failed to consider the widely recognised motivational-affective component of the pain experience. ObjectivesThe present study aimed to determine whether pain experienced during exercise involves an affective component, and whether a reduction in pain affect may account for the performance-enhancing effects of tDCS. MethodsHealthy, pain-free individuals (n = 23), including 11 males and 12 females aged 18–39 years, were recruited for participation in a randomised, placebo-controlled, participant blinded, repeated measures design study. Participants attended two testing sessions separated by at least five days. In each session, participants received either active (2 mA, 20 min) or sham (placebo control) tDCS delivered to the left dorsolateral prefrontal cortex (DLPFC). Participants then completed an endurance exercise task comprised of a sustained isometric contraction of the leg extensors performed to exhaustion at an intensity corresponding to 25% of their maximal voluntary contraction. During this task, participants provided ratings of pain intensity and pain unpleasantness at 20 s intervals. ResultsRatings of pain intensity (p < .001) and pain affect (p < .001) increased throughout the endurance exercise task. However, the tDCS intervention did not enhance endurance exercise performance (p > .05), nor manipulate perceptions of pain affect (p > .05). ConclusionsWhile the endurance exercise task induced pain affect, tDCS over the left DLPFC was not effective in reducing this component of the pain experience, nor enhancing exercise performance.

The effects of isomaltulose ingestion on gastric parameters and cycling performance in young men

Background/ObjectiveIsomaltulose is a disaccharide with a low glycaemic index and plays a role in maintaining postprandial glucose. The maintenance of glucose availability during prolonged exercise has been shown to enhance exercise performance. The present study compared the effects of pre-exercise isomaltulose versus maltodextrin ingestion on gastric parameters and cycling performance in young men. MethodsFourteen young men (mean ± S.D., age 23 ± 2 years) performed 60 min of continuous cycling at 75% of maximum heart rate followed by a 15-min exercise performance test while ingesting a 500-mL of water containing 100 mg of 13C-sodium acetate with either 50 g of isomaltulose or 50 g of maltodextrin. Gastrointestinal discomfort was assessed periodically using an 11-point visual analogue scale throughout the study. The gastric emptying rate was evaluated periodically with the 13C-sodium acetate breath test. For the exercise performance test, participants were instructed to pedal a cycle ergometer, exerting as much effort as possible at a self-selected pace. ResultsPlasma glucose and insulin concentrations measured at 30 min after ingestion were lower in the isomaltulose trial than in the maltodextrin trial. There were no differences in mean power output during the exercise performance test, gastric emptying rate or the subjective feelings of gastrointestinal discomfort between both trials. ConclusionUnder the current exercise protocol, pre-exercise ingestion of isomaltulose compared with maltodextrin provided no additional benefit relative to gastric emptying or aerobic exercise performance. Both isomaltulose and maltodextrin ingestion did not influence gastrointestinal distress during 60 min of cycling and performance test.

Mechanisms of sex differences in exercise capacity.

Sex differences are an important component of National Institutes of Health rigor. The goal of this investigation was to test the hypothesis that female mice have greater exercise capacity than male mice, and that it is due to estrogen, nitric oxide, and myosin heavy chain expression. Female C57BL6/J wild-type mice exhibited greater (P < 0.05) maximal exercise capacity for running distance (489 ± 15 m) than age-matched male counterparts (318 ± 15 m), as well as 20% greater work to exhaustion. When matched for weight or muscle mass, females still maintained greater exercise capacity than males. Increased type I and decreased type II myosin heavy chain fibers in the soleus muscle from females are consistent with fatigue resistance and better endurance in females compared with males. After ovariectomy, female mice no longer demonstrated enhanced exercise, and treatment of male mice with estrogen resulted in exercise capacity similar to that of intact females (485 ± 37 m). Nitric oxide synthase, a downstream target of estrogen, exhibited higher activity in female mice compared with male mice, P < 0.05, whereas ovariectomized females exhibited nitric oxide synthase levels similar to males. Nitric oxide synthase activity also increased in males treated with chronic estrogen to levels of intact females. Nitric oxide synthase blockade with Nω-nitro-l-arginine methyl ester eliminated the sex differences in exercise capacity. Thus estrogen, nitric oxide, and myosin heavy chain expression are important mechanisms mediating the enhanced exercise performance in females.

Altitude Training and Recombinant Human Erythropoietin: Considerations for Doping Detection.

The benefit of training at altitude to enhance exercise performance remains equivocal although the most widely accepted approach is one where the athletes live and perform lower-intensity running at approximately 2300 m with high-intensity training at approximately 1250 m. The idea is that this method maintains maximal augmentations in total hemoglobin mass while reducing the performance impairment of high-intensity sessions performed at moderate altitude and thus preventing any detraining that can occur when athletes live and train at moderate altitude. This training regimen, however, is not universally accepted and some argue that the performance enhancement is due to placebo and training camp effects. Altitude training may affect an athlete's hematological parameters in ways similar to those observed following blood doping. Current methods of detection appear insufficient to differentiate between altitude training and blood doping making the interpretation of an athlete's biological passport difficult. Further research is required to determine the optimal method for altitude training and to enhance current detection methods to be able to differentiate better blood doping and altitude exposure.

Acute Effects of Citrulline Supplementation on High-Intensity Strength and Power Performance: A Systematic Review and Meta-Analysis.

Citrulline is an increasingly common dietary supplement that is thought to enhance exercise performance by increasing nitric oxide production. In the last 5years, several studies have investigated the effects of citrulline supplements on strength and power outcomes, with mixed results reported. To date, the current authors are unaware of any attempts to systematically review this emerging body of literature. The current study sought to conduct a systematic review and meta-analysis of the literature describing the effects of citrulline supplementation on strength and power outcomes. A comprehensive, systematic search of three prominent research databases was performed to find peer-reviewed, English language, original research studies evaluating the effects of citrulline supplementation on indices of high-intensity exercise performance in healthy men and women. Outcomes included strength and power variables from performance tests involving multiple repetitive muscle actions of large muscle groups, consisting of either resistance training sets or sprints lasting 30s or less. Tests involving isolated actions of small muscle groups or isolated attempts of single-jump tasks were not included for analysis due to differences in metabolic requirements. Studies were excluded from consideration if they lacked a placebo condition for comparison, were carried out in clinical populations, provided a citrulline dose of less than 3g, provided the citrulline dose less than 30min prior to exercise testing, or combined the citrulline ingredient with creatine, caffeine, nitrate, or other ergogenic ingredients. Twelve studies, consisting of 13 total independent samples (n = 198 participants), met the inclusion criteria. Between-study variance, heterogeneity, and inconsistency across studies were low (Cochrane's Q = 6.9, p = 0.86; τ2 = 0.0 [0.0, 0.08], I2 = 0.0 [0.0, 40.0]), and no funnel plot asymmetry was present. Results of the meta-analysis identified a significant benefit for citrulline compared to placebo treatments (p = 0.036), with a small pooled standardized mean difference (SMD; Hedges' G) of 0.20 (95% confidence interval 0.01-0.39). The effect size was small (0.20), and confidence intervals for each individual study crossed the line of null effect. However, the results may be relevant to high-level athletes, in which competitive outcomes are decided by small margins. Further research is encouraged to fully elucidate the effects of potential moderating study characteristics, such as the form of citrulline supplement, citrulline dose, sex, age, and strength versus power tasks.

Transcranial Direct Current Stimulation of motor cortex enhances running performance.

Transcranial direct current stimulation (tDCS) is a technique used to modulate neuronal excitability through non-invasive brain stimulation that can enhance exercise performance. We hypothesize that tDCS would improve submaximal running time to exhaustion (TTE) and delay the increase in the rating of perceived exertion (RPE) over time. We also hypothesize that tDCS would not lead to difference in cardiorespiratory responses. We employed a randomized, single-blinded, and counterbalanced design in which 10 trained men participated. After receiving either 20 min of 1.98 mA anodal tDCS applied over the primary motor cortex (M1) or sham-operated control on separate days, participants completed a constant-load test involving running at a speed equivalent to 80% of their own maximum oxygen consumption (VO2max). During this constant-load test, RPE, heart rate (HR), VO2, pulmonary ventilation (VE), respiratory exchange ratio (RER), and ventilatory threshold (VT) were continuously monitored. TTE was recorded at the end of the test. TTEs were significantly longer in the tDCS than in the sham conditions (21.18 ± 7.13 min; 18.44 ± 6.32 min; p = 0.011). For TTE, no significant differences were found in RPE between conditions at isotime. In addition, no significant differences in HR, VO2, VE, RER, and VT were found during TTE between the two stimulation conditions at any time point. These results indicate that the application of tDCS does not induce a change of the exercise performance-related index; however, it can affect the increase of the exercise duration due to the stimuli in the M1 area.

Enhancement of Exercise Performance by 48 Hours, and 15-Day Supplementation with Mangiferin and Luteolin in Men.

The natural polyphenols mangiferin and luteolin have free radical-scavenging properties, induce the antioxidant gene program and down-regulate the expression of superoxide-producing enzymes. However, the effects of these two polyphenols on exercise capacity remains mostly unknown. To determine whether a combination of luteolin (peanut husk extract containing 95% luteolin, PHE) and mangiferin (mango leave extract (MLE), Zynamite®) at low (PHE: 50 mg/day; and 140 mg/day of MLE containing 100 mg of mangiferin; L) and high doses (PHE: 100 mg/day; MLE: 420 mg/day; H) may enhance exercise performance, twelve physically active men performed incremental exercise to exhaustion, followed by sprint and endurance exercise after 48 h (acute effects) and 15 days of supplementation (prolonged effects) with polyphenols or placebo, following a double-blind crossover design. During sprint exercise, mangiferin + luteolin supplementation enhanced exercise performance, facilitated muscle oxygen extraction, and improved brain oxygenation, without increasing the VO2. Compared to placebo, mangiferin + luteolin increased muscle O2 extraction during post-exercise ischemia, and improved sprint performance after ischemia-reperfusion likely by increasing glycolytic energy production, as reflected by higher blood lactate concentrations after the sprints. Similar responses were elicited by the two doses tested. In conclusion, acute and prolonged supplementation with mangiferin combined with luteolin enhances performance, muscle O2 extraction, and brain oxygenation during sprint exercise, at high and low doses.

Remote ischemic preconditioning increases accumulated oxygen deficit in middle-distance runners.

The mediators underlying the putative benefits of remote ischemic preconditioning (IPC) on dynamic whole body exercise performance have not been widely investigated. Our objective was to test the hypothesis that remote IPC improves supramaximal exercise performance in National Collegiate Athletic Association (NCAA) Division I middle-distance runners by increasing accumulated oxygen deficit (AOD), an indicator of glycolytic capacity. A randomized sham-controlled crossover study was employed. Ten NCAA Division I middle-distance athletes [age: 21 ± 1 yr; maximal oxygen uptake (V̇o2max): 65 ± 7 ml·kg-1·min-1] completed three supramaximal running trials (baseline, after mock IPC, and with remote IPC) at 110% V̇o2max to exhaustion. Remote IPC was induced in the right arm with 4 × 5 min cycles of brachial artery ischemia with 5 min of reperfusion. Supramaximal AOD (ml/kg) was calculated as the difference between the theoretical oxygen demand required for the supramaximal running bout (linear regression extrapolated from ~12 × 5 min submaximal running stages) and the actual oxygen demand for these bouts. Remote IPC [122 ± 38 s, 95% confidence interval (CI): 94-150] increased (P < 0.001) time to exhaustion 22% compared with baseline (99 ± 23 s, 95% CI: 82-116, P = 0.014) and sham (101 ± 30 s, 95% CI: 80-123, P = 0.001). In the presence of IPC, AOD was 47 ± 36 ml/kg (95% CI: 20.8-73.9), a 29% increase compared with baseline (36 ± 28 ml/kg, 95% CI: 16.3-56.9, P = 0.008) and sham (38 ± 32 ml/kg, 95% CI: 16.2-63.0, P = 0.024). Remote IPC considerably improved supramaximal exercise performance in NCAA Division I middle-distance athletes. Greater glycolytic capacity, as estimated by increased AOD, is a potential mediator for these performance improvements. NEW & NOTEWORTHY Our novel findings indicate that ischemic preconditioning enhanced glycolytic exercise capacity, enabling National Collegiate Athletic Association (NCAA) middle-distance track athletes to run ~22 s longer before exhaustion compared with baseline and mock ischemic preconditioning. The increase in "all-out" performance appears to be due to increased accumulated oxygen deficit, an index of better supramaximal capacity. Of note, enhanced exercise performance was demonstrated in a specific group of in-competition NCAA elite athletes that has already undergone substantial training of the glycolytic energy systems.

What's in Your Beet Juice? Nitrate and Nitrite Content of Beet Juice Products Marketed to Athletes.

Consumption of beetroot juice (BRJ) supplements has become popular among athletes, because beets tend to be rich in nitrate (NO3-), which can enhance exercise performance by increasing nitric oxide production. The NO3- content of beets can vary significantly, however, making it difficult to know how much NO3- any product actually contains. Samples from 45 different lots of 24 different BRJ products from 21 different companies were therefore analyzed for NO3- (and nitrite; NO2-) concentration using high performance liquid chromatography. The NO3- and NO2- content, i.e., amount per serving, was then calculated based on either 1) the manufacturer's recommended serving size (for prepackaged/single dose products) or 2) as used in previous studies, a volume of 500 mL (for BRJ sold in bulk containers). There was moderate-to-large variability in NO3- content between samples of the same product, with a mean coefficient of variation of 30±26% (range 2 to 83%). There was even greater variability between products, with a ~50-fold range in NO3- content between the lowest and highest. Only five products consistently provided ≥5 mmol of NO3- per serving, which seems to be the minimal dose required to enhance exercise performance in most individuals. NO2- contents were generally low (i.e., ≤0.5% compared to NO3-), although two products contained 10 and 14%. The present results may be useful to athletes and their support staff contemplating which (if any) BRJ product to utilize. These data may also offer insight into variability in the literature with respect to the effects of BRJ on exercise performance.

High tempo music prolongs high intensity exercise.

Music has been shown to reduce rating of perceived exertion, increase exercise enjoyment and enhance exercise performance, mainly in low-moderate intensity exercises. However, the effects of music are less conclusive with high-intensity activities. The purpose of this with-participant design study was to compare the effects of high tempo music (130 bpm) to a no-music condition during repeated high intensity cycling bouts (80% of peak power output (PPO)) on the following measures: time to exercise end-point, rating of perceived exertion (RPE), heart rate (HR), breathing frequency, ventilatory kinetics and blood lactate (BL). Under the music condition, participants exercised 10.7% longer (p = 0.035; Effect size (ES) = 0.28) (increase of 1 min) and had higher HR (4%; p = 0.043; ES = 0.25), breathing frequency (11.6%; p < 0.001; ES = 0.57), and RER (7% at TTF; p = 0.021; ES = 1.1) during exercise, as measured at the exercise end-point. Trivial differences were observed between conditions in RPE and other ventilatory kinetics during exercise. Interestingly, 5 min post-exercise termination, HR recovery was 13.0% faster following the music condition (p < 0.05) despite that music was not played during this period. These results strengthen the notion that music can alter the association between central motor drive, central cardiovascular command and perceived exertion, and contribute to prolonged exercise durations at higher intensities along with a quicken HR recovery.

Acute potassium phosphate intake after exercise has no effect on subsequent exercise-induced performance time, substrate oxidation, and food intake in men

Background: Phosphorus availability during exercise is believed to positively affect adenosine triphosphate availability, increase glycogen synthesis, and enhance exercise performance. Aim: The aim of the present study was to examine the effect of potassium phosphate intake after exercise on physiological responses during subsequent running at anaerobic threshold and on appetite and food intake postexercise in men. Settings and Design: Nine moderately active young men (age, 22 ± 3 years; body mass index, 22.3 ± 3.0 kg/m2; and peak oxygen uptake (VO2peak) 48.5 ± 6.3 ml/kg/min) underwent two experimental conditions. Each condition consisted of two time-to-exhaustion treadmill running tests (time to exhaustion [TTE]) (bout 1 and 2), separated by 3 h recovery. During the recovery, either 500 mg phosphorus in the form of potassium phosphate or placebo was consumed with a glucose solution (1.2 g glucose/10 ml water × body weight) over 3 h. Methods: Expired gas was collected during the running. Appetite using visual analog scale and food intake from access to an ad libitum meal were measured after the second TTE run. Exercise intensity, VO2,and running speed were 67 ± 3% VO2peak, 32.3 ± 4.5 ml/kg/min, and at 10.1 ± 1.1 km/h, respectively. Statistical Analysis Used: Data were checked for normality, and Kolmogorov–Smirnov test was performed. Physiological variables, duration of exercise tests, and postexercise food intake and appetite sensations were analyzed using univariate ANOVA with interaction of exercise order and conditions. Results: There was no group effect in running time of the 2nd TTE although running time was reduced by ~ 5% in the placebo condition and by ~ 37% in the potassium phosphate condition in comparison to running time of the 1st TTE. A group × time interaction was present for the 1st exercise bout (P = 0.03). There were no interactions of condition (placebo and potassium phosphate) and running bouts (1st and 2nd) on respiratory exchange ratio, whole-body fat oxidation, and carbohydrate oxidation, but the interaction effect on VO2trended toward significance (F = 3.97, P = 0.06). There were no differences between conditions for appetite sensations and food intake. Conclusions: An acute dose of potassium phosphate after exercise did not affect subsequent exercise performance, exercise-induced substrate oxidation, and food intake. Potassium phosphate did not seem to affect metabolic responses and appetite in an ecological setting with repeated exercise and access to food during recovery.

Effects of nine weeks L-Carnitine supplementation on exercise performance, anaerobic power, and exercise-induced oxidative stress in resistance-trained males.

[Purpose]Studies of L-carnitine in healthy athletic populations have yielded equivocal results. Further scientific-based knowledge is needed to clarify the ability of L-carnitine to improve exercise capacity and expedite the recovery process by reducing oxidative stress. This study aimed to examine the 9-week effects of L-carnitine supplementation on exercise performance, anaerobic capacity, and exercise-induced oxidative stress markers in resistance-trained males.[Methods]In a double-blind, randomized, and placebo-controlled treatment, 23 men (age, 25±2y; weight, 81.2±8.31 kg; body fat, 17.1±5.9%) ingested either a placebo (2 g/d, n=11) or L-carnitine (2 g/d, n=12) for 9 weeks in conjunction with resistance training. Primary outcome measurements were analyzed at baseline and at weeks 3, 6, and 9. Participants underwent a similar resistance training (4 d/w, upper/lower body split) for a 9-week period. Two-way ANOVA with repeated measures was used for statistical analysis.[Results]There were significant increases in bench press lifting volume at wk-6 (146 kg, 95% CI 21.1, 272) and wk-9 (245 kg, 95% CI 127, 362) with L-carnitine. A similar trend was observed for leg press. In the L-carnitine group, at wk-9, there were significant increases in mean power (63.4 W, 95% CI 32.0, 94.8) and peak power (239 W, 95% CI 86.6, 392), reduction in post-exercise blood lactate levels (-1.60 mmol/L, 95% CI -2.44, -0.75) and beneficial changes in total antioxidant capacity (0.18 mmol/L, 95% CI 0.07, 0.28).[Conclusion]L-carnitine supplementation enhances exercise performance while attenuating blood lactate and oxidative stress responses to resistance training.