Chronotype as a predictor of athletic performance in youth with mild intellectual disabilities

Aim

This study aimed to explore the influence of circadian rhythms on athletic performance in individuals with mild intellectual disabilities (ID), with a specific focus on elucidating the association between chronotype and various performance metrics.

Methods

The study was a cross-sectional study consisting of 30 male participants aged between 11 and 19 years and diagnosed with mild ID. The chronotypes of all participants were assessed using the Childhood Chronotype Questionnaire (CCQ). Performance assessments were divided into three groups. Group A tests [sit and reach, medicine ball throw (MBT), plank], group B tests [handgrip strength (HGS), standing long jump (SLJ), 20-m sprint (20 ms)] and group C tests [vertical jump (VJ), hanging with bent arm (HBA), Illinois agility test) in order to ensure adequate rest periods between tests and not to affect the results. These group tests were performed 48 h apart, between 09:00-10:00 and 17:00-18:00, after a dynamic warm-up session.

Results

Significant variations were observed in the sit-and-reach test (t = -4.154, d = -0.75, p < .001), HGS (t = -2.484, d = -0.45, p = .019), SLJ (t = -2.117, d = -0.38, p = .043), VJ (t = -5.004, d = -0.91, p < .001), and plank duration (t = -4.653, d = -0.84, p < .001). Evening performances showed improvement in MBT, HBA, 20 ms, and the Illinois agility test, although these differences were not statistically significant (p > .05). Notably, positive correlations were identified between participants' chronotypes and their performance in HBA (morning/evening; r = .693, p = .026; r = .656, p = .039, respectively) and the plank (evening; r = .717, p = .020), with negative correlations noted in the 20 ms (morning/evening; r = -.703, p = .023; r = -.710, p = .021, respectively).

Conclusion

The findings suggest that individuals with mild ID exhibit enhanced athletic performance during evening hours. These insights underscore the importance of considering chronotype in tailoring exercise interventions for this population to optimize outcomes.

Effect of circadian rhythm and menstrual cycle on physical performance in women: a systematic review

The literature has extensively investigated potential factors influencing women's performance, including the menstrual cycle and the circadian rhythm. However, review articles exploring the combined influence of both factors remain lacking in the literature. The study aimed to systematically review the literature on the relationship between the circadian rhythm and menstrual cycle on physical performance in women. The review followed the PRISMA guidelines. The search was performed on the Web of Science, PubMed, Scopus, SPORTDiscus, and Google Scholar databases. Of the 1205 records identified, four articles met the inclusion criteria. From four articles, two studies found a significant interaction between the time of day and phase of the menstrual cycle with physical performance. The isometric strength increased in the afternoon in the mid-luteal phase (versus the morning in the mid-luteal phase, p < 0.05), and the maximum cycling power was higher in the afternoon in the mid-follicular phase (versus the morning in the mid-follicular phase, p < 0.01). Our findings suggest that the time of day and the menstrual cycle phase affect physical performance, with the daytime potentially having a more significant influence. However, the results should be interpreted cautiously due to the limited studies and diverse methodologies used to monitor the menstrual cycle phase. This review reinforces the need for further investigation to understand better the combined effects of the circadian rhythm and menstrual cycle on women's physical performance.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=380965, identifier CRD42022380965.

Time-of-Day Effects of Exercise on Cardiorespiratory Responses and Endurance Performance-A Systematic Review and Meta-Analysis

ABSTRACT

Kang, J, Ratamess, NA, Faigenbaum, AD, Bush, JA, Finnerty, C, DiFiore, M, Garcia, A, and Beller, N. Time-of-day effects of exercise on cardiorespiratory responses and endurance performance-A systematic review and meta-analysis. J Strength Cond Res 37(10): 2080-2090, 2023-The time-of-day effect of exercise on human function remains largely equivocal. Hence, this study aimed to further analyze the existing evidence concerning diurnal variations in cardiorespiratory responses and endurance performance using a meta-analytic approach. Literature search was conducted through databases, including PubMed, CINAHL, and Google Scholar. Article selection was made based on inclusion criteria concerning subjects' characteristics, exercise protocols, times of testing, and targeted dependent variables. Results on oxygen uptake (V̇ o2 ), heart rate (HR), respiratory exchange ratio, and endurance performance in the morning (AM) and late afternoon or evening (PM) were extracted from the chosen studies. Meta-analysis was conducted with the random-effects model. Thirty-one original research studies that met the inclusion criteria were selected. Meta-analysis revealed higher resting V̇ o2 (Hedges' g = -0.574; p = 0.040) and resting HR (Hedges' g = -1.058; p = 0.002) in PM than in AM. During exercise, although V̇ o2 remained indifferent between AM and PM, HR was higher in PM at submaximal (Hedges' g = -0.199; p = 0.046) and maximal (Hedges' g = -0.298; p = 0.001) levels. Endurance performance as measured by time-to-exhaustion or the total work accomplished was higher in PM than in AM (Hedges' g = -0.654; p = 0.001). Diurnal variations in V̇ o2 appear less detectable during aerobic exercise. The finding that exercising HR and endurance performance were greater in PM than in AM emphasizes the need to consider the effect of circadian rhythm when evaluating athletic performance or using HR as a criterion to assess fitness or monitor training.

Chrono-modulated effects of external stressors on oxidative stress and damage in humans: A scoping review on night shift work

BACKGROUND

Oxidative stress and tissue damage (OSD) play a pivotal role as an early-stage process in chronic disease pathogenesis. However, there has been little research to better understand the temporal (χρόνος[chronos]) dimensions of OSD process associated with environmental (non-genetic, including behaviors/lifestyle) and/or occupational stressors, like night shift work. OSD processes have recently attracted attention in relation to time-resolved external stressor trajectories in personalized medicine (prevention) initiatives, as they seem to interact with circadian clock systems towards the improved delineation of the early stages of (chronic) disease process.

OBJECTIVES

This work critically reviewed human studies targeting the temporal dynamics of OSD and circadian clock system's activity in response to environmental/occupational stressors; the case of night shift work was examined.

METHODS

Being a key stressor influencing OSD processes and circadian rhythm, night shift work was evaluated as part of a scoping review of research in OSD, including inflammatory and metabolic processes to determine the extent of OSD research undertaken in human populations, methodologies, tools and biomarkers used and the extent that the temporal dimensions of exposure and biological effect(s) were accounted for. Online databases were searched for papers published from 2000 onwards, resulting in the selection of 53 original publications.

RESULTS AND DISCUSSION

The majority of studies (n = 41) took place in occupational settings, while the rest were conducted in the general population or patient groups. Most occupational studies targeted outcomes of oxidative stress/damage (n = 19), followed by the combination of OSD with inflammatory response (n = 10), and studies focused on metabolic outcomes (n = 12). Only a minor fraction of the studies measured biomarkers related to circadian rhythm, such as, melatonin, its metabolite, or cortisol. Night shift work was associated with select biomarkers of OSD and inflammation, albeit with mixed results. Although much progress in delineating the biological mechanisms of OSD process has been made, an equally thorough investigation on the temporal trajectory of OSD processes as triggered by environmental/occupational stressors in human studies has yet to fully evolve.

The Effect of Environmental Disasters on Endocrine Status, Hematology Parameters, Body Composition, and Physical Performance in Young Soccer Players: A Case Study of the Aral Sea Region

The Aral Sea region (Uzbekistan) is infamous because of the ecological disaster characterized by the disappearance of the Aral Sea due to excessive uncontrolled water intake for agriculture needs. A new desert occurrence, soil and climate aridization led to pesticide and toxic metals environment pollution. The impact of environmental conditions in some areas of Uzbekistan on the health of soccer players is not as noticeable as, for example, the effectiveness of training, so it is not widely discussed in scientific papers. The aim of the present study was to study the features of endocrine status, hematology parameters (e.g., red blood cells (RBC) and hemoglobin (Hb)), and their influence on body composition and physical fitness performance in local young soccer players of the Aral Sea region as the territory of ecological disaster. The study involved 60 male soccer players aged from 18 to 22 years. Participants were divided into two groups: the experimental group (EG), which consisted of 30 soccer players living on the territory of the Aral ecological disaster region, and the control group (CG), which included 30 soccer players, natives of the ecologically favorable region of Uzbekistan. All volunteers had anthropometric measurements, concentrations of insulin-like growth factor-1 (IGF-1), total testosterone (TT), estradiol (E2), cortisol (C), RBC, and Hb count. Moreover, Yo-Yo Intermittent Recovery Test Level 1 (YYIRT1) and professional skills tests such as dribbling shuttle test (DSt) and goal accuracy test (GAt) were assessed. When comparing the CG group to the EG group, it was observed that the EG group exhibited statistically significantly reduced levels of TT and E2 (p < 0.05). No significant statistical difference was observed between the two groups in terms of IGF-1 and C (p > 0.05). Regarding hematological parameters, Hb, Ht, and mean corpuscular volume (MCV) were found to be significantly lower in the EG compared with the CG (p < 0.05). Moreover, the distance covered in the YYIR1 test was found to be significantly lower in soccer players within the EG compared with the CG (p < 0.05). Additionally, it was determined that there was no significant difference between the groups in terms of DSt and GAt values (p > 0.05). Lastly, significant differences were observed between the EG and CG in terms of anthropometric characteristics (diameters, skinfold, and somatotype profile) (p < 0.05). The present study showed that the changes in evaluated characteristics might result from the complex influence of endocrine-disrupting chemicals, the content of which is high in the environment of the Aral Sea region. The results obtained may help monitor the health of athletes living in an environmentally unfriendly environment.

Time of the day of exercise impact on cardiovascular disease risk factors in adults: a systematic review and meta-analysis

OBJECTIVES

To compare the effect of a single bout of morning vs. evening exercise on cardiovascular risk factors in adults.

DESIGN

Systematic review and meta-analysis.

METHODS

A systematic search of studies was conducted using PubMed and Web of Science from inception to June 2022. Selected studies accomplished the following criteria: crossover design, acute effect of exercise, blood pressure, blood glucose, and/or blood lipids as the study's endpoint, a washout period of at least 24 h, and adults. Meta-analysis was performed by analyzing: 1) separated effect of morning and evening exercise (pre vs. post); and 2) comparison between morning and evening exercise.

RESULTS

A total of 11 studies were included for systolic and diastolic blood pressure and 10 studies for blood glucose. Meta-analysis revealed no significant difference between morning vs. evening exercise for systolic blood pressure (g ∆ = 0.02), diastolic blood pressure (g ∆ = 0.01), or blood glucose (g ∆ = 0.15). Analysis of moderator variables (age, BMI, sex, health status, intensity and duration of exercise, and hour within the morning or evening) showed no significant morning vs. evening effect.

CONCLUSIONS

Overall, we found no influence of the time of the day on the acute effect of exercise on blood pressure neither on blood glucose.

Morning Exercise is More Effective in Ameliorating Oxidative Stress in Patients with Type 2 Diabetes Mellitus

Introduction: Exercise has been believed to be an important step in treating and preventing Type 2 Diabetes Mellitus complications. The circadian rhythm influences systems in the body, including antioxidants in the human body. By synchronizing exercise with exercise time, it will maximize the benefits of exercise for health. Aim: Examining the effect of morning and afternoon exercise on increasing antioxidants and improving oxidative stress in patients with T2DM. Methods: Twenty-two T2DM patients were randomly assigned to morning and afternoon exercise groups. The exercise treatment in this study was in the form of diabetes Persadia gymnastic, for 10 weeks. All participants were taken venous blood before exercise and after the tenth week. The data examined consisted of GPx-1 (Glutathione Peroxidase-1) and MDA (malodialdehyde). The pre and post data were statistically processed using a comparative test. Results: After 10 weeks of exercise, GPx-1 levels increased significantly in both groups (p<0.05). The increase in this enzyme was considerably greater (p<0.05) in the morning group than in the afternoon group (130.37 ± 2.4 h/ml VS 72.38 ± 3.93 h/ml). MDA levels decreased significantly in morning and afternoon groups (p<0.05). The decrease in MDA was significantly greater (p<0.05) in the morning than in the afternoon exercise group (8.22 ± 0.36 nmol/ml VS 5.2 ± 0.86 nmol/ml). Conclusions: Exercise in the morning was more effective in improving oxidative stress by increasing glutathione peroxidase-1 enzyme and reducing malondialdehyde in patients with Type 2 Diabetes Mellitus. Keywords: Exercise; Glutathione Peroxidase; Malondialdehyde, T2DM.

Cognitive Benefits of Exercise: Is There a Time-of-Day Effect?

It is well established that physical activity benefits cognition. Further, the time of day one engages in physical activity has been suggested to influence cognition. Here, we aimed to understand if there is a time-of-day effect (morning or afternoon) of physical activity on cognition, i.e., if exercising in the morning or afternoon might bring greater cognitive benefits. A total of 56 participants were allocated to one of two groups with the same baseline cognitive performance as well as fitness level (International Physical Activity Questionnaire—IPAQ): 27 to the morning intervention (M) group; and 29 to the afternoon intervention (A) group. In both groups, the participants engaged in an intermittent recovery test (Yo-yo), 4 times a week for 12 weeks. All participants were assessed with the d2 Test of Attention and the Borg scale of perceived exertion pre- and post- acute and chronic intervention. After the first bout of exercise and after 12 weeks, we observed cognitive improvements both in the M and A groups. Surprisingly, we do not find differences between the time of day regarding cognitive benefits. Our results do not support the existence of a time-of-day effect for the attentional cognitive benefits of exercise.

Higher evening metabolic responses contribute to diurnal variation of self-paced cycling performance

This study examined the effect of time of day (TOD) on physical performance, and physiological and perceptual responses to a 10-km cycling time trial (TT_10km). Twelve physically trained subjects (20.3 ± 1.2 years, 74.3 ± 7.4 kg, 179.7 ± 5.5 cm) completed, in a randomized order, a TT_10km in the morning and in the evening. Intra-aural temperature (IAT) was measured at rest and following the TT_10km. Completion time, power output (PO), rating of perceived exertion (RPE), heart rate (HR), minute ventilation (V̇E), oxygen uptake (V̇O₂), carbon dioxide production (V̇CO₂) and respiratory exchange ratio (RER) were assessed every km during the TT_10km. Blood lactate concentration [La] and blood glucose concentration [Glu] were assessed before, during and immediately after the TT_10km. Faster completion time (Δ = 15.0s, p = 0.03) and higher IAT (Δ = 0.33°C, p = 0.02 for pre-TT_10km) were obtained in the evening compared to the morning with a significant correlation between Δ completion time and Δ IAT at post-TT_{10 km} (r = -0.83, p = 0.04). V̇O₂, [La] and [Glu] increased significantly during both test sessions (p < 0.001) with higher values in the evening compared to the morning (p = 0.015, p = 0.04, p = 0.01, respectively). However, the remaining parameters were found to be only affected by the TT_10km (p < 0.001). The TT_10km generates a higher V̇O₂ and higher [La] and [Glu] responses, contributing to a better cycling performance in the evening compared to the morning. The similar magnitude of the TOD effect on completion time and IAT at post-TT_10km confirms that core temperature is one of the underlying factors contributing to the diurnal variation in physical performance.

Influence of circadian rhythms on sports performance

Chronobiology is the scientific discipline of study of biological rhythms, a term that has gained ground in the sports world. Recently numerous studies have indicated that the time of day in which sports are practiced influences the achievement of good physical performance. The aim of this review was to study the relationship between circadian rhythms and physical performance, according to the latest published data. In addition, the physiological processes involved in the physical response and the differences according to the type of sport and athletes' characteristics were studied. A bibliographic search was carried out through five databases (Pubmed, Scopus, Researcher Gate, Google Scholar, UOC Library), focusing on articles published in the last ten years and written in English and Spanish. 36 papers met the inclusion criteria. Body temperature is a factor that shows a circadian pattern with a marked peak in the later afternoon, time of the day at which physical performance is at its highest, i.e. speed, agility, distance covered, jumping power. The perception of effort is also higher in the afternoon. Regarding the chronotype, evening types seem to be the most affected to do sports out of their optimal time-of-day. The tendency shows more morning types as age increases. Training sessions should be planned according to the optimal time of day for each athlete. It's essential to take into account individual chronotype. The desynchronization of circadian rhythms can cause a decrease in physical performance.

Does circadian rhythm have an impact on anaerobic performance, recovery and muscle damage?

This study aimed to examine the effect of circadian rhythms (CR) on anaerobic performance and subsequent recovery, muscle damage, and respiratory muscle strength. Twenty diurnally active male football players (age, 22.20 ± 3.14 y) were asked to perform the Wingate anaerobic power test three times for 30 s each at 09:00, 14:00 and 19:00 h, with a minimum recovery period of 1 week between each testing day. Pretest oral temperature, respiratory muscle strength, oxygen saturation, and rating of perceived exertion were recorded at three different time of the day. To examine post-exercise recovery, heart rate (HR) and lactic acid (LA) levels were recorded before and after the tests. Blood samples were collected 20 min after each test to assess muscle damage. The body temperature taken at 19:00 h was the highest of the three (p < .01). After the tests, the LA value at 19:00 h was higher than that at 09:00 h (p < .05). According to CR, the HR values measured after anaerobic exercise were higher at 14:00 h (p < .05). The peak power value was higher at 14:00 h than at 19:00 h (p < .058). CR does not affect muscle damage and respiratory muscle strength. Further, at 14:00 h, anaerobic power was higher and recovery occurred faster compared to the other test times of 09:00 and 19:00 h. Therefore, it is recommended that anaerobic training should be performed early in the afternoon.

Influence of Sex and Acute Beetroot Juice Supplementation on 2 KM Running Performance

Purpose: To assess the effect of acute nitrate-rich (BJ) and nitrate-depleted (PL) beetroot juice ingestion on 2 km running performance in amateur runners, and to what extent the ergogenic effect of BJ supplementation would be influenced by the sex of the participants; Methods: Twenty-four amateur long-distance runners (14 males and 10 females) performed a 2 km time trial (TT) on an outdoor athletics track 2.5 h after ingesting either 140 mL of BJ (~12.8 mmol NO3−) or PL. After the tests, blood [lactate] and ratings of perceived exertion (RPE) related to the leg muscles (RPEmuscular), cardiovascular system (RPEcardio) and general overall RPE (RPEgeneral) were assessed; Results: Compared to PL, BJ supplementation improved 2 km TT performance in both males (p < 0.05) with no supplement × sex interaction effect (p > 0.05). This improvement in 2 km running performance was a function of improved performance in the second 1 km split time in both males and females (p < 0.05). Supplementation with BJ did not alter post-exercise blood [lactate] (p > 0.05) but lowered RPEgeneral (p < 0.05); Conclusions: acute BJ supplementation improves 2 km running performance in amateur runners by enhancing performance over the second half of the TT and lowering RPEgeneral by a comparable magnitude in males and females.

Does red orange juice supplementation has a protective effect on performance, cardiovascular parameters, muscle damage and oxidative stress markers following the Yo-Yo Intermittent Recovery Test Level-1 under polluted air?

This study aimed to investigate the effect of red orange juice supplementation (ROJS) on performance, cardiovascular parameters, muscle damage and oxidative stress markers of athletes following exercise under polluted air. Eleven soccer players performed a Yo-Yo Intermittent Recovery Test Level-1 in polluted area (PA) and non-polluted area (NPA). Participants are invited to drink 500 ml of red orange or placebo (PLA) juice 2.5 h before the test. Blood samples were collected at rest and 3 min after each session to assess creatine kinase (CK), lactate dehydrogenase, malondialdehyde (MDA) and total antioxidant status. Our results showed that, VO_2max, heart rate and systolic blood pressure post-exercise were significantly altered by pollution with both supplements, but the damage was lowered more with ROJS than PLA. Concerning muscle damage and oxidative stress markers, orange juice supplementation blunted the effect of pollution on CK levels post-exercise (p > 0.05) and decreases significantly (p < 0.05) the MDA levels post-exercise in PA and NPA compared to PLA supplementation. In conclusion, ROJS seemed to be an appropriate strategy to reduce the risk of exposure to pollution especially on muscle damage and oxidative stress markers.

In Athletes, the Diurnal Variations in Maximum Oxygen Uptake Are More Than Twice as Large as the Day-to-Day Variations

In competitive sports any substantial individual differences in diurnal variations in maximal performance are highly relevant. Previous studies have exclusively focused on how the time of day affects performance and disregarded the maximal individual diurnal variation of performance. Thus, the aims of this study were (1) to investigate the maximum diurnal variation in maximum oxygen uptake (VO₂max), (2) to compare the diurnal variation of VO₂max during the day to the day-to-day variation in VO₂max, and (3) to investigate if there is a time-of-day effect on VO₂max. Ten male and seven female athletes (mean VO₂max: 58.2 ± 6.9 ml/kg/min) performed six maximal cardiopulmonary exercise tests including a verification-phase at six different times of the day (i.e., diurnal variation) and a seventh test at the same time the sixth test took place (i.e., day-to-day variation). The test times were 7:00, 10:00, 13:00, 16:00, 19:00, and 21:00. The order of exercise tests was the same for all participants to ensure sufficient recovery but the time of day of the first exercise test was randomized. We used paired t-tests to compare the nadir and peak of diurnal variations, day-to-day variations and the difference between diurnal and day-to-day variations. The mean difference in VO₂max was 5.0 ± 1.9 ml/kg/min (95% CI: 4.1, 6.0) for the diurnal variation and 2.0 ± 1.0 ml/kg/min (95% CI: 1.5, 2.5) for the day-to-day variation. The diurnal variation was significantly higher than the day-to-day variation with a mean difference of 3.0 ± 2.1 ml/kg/min (95% CI: 1.9, 4.1). The linear mixed effects model revealed no significant differences in VO₂max for any pairwise comparison between the different times of the day (all p > 0.11). This absence of a time-of-day effect is explained by the fact that peak VO₂max was achieved at different times of the day by different athletes. The diurnal variations have meaningful implications for competitive sports and need to be considered by athletes. However, the results are also relevant to research. To increase signal-to-noise-ratio in intervention studies it is necessary to conduct cardiopulmonary exercise testing at the same time of the day for pre- and post-intervention exercise tests.

In Athletes, the Diurnal Variations in Maximum Oxygen Uptake Are More Than Twice as Large as the Day-to-Day Variations

In competitive sports any substantial individual differences in diurnal variations in maximal performance are highly relevant. Previous studies have exclusively focused on how the time of day affects performance and disregarded the maximal individual diurnal variation of performance. Thus, the aims of this study were (1) to investigate the maximum diurnal variation in maximum oxygen uptake (VO₂max), (2) to compare the diurnal variation of VO₂max during the day to the day-to-day variation in VO₂max, and (3) to investigate if there is a time-of-day effect on VO₂max. Ten male and seven female athletes (mean VO₂max: 58.2 ± 6.9 ml/kg/min) performed six maximal cardiopulmonary exercise tests including a verification-phase at six different times of the day (i.e., diurnal variation) and a seventh test at the same time the sixth test took place (i.e., day-to-day variation). The test times were 7:00, 10:00, 13:00, 16:00, 19:00, and 21:00. The order of exercise tests was the same for all participants to ensure sufficient recovery but the time of day of the first exercise test was randomized. We used paired t-tests to compare the nadir and peak of diurnal variations, day-to-day variations and the difference between diurnal and day-to-day variations. The mean difference in VO₂max was 5.0 ± 1.9 ml/kg/min (95% CI: 4.1, 6.0) for the diurnal variation and 2.0 ± 1.0 ml/kg/min (95% CI: 1.5, 2.5) for the day-to-day variation. The diurnal variation was significantly higher than the day-to-day variation with a mean difference of 3.0 ± 2.1 ml/kg/min (95% CI: 1.9, 4.1). The linear mixed effects model revealed no significant differences in VO₂max for any pairwise comparison between the different times of the day (all p > 0.11). This absence of a time-of-day effect is explained by the fact that peak VO₂max was achieved at different times of the day by different athletes. The diurnal variations have meaningful implications for competitive sports and need to be considered by athletes. However, the results are also relevant to research. To increase signal-to-noise-ratio in intervention studies it is necessary to conduct cardiopulmonary exercise testing at the same time of the day for pre- and post-intervention exercise tests.