BackgroundThe Daily Mile is a physical activity programme made popular by a school in Stirling, Scotland. It is promoted by the Scottish Government and is growing in popularity nationally and internationally. The aim is that each day, during class time, pupils run or walk outside for 15 min (~1 mile) at a self-selected pace. It is anecdotally reported to have a number of physiological benefits including increased physical activity, reduced sedentary behaviour, increased fitness and improved body composition. This study aimed to investigate these reports.MethodsWe conducted a quasi-experimental repeated measures pilot study in two primary schools in the Stirling Council area: one school with, and one without, intention to introduce the Daily Mile. Pupils at the control school followed their usual curriculum. Of the 504 children attending the schools, 391 children in primary classes 1–7 (age 4–12 years) at the baseline assessment took part. The follow-up assessment was in the same academic year. Outcomes were accelerometer-assessed average daily moderate to vigorous intensity physical activity (MVPA) and average daily sedentary behaviour, 20-m shuttle run fitness test performance and adiposity assessed by the sum of skinfolds at four sites. Valid data at both time points were collected for 118, 118, 357 and 327 children, respectively, for each outcome.ResultsAfter correction for age and gender, significant improvements were observed in the intervention school relative to the control school for MVPA, sedentary time, fitness and body composition. For MVPA, a relative increase of 9.1 min per day (95% confidence interval or 95%CI 5.1–13.2 min, standardised mean difference SMD = 0.407, p = 0.027) was observed. For sedentary time, there was a relative decrease of 18.2 min per day (10.7–25.7 min, SMD = 0.437, p = 0.017). For the shuttle run, there was a relative increase of 39.1 m (21.9–56.3, SMD = 0.236, p = 0.037). For the skinfolds, there was a relative decrease of 1.4 mm (0.8–2.0 mm, SMD = 0.246, p = 0.036). Similar results were obtained when a correction for socioeconomic groupings was included.ConclusionsThe findings show that in primary school children, the Daily Mile intervention is effective at increasing levels of MVPA, reducing sedentary time, increasing physical fitness and improving body composition. These findings have relevance for teachers, policymakers, public health practitioners, and health researchers.Electronic supplementary materialThe online version of this article (10.1186/s12916-018-1049-z) contains supplementary material, which is available to authorized users.

Sleep restriction is associated with impaired glucose metabolism and insulin resistance, however, the underlying mechanisms leading to this impairment are unknown. This study aimed to assess whether the decrease in insulin sensitivity observed after sleep restriction is accompanied by changes in skeletal muscle PKB activity. Ten healthy young males participated in this randomized crossover study which included two conditions separated by a 3‐week washout period. Participants underwent two nights of habitual sleep (CON) and two nights of sleep which was restricted to 50% of habitual sleep duration (SR) in the home environment. Whole‐body glucose tolerance and insulin sensitivity were assessed by an oral glucose tolerance test after the second night of each condition. Skeletal muscle tissue samples were obtained from the vastus lateralis to determine PKB activity. Findings displayed no effect of trial on plasma glucose concentrations (P = 0.222). Plasma insulin area under the curve was higher after sleep restriction compared to the control (P = 0.013). Matsuda index was 18.6% lower in the sleep restriction (P = 0.010). Fold change in PKB activity from baseline tended to be lower in the sleep restriction condition at 30 min (P = 0.098) and 120 min (P = 0.087). In conclusion, we demonstrated decreased whole‐body insulin sensitivity in healthy young males following two nights of sleep restriction. Skeletal muscle insulin signaling findings are inconclusive and require further study to examine any potential changes.

Experimental sleep restriction (SR) has demonstrated reduced insulin sensitivity in healthy individuals. Exercise is well-known to be beneficial for metabolic health. A single bout of exercise has the capacity to increase insulin sensitivity for up to 2 days. Therefore, the current study aimed to determine if sprint interval exercise could attenuate the impairment in insulin sensitivity after one night of SR in healthy males. Nineteen males were recruited for this randomized crossover study which consisted of four conditions—control, SR, control plus exercise, and sleep restriction plus exercise. Time in bed was 8 hr (2300–0700) in the control conditions and 4 hr (0300–0700) in the SR conditions. Conditions were separated by a 1-week entraining period. Participants slept at home, and compliance was assessed using wrist actigraphy. Following the night of experimental sleep, participants either conducted sprint interval exercise or rested for the equivalent duration. An oral glucose tolerance test was then conducted. Blood samples were obtained at regular intervals for measurement of glucose and insulin. Insulin concentrations were higher in SR than control (p = .022). Late-phase insulin area under the curve was significantly lower in sleep restriction plus exercise than SR (862 ± 589 and 1,267 ± 558; p = .004). Glucose area under the curve was not different between conditions (p = .207). These findings suggest that exercise improves the late postprandial response following a single night of SR.

We thank Daly-Smith et al. for taking the time to read the results of our pilot research study, describing it as an important and welcome contribution. Nonetheless, the authors argue six points against our conclusion. We contend that we addressed three of these points in our original discussion and disagree with their remaining points. Overall, their Commentary adds little to the topic of research into the Daily Mile™ that we had not already raised in our discussion. Additionally, they attribute statements to us that we did not make and ignore the raising of key issues in our original article. Given this, we stand by our original peer-reviewed conclusion that introducing the Daily Mile™ to the primary school day appears to be an effective intervention for increasing levels of moderate to vigorous physical activity, reducing sedentary time, increasing physical fitness and improving body composition, and that these findings have relevance for teachers, policy-makers, public health practitioners and health researchers.

Evidence suggests reduced glycaemic control following sleep restriction in healthy individuals. However, it remains unknown if impairments in glycaemic control increase with each additional night of sleep restriction in a linear manner. This randomised crossover study aimed to determine if the impairment in glycaemic control increases with each additional night of sleep restriction. Ten healthy individuals underwent four nights of control sleep (eight hours in bed) and four nights of sleep restriction (four hours in bed) in a sleep laboratory. An oral glucose tolerance test was conducted each morning. Serum glucose and insulin were measured. Glucose and insulin area under the curve were higher overall in the sleep restriction trial compared to control (p < 0.001 and p = 0.033), however no effect of day (p = 0.620 and p = 0.863) or interaction effect (p = 0.152 and p = 0.285) were observed. This supports previous literature showing a detrimental impact of sleep restriction on glucose regulation. The present findings, however, suggest the impairment in glycaemic control does not increase in a linear manner with an increasing number of nights of sleep restriction. This may have implications for the design of future studies examining sleep restriction and glycaemic control. Novelty Bullets: -Four nights of sleep restriction impaired glycaemic control in healthy individuals, but did not do so in a linear manner. -No effect of number of nights of restriction was found for glucose or insulin, which may have implications for future studies.

Childhood inactivity is linked to poorer physical and mental health during childhood and is associated with chronic ill‐health in later life. The Daily Mile (DM) is an initiative introduced in a Primary School in Scotland where the pupils walk or run ~1 mile each day. The aim of the study was to describe the physical activity (PA) and obesity levels of children taking part in the DM. Consent was obtained from parents of 259 children (184 male; 177 female). Height (m) and weight (kg) were measured to calculate BMI (weight/height2). Z scores were calculated within year group by gender. On a sub‐set of participants (n = 79), PA levels were objectively measured by accelerometers to assess amount of light, and moderate to vigorous intensity physical activity (MVPA). Data were analysed by t‐test of proportions, one‐way ANOVA and GLM‐ANOVA. For presentation, data were separated into Primary 1 – 3 (P1‐3, age ~4–7 years) and Primary 4–7 (P4‐7, age ~7–11 years). The percentage of boys and girls taking part in the DM who were categorised as obese was consistently below the Scottish Health Survey 2013 norms (Scottish norm): Boys P1‐3: 7% (13%) P4‐7 13% (17%); Girls P1‐3 8% (13%) P4‐7 13% (20%). However, all of these differences were non‐significant. Objective measurement of physical activity revealed that boys averaged 51 mins/day and girls averaged 40 mins/day of MVPA with no difference between younger (P1‐3) and older (P4‐7) pupils. UK PA Guidelines define “active” as 60+ mins MVPA/day. “Somewhat active” can be characterised as 30–59 mins MVPA/day and “low active” as < 30 mins MVPA/day. In P1‐3 Boys: 26% were active, 58% somewhat active, 16% low active; and P4‐7 Boys: 26% were active, 61% somewhat active, 13% low active. In P1‐3 Girls: 11% were active, 72% somewhat active, 17% low active; and P4‐7 Girls: 5.3% active, 68% somewhat active, 26% low active. The proportion who were “somewhat active” was significantly higher than Health Survey England (HSE, 2012) data for age 4–10 years: boys 22% and girls 28%. All differences in active (HSE: boys 51%, girls 34%), or low active (HSE: boys 28%, girls 39%) were non‐significant. Rates of obesity in a school implementing ~1 mile PA/day for over 3 years were not significantly below the Scottish average. Only 25% of boys and 9% of girls in this sample currently reach the UK PA Guidelines. In this cohort the DM appears to have more children “somewhat active” than national data. However, this data is cross sectional and further research is required to assess the effects of the intervention.

The purpose of this study was to investigate the effects of acute exercise on environmentally induced symptoms of dry eye. Twelve participants without dry eye disease volunteered to complete three experimental visits in a randomized order; (1) control condition seated for 1 h at a relative humidity (RH) of 40% (CONT), (2) dry condition seated for 1 h at a RH of 20% (DRY), and (3) exercise condition seated for 40 min followed by 20 min of cycling exercise at a RH of 20% (EXER). Tear volume, tear matrix metalloproteinase 9 (MMP-9), perception of dry eye symptoms (frequency and severity), core temperature, and ocular surface temperature (OST) were measured at the end of each exposure. The perception of dry eye frequency and MMP-9 concentration were significantly higher in DRY compared to CONT (P < 0.012), with no differences in EXER compared to CONT. The results suggest that an acute bout of exercise may attenuate symptoms of environmentally induced dry eye, and warrant further research.