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This cross-sectional study examined the relationship between physical self-perceptions (PSPs), maturation, and physical activity and compared the strength of the relationships of biological and chronological age with PSPs in early adolescent girls (N = 208; mean age = 11.83 +/- 0.39 years). Participants completed the Physical Activity Questionnaire for Older Children, the Children's Physical Self-Perception Profile, and the Pubertal Development Scale. Results indicated that PSPs were significantly and moderately correlated with physical activity. There were no differences in physical activity between maturation stages. Girls who were in the early stages of maturation had significantly more positive perceptions of body attractiveness and physical self-worth than girls in the mid stages of maturation. There was no evidence of a relationship between PSPs and chronological age. This study provided further support for the relationship between PSPs and physical activity and the relationship between maturation and aspects of PSPs. In this age group, maturation does not appear to be related to physical activity or the PSPs most strongly influential on physical activity behavior. [ABSTRACT FROM AUTHOR]

Home working has increased due to COVID-19, but little is known about how this change has impacted the health risk behaviour of elevated sedentary time. The aim of this cross-sectional exploratory study was to assess occupational sitting behaviour when working at home, and use the Capability Opportunity Motivation-Behaviour (COM-B) model to identify influences on this behaviour. University staff (n = 267; 69% female; 92% white) who were predominantly working from home completed a questionnaire to assess sitting time, sitting breaks, demographic and occupational characteristics, and a 7-item COM-B questionnaire and open-ended questions to assess influences on time spent sitting whilst working from home. Data were analysed descriptively, a repeated measures ANOVA was used to determine differences in the COM-B items, and binary logistic regression was used to examine predictors of sitting time. Staff spent on average 89.5% (SD = 17.1) of their time sitting whilst working at home, and took an average of 1.36 (1.38) sitting breaks per hour. There were significant and meaningful differences in the influence of the COM factors on ability and willingness to reduce sitting behaviour (p < .0001; η p 2  = .38), and the open-ended responses added further context. The included variables accounted for 20.7% of variance in sitting behaviour, with age, sitting breaks, motivation-automatic, and opportunity-physical contributing significantly. Working from home leads to elevated levels of sitting, and the COM-B provides a useful model to identify key influences on ability and willingness to reduce sitting. Strategies incorporating regular breaks, habit formation/reversal, and restructuring the physical environment may be beneficial., Competing Interests: Competing interestsThe authors have no relevant financial or non-financial interests to disclose., (© The Author(s) 2022.)

Objective: To scope the relationships between rugby union, and health and well-being., Design: Scoping review., Data Sources: Published and unpublished reports of any age, identified by searching electronic databases, platforms and reference lists., Methods: A three-step search strategy identified relevant published primary, secondary studies and grey literature, which were screened using a priori inclusion criteria. Data were extracted using a standardised tool, to form (1) a numerical analysis and (2) a thematic summary., Results and Discussion: 6658 records were identified, and 198 studies met the inclusion criteria. All forms of rugby union can provide health-enhancing physical activity (PA). 'Non-contact' and wheelchair rugby in particular provide a wide range of physical and mental health and well-being benefits. The evidence is either mixed or unclear in relation to 'contact' rugby union and its effects on a range of physical health domains. Injury and concussion incidence rates are high for contact rugby union relative to other sports., Conclusions: A wide range of stakeholders as well as existing and potential participants can use this information to make a more informed decision about participating in and promoting rugby union as a health-enhancing activity. Industry and policy-makers can use this review to inform policies and strategies that look to increase participation rates and use rugby union as a vehicle to contribute positively to population health. Further research understanding rugby union's contribution to PA as well as to muscle-strengthening and balance is indicated, as well as research examining more health and well-being outcomes across more diverse cohorts., Competing Interests: Competing interests: SAG receives remuneration for clinical work in professional rugby union, and is employed by the Rugby Football Union as a Sports Medicine Training Fellow. AM receives remuneration from Scottish Rugby Union for clinical work. SK is employed by the Rugby Football Union as medical services director. KAS is employed by the Rugby Football Union as medical research lead., (© Author(s) (or their employer(s)) 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Competing Interests: Competing interests: SAG receives remuneration for clinical work in professional rugby union, and is employed by the Rugby Football Union as a Sports Medicine Training Fellow. AM receives remuneration from Scottish Rugby Union for clinical work. SK is employed by the rugby football union as medical services director. KAS is employed by the rugby football union as medical research lead.

Background: In order to promote walking, researchers have sought to identify the required step rate to maintain a health-enhancing walking intensity However, there is limited evidence regarding the stepping rate required to promote moderate-intensity walking in adolescent girls., Purpose: To identify the step rate equivalent to moderate-intensity physical activity (MPA) in adolescent girls and to explore the influence that different anthropometric measures may have on the step rate equating to MPA in this population., Methods: A total of 56 adolescent girls (mean age = 13.8[0.7] y) were recruited to the study. Anthropometric variables and resting metabolic rate were assessed, followed by 3 overground walking trials on a flat surface at approximately 2, 3, and 4 mph, each lasting a minimum of 4 minutes. Oxygen uptake was assessed using a portable gas analyzer and subsequently converted into metabolic equivalents (METs). Step count was assessed by real-time direct observation hand tally., Results: Employing the linear regression between step rate and METs (r2 = .20, standard error of estimates = 0.003) suggests that 120 steps per minute was representative of an MPA (3 METs) equating to 7200 steps in 60 minutes. Multiple regression and mixed-model regression confirmed weight-related variables and maturity were significant predictors of METs (P < .01)., Conclusion: The results suggest that, at population level, a step rate of 120 steps per minute may be advocated to achieve MPA in adolescent girls; although, due to the small sample size used, caution should be applied. At an individual level, other factors, such as age and weight, should be considered.

Background: Currently, it is not known how much walking should be advocated for good health in an adolescent population. Step count recommendations for minimum time in moderate-intensity activity have been translated predominantly from treadmill walking., Purpose: To compare the energy cost of walking on a treadmill with overground walking in adolescent girls., Methods: A total of 26 adolescent girls undertook resting metabolic measurements for individual determination of 1 metabolic equivalent using indirect calorimetry. Energy expenditure was subsequently assessed during treadmill and overground walking at slow, moderate, and fast walking speeds for 4 to 6 minutes. Treadmill step rates were matched overground using a metronome., Results: The energy cost of treadmill walking was found to be significantly greater than and not equivalent to overground walking at 133 steps per minute; (equivalent to the fast walking pace): V˙O2 3.90 (2.78-5.01), P < .001, mean absolute percentage error (MAPE) = 18.18%, and metabolic equivalent 0.77 (0.54-1.00), P < .001, MAPE = 18.16%. The oxygen cost per step (V˙O2 mL·step-1) was significantly greater and not equivalent on the treadmill at 120 and 133 steps per minute: 0.43 (0.12-0.56), P < .05, MAPE = 10.12% versus 1.40 (1.01-1.76), P < .001, MAPE = 17.64%, respectively., Conclusion: The results suggest that there is a difference in energy cost per step of walking on a treadmill and overground at the same step rate. This should be considered when utilizing the treadmill in energy expenditure studies. Studies which aim to provide step recommendations should focus on overground walking where most walking activity is adopted.

Background: It is currently not known how much walking should be advocated for good health in adolescent girls. The aim of this study was therefore to recommend health referenced standards for step defined physical activity relating to appropriate health criterion/indicators in a group of adolescent girls., Method: Two hundred and thirty adolescent girls aged between 12 to 15 years volunteered to take part in the study. Each participant undertook measurements (BMI, waist circumference, % body fat, and blood pressure) to define health status. Activity data were collected by pedometer and used to assess daily step counts and accumulated daily activity time over 7 consecutive days., Results: Individuals classified as 'healthy' did not take significantly more steps·day-1 nor spend more time in moderate intensity activity than individuals classified as at health risk or with poor health profiles., Conclusion: 'Healthy' adolescent girls do not walk significantly more in term of steps·day-1 or time spent in activity than girls classified as 'unhealthy.' This could suggest that adolescent girls may not walk enough to stratify health and health related outcomes and as a result the data could not be used to inform an appropriate step guideline for this population.

High-intensity interval training (HIT) has been proposed as a time-efficient alternative to traditional cardiorespiratory exercise training, but is very fatiguing. In this study, we investigated the effects of a reduced-exertion HIT (REHIT) exercise intervention on insulin sensitivity and aerobic capacity. Twenty-nine healthy but sedentary young men and women were randomly assigned to the REHIT intervention (men, n = 7; women, n = 8) or a control group (men, n = 6; women, n = 8). Subjects assigned to the control groups maintained their normal sedentary lifestyle, whilst subjects in the training groups completed three exercise sessions per week for 6 weeks. The 10-min exercise sessions consisted of low-intensity cycling (60 W) and one (first session) or two (all other sessions) brief 'all-out' sprints (10 s in week 1, 15 s in weeks 2-3 and 20 s in the final 3 weeks). Aerobic capacity ([Formula: see text]) and the glucose and insulin response to a 75-g glucose load (OGTT) were determined before and 3 days after the exercise program. Despite relatively low ratings of perceived exertion (RPE 13 ± 1), insulin sensitivity significantly increased by 28% in the male training group following the REHIT intervention (P < 0.05). [Formula: see text] increased in the male training (+15%) and female training (+12%) groups (P < 0.01). In conclusion we show that a novel, feasible exercise intervention can improve metabolic health and aerobic capacity. REHIT may offer a genuinely time-efficient alternative to HIT and conventional cardiorespiratory exercise training for improving risk factors of T2D.

The objective of this study was to determine the energy expended and intensity of physical activity achieved by adolescent girls while playing on a dance simulation game. Twenty adolescent girls were recruited from a local secondary school. Resting oxygen uptake (VO(2)) and heart rate were analysed while sitting quietly and subsequently during approximately 30 min of game play, with 10 min at each of three increasing levels of difficulty. Energy expenditure was predicted from VO(2) at rest and during game play at three levels of play, from which the metabolic equivalents (METS) of game playing were derived. Mean +/- standard deviation energy expenditure for levels 1, 2, and 3 was 3.63 +/- 0.58, 3.65 +/- 0.54, and 4.14 +/- 0.71 kcal . min(-1) respectively, while mean activity for each level of play was at least of moderate intensity (>3 METS). Dance simulation active computer games provide an opportunity for most adolescent girls to exercise at moderate intensity. Therefore, regular playing might contribute to daily physical activity recommendations for good health in this at-risk population.

This longitudinal study investigated the influence of maturation on physical self-perceptions and the relationship with physical activity in early adolescent girls (N=150; mean age=12.79+/-0.31). Physical characteristics were measured and participants completed the Physical Activity Questionnaire for Children, the Children and Youth Physical Self-Perception Profile and the Pubertal Development Scale on two occasions 12 months apart. The results demonstrated a decrease in overall physical activity levels over 12 months which was not influenced by maturational status or physical characteristics. Additional analysis indicated that physical self-perceptions partially accounted for the explained variance in physical activity change, with physical condition being an important individual predictor of physical activity. Further analysis indicated that body mass was an important individual predictor of changes in perceptions of body attractiveness and physical self-worth. At this age maturation has a limited influence on the physical activity behaviours of early adolescent girls and although the variance in physical activity was partly accounted for by physical self-perceptions, this was a relatively small contribution and other factors related to this drop in physical activity need to be considered longitudinally.

The study of VO2 kinetics offers the potential to non-invasively examine the cardiorespiratory and metabolic response to dynamic exercise and limitations to every day physical activity. Its non-invasive nature makes it hugely attractive for use with young people, both healthy and those with disease, and yet the literature, whilst growing with respect to adults, remains confined to a cluster of studies with these special populations. It is most likely that this is partly due to the methodological difficulties involved in studying VO2 kinetics in young people which are not present, or present to a lesser degree, with adults. This article reviews these methodological issues, and explains the main procedures that might be used to overcome them. Key pointsThe VO2 kinetic response to exercise represents the combined efficiency of the cardiovascular, pulmonary and metabolic systems, and an accurate assessment of the response potentially provides a great deal of useful information via non-invasive methodology.An accurate assessment of the VO2 kinetic response is however inherently difficult with children and especially those with reduced exercise tolerance, due primarily to the apparent breath-by-breath noise which masks the true underlying physiological response, and the small amplitudes of the response signal.Despite this, it is possible to assess and quantify the VO2 kinetic response with children if appropriate steps are taken to apply carefully selected methodologies and report response variables with confidence intervals. In this way, both the researcher and the reader can be confident that the data reported is meaningful.

The purpose of this study was to apply a series of mathematical models in order to investigate the nature of the kinetic response to heavy intensity exercise with children and identify a suitable model with which to estimate parameters of the response. Sixty two children (35 male, 27 female aged 10-15 years) completed four transitions from baseline pedalling to 40% of the difference between their previously determined anaerobic threshold and peak VO2 on an electronically braked cycle ergometer. Initially three models were fitted to the averaged response profiles following the end of phase 1. and their residuals compared; 1, a single exponential with a delay term; 2, an exponential and linear term with independent delays; and 3, a double exponential with independent delays. Up to 95% of the response profiles were better fitted by either model 2 or 3 (p < 0.05), and model 3 was a statistically better fit (p < 0.05) than model 2 in 77% of cases. Residual inspection confirmed the superior fit by model 3. A fourth model which consisted of a single exponential with a delay term was fitted within the phase 2 fitting window. Estimated parameters (A1 and tau1), using model 4 were not significantly different from model 3, and model 4 was identified as the model of choice due to the wide confidence intervals in tau2 and A2 using model 3. It was concluded that the nature of the response to heavy intensity exercise in children is similar to that previously reported with adults and that the response should be modelled accordingly.

It has been demonstrated that there are no sex differences in the oxygen uptake (V(.)O(2)) kinetic response to moderate intensity exercise. However, sex differences in the response to maximal exercise are readily apparent even in the prepubertal years. The purpose of this study was therefore to investigate if sex differences exist in the V(.)O(2) kinetic response to heavy-intensity exercise. Forty-eight prepubertal children (25 male, 23 female) completed four transitions from baseline to 40% of the difference between their previously determined T(V-slope) (ventilatory threshold determined by the V-slope method) and peak V(.)O(2) on an electronically braked cycle ergometer. Each subject's breath-by-breath responses were interpolated to 1 s intervals, time aligned and averaged. The data following phase 1 were fit with: (1) a double exponential model and (2) a single exponential model within a fitting window that was previously identified to exclude the slow component. There were no significant differences in the parameters of the primary component between each model. Subsequent analysis was carried out using model 2. The primary time constant (tau(1)) was significantly (P<0.05) faster in boys [17.6 (5.8) s] than girls [21.9 (8.2) s], and the slow component contribution to the total change in amplitude after 9 min was significantly greater in girls [11.8 (5.5)%] than boys [8.9 (3.7)%]. Sex differences in the kinetic response to heavy-intensity exercise were identified and suggest that during the prepubertal years, sex differences exist in the ability to deliver and/or utilise oxygen in children.

The purpose of this study was to investigate longitudinal changes with age in the kinetic response to cycling at heavy-intensity exercise in boys and girls. Twenty-two prepubertal children (13 male, 9 female) carried out a series of exercise tests on two test occasions with a 2-yr interval. On each test occasion, the subject completed multiple transitions from baseline to 40% of the difference between their previously determined V-slope and peak O(2) uptake (Vo(2)) for 9 min on an electronically braked cycle ergometer. Each subject's breath-by-breath responses were interpolated to 1-s intervals, time aligned, and averaged. The data after phase 1 were fit with 1) a double exponential model and 2) a single exponential model within a fitting window that was previously identified to exclude the slow component. There were no significant differences in the parameters of the primary component between each model. Subsequent analysis was carried out using model 2. The Vo(2) slow component was computed as the difference between the amplitude of the primary component and the end-exercise Vo(2) and was expressed as the percent contribution to the total change in Vo(2). Over the 2-yr period, the primary time constant (boys 16.8 +/- 5.3 and 21.7 +/- 5.3 s, girls 21.1 +/- 8.1 and 26.4 +/- 8.4 s, first and second occasion, respectively) and the relative amplitude of the slow component (boys 9.4 +/- 4.6 and 13.8 +/- 5.3%, girls 10.3 +/- 2.4 and 15.5 +/- 2.8%, first and second occasion, respectively) significantly increased with no sex differences. The data demonstrate that children do display a slow-component response to exercise and are consistent with an age-dependent change in the muscles' potential for O(2) utilization.

Objectives: To investigate the reliability of heart rate variability (HRV) measures at rest and during light exercise in children., Methods: Short term (five minute) HRV was assessed in 12 children (11-12 years of age). HRV measures were collected at rest with the children supine, breathing at 12 breaths/min, and during exercise on a cycle ergometer while exercising at 25% of peak oxygen uptake. Both resting and exercise data were collected twice from each child., Results: Intraclass correlation coefficients were low to moderate for most measures with wide confidence intervals for each variable in both resting and exercise conditions. Random variation (typical error) within repeated measurements ranged from 31% to 187%., Conclusions: These preliminary findings suggest that HRV measures are unreliable at rest and during light exercise in children aged 11-12 years. Tighter control of extraneous influences is recommended.

The literature suggests that the oxygen uptake (VO2) response to the onset of moderate-intensity exercise may be both mature from childhood and independent of sex. Yet the cardiorespiratory response to exercise and the metabolic profile of the muscle appear to change with growth and development and to differ between the sexes. The aim of this study was to investigate further changes in the VO2 kinetic response with age and sex. Participants completed a series of no less than four step change transitions, from unloaded pedalling to a constant work rate corresponding to 80% of their previously determined ventilatory threshold. Each participant's breath-by-breath responses were interpolated to 1 s intervals, time aligned and then averaged. A single exponential model that included a time delay was used to analyse the averaged response following phase 1 (15 s). Participants with parameter confidence intervals more than +/- 5 s were removed from the sample; the results for the remaining 13 men and 12 women (age 19-26 years), 12 boys and 11 girls (age 11-12 years) were used for statistical analysis. Children had a significantly shorter time constant than adults, both for males (19.0+/-2.0 and 27.9+/-8.6 s respectively; P<0.01) and females (21.0+/-5.5 and 26.0+/-4.5 s respectively; P<0.05). There were no significant differences in the time constant between the sexes for either adults or children (P>0.05). A significant relationship between the time constant and peak VO2 was found only in adult males (P<0.05). A shorter time constant in children may reflect an enhanced potential for oxidative metabolism.