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Rhythms can be observed at all levels of the biologic integration in humans. The observation that a biological or physiological variable shows a circadian rhythm can be explained by several multifactorial systems including external (exogenous), internal (endogenous) and psychobiological (lifestyle) mechanisms. Our body clock can be synchronized with the environment by external factors, called "synchronizers", i.e. the light-dark cycle, but it is also negatively influenced by some pathological conditions or factors, called "chronodisruptors," i.e. aging or low physical activity (PA). The desynchronization of a 24-h rhythm in a chronic manner has been recently defined "chronodisruption" or "circadian disruption." A very large number of hormonal variables, such as adrenal and gonadal stress steroids, are governed by circadian rhythmicity. Such hormones, in normal conditions, show a peak in the first part of the day, while their typical diurnal fluctuations are totally out of sync in subjects affected by cancer or metabolic diseases, such as obesity, diabetes and metabolic syndrome. In general, a flatter slope with altered peaks in cortisol and testosterone circadian rhythms has been observed in pathological individuals. PA, specifically chronic exercise, seems to play a key role as synchronizer for the whole circadian system in such pathologies even if specific data on steroids circadian pattern are still sparse and contradictory. Recently, it has been proposed that low-intensity chronic PA could be an effective intervention to decrease morning cortisol levels in pathological subjects. The standardization of all confounding factors is needed to reach more clear evidence-based results.

Background: Many variables related to sport have been shown to have circadian rhythms. Chronotype is the expression of circadian rhythmicity in an individual, and three categories of chronotype are defined: morning types (M-types), evening types (E-types), and neither types (N-types). M-types show earlier peaks of several psychophysiological variables during the day than E-types. The effect of chronotype on athletic performance has not been extensively investigated., Objective: The objective of the present review was to study the effect of chronotype on athletic performance and the psychophysiological responses to physical activity., Methods: The present review adheres to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines. We searched PubMed, Scopus, and Web of Science for scientific papers using the keywords "chronotype", "circadian typology", "morningness", and "eveningness" in combination with each of the words "sport", "performance", and "athletic." Relevant reference lists were inspected. We limited the search results to peer-reviewed papers published in English from 1985 to 2015., Results: Ten papers met our inclusion criteria. Rating of perceived exertion and fatigue scores in relation to athletic performances are influenced by chronotype: M-types perceived less effort when performing a submaximal physical task in the morning than did N- and E-types. In addition, M-types generally showed better athletic performances, as measured by race times, in the morning than did N- and E-types. Other results concerning chronotype effect on physiological responses to physical activity were not always consistent: heterogeneous samples and different kinds of physical activity could partially explain these discrepancies., Conclusions: Sports trainers and coaches should take into account the influence of both the time of day and chronotype effect when scheduling training sessions into specific time periods.

Background: An individual's chronotype influences his or her physiological rhythms. Some studies have looked at the effect of time of day on the responses to exercise, but studies on the effect of long-term training are lacking., Objective: To report the effects of an 8-week training period during the polar night in non-athletes of different chronotypes living at 70°N., Design: In all, 10 morning (M), 10 neither (N) and 10 evening (E) types were recruited, and their aerobic capacity (VO 2max ), strength, flexibility and balance before and after the training period were tested., Results: 3 E-types, 5 N-types and 6 M-types completed the protocol. An increase in VO 2max and strength was observed for the whole group. The best negative correlation (r=-0.5287) was found between the Morningness-Eveningness Questionnaire (MEQ) score and the increase in VO2max, and the best positive correlation (r=0.4395) was found between MEQ and the increase in strength. Changes in balance and flexibility did not show any clear trends., Conclusion: In an environment with no outdoor daylight, it seems that the response to 8 weeks of aerobic training is larger in the E- than in the M-types, although the M-types showed a larger improvement in strength.

It was hypothesized that an individual's chronotype might influence the response to physical activity at a given time of day. This study aimed to analyze the psychophysiological responses during a walking task at different times of day in individuals with different chronotypes. 46 students (M age=24.8 yr., SD=7.2) filled in the Morningness-Eveningness Questionnaire to determine chronotypes. Heart rate, walking time, and the rating of perceived exertion (RPE) were measured during two self-paced walking sessions: one in the morning (08:30) and one in the afternoon (15:30). A multivariate analysis of variance found a significant interaction between chronotype and time of day. The post hoc analysis showed a significant difference for RPE in the morning session, with evening types reporing a higher RPE compared with the morning types. The chronotype and the time of day when a physical task is undertaken can influence the RPE response, although it might not influence physiological or performance parameters. This has to be taken into account, because it can affect test reliability as well as possibly have a negative influence on the affective responses to a given task.

According to attention-restoration theory (ART), natural environments can provide restorative experiences. In this pilot study, a mixed-methods approach was used to examine the potential of using exercise in a natural environment to enhance exercise behaviors. The study included an assessment study and an intervention study (overall n = 19). The participants underwent a standardized exercise program including biking and circuit strength training, either indoors or outdoors in nature. Measurements included connectedness to nature, perceived exertion, perceived environmental restorativeness, enjoyment, affect, future exercise intention, and self-reported exercise behavior. The participants also wrote a brief text describing the way in which the environment influenced their feelings while exercising. Quantitative data were analyzed using the Spearman rank correlation and linear mixed-effects modeling. The qualitative information was analyzed thematically. The integrated results indicated that, in accordance with ART, exercising in nature was associated with a greater potential for restoration and affective responses, which in some participants led to enhanced intention to exercise and increased exercise behavior. However, some perceived that the indoor exercise provided a more effective workout. Further studies on larger samples are needed.

Background: Stress and mental fatigue are major health threats to employees in office-based occupations. Physical activity is widely used as a stress-management intervention for employees. Moreover, experiences in contact with nature have been shown to provide stress-reduction and restoration from mental fatigue., Objectives: In a pilot study designed as a randomized controlled trial we investigated the impact of a green-exercise intervention on psychological and physiological indicators of stress in municipality employees., Methods: Fourteen employees (7 females and 7 males, 49±8 yrs) volunteered in an exercise-based intervention in workplace either outdoors in a green/nature area or in an indoor exercise-setting. The intervention consisted of an information meeting and two exercise sessions, each including a biking bout and a circuit-strength sequence using elastic rubber bands (45-minutes, at about 55% of HR reserve, overall). Main outcomes were perceived environmental potential for restoration, affective state, blood pressure (BP) and cortisol awakening response (CAR AUC(G) and CAR AUC(I)) and cortisol levels in serum. Measurements were taken at baseline and in concomitance with the exercise sessions. Furthermore, affective state and self-reported physical activity levels were measured over a 10-weeks follow-up period., Results: Compared with the indoor group, the nature group reported higher environmental potential for restoration (p <  0.001) and Positive Affect (p <  0.01), along with improved CAR AUC(I) (p = 0.04) and, marginally, diastolic BP (p = 0.05). The nature group also reported higher ratings of Positive Affect at follow-up (p = 0.02). Differences at post-exercise were not found for any of the other components of affective state, systolic BP, CAR AUC(G) and cortisol levels measured in serum., Conclusions: Green-exercise at the workplace could be a profitable way to manage stress and induce restoration among employees. Further studies on larger samples are needed in order to improve the generalizability of the results.

BACKGROUND: Stress and mental fatigue are major health threats to employees in office-based occupations. Physical activity is widely used as a stress-management intervention for employees. Moreover, experiences in contact with nature have been shown to provide stress-reduction and restoration from mental fatigue. OBJECTIVES: In a pilot study designed as a randomized controlled trial we investigated the impact of a green-exercise intervention on psychological and physiological indicators of stress in municipality employees. METHODS: Fourteen employees (7 females and 7 males, 49±8 yrs) volunteered in an exercise-based intervention in workplace either outdoors in a green/nature area or in an indoor exercise-setting. The intervention consisted of an information meeting and two exercise sessions, each including a biking bout and a circuit-strength sequence using elastic rubber bands (45-minutes, at about 55% of HR reserve, overall). Main outcomes were perceived environmental potential for restoration, affective state, blood pressure (BP) and cortisol awakening response (CAR AUCG and CAR AUCI) and cortisol levels in serum. Measurements were taken at baseline and in concomitance with the exercise sessions. Furthermore, affective state and self-reported physical activity levels were measured over a 10-weeks follow-up period. RESULTS: Compared with the indoor group, the nature group reported higher environmental potential for restoration (p < 0.001) and Positive Affect (p < 0.01), along with improved CAR AUCI (p = 0.04) and, marginally, diastolic BP (p = 0.05). The nature group also reported higher ratings of Positive Affect at follow-up (p = 0.02). Differences at post-exercise were not found for any of the other components of affective state, systolic BP, CAR AUCG and cortisol levels measured in serum. CONCLUSIONS: Green-exercise at the workplace could be a profitable way to manage stress and induce restoration among employees. Further studies on larger samples are needed in order to improve the generalizability of the results. [ABSTRACT FROM AUTHOR]

The replenishment of blood glucose after exercise was studied in 62 healthy subjects performing a standardized exercise at 2 different times of the day in 5 different months of the year. Blood samples (fingertip) for glucose determination were drawn at the start of exercise and at 1, 5, 10 and 30 min after exercise. The total area under the glucose—time curves during the 30 min of recovery was calculated in either absolute units or as percent of the starting value. ANOVAs, with and without glucose variables from the exercise span as covariates, tested the integrated glucose—time areas for the effect of sex, time of day, and season. Exercise in the morning showed best recovery at all times of the year and females showed best recovery at each test time. In spite of significant time effects, a correlation between glucose recovery and amount of daylight could not be established. Significant differences in recovery between months, times of day and sexes were greatly influenced by glucose levels at start of the exercise, which showed a yearly rhythm. [ABSTRACT FROM AUTHOR]

Investigates the response of blood glucose to exercise throughout the year in an environment with large differences in the amount of daylight. Calculation of the total area under the glucose-time curves; Use of the analysis of variance method; Comparison of exercise between mornings and afternoons.