Clocking In, Working Out: Circadian Regulation of Exercise Physiology

Association of Physical Activity with Phenotypic Age among Populations with Different Breakfast Habits

BACKGROUND

The global aging situation has reached a serious stage, and healthy lifestyles, like regular physical activity and eating breakfast, could slow the process. Phenotypic age (PhenoAge) is regarded as a novel measure of aging. Therefore, our study aimed to quantify the impact of physical activity and eating breakfast on aging via PhenoAge and phenotypic age acceleration (PhenoAgeAccel).

METHODS

A total of 3719 adults who participated in the National Health and Nutrition Examination Survey were involved in this study. Physical activity was divided into an active group and an inactive group. According to the number of reported breakfast recalls, eating breakfast was divided into the no recalls group, one recall group, and both recalls group. Sensitivity analysis was performed by stratified analysis.

RESULTS

Active physical activity was a protective factor for PhenoAge and PhenoAgeAccel. Compared to the inactive group, the β values of the active group were -8.36 (-10.09, -6.62) for PhenoAge and -1.67 (-2.21, -1.14) for PhenoAgeAccel. The stratified analysis results showed that in the groups reporting breakfast in both recalls, one recall, and no recalls, the β values of the active group were -8.84 (-10.70, -6.98), -8.17 (-12.34, -4.00), and -3.46 (-7.74, 0.82), respectively, compared to the inactive group.

CONCLUSIONS

Active physical activity was strongly correlated with lower values of PhenoAge and PhenoAgeAccel, but the association was no longer statistically significant when combined with not regularly eating breakfast.

Multi-omic identification of key transcriptional regulatory programs during endurance exercise training

Transcription factors (TFs) play a key role in regulating gene expression and responses to stimuli. We conducted an integrated analysis of chromatin accessibility, DNA methylation, and RNA expression across eight rat tissues following endurance exercise training (EET) to map epigenomic changes to transcriptional changes and determine key TFs involved. We uncovered tissue-specific changes and TF motif enrichment across all omic layers, differentially accessible regions (DARs), differentially methylated regions (DMRs), and differentially expressed genes (DEGs). We discovered distinct routes of EET-induced regulation through either epigenomic alterations providing better access for TFs to affect target genes, or via changes in TF expression or activity enabling target gene response. We identified TF motifs enriched among correlated epigenomic and transcriptomic alterations, DEGs correlated with exercise-related phenotypic changes, and EET-induced activity changes of TFs enriched for DEGs among their gene targets. This analysis elucidates the unique transcriptional regulatory mechanisms mediating diverse organ effects of EET.

Association of Timing of Moderate-to-Vigorous Physical Activity With Changes in Glycemic Control Over 4 Years in Adults With Type 2 Diabetes From the Look AHEAD Trial

OBJECTIVE

We aimed to determine the association of the time-of-day of bout-related moderate-to-vigorous physical activity (bMVPA) with changes in glycemic control across 4 years in adults with overweight/obesity and type 2 diabetes.

RESEARCH DESIGN AND METHODS

Among 2,416 participants (57% women; mean age, 59 years) with 7-day waist-worn accelerometry recording at year 1 or 4, we assigned bMVPA timing groups based on the participants' temporal distribution of bMVPA at year 1 and recategorized them at year 4. The time-varying exposure of bMVPA (≥10-min bout) timing was defined as ≥50% of bMVPA occurring during the same time period (morning, midday, afternoon, or evening), <50% of bMVPA in any time period (mixed), and ≤1 day with bMVPA per week (inactive).

RESULTS

HbA1c reduction at year 1 varied among bMVPA timing groups (P = 0.02), independent of weekly bMVPA volume and intensity. The afternoon group had the greatest HbA1c reduction versus inactive (-0.22% [95%CI -0.39%, -0.06%]), the magnitude of which was 30-50% larger than the other groups. The odds of discontinuation versus maintaining or initiating glucose-lowering medications at year 1 differed by bMVPA timing (P = 0.04). The afternoon group had the highest odds (odds ratio 2.13 [95% CI 1.29, 3.52]). For all the year-4 bMVPA timing groups, there were no significant changes in HbA1c between year 1 and 4.

CONCLUSIONS

bMVPA performed in the afternoon is associated with improvements in glycemic control in adults with diabetes, especially within the initial 12 months of an intervention. Experimental studies are needed to examine causality.

Sleep and chronotype influence aerobic performance in young soccer players

People can be classified into three chronotypes (CT): morning-type (M-type), Neither-type (N-type) and Evening-type (E-type). M-types perform better in the morning, E-types in the evening. It seems that bad sleep worsens physical performance. The impact of sleep and CT on specific sports and populations is unclear. Therefore, we wanted to assess agility, strength and endurance in young soccer players in relation to their sleep and chronotype. 58 players (13-19 years) were recruited. Sleep and CT were assessed by questionnaires. The physical trial was performed at 8:30 a.m. and 6:00 p.m., and included three tests to determine agility, strength and endurance. The sample was classified by CT as M-types (n = 11), N-types (n = 29) and E-types (n = 18). Furthermore, they were categorized as people with Good Sleep/Wake quality (GSW, n = 28) and people with Bad Sleep/Wake quality (BSW, n = 30). Comparing the three CTs in the aerobic test, M-types performed better in the morning (p = 0.01), while E-types in the evening (p < 0.001). GSW performed better than BSW (p = 0.019) in the aerobic test in the p.m. session. These results underline the difference in aerobic power between M-and E-types during the morning and evening session; moreover, they show a difference in p.m. aerobic performance according to sleep quality.

EFFECT OF AIR ENDURANCE TRAINING ON ATHLETE’S LOWER LIMB EXPLOSIVE STRENGTH

ABSTRACT Introduction: The explosion force is the neuromuscular system's capacity to overcome resistance with the highest possible contraction speed. It is the result of a kinetic combination between power and speed. The effect of outdoor resistance training is used in several athletics areas to improve the explosive power of the lower limbs. However, there are still few studies focused on basketball athletes. Objective: Verify the effect of outdoor resistance training on the explosive power of the lower limbs of basketball players. Methods: The article uses mathematical statistics and randomized controlled trials by analytical comparison to explore the influence of compound training methods on basketball players’ lower explosive limb power. Results: There was no performance gain in the control group at 30 days. Was an improved ability in the experimental group jumping after high-intensity composite training. Conclusion: Compound training plays a crucial role in improving lower limb explosive power in college basketball players. Evidence Level II; Therapeutic Studies - Investigating the result.

Egr1 plays a major role in the transcriptional response of white adipocytes to insulin and environmental cues

It is believed that insulin regulates metabolic functions of white adipose tissue primarily at the post-translational level via the PI3K-Akt-mediated pathway. Still, changes in transcription also play an important role in the response of white adipocytes to insulin and environmental signals. One transcription factor that is dramatically and rapidly induced in adipocytes by insulin and nutrients is called Early Growth Response 1, or Egr1. Among other functions, it directly binds to promoters of leptin and ATGL stimulating the former and inhibiting the latter. Furthermore, expression of Egr1 in adipocytes demonstrates cell autonomous circadian pattern suggesting that Egr1 not only mediates the effect of insulin and nutrients on lipolysis and leptin production but also, coordinates insulin action with endogenous circadian rhythms of adipose tissue.

Effect of exercises according to the circadian rhythm in type 2 diabetes: Parallel-group, single-blind, crossover study

BACKGROUND AND AIM

To evaluate the effectiveness of structured exercise appropriate the circadian rhythm in terms of blood sample test (BST), functionality and quality of life (QoL) in individuals with type 2 diabetes.

METHODS AND RESULTS

This was a parallel-group, single-blind, crossover study. Thirty individuals with type 2 diabetes aged 35-65 years were enrolled in the study and allocated into 2 groups as the Morning Chronotype (MC) Group (n = 15) and the Evening Chronotype (EC) Group (n = 15) using Morningness-Eveningness Questionnaire which was used to determine the chronotypes. Participants were evaluated in terms of BST, functionality and QoL at the beginning of the study (T0), at 6 (T1), 12 (T2), and 18 (T3) weeks after the study started. A structured exercise program for 3 days a week over 6 weeks was applied in accordance with the chronotypes (T1-T2) and cross-controlled for the chronotypes (T2-T3). Significant differences were found in favor of the exercise given at the appropriate time for the chronotype in all parameters in both groups within groups (T0-T1-T2-T3) (p < 0.05). In the time∗group interactions, exercise in accordance with the appropriate chronotype in both groups provided the highest statistical improvement in all parameters (p < 0.05).

CONCLUSION

It was concluded that structured exercise performed at the appropriate time for chronotype improves HbA_1c, fasting blood glucose, HDL-LDL cholesterol, triglyceride, total cholesterol, functionality and quality of life in type 2 diabetes. This variation in blood values was observed to reflect the quantitative effects of exercise administered according to the circadian rhythm in individuals with type 2 diabetes.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT04427488). The protocol of the study was registered at ClinicalTrials.gov (NCT04427488).

Time to Train: The Involvement of the Molecular Clock in Exercise Adaptation of Skeletal Muscle

Circadian rhythms regulate a host of physiological processes in a time-dependent manner to maintain homeostasis in response to various environmental stimuli like day and night cycles, food intake, and physical activity. Disruptions in circadian rhythms due to genetic mutations, shift work, exposure to artificial light sources, aberrant eating habits, and abnormal sleep cycles can have dire consequences for health. Importantly, exercise training efficiently ameliorates many of these adverse effects and the role of skeletal muscle in mediating the benefits of exercise is a topic of great interest. However, the molecular and physiological interactions between the clock, skeletal muscle function and exercise are poorly understood, and are most likely a combination of molecular clock components directly acting in muscle as well as in concordance with other peripheral metabolic organ systems like the liver. This review aims to consolidate existing experimental evidence on the involvement of molecular clock factors in exercise adaptation of skeletal muscle and to highlight the existing gaps in knowledge that need to be investigated to develop therapeutic avenues for diseases that are associated with these systems.

Chronodisruption and diet associated with increased cardiometabolic risk in coronary heart disease patients: the CORDIOPREV study

Individuals with evening chronotypes are prone to suffer chronodisruption and display worse lifestyle habits than morning-types, exhibiting higher cardiovascular diseases (CVD). However, it is unknown whether CVD patients, who are evening chronotypes, have higher cardiometabolic risk than morning-types. This study explored whether individual chronotypes were associated with cardiometabolic risk in patients from the CORDIOPREV study (n = 857). We also investigated whether potential associations were moderated by long-term consumption of two healthy diets (Mediterranean and Low-fat diets). This population was classified into chronotypes using the Morningness-Eveningness Questionnaire. Seven-day daily rhythms in wrist temperature (T), rest-activity (A) and position (P) were recorded in a subset of patients (n = 168), and an integrative variable TAP was determined. Metabolic Syndrome (MetS) was determined at baseline, and metabolic and inflammation markers were measured at baseline and yearly during the 4 years of follow-up. Differences in several lifestyle factors were analyzed according to chronotype. At all times, evening-types had higher triglycerides, C-reactive protein and homocysteine and lower high density lipoprotein cholesterol than morning-types (P < 0.05). Evening-types had a higher prevalence of MetS (OR 1.58 IC 95% [1.10 - 2.28], P = 0.01). Moreover, they were more sedentary, displayed less and delayed physical activity and ate and slept later. In addition, evening-types had lower amplitude, greater fragmentation, lower robustness and less stable circadian pattern at TAP (P < 0.01), all related to a less healthy circadian pattern. In conclusion, evening-types with CVD had higher cardiometabolic risk and less robust circadian-related rhythms than morning-types, regardless of the nutritional intervention.

Daily running enhances molecular and physiological circadian rhythms in skeletal muscle

Objective

Exercise is a critical component of a healthy lifestyle and a key strategy for the prevention and management of metabolic disease. Identifying molecular mechanisms underlying adaptation in response to chronic physical activity is of critical interest in metabolic physiology. Circadian rhythms broadly modulate metabolism, including muscle substrate utilization and exercise capacity. Here, we define the molecular and physiological changes induced across the daily cycle by voluntary low intensity daily exercise.

Methods

Wildtype C57BL6/J male and female mice were housed with or without access to a running wheel for six weeks. Maximum running speed was measured at four different zeitgeber times (ZTs, hours after lights on) using either electrical or manual stimulation to motivate continued running on a motorized treadmill. RNA isolated from plantaris muscles at six ZTs was sequenced to establish the impact of daily activity on genome-wide transcription. Patterns of gene expression were analyzed using Gene Set Enrichment Analysis (GSEA) and Detection of Differential Rhythmicity (DODR). Blood glucose, lactate, and ketones, and muscle and liver glycogen were measured before and after exercise.

Results

We demonstrate that the use of mild electrical shocks to motivate running negatively impacts maximum running speed in mice, and describe a manual method to motivate running in rodent exercise studies. Using this method, we show that time of day influences the increase in exercise capacity afforded by six weeks of voluntary wheel running: when maximum running speed is measured at the beginning of the nighttime active period in mice, there is no measurable benefit from a history of daily voluntary running, while maximum increase in performance occurs at the end of the night. We show that daily voluntary exercise dramatically remodels the murine muscle circadian transcriptome. Finally, we describe daily rhythms in carbohydrate metabolism associated with the time-dependent response to moderate daily exercise in mice.

Conclusions

Collectively, these data indicate that chronic nighttime physical activity dramatically remodels daily rhythms of murine muscle gene expression, which in turn support daily fluctuations in exercise performance.

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Daily voluntary running dramatically remodels the mouse muscle circadian transcriptome.

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Daily voluntary running maximally increases mouse running speed in the late active period.

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Muscle and liver glycogen content exhibit robust daily rhythms in laboratory mice.

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Use of mild electric shocks to motivate running in mice impairs maximum running speed.

Diurnal variation of fat oxidation rate and energy expenditure in an acute bout of endurance exercise by young healthy males

Background:

Few studies have reported that circadian rhythm affects fat oxidation (FOx) during exercise. Time-of-day causing greater FOx and energy expenditure (EE) during exercise would be beneficial in the prevention of physical inactivity-related health disorders such as metabolic syndrome. The study aims to compare EE and FOx rate after an endurance exercise session done in the morning and late-afternoon hours by apparently healthy young male participants.

Material and Methods:

The present crossover quasi-experimental study involved 10 moderately active but physically untrained male participants of age 18–25 years with normal body mass index. Participants did a steady-state exercise on a motorized treadmill for 30 minutes at a moderate-intensity (50 ± 2% of their heart rate reserve) on two separate occasions at 9:00–10:00 and 15:00–16:00. A similar meal followed by 2 hours of fasting was done before each trial session. During the last 2 minutes of the exercise session, the respiratory gas analysis estimated volume of oxygen (VO₂) and volume of carbon dioxide (VCO₂) consumed in L/min. Indirect calorimetry equations assessed FOx (mg/min), EE (Kcal/min) and respiratory exchange ratio (RER). Data of one participant were removed to adjust for extreme chronotype. Paired t-test was applied, and P ≤ 0.05 was considered significant.

Results:

Morning versus late-afternoon variations in FOx (269 ± 110 vs 290 ± 110, P = 0.016), RER (0.86 ± 0.05 vs 0.85 ± 0.05, P = 0.040), EE (5.454 ± 0.987 vs 5.494 ± 0.959, P = 0.079) and VO2 (1.104 ± 0.201 vs 1.113 ± 0.196, P = 0.035) were present after adjustment for chronotype.

Conclusion:

In an acute bout of endurance, exercise done by young and healthy male individuals, FOx was significantly higher, while EE tends to be higher in late-afternoon than in the morning.

Perception and sensory acceptance of sweet taste by individuals that who work/study on different shifts

ABSTRACT Objective This study aimed to evaluate the perception and sensory acceptance of sweet taste by individuals who work/study on different shifts. Methods Three groups of individuals were recruited: the Control group (individuals that study during the day and do not work at night), Group 1 (individuals that study in the evening) and Group 2 (individuals that work overnight). The individuals were submitted to a detection threshold test using sucrose solutions and a sensory acceptance test using a structured hedonic scale and a Just-About-Right scale for sweet taste in blancmange. Results The detection thresholds were significantly higher for Groups 1 and 2. Individuals of Group 2 had a preference by blancmanges when having high sucrose concentrations, as well as had an ideal concentration of 10.50% sucrose against 5.95% sucrose for the Control group. Conclusion Our study shows a relationship between changes in the circadian cycle and the sensory perception and acceptance of sweet taste. More studies need to be performed to understand such relationships and their repercussions better.

The association between time-of-day of habitual exercise training and changes in relevant cancer health outcomes among cancer survivors

OBJECTIVE

To assess the relationship between time-of-day of exercise training and changes in relevant cancer health outcomes among cancer survivors.

METHODS

Retrospective analysis of data collected from 2016-2019 from a hospital-based exercise oncology program. Descriptive statistics were calculated for demographic, clinical, and exercise timing characteristics (e.g. AM, PM, or mix) among survivors with available data for exercise training time (n = 233). For the total sample and a breast cancer sub-analysis, univariate analysis of covariance, adjusted for age, was carried out by exercise training time, for change in the following outcomes collected during the program's assessment sessions: cardiorespiratory fitness and muscular endurance (human performance variables), physical function, anthropometrics, self-reported fatigue, and quality of life (QoL). Change in body mass index (BMI) and body weight was included in the breast cancer analysis.

RESULTS

Overall, 37.3% of survivors habitually engaged in AM exercise (e.g. ≥ 75% AM training), 34.3% in PM exercise, and 28.3% in a mix of AM and PM exercise training throughout the program. Median time in the program was 17 weeks. Significant improvements in most human performance and physical function variables were observed in the total sample regardless of exercise training time-of-day. Among breast cancer survivors, PM but not AM or mixed was associated with improvements in fitness, and lower-body muscular endurance and function. Mixed exercise timing was linked with greater increase in waist circumference (total sample: 3.02cm, 95%CI 1.55, 4.49; breast cancer: 3.57cm 95%CI 0.96, 6.18), body weight (breast cancer: 1.6kg, 95%CI 0.3, 2.8) and BMI (breast cancer: 0.6kg/m2, 95%CI 0.1, 1.0). AM and PM exercise, but not mixed, was associated with improvements in fatigue and QoL.

CONCLUSION

Time-of-day of exercise training may differentially impact changes in human performance and physical function variables. Mixed exercise training time may result in less favorable outcomes related of weight management variables among cancer survivors.

Clock proteins and training modify exercise capacity in a daytime-dependent manner

Exercise and circadian biology are closely intertwined with physiology and metabolism, yet the functional interaction between circadian clocks and exercise capacity is only partially characterized. Here, we tested different clock mutant mouse models to examine the effect of the circadian clock and clock proteins, namely PERIODs and BMAL1, on exercise capacity. We found that daytime variance in endurance exercise capacity is circadian clock controlled. Unlike wild-type mice, which outperform in the late compared with the early part of their active phase, PERIODs- and BMAL1-null mice do not show daytime variance in exercise capacity. It appears that BMAL1 impairs and PERIODs enhance exercise capacity in a daytime-dependent manner. An analysis of liver and muscle glycogen stores as well as muscle lipid utilization suggested that these daytime effects mostly relate to liver glycogen levels and correspond to the animals' feeding behavior. Furthermore, given that exercise capacity responds to training, we tested the effect of training at different times of the day and found that training in the late compared with the early part of the active phase improves exercise performance. Overall, our findings suggest that clock proteins shape exercise capacity in a daytime-dependent manner through changes in liver glycogen levels, likely due to their effect on animals' feeding behavior.

Monitoring daytime differences in moderate intensity exercise capacity using treadmill test and muscle dissection

There is growing interest in medicine and sports in uncovering exercise modifiers that enhance or limit exercise capacity. Here, we detail a protocol for testing the daytime effect on running capacity in mice using a moderate intensity treadmill effort test. Instructions for dissecting soleus, gastrocnemius plantaris, and quadriceps muscles for further analysis are provided as well. This experimental setup is optimized for addressing questions regarding the involvement of daytime and circadian clocks in regulating exercise capacity.

For complete details on the use and execution of this protocol, please refer to Ezagouri et al. (2019).

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Exercise capacity is influenced by the time of day

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Protocol for determining moderate intensity exercise capacity using treadmill test

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Instructions for muscle dissection

The role of the molecular circadian clock in human energy homeostasis

PURPOSE OF REVIEW

The aim of this review is to present the latest findings on the role of the circadian clock in the control of metabolism, and the therapeutic potential of chronotherapy to regulate energy homeostasis in humans.

RECENT FINDINGS

We summarized the recent advances related to circadian clock regulation of food intake and energy expenditure. In peripheral organs, mitochondrial oxidative capacity and lipolysis show circadian pattern in humans, and rhythms disruption may be involved in the pathogenesis of metabolic diseases. Indeed, circadian desynchrony affects food intake, insulin sensitivity, and increases the risk of developing metabolic disease. Time-targeted strategies, which aim to synchronize external cues with the molecular clock to improve metabolic outcomes, have positive effects on metabolism in humans, with several studies showing that time-targeted feeding improves body weight loss and glucose tolerance.

SUMMARY

The interest in time-targeted strategies to prevent or manage metabolic disturbances has grown this past year with encouraging health benefits. To maximize the therapeutic effect of these strategies, further research is warranted to delineate the molecular regulation of metabolic processes controlled by the clock and especially its modulation in contexts such as aging, sex differences, or metabolic diseases.

A matter of time: Circadian clocks in osteoarthritis and the potential of chronotherapy

Osteoarthritis (OA) is a common and debilitating joint disease which develops and progresses with age. Despite extensive research into the disease, potent disease-modifying drugs remain elusive. Changes to the character and function of chondrocytes of the articular cartilage underly the pathogenesis of OA. A recently emerging facet of chondrocyte biology that has been implicated in OA pathogenesis is the role of circadian rhythms, and the cellular clock which governs rhythmic gene transcription. Here, we review the role of the chondrocyte's cellular clock in governing normal homeostasis, and explore the wide range of consequences that contribute to OA development when the clock is dysregulated by aging and other factors. Finally, we explore how harnessing this understanding of clock mechanics in aging and OA can be translated into novel treatment strategies, or 'chronotherapies', for patients.

Consistent Morning Exercise May Be Beneficial for Individuals With Obesity

This review explores the hypothesis that a consistent exercise time, especially consistent morning exercise, improves exercise adherence and weight management for individuals with overweight or obesity. We discuss data supporting this premise, identify limitations of current research, and outline directions for future research on exercise timing to more robustly evaluate our thesis.

Mild Exercise Does Not Prevent Atherosclerosis in APOE*3-Leiden.CETP Mice or Improve Lipoprotein Profile of Men with Obesity

OBJECTIVE

Exercise has been shown to improve cardiometabolic health, yet neither the molecular connection nor the effects of exercise timing have been elucidated. The aim of this study was to investigate whether ad libitum or time-restricted mild exercise reduces atherosclerosis development in atherosclerosis-prone dyslipidemic APOE*3-Leiden.CETP mice and whether mild exercise training in men with obesity affects lipoprotein levels.

METHODS

Mice were group-housed and subjected to ad libitum or time-restricted (first or last 6 hours of the active phase) voluntary wheel running for 16 weeks while on a cholesterol-rich diet, after which atherosclerosis development was assessed in the aortic root. Furthermore, nine men with obesity followed a 12-week mild exercise training program. Lipoprotein levels were measured by nuclear magnetic resonance spectroscopy in plasma collected pre and post exercise training.

RESULTS

Wheel running did not affect plasma lipid levels, uptake of triglyceride-derived fatty acids by tissues, and aortic atherosclerotic lesion size or severity. Markers of training status were unaltered. Exercise training in men with obesity did not alter lipoprotein levels.

CONCLUSIONS

Mild exercise training does not reduce dyslipidemia or atherosclerosis development in APOE*3-Leiden.CETP mice or affect lipoprotein levels in humans. Future research on the effects of (time-restricted) exercise on atherosclerosis or lipid metabolism should consider more vigorous exercise protocols.

Circadian modulation of the cardiac proteome underpins differential adaptation to morning and evening exercise training: an LC-MS/MS analysis

All living beings on earth are influenced by the circadian rhythm, the rising and the setting of the sun. The ubiquitous effect of exercise is widely believed to maximize health benefits but has not been formally investigated for cardiac responses in the exercise-induced circadian rhythms. We hypothesized that the exercise-related proteome is differentially influenced by circadian rhythm and analyzed the differences between the effects of morning and evening exercise. Twenty-four Sprague-Dawley rats were randomly divided into four groups (n = 6 per group): morning control, morning exercise, evening control, and evening exercise groups. The exercise groups were subjected to 12-week treadmill exercise (5 days/week) performed either during daytime or nighttime. After 12 weeks, the physiological characteristics (e.g., body weight, heart weight, visceral fat, and blood metabolites), cardiovascular capacity (ejection fraction (%) and fractional shortening (%)), circadian gene expression levels (clock, ball1, per1, per2, cry1, and cry2), and the proteomic data were obtained and subjected to univariate and multivariate analysis. The mRNA levels of per1 and cry2 increased in the evening group compared with those in the morning group. We also found that per2 decreased and cry2 increased in the evening exercise groups. The evening exercise groups showed more decreased triacylglycerides and increased blood insulin levels than the morning exercise group. The principal component analysis, partial least squares discriminant analysis, and orthogonal partial least squares discriminant analysis indicated that the circadian rhythm differently influenced the protein networks of the exercise groups. In the morning exercise group, the transcription-translation feedback loop (TTFL) (clock, per1, per2, cry1, and cry2) formed a protein-protein interaction network with Nme2, Hint1, Ddt, Ndufb8, Ldha, and Eef1a2. In contrast, the TTFL group appeared close to Maoa, Hist2h4, and Macrod1 in the evening exercise group. Interestingly, the evening exercise group decreased the mRNA level of per2 but not per1. Per1 and Per2 are known to transport Cry1 and Cry2 into the nucleus. Taken together, we summarized the characteristics of enriched proteins in the aspect of their molecular function, cellular component, and biological process. Our results might provide a better understanding of the circadian effect on exercise-related proteins.

The dosing of aerobic exercise therapy on experimentally-induced pain in healthy female participants

Knowledge of efficacious dosing respective to exercise type and pain condition is extremely limited in the literature. This study aimed to determine the impact of dose of moderate intensity treadmill walking on experimentally-induced pain in healthy human participants. Forty females were divided into 4 groups: control (no exercise), low dose exercise (3×/wk), moderate dose exercise (5×/wk) or high dose exercise (10×/wk). Over a 7-day period, subjects performed treadmill walking during assigned exercise days. Both qualitative and quantitative measures of pain were measured at baseline, during the trial, and 24 hrs post-final intervention session via sensitivity thresholds to painful thermal and painful pressure stimulation. Significant effects of treatment were found post-intervention for constant pressure pain intensity (p = 0.0016) and pain unpleasantness ratings (p = 0.0014). Post-hoc tests revealed significant differences between control and moderate and control and high dose groups for constant pressure pain intensity (p = 0.0015), (p = 0.0094), respectively and constant pressure pain unpleasantness (p = 0.0040), (p = 0.0040), respectively. Moderate and high dose groups had the greatest reductions in ratings of pain, suggesting that our lowest dose of exercise was not sufficient to reduce pain and that the moderate dose of exercise may be a sufficient starting dose for exercise-based adjuvant pain therapy.