Daytime naps can be used to supplement night-time sleep in athletes

ABSTRACT

This study examined the efficacy of daytime napping to supplement night-time sleep in athletes. Twelve well-trained male soccer players completed three conditions in a randomised, counterbalanced order: 9 h in bed overnight with no daytime nap (9 h + 0 h); 8 h in bed overnight with a 1-h daytime nap (8 h + 1 h); and 7 h in bed overnight with a 2-h daytime nap (7 h + 2 h). Sleep was assessed using polysomnography. The total amount of sleep obtained in the three conditions was similar, i.e. 8.1 h (9 h + 0 h), 8.2 h (8 h + 1 h), and 8.0 h (7 h + 2 h). Daytime napping may be an effective strategy to supplement athletes’ night-time sleep.     

Effect of the period of resting in elite judo athletes

The purpose of this study was to evaluate the effect of the resting period on hematological and copper-zinc-dependent antioxidant indices in Brazilian elite judo athletes (n=7). Venous blood samples were collected after 24-h and 5-d periods of resting following a competition, with an interval of 30 d between collections. Two months prior to and during the study, each athlete received an individualized adequate diet. Body composition was determined at both study periods. The following were analyzed: in whole blood, hemoglobin, hematocrit, red cell count, mean corpuscular volume, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, red cell distribution width, and white cell count; in plasma, zinc, copper, iron, ceruloplasmin, and total iron-binding capacity; in erythrocytes, metallothionein, copper/zinc superoxide dismutase, and osmotic fragility. Dietary intake and body composition did not affect the biochemical measurements. A significant reduction in ceruloplasmin and superoxide dismutase activity was found after 5 d compared to 24 h of resting. A significant correlation between erythrocyte metallothionein and red cell distribution width was observed after 24 h of resting (r=−0.83, p=0.02) whereas positive correlations of metallothionein with hemoglobin, red cell count, and mean corpuscular hemoglobin concentration were observed after 5 d of resting (r≥0.76, p≤0.05). Our results suggest that a longer resting period favors homeostatic adjustments in the erythrocyte population and in the copper/zinc-dependent antioxidant system in elite judo athletes.     

Increased p wave dispersion in elite athletes

Background

Few studies have been performed on P wave indices in athletes. The aim of this study was to determine the behaviour of maximum P wave duration (Pmax), minimum P wave duration (Pmin) and P wave dispersion (PWD) in young high performance athletes, as well as the relationship of PWD with training history, heart rate (HR) and echocardiographic parameters.

Methods

We performed a cross-sectional observational study in 38 athletes of high performance in sports: water polo, distance running and weight lifting compared with 34 sedentary controls.

Results

The average age in both groups was 20.6 years. Note that PWD was increased in athletes (57 ± 14 ms vs. 40 ± 12 ms, p <0.001) while Pmin was significantly lower (57 ± 13 ms vs. 72 ± 13 ms, p <0.001), and there was no difference when comparing Pmax (114 ± 9 ms vs. 117 ± 14 ms, p> 0.05). The correlation between the duration of training (r = 0.511) and resting HR (r = 0.461) with PWD was significant (p <0.01).

Conclusions

PWD is increased in young athletes of high performance and was positively correlated with duration of training and baseline HR. The increase in PWD was secondary to a significant decrease in Pmin.     

Sleep quality and high intensity interval training at two different times of day: A crossover study on the influence of the chronotype in male collegiate soccer players

The influence of the chronotype on the sleep quality in male collegiate soccer players in response to acute high intensity interval training (HIIT) performed at two different times of day was evaluated. The sleep quality was poorer in the morning-type than in the evening-type players after the evening HIIT session, whereas no significant changes in the sleep quality of the two chronotypes after the morning HIIT session was observed. The results suggest that an athlete’s chronotype should be taken into account when scheduling training sessions and to promote faster recovery processes.     

Sleep duration and social jetlag are independently associated with anxious symptoms in adolescents

Although short total sleep time (TST) is associated with increased anxious symptoms in adolescents, it is unknown whether social jetlag, a misalignment between sleep timing on the weekend and school week, is independently associated with anxious symptoms. In the current study, sleep timing, anxious symptoms, and demographic information were assessed from 3097 adolescents (48% female, mean ± SD age 15.59 ± .77 years) from the age 15 wave of the Fragile Families and Child Wellbeing Study. Social jetlag was calculated as the absolute value of the midpoint of sleep on the weekend minus the midpoint of sleep during the school week. Anxious symptoms were measured through the 6-item anxiety subscale of the Brief Symptom Inventory 18. We assessed associations between sleep variables and anxious symptoms using multiple linear regression. Adjusted analyses controlled for sex, race/ethnicity, age in years, body mass index percentile, number of other children below the age of 18 in the household, and primary caregiver (PCG) married/cohabiting with youth’s biological parent, PCG employment status, PCG household income and PCG education level. In fully adjusted models (R² = .034), school night TST (b = ?.04, ?R² = .005, p < .001) was negatively associated with anxiety symptoms, while social jetlag (b = .04, ?R² = .009, p < .001) was positively and independently associated with anxiety symptoms. Findings indicate small associations of school night TST and social jetlag with anxious symptoms. Thus, maintenance of optimal emotional health in adolescents may require both sufficient sleep duration and regularity of sleep timing across the week.     

Adaptive control of copulation duration by males under sperm competition in the mite,Macrocheles muscaedomesticae

In a manure-inhabiting predatory mite, Macrocheles muscaedomesticae (Gamasida, Macrochelidae), when the female mates with two males, the first male takes nearly perfect fertilization priority (Yasui, 1988). The present study examined whether the first-male's sperm precedence is influenced by the copula-duration of the first and second males mating with the same female, and whether males control their copulation duration by assessing the probability that the mate has been inseminated by other males. Results of the artificial interruption of copulation showed that sperm precedence value, P₂ (the proportion of the offspring fathered by the second male), was negatively correlated with the copulation duration of the first male but positively correlated with that of the second male. There was a threshold (ca. 180–300 seconds) in the first-male's copulation duration beyond which P₂ decreased drastically; when length of the first copulation exceeded this threshold, the second males did not fertilize eggs, whereas they fertilized more than half of the eggs when the first-copulation duration was shorter than the threshold. Almost all males copulated for a longer period (average 509.8 seconds) than this threshold if the copulation duration of the previous male had not exceeded the threshold, but if it was longer than the threshold, second males had shortened their copulation (67.6 seconds). These results suggest that males are able to assess the insemination status of their mates and to adjust their copulation duration depending on the probability of fertilizing eggs by their own sperm. A mechanistic explanation for sperm precedence (i.e., plug-formation within sperm receptive organ of the females) is proposed.     

Sleep quality and sleep duration,but not circadian parameters are associated with decreased insulin sensitivity in Type 1 diabetes

ABSTRACT

The objective of this cross-sectional analysis was to investigate in 109 adults with type 1 diabetes the relationship between sleep, circadian parameters and insulin sensitivity, as assessed by estimated glucose disposal rate (eGDR). In multiple regression analysis only poor sleep quality and sleep duration were negatively associated with eGDR (β = ?0.219 [95%CI:-1.977; ?0.445], p = .002 for poor sleep quality; β = ?0.183 [95%CI: ?0.645; ?0.111], p = .006 for sleep duration) independent of age, gender, smoking status and body mass index. In conclusion, poor sleep quality and longer sleep duration were significant predictors of decreased insulin sensitivity. Social jetlag, chronotype, and sleep debt had no effect on insulin sensitivity.     

Effects of Transitions into and out of Daylight Saving Time on the Quality of the Sleep/Wake Cycle: an Actigraphic Study in Healthy University Students

The main goal of the present study was to examine the effects of transition into and out of daylight saving time (DST) on the quality of the sleep/wake cycle, assessed through actigraphy. To this end, 14 healthy university students (mean age: 26.86?±?3.25?yrs) wore an actigraph for 7?d before and 7?d after the transition out of and into DST on fall 2009 and spring 2010, respectively. The following parameters have been compared before and after the transition, separately for autumn and spring changes: bedtime (BT), get-up time (GUT), time in bed (TIB), sleep onset latency (SOL), fragmentation index (FI), sleep efficiency (SE), total sleep time (TST), wake after sleep onset (WASO), mean activity score (MAS), and number of wake bouts (WB). After the autumn transition, a significant advance of the GUT and a decrease of TIB and TST were observed. On the contrary, spring transition led to a delay of the GUT, an increase of TIB, TST, WASO, MAS, and WB, and a decrease of SE. The present results highlight a more strong deterioration of sleep/wake cycle quality after spring compared with autumn transition, confirming that human circadian system more easily adjusts to a phase delay (autumn change) than a phase advance (spring transition).     

Time or retiring and sleep quality may be predictors of academic performance and psychosomatic disorder in university students

In an effort to improve school performance, we have examined the effect of sleep–wake patterns, particularly time in bed, and morning psychosomatic conditions in adolescents. A psychosomatic disorder questionnaire was administered to 135 physically healthy students, who were divided into four groups according to time they went to bed: 23–24, 24–01, 01–02 and 02–03 h. (1) The 23–24 and 24–01 h groups had significantly higher grade point averages than the 02–03 h group. (2) Partial correlations, controlling for sleep quality, revealed significant associations between time to bed and psychosomatic disorder, with regard to whole-body fatigue, lack of motivation and the desire to rest. Our results suggest that the sleep–wake pattern, especially the time of retiring, may predict academic performance and psychosomatic disorder.     

Time-of-day variation in sustained attentional control

Sustained attention is a fundamental cognitive function underlying many activities in daily life including workplace safety, but its natural variation throughout the day is incompletely characterized. To examine time-of-day variation, we collected a large online data set (N = 6,363) with participation throughout the day and around the world on the gradual-onset continuous performance task, a sensitive measure of sustained attention. This allowed us to examine accuracy, attentional stability, and strategy. Results show that both accuracy and attentional stability peak between 9:00 and 11:00 a.m. and progressively decline throughout the day, whereas strategy is more stable.     

Adult Male Density Influences Juvenile Microhabitat Use in a Territorial Lizard

Habitat choice often has strong effects on performance and fitness. For many animals, optimal habitats differ across age or size classes, and individuals shift habitat use through ontogeny. Although many studies document ontogenetic habitat shifts for various taxa, most are observational and do not identify the causal factor of size‐specific habitat variation. Field observations of the brown anole lizard (Anolis sagrei) show that juveniles perch on shorter and thinner vegetation than adults. We hypothesized that this variation is due to adult males forcing smaller juveniles to less preferred habitat. To test this assertion, we manipulated adult male densities in mesh enclosures with artificial trees to examine the response of juvenile microhabitat choice. We found that adult male density had strong effects on juvenile perch height, perch width, and substrate use, suggesting that age‐class competition contributes to the observed ontogenetic differences in habitat choice. We also found that time of day significantly affected juvenile perch height and substrate use. In many cases, our results suggest that juveniles distance themselves from adults using different microhabitats from those used in our control ‘no‐adult’ treatment. However, these findings were often body size dependent and varied depending upon time of day. This study highlights the complexity of juvenile perching behavior and demonstrates the role of intraspecific interactions in shaping habitat use by juvenile animals.     

Shoot development in grapevine (Vitis vinifera) is affected by the modular branching pattern of the stem and intra- and inter-shoot trophic competition

BACKGROUND AND AIMS: Shoot architecture variability in grapevine (Vitis vinifera) was analysed using a generic modelling approach based on thermal time developed for annual herbaceous species. The analysis of shoot architecture was based on various levels of shoot organization, including pre-existing and newly formed parts of the stem, and on the modular structure of the stem, which consists of a repeated succession of three phytomers (P0-P1-P2). METHODS: Four experiments were carried out using the cultivar 'Grenache N': two on potted vines (one of which was carried out in a glasshouse) and two on mature vines in a vineyard. These experiments resulted in a broad diversity of environmental conditions, but none of the plants experienced soil water deficit. KEY RESULTS: Development of the main axis was highly dependent on air temperature, being linearly related to thermal time for all stages of leaf development from budbreak to veraison. The stable progression of developmental stages along the main stem resulted in a thermal-time based programme of leaf development. Leaf expansion rate varied with trophic competition (shoot and cluster loads) and environmental conditions (solar radiation, VPD), accounting for differences in final leaf area. Branching pattern was highly variable. Classification of the branches according to ternary modular structure increased the accuracy of the quantitative analysis of branch development. The rate and duration of leaf production were higher for branches derived from P0 phytomers than for branches derived from P1 or P2 phytomers. Rates of leaf production, expressed as a -function of thermal time, were not stable and depended on trophic competition and environmental conditions such as solar radiation or VPD. CONCLUSIONS: The application to grapevine of a generic model developed in annual plants made it possible to identify constants in main stem development and to determine the hierarchical structure of branches with respect to the modular structure of the stem in response to intra- and inter-shoot trophic competition.