International journal of sport nutrition and exercise metabolism最新文献

Marine-derived proteins, such as blue whiting-derived protein hydrolysates (BWPH), represent high-quality sources of dietary protein, but their ability to support postexercise anabolism is not established. The impact of BWPH on whole-body anabolism was compared with an isonitrogenous whey protein isolate (WPI) and nonessential amino acid (NEAA) control in 10 trained young males (31 ± 4 years) who, on three separate visits, performed a session of whole-body resistance exercise and then consumed, in randomized crossover fashion, BWPH, WPI, or NEAA (0.33 g/kg; 19, 33, and 0 mg/kg leucine, respectively) with L-[1-13C]leucine. Breath, blood, and urine samples were collected for 6-hr postprandial to assess dietary leucine oxidation, amino acid (AA) concentrations, and 3-methylhistidine: creatinine ratio. Peak and area under the curve concentrations for leucine, branched-chain amino acids, and essential amino acids were greater in WPI compared with BWPH (all p < .05) but with no differences in time to peak concentration. Total oxidation reflected leucine intake (WPI > BWPH > NEAA; p < .01), whereas relative oxidation was greater (p < .01) in WPI (28.6 ± 3.6%) compared with NEAA (21.3 ± 4.2%), but not BWPH (28.6 ± 8.8%). Leucine retention, a proxy for whole-body protein synthesis, was greater in WPI (185.6 ± 9.5 μmol/kg) compared with BWPH (109.3 ± 14.1 μmol/kg) and NEAA (5.74 ± 0.30 μmol/kg; both p < .01), with BWPH being greater than NEAA (p < .01). Urinary 3-methylhistidine: creatinine ratio did not differ between conditions. Both WPI and BWPH produced essential aminoacidemia and supported whole-body anabolism after resistance exercise, but a higher intake of BWPH to better approximate the leucine and EAA content of WPI may be needed to produce an equivalent anabolic response.

Background: Preexercise caffeine intake has proven to exert ergogenic effects on cycling performance. However, whether these benefits are also observed under fatigue conditions remains largely unexplored. We aimed to assess the effect of caffeine ingested during prolonged cycling on subsequent time-trial performance in trained cyclists.

Methods: The study followed a triple-blinded, randomized, placebo-controlled cross-over design. Eleven well-trained junior cyclists (17 ± 1 years) performed a field-based 8-min time trial under "fresh" conditions (i.e., after their usual warm-up) or after two work-matched steady-state cycling sessions (total energy expenditure∼20 kJ/kg and ∼100 min duration). During the latter sessions, participants consumed caffeine (3 mg/kg) or a placebo ∼60 min before the time trial. We assessed power output, heart rate, and rating of perceived exertion during the time trial and mood state (Brunel Mood Scale) before and after each session.

Results: No significant condition effect was found for the mean power output attained during the time trial (365 ± 25, 369 ± 31, and 364 32 W for "fresh," caffeine, and placebo condition, respectively; p = .669). Similar results were found for the mean heart rate (p = .100) and rating of perceived exertion (p = 1.000) during the time trial and for the different mood domains (all p > .1).

Conclusions: Caffeine intake during prolonged exercise seems to exert no ergogenic effects on subsequent time-trial performance in junior cyclists. Future studies should determine whether significant effects can be found with larger caffeine doses or after greater fatigue levels.

Purpose: This study investigated the effect of menthol (MEN) mouth rinsing (MR) on cycling performance during a modified variable cycle test (M-VCT) in adolescent athletes under hot conditions (31.4 ± 0.9 °C, 23.4 ± 3.7% relative humidity).

Methods: Trained adolescent male cyclists (n = 11, 16.7 ± 1.3 years, height 176.6 ± 8.8 cm, body mass 65.8 ± 11.6 kg, maximal oxygen uptake 62.97 ± 7.47 ml·kg-1·min-1) voluntarily completed three trials (familiarization and two experimental) of a 30-min M-VCT, which included five 6-min laps consisting of three 6-s accelerations and three 10-s sprints throughout each lap. In a randomized crossover design, MEN (0.01%) or placebo (PLA) (crystal-light), was swilled for 5 s before the start of each lap (total of 6 MR). Power output, distance (in kilometers), core temperature, heart rate, perceptual exertion, thermal stimulation (thermal comfort and thermal sensation), and blood lactate concentration were recorded.

Results: MEN MR significantly improved M-VCT mean power output by 1.81 ± 1.57% compared to PLA (MEN, 177.8 ± 31.4 W; PLA, 174.7 ± 30.5 W, p < .001, 95% confidence interval [1.73, 4.46], d = 1.53). For maximal intermittent sprints, 6- and 10-s mean power output was significantly higher with MEN than PLA (6 s, p = .041, 95% confidence interval [0.73, 27.19], d = 0.71; 10 s, p = .002, 95% confidence interval [11.08, 35.22], d = 1.29). There was no significant difference in core temperature, heart rate, blood lactate concentration, or any perceptual measure between trials (p > .05) despite significantly higher work with MEN.

Conclusion: 64% of athletes (7/11) improved M-VCT performance with MEN. The results of this investigation suggest that a MEN MR may improve power output during a sport-specific stochastic cycling task in elite adolescent male cyclists.

It is important for athlete and public health that we continue to develop our understanding of the effects of exercise and nutrition on bone health. Bone turnover markers (BTMs) offer an opportunity to accelerate the progression of bone research by revealing a bone response to exercise and nutrition stimuli far more rapidly than current bone imaging techniques. However, the association between short-term change in the concentration of BTMs and long-term bone health remains ambiguous. Several other limitations also complicate the translation of acute BTM data to applied practice. Importantly, several incongruencies exist between the effects of exercise and nutrition stimuli on short-term change in BTM concentration compared with long-term bone structural outcomes to similar stimuli. There are many potential explanations for these inconsistencies, including that short-term study designs fail to encompass a full remodeling cycle. The current article presents the opinion that data from relatively acute studies measuring BTMs may not be able to reliably inform applied practice aiming to optimize bone health. There are important factors to consider when interpreting or translating BTM data and these are discussed.

This study aimed to determine whether caffeine gum influenced perceptual-cognitive and physical performance during the extra-time period of simulated soccer match-play. Semiprofessional male soccer players (n = 12, age: 22 ± 3 years, stature: 1.78 ± 0.06 m, mass: 75 ± 9 kg) performed 120-min soccer-specific exercise on two occasions. In a triple-blind, randomized, crossover design, players chewed caffeinated (200 mg; caffeine) or control (0 mg; placebo) gum for 5 min following 90 min of soccer-specific exercise. Perceptual-cognitive skills (i.e., passing accuracy, reaction time, composure, and adaptability) were assessed using a soccer-specific virtual reality simulator, collected pre- and posttrial. Neuromuscular performance (reactive-strength index, vertical jump height, absolute and relative peak power output, and negative vertical displacement) and sprint performance (15 and 30 m) were measured at pretrial, half-time, 90 min, and posttrial. Caffeine gum attenuated declines in reaction time (pre: 90.8 ± 0.8 AU to post: 90.7 ± 0.8 AU) by a further 4.2% than placebo (pre: 92.1 ± 0.8 AU to post: 88.2 ± 0.8 AU; p < .01). Caffeine gum reduced composure by 4.7% (pre: 69.1 ± 0.8 AU to post: 65.9 ± 0.8 AU) versus placebo (pre: 68.8 ± 0.8 AU to post: 68.3 ± 0.8 AU; p < .01). Caffeine gum did not influence any other variables (p > .05). Where caffeine gum is consumed by players prior to extra-time, reaction time increases but composure may be compromised, and neuromuscular and sprint performance remain unchanged. Future work should assess caffeine gum mixes with substances like L-theanine that promote a relaxed state under stressful conditions.

The main objective of this placebo-controlled, triple-blind, balanced crossover study was to assess the acute effects of phenylcapsaicin (PC) intake (2.5 mg) on intraocular pressure (IOP), ocular perfusion pressure (OPP), and heart rate (HR) during a 30-min cycling task performed at 15% of the individual maximal power. Twenty-two healthy young adults performed the cycling task 45 min after ingesting PC or placebo. IOP was measured with a rebound tonometer before exercise, during cycling (every 6 min), and after 5 and 10 min of recovery. OPP was assessed before and after exercise. HR was monitored throughout the cycling task. We found an acute increase of IOP levels related to PC consumption while cycling (mean difference = 1.91 ± 2.24 mmHg; p = .007, ηp2=.30), whereas no differences were observed for OPP levels between the PC and placebo conditions (mean difference = 1.33 ± 8.70 mmHg; p = .608). Mean HR values were higher after PC in comparison with placebo intake (mean difference = 3.11 ± 15.87 bpm, p = .019, ηp2=.24), whereas maximum HR did not differ between both experimental conditions (p = .199). These findings suggest that PC intake before exercise should be avoided when reducing IOP levels is desired (e.g., glaucoma patients or those at risk). Future studies should determine the effects of different ergogenic aids on IOP and OPP levels with other exercise configurations and in the long term.