The effect of caffeine chewing gum on muscle performance and fatigue after severe-intensity exercise: isometric vs. dynamic assessments in trained cyclists.

This study investigated the effect of caffeinated chewing gum (GUMCAF) on muscle fatigue (isometric vs. dynamic) after severe-intensity cycling bouts. Fifteen trained male cyclists participated in four visits. Each visit involved two severe-intensity cycling bouts (Δ1 and Δ2) lasting 6 min, separated by a 5-min recovery period. Muscle fatigue was assessed by isometric maximal voluntary knee extension contraction (IMVC) with twitch interpolation technique and dynamically by 7 s all-out cycling sprints. Assessments were performed before GUMCAF (Pre-GUM) and after the cycling bouts (Post-Exercise). GUMCAF and placebo gum (GUMPLA) were administered in a randomized double-blind procedure with participants receiving each gum type (GUMCAF and GUMPLA) during two separate visits. The results showed no significant interaction between gum types and time for the isometric and dynamic measurements (p > 0.05). The percentage change in performance from Pre-GUM to Post-Exercise showed no significant difference between GUMCAF and GUMPLA for either the dynamic-derived TMAX (~ -17.8% and -15.1%, respectively; p = 0.551) or isometric IMVC (~ -12.3% and -17.7%, respectively; p = 0.091) measurements. Moderate to large correlations (r = 0.31-0.51) were found between changes in sprint maximal torque and maximal power output measurements and isometric force, for both gum conditions. GUMCAF was not effective in attenuating muscle force decline triggered by severe-intensity cycling exercises, as measured by both isometric and dynamic methods. The correlations between IMVC and cycling maximal torque and power output suggest caution when interpreting isometric force as a direct measure of fatigue during dynamic cycling exercises.

No Combined Effect of Caffeinated Chewing Gum and Priming Exercise on Oxygen Uptake and Muscle Near-Infrared Spectroscopy-Derived Kinetics: A Double-Blind Randomized Crossover Placebo-Controlled Trial in Cyclists.

This study aimed to investigate the effects of caffeine ingestion by chewing gum (GUMCAF) combined with priming exercise on pulmonary oxygen uptake (V˙O2) and near-infrared spectroscopy-derived muscle oxygen extraction (HHb + Mb) kinetics during cycling performed in a severe-intensity domain. Fifteen trained cyclists completed four visits: two under a placebo gum (GUMPLA) and two under GUMCAF ingestion. Each visit consisted of two square-wave cycling bouts at Δ70 intensity (70% of difference between the V˙O2 at first ventilatory threshold and V˙O2max) with duration of 6 min each and 5 min of passive rest between the bouts. The GUMPLA or GUMCAF (400 mg) was chewed for 5 min, 12 min before the first Δ70 bout in a randomized double-blind procedure. The fundamental phase and slow component of HHb + Mb and V˙O2 kinetics were evaluated. For HHb + Mb kinetics, regardless of ingested gum, priming exercise effects occurred on the time constant (GUMCAF 16.0 ± 4.0 vs. 13.9 ± 2.9 s; GUMPLA 15.7 ± 6.1 vs. 13.2 ± 2.5 s), amplitude, slow component, time delay, and mean response time parameters (p ≤ .032). For V˙O2 kinetics, there were significant effects of bouts on the amplitude, slow component, end V˙O2, and the gain kinetics parameters (p < .017). Baseline V˙O2 was higher during GUMCAF than GUMPLA (p = .020). No significant effects occurred for the interaction between gum and bout in any parameter of V˙O2 or HHb + Mb kinetics. Therefore, unlike the priming exercise in severe-intensity exercise, GUMCAF is not an effective strategy for improving V˙O2 or HHb + Mb kinetics acceleration.

Reliability and Validity of Cycling Sprint Performance at Isolinear Mode Without Torque Factor: A Preliminary Study in Well-Trained Male Cyclists.

Purpose: This study aimed to compare the performance-derived parameters utilizing isolinear (ISOLIN) and isovelocity (ISOVEL) sprint cycling modes. Method: For that, 20 male trained cyclists performed 2 sprints of 7 s on an electromagnetically braked cycle ergometer in ISOLIN and six sprints in ISOVEL mode with cadences between 90 and 180 rpm, each separated by 3-min. A linear function modeled the sprints within each mode to extrapolate maximal cadence (CMAX) and torque (TMAX), and a quadratic function was used to extrapolate the apex defined as optimal cadence power (OPTCAD) and peak power output (PMAX). Fifteen subjects performed another 4 sprints at ISOLIN mode on different days to verify the reliability. Results: The measures from the power-cadence relationship were not different between the ISOLIN and ISOVEL modes. Although significant differences were detected in the T-C relationship, TMAX was greater at ISOLIN than ISOVEL (p = .006). On the other hand, CMAX was higher at ISOVEL than ISOLIN (p < .001). The correlation between parameters was large to very large (r = 0.51 to 0.89). However, high limits of agreement were verified. The ISOLIN presented consistency during the trials, and the random errors were acceptable (CV = 5.3% to 11.5%). Conclusion: Using the power-cadence relationship, PMAX and OPTCAD could be detected similarly between the two sprint modes (ISOLIN and ISOVEL). Thus, the findings demonstrated that a single ISOLIN sprint test could be a suitable tool for quantifying the time course of muscle fatigue during and after cycling exercises in well-trained male cyclists.

Prediction of Exercise Tolerance in the Severe and Extreme Intensity Domains by a Critical Power Model.

This study aimed to assess the predictive capability of different critical power (CP) models on cycling exercise tolerance in the severe- and extreme-intensity domains. Nineteen cyclists (age: 23.0 ± 2.7 y) performed several time-to-exhaustion tests (Tlim) to determine CP, finite work above CP (W'), and the highest constant work rate at which maximal oxygen consumption was attained (IHIGH). Hyperbolic power-time, linear power-inverse of time, and work-time models with three predictive trials were used to determine CP and W'. Modeling with two predictive trials of the CP work-time model was also used to determine CP and W'. Actual exercise tolerance of IHIGH and intensity 5% above IHIGH (IHIGH+5%) were compared to those predicted by all CP models. Actual IHIGH (155 ± 30 s) and IHIGH+5% (120 ± 26 s) performances were not different from those predicted by all models with three predictive trials. Modeling with two predictive trials overestimated Tlim at IHIGH+5% (129 ± 33 s; p = 0.04). Bland-Altman plots of IHIGH+5% presented significant heteroscedasticity by all CP predictions, but not for IHIGH. Exercise tolerance in the severe and extreme domains can be predicted by CP derived from three predictive trials. However, this ability is impaired within the extreme domain.

Barriers to physical activity practice and associated factors in patients with hypertension / Barreiras para a prática de atividade física e fatores associados em pacientes com hipertensão arterial

Abstract The identification of barriers to regular physical activity (PA) is a form of an initial and effective strategy to encourage behavior modification and adherence to a more active lifestyle in hypertensive patients. This cross-sectional study aimed to identify the barriers to PA practice in patients with hypertension classified as physically inactive and to analyze the association of the number of these barriers with sociodemographic factors and health indicators. Two hundred one hypertensive patients of both sexes (61.7±12.7 years) answered an anamnesis with health information and sociodemographic data, a PA level questionnaire, and a barrier questionnaire for the practice of PA. Regarding the level of PA of the participants, 48.8% were classified as physically inactive and reported, on average, 6.1 (±3.8) barriers to PA practice, with the barrier "fear of falling or getting hurt" the most commonly reported. Furthermore, women and patients with low education, negative perception of health, and a greater presence of comorbidities reported a greater number of barriers to PA practice. PA practice as a non-pharmacological tool for the treatment of hypertension should focus on women and patients with low education, negative perception of health, and a greater presence of associated comorbidities.

Resumo A identificação de barreiras à atividade física regular (AF) é uma forma de estratégia inicial e eficaz para encorajar a modificação do comportamento e a adesão a um estilo de vida mais ativo em pacientes hipertensivos. Este estudo transversal visou identificar as barreiras à prática de AF em pacientes com hipertensão classificados como fisicamente inativos e analisar a associação do número destas barreiras com fatores sociodemográficos e indicadores de saúde. Duzentos e um pacientes hipertensos de ambos os sexos (61.7±12.7 anos) responderam a uma anamnese com informações de saúde e dados sociodemográficos, um questionário de nível de AF, e um questionário de barreira para a prática de AF. Relativamente ao nível de AF dos participantes, 48,8% foram classificados como fisicamente inativos e reportaram, em média, 6,1 (±3,8) barreiras à prática de AF, sendo a barreira "medo de cair ou de se magoar" a mais frequentemente reportada. Além disso, mulheres e pacientes com baixa educação, percepção negativa da saúde, e uma maior presença de comorbidades reportaram um maior número de barreiras à prática de AF. A prática de AF como ferramenta não farmacológica para o tratamento da hipertensão deve ter como foco mulheres e pacientes com baixa escolaridade, percepção negativa de saúde e maior presença de comorbidades associadas.

Desempenho de corrida e natação de guarda-vidas civis após uma temporada de verão / Running and swimming performance of civilian lifeguards after a summer season

O objetivo do presente estudo foi verificar o desempenho de corrida e natação de guarda-vidas civis após uma temporada de verão em Florianópolis ­ SC. Quatorze guarda-vidas civis (idade: 23.4 ± 5.0 anos; massa corporal: 74.6 ± 8.9 kg; estatura: 176 ± 0.1 cm) realizaram testes de 500m de natação e 1600m de corrida antes e após uma temporada de verão de 5 meses. Não foi realizada nenhuma intervenção na rotina dos guarda -vidas durante esse período. A comparação no desempenho pré e pós temporada foi realizada pelo teste t de Student para dados pareados (bicaudal), enquanto as correlações entre as variáveis foram verificadas pelo coeficiente de correlação de Pearson, com nível de significância de 5% (p < 0.05). Houve piora nos tempos dos testes de 500m de natação (Pré: 501.4 ± 77.9; Pós: 523.1 ± 84.6 s; p < 0.01) e 1600m de corrida (Pré: 371.6 ± 42.3 s; Pós: 393.9 ± 42.7 s; p < 0.01), sem associação entre o tempo de desempenho pré-temporada no teste de natação (r = 0.441, p = 0.115) ou corrida (r = -0.179, p = 0.541) com as magnitudes de piora. Concluiu-se que houve uma piora no desempenho de corrida e natação ao término da temporada de verão nos guarda-vidas civis, o que pode levar a uma perda no rendimento nas atividades que são submetidos rotineiramente. Dessa forma, tornam-se importantes estratégias, como o treinamento sistematizado, para minimizar essa queda no rendimento dos guarda-vidas civis, evitando o risco a si mesmo e a potenciais vítimas.(AU)

: The aim of this study was verify the performance of the running and swimming of civilian lifeguards after a summer season in Florianópolis - SC. Fourteen civilian lifeguards (age: 23.4 ± 5.0 years; body mass: 74.6 ± 8.9 kg; height: 176 ± 0.1 cm) performed tests of 500m swimming and 1600m running before and after a summer season of 5 months. There was no intervention in the routine of the lifeguards during this period. Statistical analysis consisted of a paired t-test (two-tailed) for the pre and post-season comparison, with the correlations between the variables being verified by Pearson's correlation coefficient, with level of significance of 5% (p < 0.05) for all tests. There was an impairment in the 500m swimming test (Pre: 501.4 ± 77.9; Post: 523.1 ± 84.6 s; p <0.01) and 1600m running test (Pre: 371.6 ± 42.3 s; Post: 393.9 ± 42.7 s; p <0.01), without association between the pre-season performance time and the swimming (r = 0.441, p = 0.115) or running (r= -0.179, p = 0.541) impairment magnitudes. It was concluded that running and swimming performance are impaired at the end of the summer season on civilian lifeguards, which could cause a loss of performance in routine activities. Thus, become important strategies, such as systematic training, to minimize this fall in the performance of civilian lifeguards, avoiding the risk to themselves and potential victims. (AU)