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1.
Phys Sportsmed ; 47(4): 421-426, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-30978146

RESUMO

Objectives: This study sought to investigate the perceptions and practices of achieving 'race weight' in a population of trained male cyclists. A secondary focus was to investigate the use of gym-based strength training, a possible attenuator of the side effects associated with weight reduction.Methods: A total of n = 97 well-trained cyclists ranging from local club level to international standard completed an online survey capturing data on the aforementioned topics.Results: Forty-nine percent of respondents indicated they were unsatisfied with their current bodyweight, with a similar percentage across club, national and international level riders. Riders who identified as climbers had lower reported bodyweight; however, all categories of riders expressed a desire to reduce bodyweight by a similar percentage (1.9%, ± 3.4%; 90% CL). Seventy-seven percent of respondents indicated that they had recently tried or were currently trying to reduce bodyweight, most commonly by reducing food intake and avoiding sugary foods. Nine percent indicated they were using either supplements or medications to lower bodyweight, and 27% reported having sought advice from a health professional. A higher proportion of international riders engaged in strength training (85%), compared to national (50%) and club (55%) riders (p< 0.05). The most cited reasons for not strength training were time constraints and believing it was not beneficial to their cycling performance.Conclusion: These data suggest that trained male cyclists are a highly weight-conscious population who engage in a variety of practices to reduce weight. Practitioners should be aware of these tendencies, as they may carry significant health implications if poorly implemented.


Assuntos
Atletas , Atitude , Ciclismo , Treinamento Resistido , Redução de Peso , Adulto , Peso Corporal , Humanos , Masculino
2.
Eur J Sport Sci ; 15(8): 712-9, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26681629

RESUMO

This study examined the effect of dietary supplementation with inorganic nitrate ([Formula: see text] ) on markers of contractile function in human knee extensors. In a double-blinded, randomized cross-over design, 18 (12 M) healthy participants undertook four days of supplementation with either nitrate-rich beetroot juice (NITRATE; days 1-3: 525 mg [Formula: see text], day 4: 1050 mg [Formula: see text]) or nitrate-depleted beetroot juice (PLACEBO). On the fourth day, isometric knee extension force was assessed during a series of voluntary and electrically evoked (stimulation) tests. In addition, muscular fatigue was examined in two separate continuous-stimulation (0.8 s tetanus with a 1:1 work:rest ratio for 102.4 s) fatigue tests, one with and one without blood flow restriction. There were no differences for maximum voluntary contraction, peak twitch force, half-relaxation time and the force-frequency relationship for stimulations up to 100 Hz between the NITRATE and PLACEBO trials. No differences between trials were observed in the non-restricted fatigue test, however NITRATE was found to attenuate the decline in force during the restricted test, such that the force at the 80 s mark (PLACEBO: 66 ± 11 vs. NITRATE 74 ± 9% of initial force; P = .01) and 102 s mark (PLACEBO: 47 ± 8% vs. NITRATE 55 ± 8%; P < .01) were significantly higher. These results suggest that four days of [Formula: see text] supplementation elicits peripheral responses in muscle that attenuate muscular fatigue during exhaustive exercise under hypovolemic conditions. This ergogenic action is likely attributable to improved Ca(2+) handling in the muscle, or enhanced perfusion during ischemia.


Assuntos
Contração Muscular/efeitos dos fármacos , Nitratos/farmacologia , Adulto , Beta vulgaris , Biomarcadores/metabolismo , Estudos Cross-Over , Suplementos Nutricionais , Método Duplo-Cego , Tolerância ao Exercício/efeitos dos fármacos , Feminino , Voluntários Saudáveis , Humanos , Articulação do Joelho/efeitos dos fármacos , Masculino , Fadiga Muscular/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Dor Musculoesquelética/fisiopatologia , Nitratos/administração & dosagem , Extratos Vegetais/administração & dosagem , Extratos Vegetais/farmacologia , Estimulação Elétrica Nervosa Transcutânea
4.
Appl Physiol Nutr Metab ; 39(9): 1043-9, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24951296

RESUMO

Consumption of inorganic nitrate (NO3(-)) is known to enhance endurance exercise performance in recreationally trained subjects. Here we report the effect on a high-intensity performance task in national-level cyclists. The performance test consisted of 2 cycle ergometer time trials of 4 min duration with 75 min between trials. In a randomized crossover design, 26 cyclists performed the test under the following 4 conditions (each separated by a 6-day washout): consumption of 70 mL of nitrate-rich beetroot juice at 150 min or 75 min before the first time trial, addition of a 35 mL "top-up dose" following the first time trial in the 150 min condition, and consumption of a placebo. A linear mixed model with adjustments for learning effects and athlete fitness (peak incremental power) was used to estimate effects on mean power, with probabilistic inferences based on a smallest important effect of 1.0%. Peak plasma nitrite (NO2(-)) concentration was greatest when nitrate was taken 75 min before the first time trial. Relative to placebo, the mean effect of all 3 nitrate treatments was unclear in the first time trial (1.3%, 90% confidence limits: ±1.7%), but possibly harmful in the second time trial (-0.3%, ±1.6%). Differences between nitrate treatments were unclear, as was the estimate of any consistent individual response to the treatments. Allowing for sampling uncertainty, the effect of nitrate on performance was less than previous studies. Under the conditions of our experiment, nitrate supplementation may be ineffective in facilitating high-intensity exercise in competitive athletes.


Assuntos
Desempenho Atlético/fisiologia , Ciclismo/fisiologia , Suplementos Nutricionais , Nitratos/farmacologia , Estudos Cross-Over , Humanos , Masculino , Nitratos/administração & dosagem , Adulto Jovem
5.
Int J Sports Physiol Perform ; 9(4): 615-20, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24085341

RESUMO

CONTEXT: Beetroot juice is a naturally rich source of inorganic nitrate (NO(3-)), a compound hypothesized to enhance endurance performance by improving exercise efficiency. PURPOSE: To investigate the effect of different doses of beetroot juice on 2000-m ergometer-rowing performance in highly trained athletes. METHODS: Ten highly trained male rowers volunteered to participate in a placebo-controlled, double-blinded crossover study. Two hours before undertaking a 2000-m rowing-ergometer test, subjects consumed beetroot juice containing 0 mmol (placebo), 4.2 mmol (SINGLE), or 8.4 mmol (DOUBLE) NO(3-). Blood samples were taken before supplement ingestion and immediately before the rowing test for analysis of plasma [NO(3-)] and [nitrite (NO(2-))]. RESULTS: The SINGLE dose demonstrated a trivial effect on time to complete 2000 m compared with placebo (mean difference: 0.2 ± 2.5 s). A possibly beneficial effect was found with DOUBLE compared with SINGLE (mean difference -1.8 ± 2.1 s) and with placebo (-1.6 ± 1.6 s). Plasma [NO(2-)] and [NO(3-)] demonstrated a dose-response effect, with greater amounts of ingested nitrate leading to substantially higher concentrations (DOUBLE > SINGLE > placebo). There was a moderate but insignificant correlation (r = -.593, P = .055) between change in plasma [NO(2-)] and performance time. CONCLUSION: Compared with nitratedepleted beetroot juice, a high (8.4 mmol NO(3-)) but not moderate (4.2 mmol NO(3-)) dose of NO(3-) in beetroot juice, consumed 2 h before exercise, may improve 2000-m rowing performance in highly trained athletes.


Assuntos
Beta vulgaris , Bebidas , Nitratos/administração & dosagem , Substâncias para Melhoria do Desempenho/administração & dosagem , Resistência Física/efeitos dos fármacos , Extratos Vegetais/administração & dosagem , Esportes , Administração Oral , Estudos Cross-Over , Relação Dose-Resposta a Droga , Método Duplo-Cego , Teste de Esforço , Humanos , Masculino , Nitratos/sangue , Consumo de Oxigênio/efeitos dos fármacos , Substâncias para Melhoria do Desempenho/sangue , Extratos Vegetais/sangue , Raízes de Plantas , Análise e Desempenho de Tarefas , Fatores de Tempo , Adulto Jovem
6.
Int J Sport Nutr Exerc Metab ; 23(5): 522-32, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23580439

RESUMO

The purpose of this review was to examine the effect of nitrate supplementation on exercise performance by systematic review and meta-analysis of controlled human studies. A search of four electronic databases and cross-referencing found 17 studies investigating the effect of inorganic nitrate supplementation on exercise performance that met the inclusion criteria. Beetroot juice and sodium nitrate were the most common supplements, with doses ranging from 300 to 600 mg nitrate and prescribed in a manner ranging from a single bolus to 15 days of regular ingestion. Pooled analysis showed a significant moderate benefit (ES = 0.79, 95% CI: 0.23-1.35) of nitrate supplementation on performance for time to exhaustion tests (p = .006). There was a small but insignificant beneficial effect on performance for time trials (ES = 0.11, 95% CI: -0.16-0.37) and graded exercise tests (ES = 0.26, 95% CI: -0.10-0.62). Qualitative analysis suggested that performance benefits are more often observed in inactive to recreationally active individuals and when a chronic loading of nitrate over several days is undertaken. Overall, these results suggest that nitrate supplementation is associated with a moderate improvement in constant load time to exhaustion tasks. Despite not reaching statistical significance, the small positive effect on time trial or graded exercise performance may be meaningful in an elite sport context. More data are required to clarify the effect of nitrate supplementation on exercise performance and to elucidate the optimal way to implement supplementation.


Assuntos
Suplementos Nutricionais , Exercício Físico/fisiologia , Nitratos/farmacologia , Resistência Física/efeitos dos fármacos , Beta vulgaris/química , Humanos , Resistência Física/fisiologia
7.
Int J Sport Nutr Exerc Metab ; 23(5): 458-69, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23535809

RESUMO

PURPOSE: The purpose of this study was to establish whether sensory factors associated with cold-beverage ingestion exert an ergogenic effect on endurance performance independent of thermoregulatory or cardiovascular factors. METHODS: Ten males performed three trials involving 90 min of steady state cycling (SS; 62% VO2max) in the heat (32.1 ± 0.9 °C, 40 ± 2.4% relative humidity) followed by a 4 kJ/kg body mass time trial (TT). During SS, participants consumed an identical volume (260 ± 38 g) of sports beverage (7.4% carbohydrate) every 15 min as either ice slushy (-1 °C; ICE), thermoneutral liquid (37 °C; CON), or thermoneutral liquid consumption with expectorated ice slushy mouthwash (WASH). RESULTS: Rectal temperature, hydration status, heart rate, and skin blood flow were not different between trials. Gastrointestinal (pill) temperature was lower in ICE (35.6 ± 2.7 °C) versus CON (37.4 ± 0.7 °C, p = .05). Heat storage tended to be lower with ICE during SS (14.7 ± 8.4 W.m(-2), p = .08) and higher during TT (68.9 ± 38.6 W.m(-2), p = .03) compared with CON (22.1 ± 6.6 and 31.4 ± 27.6 W.m(-2)). ICE tended to lower the rating of perceived exertion (RPE, 12.9 ± 0.6, p = .05) and improve thermal comfort (TC, 4.5 ± 0.2; p = .01) vs. CON (13.8 ± 1.0 and 5.2 ± 0.2 respectively). WASH RPE (13.0 ± 0.8) and TC (4.8 ± 0.2) tended to be lower versus CON (p = .07 and p = .09 respectively). ICE improved performance (18:28 ± 1:03) compared with CON (20:24 ± 1:46) but not WASH (19:45 ± 1:43). CONCLUSION: Improved performance with ICE ingestion likely resulted from the creation of a gastrointestinal heat sink, reducing SS heat storage. Although the benefits of cold-beverage consumption are more potent when there is ingestion, improved RPE, TC, and meaningful performance improvement with WASH supports an independent sensory effect of presenting a cold stimulus to the mouth.


Assuntos
Regulação da Temperatura Corporal , Temperatura Corporal , Exercício Físico/fisiologia , Gelo , Resistência Física/fisiologia , Temperatura , Sensação Térmica , Adulto , Bebidas , Ciclismo , Temperatura Baixa , Exercício Físico/psicologia , Teste de Esforço , Trato Gastrointestinal/fisiologia , Temperatura Alta , Humanos , Masculino , Boca/fisiologia , Percepção , Esforço Físico/fisiologia , Adulto Jovem
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