argument is often, if not acrimonious, at least heated. It gives an impression of the fluidity of opinion on many fundamental ideas under discussion and of the urgency with which cardiac cyanosis in the newborn is regarded. When Dr. William Muscott says that the earliest he has operated for pulmonary stenosis is on an infant 3 days old, and Sir Russell Brock agrees that the earlier in the first month that operation is undertaken the better, and when Dr. Varco asks Dr. Senning 'so far as I know they have never yet catheterized any child intrauterine in Sweden, but they have done it through the delivery canal sometimes-would you tell us the indications of the Scandinavian group for catheterization in the immediate newborn period?', one is indeed being kept up with the times. But that was two years ago and already some of the questions then debated have since been answered. This beautifully printed and well-illustrated stiff paperbacked volume is, and will for a few years yet remain, an invaluable companion to a full-scale textbook on congenital heart disease.

Growth at Adolescence.

Principles and Practice of Sleep Medicine

Heart rate variability (HRV), the change in the time intervals between adjacent heartbeats, is an emergent property of interdependent regulatory systems that operate on different time scales to adapt to challenges and achieve optimal performance. This article briefly reviews neural regulation of the heart, and its basic anatomy, the cardiac cycle, and the sinoatrial and atrioventricular pacemakers. The cardiovascular regulation center in the medulla integrates sensory information and input from higher brain centers, and afferent cardiovascular system inputs to adjust heart rate and blood pressure via sympathetic and parasympathetic efferent pathways. This article reviews sympathetic and parasympathetic influences on the heart, and examines the interpretation of HRV and the association between reduced HRV, risk of disease and mortality, and the loss of regulatory capacity. This article also discusses the intrinsic cardiac nervous system and the heart-brain connection, through which afferent information can influence activity in the subcortical and frontocortical areas, and motor cortex. It also considers new perspectives on the putative underlying physiological mechanisms and properties of the ultra-low-frequency (ULF), very-low-frequency (VLF), low-frequency (LF), and high-frequency (HF) bands. Additionally, it reviews the most common time and frequency domain measurements as well as standardized data collection protocols. In its final section, this article integrates Porges’ polyvagal theory, Thayer and colleagues’ neurovisceral integration model, Lehrer et al.’s resonance frequency model, and the Institute of HeartMath’s coherence model. The authors conclude that a coherent heart is not a metronome because its rhythms are characterized by both complexity and stability over longer time scales. Future research should expand understanding of how the heart and its intrinsic nervous system influence the brain.

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A healthy heart is not a metronome: an integrative review of the heart's anatomy and heart rate variability.

Mental health symptoms and disorders are common among elite athletes, may have sport related manifestations within this population and impair performance. Mental health cannot be separated from physical health, as evidenced by mental health symptoms and disorders increasing the risk of physical injury and delaying subsequent recovery. There are no evidence or consensus based guidelines for diagnosis and management of mental health symptoms and disorders in elite athletes. Diagnosis must differentiate character traits particular to elite athletes from psychosocial maladaptations.Management strategies should address all contributors to mental health symptoms and consider biopsychosocial factors relevant to athletes to maximise benefit and minimise harm. Management must involve both treatment of affected individual athletes and optimising environments in which all elite athletes train and compete. To advance a more standardised, evidence based approach to mental health symptoms and disorders in elite athletes, an International Olympic Committee Consensus Work Group critically evaluated the current state of science and provided recommendations.

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Mental health in elite athletes: International Olympic Committee consensus statement (2019).

Although its true function remains unclear, sleep is considered critical to human physiological and cognitive function. Equally, since sleep loss is a common occurrence prior to competition in athletes, this could significantly impact upon their athletic performance. Much of the previous research has reported that exercise performance is negatively affected following sleep loss; however, conflicting findings mean that the extent, influence, and mechanisms of sleep loss affecting exercise performance remain uncertain. For instance, research indicates some maximal physical efforts and gross motor performances can be maintained. In comparison, the few published studies investigating the effect of sleep loss on performance in athletes report a reduction in sport-specific performance. The effects of sleep loss on physiological responses to exercise also remain equivocal; however, it appears a reduction in sleep quality and quantity could result in an autonomic nervous system imbalance, simulating symptoms of the overtraining syndrome. Additionally, increases in pro-inflammatory cytokines following sleep loss could promote immune system dysfunction. Of further concern, numerous studies investigating the effects of sleep loss on cognitive function report slower and less accurate cognitive performance. Based on this context, this review aims to evaluate the importance and prevalence of sleep in athletes and summarises the effects of sleep loss (restriction and deprivation) on exercise performance, and physiological and cognitive responses to exercise. Given the equivocal understanding of sleep and athletic performance outcomes, further research and consideration is required to obtain a greater knowledge of the interaction between sleep and performance.

Sleep and athletic performance: the effects of sleep loss on exercise performance, and physiological and cognitive responses to exercise.

The purpose of this study was to determine whether delaying bedtime or advancing rising time by 4 h affects anaerobic performance of individuals the following day in the morning and afternoon. Eleven subjects participated in the study, during which we measured the maximal, peak, and mean powers (i.e., P(max) [force-velocity test], P(peak), and P(mean) [Wingate test], respectively). Measurements were performed twice daily, at 07:00 and 18:00 h, following a reference normal sleep night (RN), a partial sleep deprivation timed at the beginning of the night (SDB), and a partial sleep deprivation timed at the end of the night (SDE), and oral temperature was measured every 4 h. Each of the three experimental conditions was separated by a one-week period. Our results showed a circadian rhythm in oral temperature, and analysis of variance revealed a significant sleep x test-time effect on peak power (P(peak)), mean power (P(mean)), and maximal power (P(max)). These variables improved significantly from the morning to the afternoon for all three experimental conditions. Whereas the morning-afternoon improvement in the measures was similar after the RN and SDB conditions, it was smaller following the SDE condition. There was no significant difference in the effect of the two sleep-deprivation conditions on anaerobic performances at 07:00 and at 18:00 h under the SDB condition in comparison with the post-reference night. However, the performance variables were significantly lower at 18:00 h after the SDE condition. In conclusion, a 4 h partial sleep deprivation at the end of the night appears to be more disturbing than partial sleep deprivation at the beginning of the night.

Effect of Time of Day and Partial Sleep Deprivation on Short‐Term, High‐Power Output

This study assessed the effects of partial sleep deprivation on short-term maximal performances of judokas in the morning and afternoon of the following day. In a randomized design, 12 judokas completed the maximal voluntary contraction, the handgrip, and the Wingate tests before and after a judo combat. Measurements were performed at 09:00 and 16:00 hours after a reference-normal sleep night and 2 conditions of 4-hour partial sleep deprivation timed at the beginning (SDB) or at the end of the night (SDE). The results showed that muscle power and strength were significantly higher at 16:00 than 09:00 hours (p < 0.05). These diurnal variations disappeared after SDB and SDE and after the combat. In addition, SDE resulted in significant decreases of short-term maximal performance in the afternoon (p < 0.01). In conclusion, SDE decreased muscle strength and power at 16:00 hours and, therefore, might have blunted the diurnal variations of short-term maximal exercise. Thus, early rising is more detrimental than late bedtime to muscle strength and power for judo athletes when competitions are scheduled in the afternoon hours.

Effects of time-of-day and partial sleep deprivation on short-term maximal performances of judo competitors.

The purpose of this investigation was to assess the effects of training and tapering at the same time of the day on the diurnal variations of short exercise performances. Thirty-one physically active men underwent 12 weeks of lower-extremity resistance training and 2 weeks of tapering. These subjects were matched and randomly assigned to a morning training group (MTG, training times 0700-0800 hours, n = 10), an evening training group (ETG, training times 1700-1800 hours, n = 11), and a control group (CG, completed all tests but did not train, n = 10). Muscular strength and power testing was conducted before (T0) and after 12 weeks of training (T1) and after 2 weeks of tapering (T2) in the morning (0700-0800 hours) and in the evening (1700-1800 hours). All morning and evening tests were performed in separate sessions (minimum interval = 36 hours) in a randomized design. In T0, the oral temperature and performances during the Wingate, vertical jump (squat jump and countermovement jump), and maximal voluntary contraction tests were higher in the evening than in the morning for all the groups. In T1, these diurnal variations were blunted in the MTG and persisted in the ETG and CG. In T2, the 2 weeks of tapering resulted in further time of day-specific adaptations and increases in short-term maximal performances. However, there was no significant difference in the relative increase between the MTG and the ETG after both training and tapering. From a practical point of view, if the time of competition is known, training and tapering sessions before a major competition must be conducted at the same time of the day at which one's critical performance is programmed. Moreover, if the time of the competition is not known, a tapering phase after resistance training program could be performed at any time of the day with the same benefit.

The effect of training at the same time of day and tapering period on the diurnal variation of short exercise performances.

The present study was designed to evaluate time-of-day effects on electromyographic (EMG) activity changes during a short-term intense cycling exercise. In a randomized order, 22 male subjects were asked to perform a 30-s Wingate test against a constant braking load of 0.087 kg·kg−1 body mass during two experimental sessions, which were set up either at 07:00 or 17:00 h. During the test, peak power (Ppeak), mean power (Pmean), fatigue index (FI; % of decrease in power output throughout the 30 s), and evolution of power output (5-s span) throughout the exercise were analyzed. Surface EMG activity was recorded in both the vastus lateralis and vastus medialis muscles throughout the test and analyzed over a 5-s span. The root mean square (RMS) and mean power frequency (MPF) of EMG were calculated. Neuromuscular efficiency (NME) was estimated from the ratio of power to RMS. Resting core temperature, Ppeak, Pmean, and FI were significantly higher (p < .05) in the evening than morning test (e.g., Ppeak: 11.6 ± 0...

Diurnal variation in Wingate-test performance and associated electromyographic parameters.

This study examined the effects of Ramadan fasting on anaerobic performances and their diurnal fluctuations. In a balanced and randomized study design, 12 subjects were measured for maximal power (P(max); force-velocity test), peak power (P(peak)), and mean power (P(mean)) with the Wingate test at 07:00, 17:00, and 21:00 h on four different occasions: one week before Ramadan (BR), the second week of Ramadan (SWR), the fourth week of Ramadan (ER), and two weeks after Ramadan (AR). There was an interval of 28 h between any two successive tests. Oral temperature was measured before each test. Under each condition, the results showed a time-of-day effect on oral temperature. Analysis of variance revealed a significant (Ramadanxtime-of-day of test) interaction effect on P(max). This variable improved significantly from morning to evening before Ramadan (1.1+/-0.2 W x kg(-1)), during the second week of Ramadan (0.6+/-0.2 W x kg(-1)), and two weeks after the end of Ramadan (0.9+/-0.2 W x kg(-1)). However, daily fluctuations disappeared during the fourth week of Ramadan. For P(peak) and P(mean), there was no significant Ramadan x test-time interaction. These variables improved significantly from morning to evening before Ramadan ([1+/-0.3 W x kg(-1)] for P(peak) and [1.7+/-1.6 W x kg(-1)] for P(mean)) and in the second week of Ramadan ([0.9+/-0.6 W x kg(-1)] for P(peak) and [1.7+/-1.5 W x kg(-1)] for P(mean)). However, they were not affected by time-of-day in the fourth week of Ramadan. Considering the effect of Ramadan on anaerobic performances, in comparison with before Ramadan, no significant difference was observed during Ramadan at 07:00 h. The variables were significantly lower in the second week of Ramadan and in the fourth week of Ramadan at 17:00 h and 21:00 h. P(mean) was not affected during the second week of Ramadan. In conclusion, the time-of-day effect on anaerobic power variables tends to disappear during Ramadan. In comparison with the period before Ramadan, anaerobic performances were unaffected in the morning but impaired in the evening during Ramadan.

Mohamed Dogui

Papers

Effect of Time of Day and Partial Sleep Deprivation on Short‐Term, High‐Power Output

Effects of time-of-day and partial sleep deprivation on short-term maximal performances of judo competitors.

The effect of training at the same time of day and tapering period on the diurnal variation of short exercise performances.

Diurnal variation in Wingate-test performance and associated electromyographic parameters.

Effect of Ramadan on the diurnal variation in short-term high power output.