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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 (Mage = 24.8yr., 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 hocanalysis 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.

A survey in a high school in the city of Tromsø in the spring of 1988 was designed to examine the characteristics of sleep and factors promoting and disturbing sleep. Out of 621 students 465 (74.9%) responded to 11 questions about last night's sleep and what the individual perceived as usual sleep (10 questions). On this information two sleep-quality scores, a special score for last night's sleep and a general score for what is perceived as usual sleep, were computed. The sleep-quality score was the sum of answers identical to a preset “right” answer indicating good sleep-quality. Multiple regression analyses separately by sex showed that different variables influence sleep-quality of boys and girls. Activity and intensity of exercise were taken into the regression model for the special sleep-score for boys but not for girls. For girls psychological factors seemed of greater importance to sleep-quality than exercise.

Eight high-school girls participating in competitive sports and six non-participating girls living north of the polar circle recorded their sleep once a week during the Fall, including the period when the sun does not rise above the horizon. Sleep-quality scores were computed as the sum of answers identical to a preset “right” answer indicating good sleep-quality. Significant differences on sleep-quality between the two groups were found, but a significant influence of amount of daylight or exercise could not be confirmed. When sleep-quality was ranked during three periods through the Fall, the girls participating in competitive sports showed a trend of increasing sleep-quality and the nonparticipants a decreasing one. An explanation based on influence of exercise thresholds upon sleep-quality is presented.

ABSTRACTBackground: 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 (VO2max), 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 VO2maxand 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.

ABSTRACTLong-distance dog sled races, e.g. Iditarod (Alaska) and Finnmarksløpet (Northern Norway), are extremely demanding sporting events that might expose mushers, handlers and a large number of organisers and volunteers to risks for their health. The purpose of this systematic literature review (PROSPERO registration n. CRD42017069136) was to identify and summarise all available scientific literature relative to health issues connected to participating in these races. Using a literature search strategy in line with PRISMA guidelines, 117 scientific studies, sought through databases (Google Scholar and PubMed, between 2ndand 9thMay 2017) and scrutiny of reference lists, were screened. Studies published in English treating any health issues assessed during or after a long-distance dog sled race were included, with no restriction in relation to their study design or the characteristics of participants studied. The quality of the studies was assessed using a standardised checklist. Ten studies met the criteria for being included in a qualitative analysis. The data synthesis showed that participants underwent strenuous psychophysical load, with insufficient sleep/rest and inadequate energy intake. Findings on hydrations are mixed. The risk of incurring in life-threatening injuries or infections was low, although injuries and infections of minor severity were common. No alterations of blood markers were observed from before to after the races. These findings will help planning prevention and treatment strategies in long-distance dog sled races. However, more research is needed in this field in the future.

After a 30-min. standardized bicycle exercise at two times of day in 5 mo. of the year, 62 subjects showed a yearly variation in their glycemic response that was about 5 months out of phase with the peak levels in the light sensitive hormone melatonin, suggesting a reciprocal relationship between melatonin and glucose utilization.

The response to sub-maximal physical activity performed in the morning and late afternoon by individuals with different chronotypes was investigated. 22 participants filled out the Morningness-Eveningness Questionnaire and underwent a self-paced walking task that consisted of walking from the top to the bottom of a hill and back three times (1,836 meters, with a slope of 14.16%). The task was repeated twice: late afternoon (16:30) and early morning (08:30). Walking speed (time for completion in seconds), heart rate, and perceived exertion were measured during each task, with overall results given as a general descriptive analysis. Preliminary findings suggest that chronotype is likely to influence the responses to exercise, mostly with evening-types seeming at a disadvantage when performing a physical task in the morning. Individuals can be classified by circadian typology or chronotype, which is the propensity to be a morning-type, evening-type, or neither-type. The circadian typology, commonly referred to as being a morning person or an evening person or somewhere in between, is involved not only in the expression of physiological rhythms, but also in habits and lifestyles, such as sleeping patterns (Park, Matsumoto, Seo, & Shinkoda, 1999) that emerge especially during adolescence (Park, Matsumoto, Seo, Kang, & Nagashima, 2002) and remain throughout adult life (Koukkari & Sothern, 2006).