Ventilatory response to peripheral chemoreflex and muscle metaboreflex during static handgrip in healthy humans: evidence of hyperadditive integration.

NEW FINDINGS: What is the central question of this study? What is the effect of peripheral chemoreflex and muscle metaboreflex integration on ventilation regulation, and what is the effect of integration on breathing-related sensations and emotions? What is the main finding and its importance? Peripheral chemoreflex and muscle metaboreflex coactivation during isocapnic static handgrip exercise appeared to elicit a hyperadditive effect with regard to ventilation and an additive effect with regard to breathing-related sensations and emotions. These findings reveal the nature of the integration between two neural mechanisms that operate during small-muscle static exercise performed under hypoxia. ABSTRACT: Exercise augments the hypoxia-induced ventilatory response in an exercise intensity-dependent manner. A mutual influence of hypoxia-induced peripheral chemoreflex activation and exercise-induced muscle metaboreflex activation might mediate the augmentation phenomenon. However, the nature of these reflexes' integration (i.e., hyperadditive, additive or hypoadditive) remains unclear, and the coactivation effect on breathing-related sensations and emotions has not been explored. Accordingly, we investigated the effect of peripheral chemoreflex and muscle metaboreflex coactivation on ventilatory variables and breathing-related sensations and emotions during exercise. Fourteen healthy adults performed 2-min isocapnic static handgrip, first with the non-dominant hand and immediately after with the dominant hand. During the dominant hand exercise, we (a) did not manipulate either reflex (control); (b) activated the peripheral chemoreflex by hypoxia; (c) activated the muscle metaboreflex in the non-dominant arm by post-exercise circulatory occlusion (PECO); or (d) coactivated both reflexes by simultaneous hypoxia and PECO use. Ventilation response to coactivation of reflexes (mean ± SD, 13 ± 6 l/min) was greater than the sum of responses to separated activations of reflexes (mean ± SD, 8 ± 8 l/min, P = 0.005). Breathing-related sensory and emotional responses were similar between coactivation of reflexes and the sum of separate activations of reflexes. Thus, the peripheral chemoreflex and muscle metaboreflex integration during exercise appeared to be hyperadditive with regard to ventilation and additive with regard to breathing-related sensations and emotions in healthy adults.

How much does sleep deprivation impair endurance performance? A systematic review and meta-analysis.

We conducted a systematic review and meta-analysis to investigate the effect of sleep deprivation on endurance performance, as well as possible effect-modifying factors. Searches were done in Pubmed, Web of Science, Embase, and Scopus on 12 July 2022. We additionally searched the bibliographic references and citations on Google Scholar of the papers whose full text was analyzed. Eligible studies were randomized and non-randomized controlled trials that compared sleep deprivation and habitual-sleep night effects on endurance performance in healthy humans. The studies' quality was examined by the Cochrane Collaboration's risk of bias tool. We calculated the pooled standardized mean differences (pooled SMD) and 95% confidence interval (95%CI) by a random-effects model. A mixed-effects model analyzed subgroups. Thirty-one studies were analyzed (n = 478), generating 38 effect sizes in full. The overall risk of bias was low in 8% of the studies, unclear in 74%, and high in 18%. Sleep deprivation in general had a moderate negative effect on endurance performance (polled SMD [95%CI] = -0.52 [-0.67; -0.38]). Training status, sleep deprivation magnitude, assessment time, exercise mode, and endpoint type did not influence the sleep deprivation effect, whereas longer exercises (>30 min) were more affected by sleep deprivation than shorter ones (P = 0.035). Therefore, the available evidence supports that sleep deprivation's deleterious effect on endurance performance is of moderate size and depends on exercise duration. This information can be useful to estimate the performance decrement of endurance exercise practitioners under sleep deprivation in training routines and competitions.PROSPERO registration number CRD42021229717.

Sleep deprivation causes a moderate deleterious effect on endurance performance.Sleep deprivation similarly impairs endurance performance in untrained, recreationally-trained, and trained people, but its effect on well-trained and professional endurance athletes is unknown.One or more nights of partial sleep deprivation or one night of total sleep deprivation similarly compromise endurance performance. Uncertainties about the effect of more than one night of total sleep deprivation warrant more studies.Sleep deprivation impairs walking, running, and cycling endurance performance regardless of the exercise endpoint being unknown (i.e. incremental or constant load tests) or known (i.e. time trial tests) and assessment time. However, sleep deprivation causes a more deleterious effect on endurance performance in exercises lasting more than 30 min.

Perceived Exertion: Revisiting the History and Updating the Neurophysiology and the Practical Applications.

The perceived exertion construct creation is a landmark in exercise physiology and sport science. Obtaining perceived exertion is relatively easy, but practitioners often neglect some critical methodological issues in its assessment. Furthermore, the perceived exertion definition, neurophysiological basis, and practical applications have evolved since the perceived exertion construct's inception. Therefore, we revisit the careful work devoted by Gunnar Borg with psychophysical methods to develop the perceived exertion construct, which resulted in the creation of two scales: the rating of perceived exertion (RPE) and the category-ratio 10 (CR10). We discuss a contemporary definition that considers perceived exertion as a conscious perception of how hard, heavy, and strenuous the exercise is, according to the sense of effort to command the limbs and the feeling of heavy breathing (respiratory effort). Thus, other exercise-evoked sensations would not hinder the reported perceived exertion. We then describe the neurophysiological mechanisms involved in the perceived exertion genesis during exercise, including the influence of the peripheral feedback from the skeletal muscles and the cardiorespiratory system (i.e., afferent feedback) and the influence of efferent copies from the motor command and respiratory drive (i.e., corollary discharges), as well as the interaction between them. We highlight essential details practitioners should consider when using the RPE and CR10 scales, such as the perceived exertion definition, the original scales utilization, and the descriptors anchoring process. Finally, we present how practitioners can use perceived exertion to assess cardiorespiratory fitness, individualize exercise intensity prescription, predict endurance exercise performance, and monitor athletes' responses to physical training.

No Sex Difference in Mental Fatigue Effect on High-Level Runners' Aerobic Performance.

PURPOSE: Some evidence suggests that sedentary women may be more vulnerable to cognitive task-induced mental fatigue. Mental fatigue, in turn, may worse aerobic exercise performance, presumably via increased perceived effort. However, it remains unclear whether acute mental fatigue induction increases perceived effort and worsens endurance performance in high-level professional athletes and whether such effects are influenced by sex. METHODS: We studied 30 athletes (15 women and 16 men) in a single-blinded, randomized, controlled and crossover protocol. In separate visits, athletes either performed a 45-min cognitive task (Stroop's color-word conflict test) to induce mental fatigue or watched a 45-min documentary as control. Then athletes performed a time-to-exhaustion test on a treadmill. RESULTS: Perceptual measures and cognitive performance indicated that the prolonged cognitive task induced a similar mental fatigue state in women and men. Cardiorespiratory and metabolic responses to the TEE did not change with mental fatigue in both sexes. Mental fatigue increased perceived effort during the time-to-exhaustion test, anticipated attainment of maximal effort, and shortened time to exhaustion similarly in women and men (mean ± SE, -27.3 ± 20.9 s for women vs -26.7 ± 15.1 s for men; P = 0.98). CONCLUSIONS: The prolonged cognitive task provoked mental fatigue, anticipated attainment of maximal perceived effort, and worsened aerobic performance in professional runners with no sex differences. Although we did not contrasted athletes with nonathletes, our results suggest that being an athlete may somehow prevent women from developing greater mental fatigue and suffering more from its underlying effects compared with men.

Correction: Effects of moderate vs. high iso-inertial loads on power, velocity, work and hamstring contractile function after flywheel resistance exercise.

[This corrects the article DOI: 10.1371/journal.pone.0211700.].

Effects of moderate vs. high iso-inertial loads on power, velocity, work and hamstring contractile function after flywheel resistance exercise.

Flywheel iso-inertial training has been shown to positively affect muscular strength and sports performance (e.g. agility). However, implementing such eccentrically-biased training during a microcycle needs to be carefully planned due to its purported effects on the neuromuscular system that can last for hours/days post-exercise. This study aimed at using tensiomyography to verify the effects of different inertias during the hip extension exercise on the contractile function of biceps femoris and semitendinosus muscles of the dominant leg for up to 72 hours post-exercise. Thirty participants (24.4 ± 3.4 years) were divided into 0.075 or 0.1 kg·m2 inertia groups and a control group. Magnitude-based analysis was used for the comparisons. Several tensiomyography parameters were changed after both intensities of flywheel exercise (in most cases indicating a decrement in muscle stiffness), whereas most between-group differences suggested that in the semitendinosus muscle, the higher inertia (0.1 kg·m2) influenced the muscle stiffness parameters more (e.g. Dm = maximal radial displacement) while in the biceps femoris, the greater effect was caused by the lower inertia (0.075 kg·m2) (e.g. Tc = contraction time). Most changes in contractile properties of the investigated muscles occur within 24 hours post-exercise, but can persist for up to 72 hours. However, higher inertia (0.1 kg·m2) influenced the stiffness of the semitendinosus muscle more, while in the biceps femoris, the greater effect was caused by the lower inertia (0.075 kg·m2). These findings should be considered by practitioners when prescribing flywheel iso-inertial training.

Mental fatigue does not affect heart rate recovery but impairs performance in handball players / Fadiga mental não altera a recuperação da frequência cardíaca, mas afeta o desempenho de jogadores de handebol / Fatiga mental no varía la reparación de frecuencia cardiaca y muda el rendimiento en balonmano

INTRODUCTION: This study involved an analysis of the impact of mental fatigue on heart rate recovery (HRR), subjective measures of fatigue and intermittent running performance in handball players. OBJECTIVE: This study was aimed at (1) examining the effects of an induced state of mental fatigue on the aerobic performance of handball players, as measured by the Yo-Yo IR1 test, and (2) exploring possible changes in heart rate regulation through HRR analysis. METHODS: Twelve handball players (age: 17.50 ± 3.63 years; 5 ± 2.2 years of practice) undertook a Yo-Yo IR1 test on two occasions, separated by an interval of at least 72 hours. The Yo-Yo IR1 test was preceded by a 30-min treatment, consisting of the Stroop Color-Word Test, to induce mental fatigue. Participants in the control condition watched an emotionally neutral video. RESULTS: Higher ratings of mental fatigue and mental effort following the Stroop Test were observed for the experimental group. No differences in motivation were observed between conditions. Moreover, the induction of mental fatigue impaired running performance and led to a higher RPE during the Yo-Yo IR1 test. Notwithstanding, no changes in HRR or blood lactate levels were observed across conditions. CONCLUSION: Altogether, these results suggest that mental fatigue impairs intermittent running performance, without affecting HRR values. Level of Evidence III; Case-Control study.

INTRODUÇÃO: Este estudo envolveu uma análise do impacto da fadiga mental sobre a recuperação da frequência cardíaca (RFC), medidas subjetivas de fadiga e desempenho de corrida intermitente em jogadores de handebol. OBJETIVO: Este estudo visou (1) examinar os efeitos de um estado induzido de fadiga mental no desempenho aeróbico de jogadores de handebol, medido pelo teste Yo-Yo IR1 e (2) explorar possíveis alterações na regulação da frequência cardíaca através da análise da RFC. MÉTODOS: Doze jogadores de handebol (idade: 17,50 ± 3,63 anos, 5 ± 2,2 anos de prática) realizaram um teste Yo-Yo IR1 em duas ocasiões, com pelo menos 72 horas de intervalo. O teste Yo-Yo IR1 foi precedido por tratamento de 30 minutos que consistiu no teste Stroop Color-Word para induzir estado de fadiga mental. Os participantes na condição de controle assistiram a um vídeo emocionalmente neutro. RESULTADOS: Foram observadas taxas mais elevadas de fadiga mental e esforço mental após o teste Stroop para o grupo experimental. Não foram observadas diferenças na motivação entre as condições. Além disso, a indução de fadiga mental prejudicou o desempenho de corrida e levou a maior PSE durante o teste Yo-Yo IR1. Não obstante, não foram observadas alterações na RFC nem nas concentrações de lactato sanguíneo entre as condições. CONCLUSÃO: Em conjunto, esses resultados sugerem que a fadiga mental afeta o desempenho de corrida intermitente, sem alterar os valores de RFC. Nível de Evidência III; Estudo de caso-controle.

INTRODUCCIÓN: En el presente estudio se analizó el impacto de la fatiga mental en la recuperación de la frecuencia cardíaca (RFC), las medidas subjetivas de fatiga y el rendimiento intermitente en atletas de handball. OBJETIVO: los objetivos de este estudio fueron (1) examinar los efectos de un estado inducido de fatiga mental en el rendimiento aeróbico de atletas de handball, medida por el Yo-Yo IR1, y (2) explorar las posibles alteraciones en la regulación de la frecuencia cardíaca a través del análisis RFC. MÉTODOS: Doce atletas (edad: 17,50 ± 3,63 años, 5 ± 2,2 años de práctica) realizaron un test Yo-Yo IR1 en dos ocasiones, separados por un intervalo de al menos 72 horas. El test Yo-Yo IR1 fue precedido por un tratamiento de 30 minutos, consistente en el Stroop Color-Word Test, para inducir un estado de fatiga mental. Los participantes en la condición de control asistieron un video emocionalmente neutro. RESULTADOS: Se observaron altas percepciones de fatiga y esfuerzo mental después del test de Stroop para el grupo experimental. No se observaron diferencias de motivación entre las condiciones. Además, la inducción de fatiga mental perjudicó el desempeño de carrera y llevó a un mayor PSE durante el test Yo-Yo IR1. No obstante, no se observaron alteraciones en la RFC y en las concentraciones de lactato sanguíneo entre las condiciones. CONCLUSIÓN: En conjunto, estos resultados sugieren que la fatiga mental afecta el rendimiento intermitente de la carrera, sin alterar los valores de FCR. Nivel de Evidencia III; Estudio de caso-control.

Análise renal de ultramaratonista em prova de 75 km / Renal analysis in 75 km ultra-marathon participants / Análisis renal de corredora en la prueba de 75 kilómetros

Objetivo: Identificar alterações urinárias compatíveis com comprometimento renal em ultramaratonista e "pacer" (ciclista de apoio) ao longo de uma prova de 75 quilômetros. Métodos: Para tal, utilizou-se teste de urina com fita reagente em quatro tempos diferentes, além de avaliação antropométrica. Resultados: As medidas concernentes a ultramaratonista a classificaram como eutrófica, assim como o "pacer". Observou-se, assim, associação entre os momentos de esforço físico máximo e a detecção de alterações urinárias, definidas pela presença de hematúria e, por vezes, positivação da proteinúria. Conclusão: Foi possível ilustrar alteração transitória em dois indivíduos saudáveis submetidos a exercício intenso.

Objective: To identify urinary abnormalities, indicative of renal involvement, in 75 km ultra-marathon racer and pacer (cyclist that gives support to the racer). Methods: Renal analysis consisted of urine dipstick tests in four different times and anthropometric measures. Results: Both the racer and the pacer were in eutrophic conditions. There was an association between the capacity for maximum physical effort and detection of urinary abnormalities determined by the presence of hematuria and/or proteinuria. Conclusion: Renal analysis allowed the identification of transitory renal involvement in both healthy individuals during intense exercise.

Objetivo: Identificar alteraciones urinarias compatibles con compromiso renal en una corredora y un "pacer" (ciclista de apoyo) a lo largo de una prueba de 75 Kilómetros. Métodos: Para tal efecto, se utilizó un test de orina con cinta reactiva aplicado en cuatro tiempos diferentes, además de una evaluación antropométrica. Resultados: Las medidas concernientes a la corredora la clasificaron como eutrófica, así como el "pacer". Se observó que existe asociación entre los momentos de esfuerzo físico máximo y la detección de alteraciones urinarias, definidas por la presencia de hematuria y, a veces, proteinuria. Conclusión: Fue posible demostrar la alteración transitoria en dos individuos saludables sometidos a ejercicio intenso.