Effects of beta-alanine supplementation on brain homocarnosine/carnosine signal and cognitive function: an exploratory study.

OBJECTIVES: Two independent studies were conducted to examine the effects of 28 d of beta-alanine supplementation at 6.4 g d(-1) on brain homocarnosine/carnosine signal in omnivores and vegetarians (Study 1) and on cognitive function before and after exercise in trained cyclists (Study 2). METHODS: In Study 1, seven healthy vegetarians (3 women and 4 men) and seven age- and sex-matched omnivores undertook a brain 1H-MRS exam at baseline and after beta-alanine supplementation. In study 2, nineteen trained male cyclists completed four 20-Km cycling time trials (two pre supplementation and two post supplementation), with a battery of cognitive function tests (Stroop test, Sternberg paradigm, Rapid Visual Information Processing task) being performed before and after exercise on each occasion. RESULTS: In Study 1, there were no within-group effects of beta-alanine supplementation on brain homocarnosine/carnosine signal in either vegetarians (p = 0.99) or omnivores (p = 0.27); nor was there any effect when data from both groups were pooled (p = 0.19). Similarly, there was no group by time interaction for brain homocarnosine/carnosine signal (p = 0.27). In study 2, exercise improved cognitive function across all tests (P < 0.05), although there was no effect (P>0.05) of beta-alanine supplementation on response times or accuracy for the Stroop test, Sternberg paradigm or RVIP task at rest or after exercise. CONCLUSION: 28 d of beta-alanine supplementation at 6.4 g d(-1) appeared not to influence brain homocarnosine/carnosine signal in either omnivores or vegetarians; nor did it influence cognitive function before or after exercise in trained cyclists.

Effect of whey protein isolate on rehydration after exercise.

Studies have examined adding protein to carbohydrate-electrolyte rehydration drinks, but the effects of protein in isolation remain unknown. Ten subjects completed two trials in which they were dehydrated (~2 % of pre-exercise body mass) by intermittent cycling in the heat. Subjects then rehydrated (150 % total mass loss) over 1 h with mineral water (W) or mineral water plus 20 g L(-1) whey protein isolate (WP) and remained in the laboratory for a further 4 h. Blood and urine samples were provided pre-exercise, post-exercise, post-rehydration and every hour thereafter. From blood samples, serum osmolality, change in plasma volume and plasma albumin content was determined, whilst the volume and osmolality of urine samples were determined. There was no difference between trials for total urine volume [W: 1,234 (358) mL; WP: 1,306 (268) mL; P = 0.409], drink retention [W: 40 (14) %; WP: 37 (14) %; P = 0.322] or net fluid balance [W: -605 (318) mL; WP: -660 (274) mL; P = 0.792] 4-h post-rehydration. Plasma volume was greater 3 and 4 h post-drinking during WP, and plasma albumin content relative to pre-exercise was increased 1-4 h post-drinking in WP only. These results suggest that addition of 20 g L(-1) whey protein isolate neither enhances nor inhibits post-exercise rehydration, when a volume equivalent to 150 % of sweat losses is ingested in 1 h. As post-exercise nutritional requirements are multifactorial (rehydration, glycogen resynthesis, myofibrillar/mitochondrial protein synthesis), these data demonstrate that when post-exercise protein intake might benefit recovery or adaptation, this can be achieved without compromising rehydration.

Effect of sodium bicarbonate supplementation on 2000-m rowing performance.

UNLABELLED: The ability to buffer H+ could be vital to exercise performance, as high concentrations of H+ contribute to the development of fatigue. PURPOSE: The authors examined the effect of sodium bicarbonate (SB) supplementation on 2000-m rowing-ergometer performance. METHODS: Twenty male rowers (age 23 ± 4 y, height 1.85 ± 0.08 m, mass 82.5 ± 8.9 kg, 2000-m personal-best time 409 ± 16 s) completed two 2000-m rowing-ergometer time trials, separated by 48 h. Participants were supplemented before exercise with 0.3 g/kg body mass of SB or a placebo (maltodextrin; PLA). The trials were conducted using a double-blinded, randomized, counterbalanced crossover study design. Time to complete the 2000-m and time taken for each 500-m split were recorded. Blood lactate, bicarbonate, pH, and base excess were determined preexercise, immediately postexercise, and 5 min postexercise. Performance data were analyzed using paired t tests, as well as magnitude-based inferences; hematological data were analyzed using a repeated-measures ANOVA. RESULTS: Using paired t tests, there was no benefit of SB over PLA (P = .095). However, using magnitude-based inferences there was a likely beneficial effect of SB compared with PLA (PLA 412.0 ± 15.1 s, SB 410.7 ± 14.9 s). Furthermore, SB was 0.5 ± 1.2 s faster than PLA in the third 500 m (P = .035; possibly beneficial) and 1.1 ± 1.7 s faster in the fourth 500 m (P = .004; very likely beneficial). All hematological data were different between SB and PLA and were different from preexercise to postexercise. CONCLUSION: SB supplementation is likely to be beneficial to the performance of those competing in 2000-m rowing events, particularly in the second half of the event.

Carnosine: from exercise performance to health.

Carnosine was first discovered in skeletal muscle, where its concentration is higher than in any other tissue. This, along with an understanding of its role as an intracellular pH buffer has made it a dipeptide of interest for the athletic population with its potential to increase high-intensity exercise performance and capacity. The ability to increase muscle carnosine levels via ß-alanine supplementation has spawned a new area of research into its use as an ergogenic aid. The current evidence base relating to the use of ß-alanine as an ergogenic aid is reviewed here, alongside our current thoughts on the potential mechanism(s) to support any effect. There is also some emerging evidence for a potential therapeutic role for carnosine, with this potential being, at least theoretically, shown in ageing, neurological diseases, diabetes and cancer. The currently available evidence to support this potential therapeutic role is also reviewed here, as are the potential limitations of its use for these purposes, which mainly focusses on issues surrounding carnosine bioavailability.

Effect of beta-alanine, with and without sodium bicarbonate, on 2000-m rowing performance.

PURPOSE: To examine the effect of beta-alanine only and beta-alanine with sodium bicarbonate supplementation on 2,000-m rowing performance. METHODS: Twenty well-trained rowers (age 23 ± 4 y; height 1.85 ± 0.08 m; body mass 82.5 ± 8.9 kg) were assigned to either a placebo or beta-alanine (6.4 g · d(-1) for 4 weeks) group. A 2,000-m rowing time trial (TT) was performed before supplementation (Baseline) and after 28 and 30 days of supplementation. The post supplementation trials involved supplementation with either maltodextrin or sodium bicarbonate in a double-blind, crossover design, creating four study conditions (placebo with maltodextrin; placebo with sodium bicarbonate; beta-alanine with maltodextrin; beta-alanine with sodium bicarbonate). Blood lactate, pH, bicarbonate, and base excess were measured pre-TT, immediately post-TT and at TT+5 min. Performance data were analyzed using magnitude based inferences. RESULTS: Beta-alanine supplementation was very likely to be beneficial to 2,000-m rowing performance (6.4 ± 8.1 s effect compared with placebo), with the effect of sodium bicarbonate having a likely benefit (3.2 ± 8.8 s). There was a small (1.1 ± 5.6 s) but possibly beneficial additional effect when combining chronic beta-alanine supplementation with acute sodium bicarbonate supplementation compared with chronic beta-alanine supplementation alone. Sodium bicarbonate ingestion led to increases in plasma pH, base excess, bicarbonate, and lactate concentrations. CONCLUSIONS: Both chronic beta-alanine and acute sodium bicarbonate supplementation alone had positive effects on 2,000-m rowing performance. The addition of acute sodium bicarbonate to chronic beta-alanine supplementation may further enhance rowing performance.

Acute tryptophan depletion does not improve endurance cycling capacity in a warm environment.

Newsholme's theory of central fatigue suggests that acute tryptophan depletion should improve endurance exercise capacity in a warm environment by reducing serotonergic activity in the brain. Eight males cycled to volitional exhaustion at 55 % VO(2) peak in 30.1 ± 0.5 °C and 30 ± 7 % relative humidity on two separate occasions, after consuming either an amino acid load to deplete their circulating tryptophan concentration (TD), or a control amino acid load (CON). Blood samples were taken before ingesting the amino acids, before the start of exercise, every 15 min during exercise and at the point of exhaustion. Heart rate (HR), core (Tc) and skin (Tsk) temperatures and ratings of perceived exertion (RPE) and thermal comfort (TC) were also monitored every 10 min during exercise. Plasma tryptophan (P = 0.003) and free tryptophan (P < 0.001) concentrations, and the free tryptophan to branched-chain amino acid ratio (P = 0.004) were all lower on the TD trial than on the CON trial. There was no difference in endurance exercise capacity (TD 99.2 ± 24.4 min as compared to CON 108.4 ± 21.6 min; P = 0.088). There was a tendency for HR (P = 0.053) and Tc (P = 0.069) to be higher on the TD trials. There were no differences for any of the other parameters. Endurance cycling capacity in a warm environment is not improved by acute tryptophan depletion, suggesting tryptophan availability is not a significant factor in the development of fatigue in such situations.

Hydration status and the diuretic action of a small dose of alcohol.

AIM: This study was conducted to examine the effect of consuming a dilute alcohol solution (weak beer) on urine production in euhydrated and hypohydrated individuals. METHODS: Twelve males completed an intermittent cycle protocol in hot (35.1 +/- 0.3 degrees C), humid (68 +/- 2%) conditions to dehydrate by 1.9 +/- 0.3% body mass in the evening. Twice they were then fed and rehydrated, while on two other occasions they were fed the same meal but remained hypohydrated. The following morning they were given 1 l of beer to drink. On two occasions the beer was alcohol-free, while on the other two occasions the same beer contained 4% ethanol. Participants remained in the laboratory for monitoring over the subsequent 4 h. Blood and urine samples were taken prior to dehydration, prior to drink administration and once every hour of the monitoring period. RESULTS: No difference existed in the volume of urine produced between the alcohol (261 +/- 138 ml; mean +/- SD) and non-alcohol (174 +/- 61 ml) beer when hypohydrated (P = 0.057), but there was a difference when euhydrated (1279 +/- 256 vs 1121 +/- 148 ml alcohol and non-alcohol, respectively; P < 0.001). Unsurprisingly, more urine was produced on both euhydrated trials than either of the hypohydrated trials (P < 0.001). Blood alcohol concentration was elevated (P < 0.001) 1 h after drinking to 7.1 +/- 1.8 and 6.0 +/- 2.7 mmol/l (hypohydrated and euhydrated, respectively) on the alcohol trials. Serum osmolality was higher 1 h after drinking on both the alcohol trials (303 +/- 5 and 298 +/- 5 mosmol/l) than on their non-alcohol, equivalent hydration trials (290 +/- 8 and 284 +/- 5 mosmol/l hypohydrated and euhydrated, respectively; P < 0.001). CONCLUSION: These results suggest that the diuretic action of alcohol is blunted when the body is hypohydrated.

Exercise capacity in the heat is greater in the morning than in the evening in man.

PURPOSE: This study investigated the effect of time of day on endurance exercise capacity in a warm environment. METHODS: Nine males cycled to exhaustion at 65% .VO2peak in an ambient temperature of 35 degrees C (60% relative humidity) at 0645 h (AM) and 1845 h (PM). Rectal temperature (Tc), skin temperature (Tsk), and heart rate (HR) were recorded and blood and expired air samples collected at rest every 5 min during exercise and during recovery. RESULTS: Time to exhaustion was longer in the AM trial (45.8 +/- 10.7 min) than in the PM trial (40.5 +/- 9.0 min; P = 0.009). Resting Tc was lower in the AM trial and remained lower for the first 25 min of exercise (P < 0.001). Tc was not different between trials at the point of exhaustion (AM = 38.7 +/- 0.9 degrees C, PM = 38.8 +/- 0.6 degrees C; P = 0.847). Tsk followed a similar pattern, being lower at rest (P = 0.003) and during the initial stages of exercise (P < 0.05) in the AM trial but not different at exhaustion (P = 0.896). The rate of rise of Tc tended to be greater in the AM trial (P = 0.052), and the rate of rise of Tsk (P = 0.032) and of body heat content (P = 0.009) was also greater in the AM trial. HR was initially higher in the PM trial, but there was no difference at exhaustion. There were no differences between trials in blood glucose concentration or plasma volume change. CONCLUSION: The results of this study suggest that endurance exercise capacity in the heat was significantly greater in the morning than the evening, possibly due to a lower initial Tc.