When ingested alone, beetroot juice and sodium bicarbonate are ergogenic for high-intensity exercise performance. This study sought to determine the independent and combined effects of these supplements. Eight endurance trained (VO2max 65 mL·kg·min-1) male cyclists completed four × 4-km time trials (TT) in a doubleblind Latin square design supplementing with beetroot crystals (BC) for 3 days (15 g·day-1 + 15 g 1 h before TT, containing 300 mg nitrate per 15 g), bicarbonate (Bi 0.3 g·kg-1 body mass [BM] in 5 doses every 15 min from 2.5 h before TT); BC+Bi or placebo (PLA). Subjects completed TTs on a Velotron cycle ergometer under standardized laboratory conditions. Plasma nitrite concentrations were significantly elevated only in the BC+Bi trial before the TT (1520 ± 786 nmol·L-1) compared with baseline (665 ± 535 nmol·L-1, p = .02) and the Bi and PLA conditions (Bi: 593 ± 203 nmol·L-1, p < .01; PLA: 543 ± 369 nmol·L-1, p < .01). Plasma nitrite concentrations were not elevated in the BC trial before the TT (1102 ± 218 nmol·L-1) compared with baseline (975 ± 607 nmol·L-1, p > .05). Blood bicarbonate concentrations were increased in the BC+Bi and Bi trials before the TT (BC+Bi: 30.9 ± 2.8 mmol·L-1; Bi: 31.7 ± 1.1 mmol·L-1). There were no differences in mean power output (386–394 W) or the time taken to complete the TT (335.8–338.1 s) between any conditions. Under the conditions of this study, supplementation was not ergogenic for 4-km TT performance.
Marcus J. Callahan, Evelyn B. Parr, John A. Hawley and Louise M. Burke
Enda F. Whyte, Nicola Gibbons, Grainne Kerr and Kieran A. Moran
Context: Determination of return to play (RTP) after sport-related concussion (SRC) is critical given the potential consequences of premature RTP. Current RTP guidelines may not identify persistent exercise-induced neurocognitive deficits in asymptomatic athletes after SRC. Therefore, postexercise neurocognitive testing has been recommended to further inform RTP determination. To implement this recommendation, the effect of exercise on neurocognitive function in healthy athletes should be understood. Objective: To examine the acute effects of a high-intensity intermittent-exercise protocol (HIIP) on neurocognitive function assessed by the Symbol Digits Modality Test (SDMT) and Stroop Interference Test. Design: Cohort study. Setting: University laboratory. Participants 40 healthy male athletes (age 21.25 ± 1.29 y, education 16.95 ± 1.37 y). Intervention: Each participant completed the SDMT and Stroop Interference Test at baseline and after random allocation to a condition (HIIP vs control). A mixed between-within-subjects ANOVA assessed time- (pre- vs postcondition) -by-condition interaction effects. Main Outcome Measures: SDMT and Stroop Interference Test scores. Results: There was a significant time-by-condition interaction effect (P < .001, η 2 = .364) for the Stroop Interference Test scores, indicating that the HIIP group scored significantly lower (56.05 ± 9.34) postcondition than the control group (66.39 ± 19.6). There was no significant time-by-condition effect (P = .997, η 2 < .001) for the SDMT, indicating that there was no difference between SDMT scores for the HIIP and control groups (59.95 ± 10.7 vs 58.56 ± 14.02). Conclusions: In healthy athletes, the HIIP results in a reduction in neurocognitive function as assessed by the Stroop Interference Test, with no effect on function as assessed by the SDMT. Testing should also be considered after high-intensity exercise in determining RTP decisions for athletes after SRC in conjunction with the existing recommended RTP protocol. These results may provide an initial reference point for future research investigating the effects of an HIIP on the neurocognitive function of athletes recovering from SRC.
Deborah K. Fletcher and Nicolette C. Bishop
This study investigated the effect of a high and low dose of caffeine on antigen-stimulated natural killer (NK) cell (CD3−CD56+) activation after prolonged, strenuous cycling, as assessed by the early-activation molecule CD69. In a randomized crossover design, 12 healthy male endurance-trained cyclists cycled for 90 min at 70% VO2peak 60 min after ingesting either 0 (PLA), 2 (2CAF), or 6 (6CAF) mg/kg body mass of caffeine. Whole blood was stimulated with Pediacel (5 in 1) vaccine. A high dose of caffeine (6CAF) increased the number of CD3−CD56+ cells in the circulation immediately postexercise compared with PLA (p < .05). For both 2CAF and 6CAF, the geometric mean fluorescence intensity (GMFI) of CD69+ expression on unstimulated CD3−CD56+ cells was significantly higher than with PLA (both p < .05). When cells were stimulated with antigen, the GMFI of CD69 expression remained significantly higher with 2CAF than with PLA 1 hr postexercise (p < .05). Although not achieving statistical significance, 6CAF also followed a similar trend when stimulated (p = .09). There were no differences in GMFI of CD69 expression between 2CAF and 6CAF. These results suggest that a high (6 mg/kg) dose of caffeine was associated with the recruitment of NK cells into the circulation and that both a high and low (2 mg/kg) dose of caffeine increased unstimulated and antigen-stimulated NK-cell activation 1 hr after high-intensity exercise. Furthermore, there does not appear to be a dose-dependent effect of caffeine on NK-cell activation 1 hr after prolonged intensive cycling.
Kellie R. Pritchard-Peschek, David G. Jenkins, Mark A. Osborne and Gary J. Slater
The aim of the current study was to investigate the effect of 180 mg of pseudoephedrine (PSE) on cycling time-trial (TT) performance. Six well-trained male cyclists and triathletes (age 33 ± 2 yr, mass 81 ± 8 kg, height 182.0 ± 6.7 cm, VO2max 56.8 ± 6.8 ml ⋅ kg−1 ⋅ min−1; M ± SD) underwent 2 performance trials in which they completed a 25-min variable-intensity (50–90% maximal aerobic power) warm-up, followed by a cycling TT in which they completed a fixed amount of work (7 kJ/kg body mass) in the shortest possible time. Sixty minutes before the start of exercise, they orally ingested 180 mg of PSE or a cornstarch placebo (PLA) in a randomized, crossover, double-blind manner. Venous blood was sampled immediately pre- and postexercise for the analysis of pH plus lactate, glucose, and norepinephrine (NE). PSE improved cycling TT performance by 5.1% (95% CI 0–10%) compared with PLA (28:58.9 ± 4:26.5 and 30:31.7 ± 4:36.7 min, respectively). There was a significant Treatment × Time interaction (p = .04) for NE, with NE increasing during the PSE trial only. Similarly, blood glucose also showed a trend (p = .06) for increased levels postexercise in the PSE trial. The ingestion of 180 mg of PSE 60 min before the onset of high-intensity exercise improved cycling TT performance in well-trained athletes. It is possible that changes in metabolism or an increase in central nervous system stimulation is responsible for the observed ergogenic effect of PSE.
John Hough, Caroline Robertson and Michael Gleeson
This study examined the influence of 10 days of intensified training on salivary cortisol and testosterone responses to 30-min, high-intensity cycling (55/80) in a group of male elite triathletes.
Seven elite male triathletes (age 19 ± 1 y, V̇O2max 67.6 ± 4.5 mL · kg–1 · min–1) completed the study. Swim distances increased by 45%. Running and cycling training hours increased by 25% and 229%, respectively. REST-Q questionnaires assessed mood status before, during, and after the training period. Unstimulated saliva samples were collected before, after, and 30 min after a continuous, high-intensity exercise test. Salivary cortisol and testosterone concentrations were assessed.
Compared with pretraining, blunted exercise-induced salivary testosterone responses to the posttraining 55/80 were found (P = .004). The absolute response of salivary testosterone concentrations to the 55/80 decreased pretraining to posttraining from 114% to 85%. No changes were found in exercise-induced salivary cortisol concentration responses to the 55/80. REST-Q scores indicated no changes in the participants’ psychological stress–recovery levels over the training camp.
The blunted exercise-induced salivary testosterone is likely due to decreased testicular testosterone production and/or secretion, possibly attributable to hypothalamic dysfunction or reduced testicular blood flow. REST-Q scores suggest that the triathletes coped well with training-load elevations, which could account for the finding of no change in the exercise-induced salivary cortisol concentration. Overall, these findings suggest that the 55/80 can detect altered exercise-induced salivary testosterone concentrations in an elite athletic population due to increased training stress. However, this alteration occurs independently of a perceived elevation of training stress.
Andrew J.R. Cochran, Michael E. Percival, Sara Thompson, Jenna B. Gillen, Martin J. MacInnis, Murray A. Potter, Mark A. Tarnopolsky and Martin J. Gibala
Sprint interval training (SIT), repeated bouts of high-intensity exercise, improves skeletal muscle oxidative capacity and exercise performance. β-alanine (β-ALA) supplementation has been shown to enhance exercise performance, which led us to hypothesize that chronic β-ALA supplementation would augment work capacity during SIT and augment training-induced adaptations in skeletal muscle and performance. Twenty-four active but untrained men (23 ± 2 yr; VO2peak = 50 ± 6 mL·kg−1·min−1) ingested 3.2 g/day of β-ALA or a placebo (PLA) for a total of 10 weeks (n = 12 per group). Following 4 weeks of baseline supplementation, participants completed a 6-week SIT intervention. Each of 3 weekly sessions consisted of 4–6 Wingate tests, i.e., 30-s bouts of maximal cycling, interspersed with 4 min of recovery. Before and after the 6-week SIT program, participants completed a 250-kJ time trial and a repeated sprint test. Biopsies (v. lateralis) revealed that skeletal muscle carnosine content increased by 33% and 52%, respectively, after 4 and 10 weeks of β-ALA supplementation, but was unchanged in PLA. Total work performed during each training session was similar across treatments. SIT increased markers of mitochondrial content, including cytochome c oxidase (40%) and β-hydroxyacyl-CoA dehydrogenase maximal activities (19%), as well as VO2peak (9%), repeated-sprint capacity (5%), and 250-kJ time trial performance (13%), but there were no differences between treatments for any measure (p < .01, main effects for time; p > .05, interaction effects). The training stimulus may have overwhelmed any potential influence of β-ALA, or the supplementation protocol was insufficient to alter the variables to a detectable extent.
Nicolette C. Bishop, Michael Gleeson, Ceri W. Nicholas and Ajmol Ali
Ingesting carbohydrate (CHO) beverages during prolonged, continuous heavy exercise results in smaller changes in the plasma concentrations of several cytokines and attenuates a decline in neutrophil function. In contrast, ingesting CHO during prolonged intermittent exercise appears to have negligible influence on these responses, probably due to the overall moderate intensity of these intermittent exercise protocols. Therefore, we examined the effect of CHO ingestion on plasma interIeukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and lipopolysaccharide (LPS)-stimuIated neutrophil degranulation responses to high-intensity intermittent running. Six trained male soccer players performed 2 exercise trials, 7 days apart, in a randomized, counterbalanced design. On each occasion, they completed six 15-min periods of intermittent running consisting of maximal sprinting interspersed with less intense periods of running and walking. Subjects consumed either CHO or artificially sweetened placebo(PLA) beverages immediately before and at 15-min intervals during the exercise. At 30 min post-exercise, CHO versus PLA was associated with a higher plasma glucose concentration (p< .01), a lower plasma cortisol and IL-6 concentration (p < .02), and fewer numbers of circulating neutrophils (p < .05). Following the exercise, LPS-stimulated elastase release per neutrophil fell 31 % below baseline values on the PLA trial (p = .06) compared with 11% on the CHO trial (p = .30). Plasma TNF-α concentration increased following the exercise (main effect of time, p < .001) but was not affected by CHO. These data indicate that CHO ingestion attenuates changes in plasma IL-6 concentration, neutrophil trafficking, and LPS-stimulated neutrophil degranulation in response to intermittent exercise that involves bouts of very high intensity exercise.
Éder Ricardo Petry, Vinicius Fernandes Cruzat, Thiago Gomes Heck, Paulo Ivo Homem de Bittencourt Jr. and Julio Tirapegui
Liver L-glutamine is an important vehicle for the transport of ammonia and intermediary metabolism of amino acids between tissues, particularly under catabolic situations, such as high-intensity exercise. Hence, the aim of this study was to investigate the effects of oral supplementations with L-glutamine in its free or dipeptide forms (with L-alanine) on liver glutamine-glutathione (GSH) axis, and 70 kDa heat shock proteins (HSP70)/heat shock transcription factor 1 (HSF1) expressions. Adult male Wistar rats were 8-week trained (60 min/day, 5 days/week) on a treadmill. During the last 21 days, the animals were daily supplemented with 1 g of L-glutamine/kg body weight per day in either l-alanyl-L-glutamine dipeptide (DIP) form or a solution containing L-glutamine and l-alanine in their free forms (GLN+ALA) or water (controls). Exercise training increased cytosolic and nuclear HSF1 and HSP70 expression, as compared with sedentary animals. However, both DIP and GLN+ALA supplements enhanced HSF1 expression (in both cytosolic and nuclear fractions) in relation to exercised controls. Interestingly, HSF1 rises were not followed by enhanced HSP70 expression. DIP and GLN+ALA supplements increased plasma glutamine concentrations (by 62% and 59%, respectively) and glutamine to glutamate plasma ratio in relation to trained controls. This was in parallel with a decrease in plasma ammonium levels. Supplementations increased liver GSH (by 90%), attenuating the glutathione disulfide (GSSG) to GSH ratio, suggesting a redox state protection. In conclusion, oral administration with DIP and GLN+ALA supplements in endurance-trained rats improve liver glutamine-GSH axis and modulate HSF1 pathway.
Simon P. Roberts, Keith A. Stokes, Lee Weston and Grant Trewartha
This study presents an exercise protocol utilizing movement patterns specific to rugby union forward and assesses the reproducibility of scores from this test.
After habituation, eight participants (mean ± SD: age = 21 ± 3 y, height = 180 ± 4 cm, body mass = 83.9 ± 3.9 kg) performed the Bath University Rugby Shuttle Test (BURST) on two occasions, 1 wk apart. The protocol comprised 16 × 315-s cycles (4 × 21-min blocks) of 20-m shuttles of walking and cruising with 10-m jogs, with simulated scrummaging, rucking, or mauling exercises and standing rests. In the last minute of every 315-s cycle, a timed Performance Test was carried out, involving carrying a tackle bag and an agility sprint with a ball, followed by a 25-s recovery and a 15-m sprint.
Participants traveled 7078 m, spending 79.8 and 20.2% of time in low- and high-intensity activity, respectively. The coefficients of variation (CV) between trials 1 and 2 for mean time on the Performance Test (17.78 ± 0.71 vs 17.58 ± 0.79 s) and 15-m sprint (2.69 ± 0.15 vs 2.69 ± 0.15 s) were 1.3 and 0.9%, respectively. There was a CV of 2.2% between trials 1 and 2 for mean heart rate (160 ± 5 vs 158 ± 5 beats⋅min−1) and 14.4% for blood lactate (4.41 ± 1.22 vs 4.68 ± 1.68 mmol⋅L−1).
Results suggest that measures of rugby union-specifc high-intensity exercise performed during the BURST were reproducible over two trials in habituated participants.
Peter Peeling, Brian Dawson, Carmel Goodman, Grant Landers, Erwin T. Wiegerinck, Dorine W. Swinkels and Debbie Trinder
Urinary hepcidin, inflammation, and iron metabolism were examined during the 24 hr after exercise. Eight moderately trained athletes (6 men, 2 women) completed a 60-min running trial (15-min warm-up at 75–80% HRpeak + 45 min at 85–90% HRpeak) and a 60-min trial of seated rest in a randomized, crossover design. Venous blood and urine samples were collected pretrial, immediately posttrial, and at 3, 6, and 24 hr posttrial. Samples were analyzed for interleukin-6 (IL-6), C-reactive protein (CRP), serum iron, serum ferritin, and urinary hepcidin. The immediate postrun levels of IL-6 and 24-hr postrun levels of CRP were significantly increased from baseline (6.9 and 2.6 times greater, respectively) and when compared with the rest trial (p ≤ .05). Hepcidin levels in the run trial after 3, 6, and 24 hr of recovery were significantly greater (1.7–3.1 times) than the pre- and immediate postrun levels (p ≤ .05). This outcome was consistent in all participants, despite marked variation in the magnitude of rise. In addition, the 3-hr postrun levels of hepcidin were significantly greater than at 3 hr in the rest trial (3.0 times greater, p ≤ .05). Hepcidin levels continued to increase at 6 hr postrun but failed to significantly differ from the rest trial (p = .071), possibly because of diurnal influence. Finally, serum iron levels were significantly increased immediately postrun (1.3 times, p ≤ .05). The authors concluded that high-intensity exercise was responsible for a significant increase in hepcidin levels subsequent to a significant increase in IL-6 and serum iron.