Correlates of Mood and RPE During Multi-Lap Off-Road Cycling.

This study examined the relationship between mood and rating of perceived exertion (RPE) during a simulated multiple-lap time trial (MLTT). Nineteen male cyclists performed a MLTT consisting of four 9.9 km laps, each lap with a gradient ranging from 0 to 10 %. Mood as measured by the Profile of Mood States Questionnaire (POMS) and perceived exertion as measured by the Borg CR100 scale (RPE) were obtained at the end of each lap. A categorical multiple regressive model, having median of POMS subscales as independent variables, was obtained to explain the variance in median RPE responses. Increases in POMS fatigue scores and decreases in POMS vigour scores were observed throughout the MLTT (P < 0.001). A linear increase in RPE during the MLTT was also observed (P < 0.001). POMS fatigue subscale scores accounted for 88 % of the variance in RPE during the MLTT (R(2) = 0.88, P = 0.002), and no other POMS subscale improved the final predictive model. With the exception of fatigue these results suggest that most aspects of mood do not have a discernable effect on RPE during a MLTT. The rate of increase in RPE can predict the MLTT endpoint.

Self-selected or imposed exercise? A different approach for affective comparisons.

The aim of this study was to compare the psychological and physiological responses of self-selected and imposed sessions of equivalent intensities and durations and allowing to participants a free control of pace during the self-selected session. Seventeen participants completed three sessions on a cycle ergometer. Participant's VO2Peak and lactate threshold were measured during an incremental exercise test. During the second and third sessions, participants could view a virtual cyclist on a monitor. During the self-selected session, participants were allowed free control of the intensity and duration. To ensure that the imposed session replicated the self-selected session in intensity, participants were instructed to follow an additional virtual cyclist, which was displayed on a monitor using the CompuTrainer 3D software. Power output and physiological and psychological variables were recorded during the sessions. A two-way ANOVA showed no effect of condition for power output (P = 0.940), heart rate (HR) (P = 0.965), VO2 (P = 0.898), blood lactate (P = 0.667), Feeling Scale (P = 0.877), Felt Arousal Scale (P = 0.924) and CR100 (P = 0.939). A paired t-test showed no significant difference in Physical Activity Enjoyment Scale scores between sessions (P = 0.054). In contrast to previous studies, the self-selected session did not provide better affective responses than the imposed session with same intensity and duration.

Correction: Caffeine increases motor output entropy and performance in 4 km cycling time trial.

[This corrects the article DOI: 10.1371/journal.pone.0236592.].

Caffeine Increased Muscle Endurance Performance Despite Reduced Cortical Activation and Unchanged Neuromuscular Efficiency and Corticomuscular Coherence.

The central and peripheral effects of caffeine remain debatable. We verified whether increases in endurance performance after caffeine ingestion occurred together with changes in primary motor cortex (MC) and prefrontal cortex (PFC) activation, neuromuscular efficiency (NME), and electroencephalography-electromyography coherence (EEG-EMG coherence). Twelve participants performed a time-to-task failure isometric contraction at 70% of the maximal voluntary contraction after ingesting 5 mg/kg of caffeine (CAF) or placebo (PLA), in a crossover and counterbalanced design. MC (Cz) and PFC (Fp1) EEG alpha wave and vastus lateralis (VL) muscle EMG were recorded throughout the exercise. EEG-EMG coherence was calculated through the magnitude squared coherence analysis in MC EEG gamma-wave (CI > 0.0058). Moreover, NME was obtained as the force-VL EMG ratio. When compared to PLA, CAF improved the time to task failure (p = 0.003, d = 0.75), but reduced activation in MC and PFC throughout the exercise (p = 0.027, d = 1.01 and p = 0.045, d = 0.95, respectively). Neither NME (p = 0.802, d = 0.34) nor EEG-EMG coherence (p = 0.628, d = 0.21) was different between CAF and PLA. The results suggest that CAF improved muscular performance through a modified central nervous system (CNS) response rather than through alterations in peripheral muscle or central-peripheral coupling.

The Impact of Sex and Performance Level on Pacing Behavior in a 24-h Ultramarathon.

Purpose: We analyzed the impact of sex, performance level and substantial speed reductions (SSR) on pacing in the VI Rio 24-h Marines Ultramarathon. This will provide insights into the importance of minimizing speed variations in relation to optimal pacing in endurance events. Methods: Runners (30 males and 21 females), classified as high- (HP) and low-performance (LP) ran the race while having their time recorded every 400 m. The pacing was analyzed as the first 10% (initial epoch), the following 80% (intermediate epoch) and the last 10% of the race (final epoch). The time percentage spent at speeds <3.5 km·h-1 (SSR), 3.5 to 5.9 km·h-1 (walking speed), 6.0 to 8.0 km·h-1 (walk-to-running transition speed) and > 8.0 km·h-1 (running speed) was calculated. Results: Runners showed a reverse J-shaped pacing (P < 0.001) regardless of sex and performance level, although male (P < 0.004) and HP runners (P < 0.001) have preserved a higher mean speed throughout the race. Male and HP runners spent more time at running speed (P < 0.001) and less time at SSR (P < 0.001) than female and LP runners. Total distance was inversely correlated with the number of SSR and speed CV in male (r = -0.47 and r = -0.64, respectively) and female (r = -0.61 and r = -0.47, respectively). Conclusion: Male, HP runners showed less SSR, conserving a higher mean speed with less variation throughout the race. Results suggest that conservative pacing strategies, with lower speeds in the beginning and higher speeds toward the end, may be the most adequate for different endurance running disciplines. Results also show different competition dynamics between men and women, which warrants further exploration in ultramarathons as well as other IAAF events.

Pacing Strategy During Simulated Mountain Bike Racing.

Cross-country mountain biking (XCO) is a popular high-intensity endurance cycling event, but XCO pacing strategy has not been fully examined. This study examined the pacing strategies of different XCO athletes during a laboratory-simulated XCO performance test. Brazilian cyclists classified as performance-cohort level 3 performed an XCO race simulation. The simulation consisted of four 10-km laps with a gradient of 0-10%. No group-vs-time interaction was found in lap time (P = .169), absolute (P = .719) and relative (P = .607) power output, ratings of perceived exertion (P = .182), or heart rate (P = .125). There was a time main effect, as athletes decreased power output by 0.3 W/kg throughout the XCO simulation, thereby resulting in a 1.6-min decrement per lap. The power output corresponding to the onset of blood lactate accumulation adequately represented the mean power of the first lap. These results showed that 2 groups of cyclists with different training status adopted similar pacing strategies during an XCO race simulation, as they both used a fast-starting pacing strategy followed by positive pacing that resulted in a linear decrease in power output at every lap.

Prediction of Affective Responses in Aerobic Exercise Sessions.

The objective of the present study was to verify which physiological (percentage of maximum oxygen consumption--%VO2 or percentage of maximum heart rate--%HR) or psychological (ratings of perceived exertion--RPE) variable is the best predictor of affective responses during continuous (CT) and interval (HIT) exercise sessions. Fourteen men underwent 3 exercise sessions on the treadmill. In the first session, a graded exercise test was performed to determine the maximum HR, peak VO2, and the respiratory compensation point (RCP). Then, participants performed the CT and HIT exercise in a counterbalanced order. The HIT session consisted of 2 min stimuli with an intensity of 100% of peak VO2 interspersed with periods of passive recovery. The average intensities of both exercise sessions were equalized at 85% of RCP. Linear regression analyses of both exercise sessions showed higher prediction values of RPE (CT--R2=.54, p <.01; HIT--R2=.68, p<.01) compared to %VO2 (CT--R2=.04, p=.08; HIT--R2=0.3, p=.12) and %HR (CT--R2=.07, p=.02; HIT--R2=.05, p=.05). Additionally, the results of the linear regression analysis between the Feeling Scale and physiological variables were not significant, indicating that the slope of the regression analysis was not different from zero. These results may be explained by the conscious mental processing required for the manifestation of both the RPE and the affective responses. In conclusion, the affective responses seem to be modulated not only by the intensity of exercise but also mostly by how the individual perceives this intensity.

Traditional models of fatigue and physical performance / Modelos tradicionais de fadiga e desempenho físico

ABSTRACT The origin of fatigue has been the focus of studies involved in sports performance, due to the necessity to clarify the mechanistic bases for the reduced capacity to perform considerable effort intensities. According to the traditional conception of fatigue, mechanisms may encompass peripheral and central sites of fatigue. Peripheral fatigue is understood as events related to an inefficient tissue oxygen delivery, metabolic accumulation, muscular acidosis and muscle substrate depletion. In contrast, the central fatigue is mostly related to events in the central nervous system (CNS) that may involve neurotransmitters changes, altered metabolic profile and elevated temperature. Therefore, the current review aimed to discuss the peripheral and central mechanisms of fatigue, thus driving interpretations of the phenomenon.

RESUMO A etiologia da fadiga tem sido objeto de estudo em pesquisas relacionadas ao desempenho esportivo em função da necessidade de esclarecer os mecanismos que reduzem a capacidade de manutenção do desempenho em intensidades elevadas de esforço. A concepção tradicional de fadiga assume que os mecanismos possam ser desencadeados em sítios de ação central ou periférica. A fadiga periférica é compreendida como uma oferta inadequada de oxigênio tecidual, acúmulo de metabólitos e depleção de substrato energético acelerando a acidose muscular. A fadiga central, por sua vez, oriunda do sistema nervoso central (SNC), apresenta alterações nos neurotransmissores, podendo alterar o perfil metabólico e temperatura do SNC. Desta forma, a presente revisão tem como intuito abordar os mecanismos de fadiga central e periférica, norteando futuras interpretações sobre o fenômeno.

Two-year citations of JAPPL original articles: evidence of a relative age effect.

Several indicators have been used to analyze scientific journals, with the impact factor and the number of citations in a 2-yr calendar time frame (2-YRC) being the most common factors. However, considering that the Journal of Applied Physiology (JAPPL) appears monthly and that calculations of these indicators are based on citations of papers published in previous years, we hypothesized that articles published at the beginning of the year would be cited more in the 2-YRC compared with those appearing in the last issues of the year, a phenomena known as a relative age effect. Our objective was to confirm the existence of a relative age effect in the 2-YRC for original articles published in JAPPL. From 2005 to 2008, a total of 1,726 original articles were published, according to the Web of Science, and 9,973 citations in 2-YRC, varying from 0 to 45, with a mean of 5.78 for individual papers. Although there were no differences in the number of original articles published in a given month (P = 0.99), the 2-YRC varied considerably throughout the year, being higher for those earlier issues of the year, as shown by the linear regression analysis (r(2) = 0.76; P < 0.001). The 2-YRC began at 6.62 during the first 3 mo of the year, dropping by 10% at each 3-mo period. In summary, the longer an article has been out there, the more citations it collects. The relative age effect is a potential confounding variable for the assessment and interpretation of 2-YRC (using calendar years) from JAPPL original articles.

Provável reserva neurofisiológica na execução de exercícios aeróbios máximos / Probable reserves neurophysiological in the execution of maximum aerobic exercises

O modelo tradicional de fisiologia do exercício assume que existe um limite periférico (muscular) em todo exercício aeróbio máximo, devido à hipóxia severa causada pela oferta inadequada de oxigênio ao músculo esquelético. Este evento seria coincidente com o recrutamento de todas as unidades motoras disponíveis no músculo ativo, no mesmo instante. Entretanto, evidências recentes não se ajustam a estas predições. Pelo contrário, um modelo de regulação central do esforço defende a existência de reserva neurofisiológica em todo exercício aeróbio máximo. Nessa nova interpretação, o sistema nervoso central (SNC) modularia o recrutamento muscular para impedir a ativação de todas as unidades motoras ao mesmo tempo, e evitar o excesso de dano à matriz celular. Tal modulação realizada pelo SNC seria um mecanismo natural de defesa do organismo contra a falha catastrófica e o rigor mortis. Alguns resultados obtidos pelo Grupo de Estudo em Psicofisiologia do Exercício poderiam ser interpretados de acordo com a presença de uma reserva neurofisiológica, pois a potência mecânica máxima (WMAX) num teste incremental máximo foi aumentada após ingestão de cafeína e placebo percebido como cafeína, porém, sem alteração no consumo máximo de oxigênio (VO2MAX), sugerindo não haver limitação periférica. Entretanto, estudos devem ser desenhados para responder essa questão de forma mais consistente, incluindo medidas metabólicas e de excitabilidade dos músculos esqueléticos, mas também do SNC, durante exercício.

The traditional model of exercise physiology assumes that there would be a peripheral (muscular) limit in maximal aerobic exercises due to severe hypoxia derived from inadequate oxygen supply to the skeletal muscles. This event is to be coincident with the total recruitment of available motor units in the active muscles. However, recent evidence does not agree with these predictions. Rather, a centrally-regulated effort model argues that there is a neurophysiological reserve in all maximal aerobic exercises. In this new interpretation the central nervous system (CNS) would modulate the muscle recruitment to prevent the recruitment of all available motor units at the same time in order to avoid excessive harm in cellular matrixes. Such modulation performed by the CNS would be a natural mechanism to defend the body against catastrophic failure and rigor mortis. Some results obtained by the Exercise Psychophysiology Research Group may be interpreted according to this neurophysiological reserve as the peak power output (WPEAK) in a maximum incremental test was increased after caffeine and placebo perceived as caffeine ingestion, but without change in maximal oxygen consumption (VO2MAX), suggesting no peripheral limitation. Yet, studies including measures of metabolic and skeletal muscle excitability in addition to the CNS function during exercise may answer this question closer.

Reprodutibilidade do VO2Máx estimado na corrida pela frequência cardíaca e consumo de oxigênio de reserva / Reliability of VO2Max estimated in treadmill running by heart rate reserve and power outpuT

Objetivou-se comparar os efeitos de utilização da frequência cardíaca máxima medida (FCpico) vs. predita (FC Predita) na estimativa do VO2Máx em esteira pelo método de FC e VO2 de reserva. Dezoito homens (27,5 ± 7,1 anos, 73,7 ± 12,6 kg, 174,8 ± 10,2 cm) realizaram na primeira visita um teste progressivo máximo para determinar a FCpico. Nas duas visitas seguintes foram realizados os testes aeróbios submáximos em esteira com estágio de 6 min a 75% da FC de reserva. O VO2Máx foi estimado pelo uso conjunto das equações de FC, VO2 de reserva e equação de corrida do ACSM. Não foi observada diferença significativa (teste t) entre as estimativas de VO2Máx a partir da FCpredita e FCpico. O coeficiente de correlação intraclasse e erro típico da medida utilizando FCpredita e FCpico foram 0,89, 2,43 mL.kg-1.min-1 (5%) e 0,83, 2,43 mL.kg-1.min-1 (4,9%), respectivamente. O uso da abordagem estimada para determinação da FC máxima mostrou-se adequado para a determinação do VO2Máx com um pequeno erro típico da medida.

The objective was to determine the reliability of the VO2Max estimate on a treadmill using the measured (HRpeak) vs. the predicted (HRpredicted) maximum heart rate (HR). Eighteen men (27.5 ± 7.1 years, 73.7± 12.6 kg, 174.8 ± 10.2 cm) performed, in the first visit, a progressive test to determine the HRpeak. In the two following visits, submaximal aerobic tests were performed on a treadmill with a 6 min at 75% HR reserve. VO2Max was estimated by means of the equations of HR, VO2 reserve and the ACSM running equation. The intraclass correlation coefficient and the typical error of measurement using HRPredicted and HRpeak were 0.89, 2.43 ml.kg-1.min-1 (5%) and 0.83, 2.43 mL.kg-1.min-1 (4.9%), respectively. There was no significant difference (t test) between the estimates of VO2Max from the HRpeak and HRpredicted. The use of the HRpredicted was considered appropriate for VO2Max estimation, with a small typical error of measurement.