The ABC of Physical Activity for Health: A consensus statement from the British Association of Sport and Exercise Sciences

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Our understanding of the relationship between physical activity and health is constantly evolving. Therefore, the British Association of Sport and Exercise Sciences convened a panel of experts to review the literature and produce guidelines that health professionals might use. In the ABC of Physical Activity for Health, A is for All healthy adults, B is for Beginners, and C is for Conditioned individuals. All healthy adults aged 18–65 years should aim to take part in at least 150 min of moderate-intensity aerobic activity each week, or at least 75 min of vigorous-intensity aerobic activity per week, or equivalent combinations of moderate- and vigorous-intensity activities. Moderate-intensity activities are those in which heart rate and breathing are raised, but it is possible to speak comfortably. Vigorous-intensity activities are those in which heart rate is higher, breathing is heavier, and conversation is harder. Aerobic activities should be undertaken in bouts of at least 10 min and, ideally, should be performed on five or more days a week. All healthy adults should also perform muscle-strengthening activities on two or more days a week. Weight training, circuit classes, yoga, and other muscle-strengthening activities offer additional health benefits and may help older adults to maintain physical independence. Beginners should work steadily towards meeting the physical activity levels recommended for all healthy adults. Even small increases in activity will bring some health benefits in the early stages and it is important to set achievable goals that provide success, build confidence, and increase motivation. For example, a beginner might be asked to walk an extra 10 min every other day for several weeks to slowly reach the recommended levels of activity for all healthy adults. It is also critical that beginners find activities they enjoy and gain support in becoming more active from family and friends. Conditioned individuals who have met the physical activity levels recommended for all healthy adults for at least 6 months may obtain additional health benefits by engaging in 300 min or more of moderate-intensity aerobic activity per week, or 150 min or more of vigorous-intensity aerobic activity each week, or equivalent combinations of moderate- and vigorous-intensity aerobic activities. Adults who find it difficult to maintain a normal weight and adults with increased risk of cardiovascular disease or type 2 diabetes may in particular benefit from going beyond the levels of activity recommended for all healthy adults and gradually progressing towards meeting the recommendations for conditioned individuals. Physical activity is beneficial to health with or without weight loss, but adults who find it difficult to maintain a normal weight should probably be encouraged to reduce energy intake and minimize time spent in sedentary behaviours to prevent further weight gain. Children and young people aged 5–16 years should accumulate at least 60 min of moderate-to-vigorous-intensity aerobic activity per day, including vigorous-intensity aerobic activities that improve bone density and muscle strength.     

The effect of digitisation of the humeral epicondyles on quantifying elbow kinematics during cricket bowling

Abstract

In the sport of cricket the objective of the “no-ball” law is to allow no performance advantage through elbow extension during ball delivery. However, recently it has been shown that even bowlers with actions that are considered within the law show some elbow extension. The objective of this study was to investigate: [1] the effect of elbow orientation during anatomical landmark digitisation and [2] the choice of upper arm tracking cluster on the measurement of elbow angles during cricket bowling.

We compared the mean elbow angles for four different elbow postures; with the joint flexed at approximately 130°, 90°, in full extension and with the elbow flexed with the humerus internally rotated, and two upper arm clusters in two different situations: [1] during a controlled movement of pure flexion-extension and [2] during cricket bowling. The digitised postures of the anatomical landmarks where the elbow was extended and at 90° of flexion were more repeatable than the other two postures. The recommendation of this study when analysing cricket bowling is to digitise the humeral epicondyles with the joint flexed at 90°, or in full extension, and to relate their positions to an upper arm cluster fixed close to the elbow.     

Sleep restriction impairs maximal jump performance and joint coordination in elite athletes

ABSTRACT

The study objective was to examine the effects of three days of sleep restriction on maximal jump performance and joint coordination. Eleven elite cyclists obtained a one-week baseline of habitual sleep then restricted sleep to 4 h/night (SR) for three nights assessed through self-report and actigraphy. Pre and post-intervention measures were a box drop maximal vertical jump with 3D motion capture to assess physical performance and biomechanical changes, and Psychomotor Vigilance Task (PVT) assessed changes in response time. Associations between biomechanical, physical, and cognitive performance measures were assessed. Participants restricted reported sleep from 7.4 ± 0.5 h/night at baseline to 4.0 ± 0.2 h/night and actigraphy indicated 6.7 ± 0.7 to 3.7 ± 0.2 h/night. Following SR, jump height decreased (0.44 ± 0.09 vs. 0.42 ± 0.10 m, p = 0.02, g = 0.21). Hip sagittal/knee frontal (Δ15.5°, p = 0.04, g = 0.40) and hip frontal/knee frontal (Δ11.0°, p < 0.01, g = 0.44) plane coordination variability increased after SR. Hip sagittal/knee frontal plane coordination variability after SR was associated with increasingly slower PVT response time (r = 0.63, p = 0.03). These findings suggest SR for three days decreased maximal jump performance. SR increased joint coordination variability and was associated with greater impairment in response time. SR leads to deviations from preferred movement patterns, which may have implications for decrements in athlete performance and increased injury risk.     

Examining the Moderating Effect of Appearance Impression Motivation on the Relationship Between Perceived Physical Appearance and Social Physique Anxiety

We measured the effects of stride rate, resistance, and combined arm-leg use on energy expenditure during elliptical trainer exercise and assessed the accuracy of the manufacturer's energy expenditure calculations. Twenty-six men and women (M age = 29 years, SD = 8; M body weight = 73.0 kg, SD = 15.2) participated. Twenty-two participants performed two tests, one without the arm poles (leg-only) and the other with arm poles (combined arm-leg). The other 4 participants performed one test without the arm poles. Both tests consisted of six 5-min stages (two stride rates, 110 and 134 strides^.min^-1, and three resistance settings: 2, 5, and 8). Steady-state oxygen uptake (VO₂), minute ventilation (VE), heart rate (HR) and rating of perceived exertion (RPE) were measured. Repeated measures analysis of variance determined higher (p < .001) VO₂, VE, and RPE, but not HR, during combined arm-leg versus leg-only exercise at any given intensity. Increases in stride rate and resistance increased VO₂, VE, RPE, and HR with the greatest effect on VE and HR from Levels 5 to 8. The manufacturer's calculated energy expenditure was overestimated during both tests. Although the oxygen cost for elliptical trainer exercise was calculated to be approximately 0.1 ml^.kg^-1 per stride and 0.7 ml^.kg^-1.min^-1 per resistance level, VO₂ varied widely among individuals, possibly due to differences in experience using the elliptical trainer, gender, and body composition. The elliptical trainer offers (a) a variety of intensities appropriate for most individuals and (b) both arm and leg exercise. Due to the wide variability in VO₂, predicting the metabolic cost during elliptical trainer exercise for an individual is not appropriate.     

Estimating Energy Expenditure With the RT3 Triaxial Accelerometer

The RT3 is a relatively new triaxial accelerometer that has replaced the TriTrac. The aim of this study was to validate the RT3 against doubly labeled water (DLW) in a free-living, mixed weight sample of adults. Total energy expenditure (TEE) was measured over a 15-day period using DLW. Activity-related energy expenditure (AEE) was estimated by subtracting resting energy expenditure and thermic effect of feeding from TEE. The RT3 triaxial accelerometer was worn over 14 consecutive days. TEE and AEE were estimated using the RT3 proprietary equation. Thirty-six adults ages 18–56 years (56% women) with an average weight of 75.9 kg (SD = 14.8) completed all measurements. Compared to DLW, the RT3 underestimated TEE by 539 kJ (4%) and AEE by 485 kJ (15%) on average. The RT3 provided a relatively accurate assessment of free-living activity-related energy expenditure at the group level and generally underestimated total and activity-related energy expenditure compared to DLW.     

Testing Social-Cognitive Theory to Explain Physical Activity Change in Adolescent Girls From Low-Income Communities

Purpose

The aim of this study was to test the hypothesized structural paths in Bandura's social-cognitive theory (SCT) model on adolescent girls' physical activity following a 12-month physical activity and dietary intervention to prevent obesity.

Method

We conducted a 12-month follow-up study of 235 adolescent girls (M _age = 13.2 years, SD = 0.4) from 12 secondary schools located in low-income communities. At baseline, participants completed SCT scales related to physical activity (i.e., self-efficacy, intention, parental support, and outcome expectations). At baseline and 12-month follow-up (postintervention), participants wore accelerometers for 7 days. Structural equation modeling was used to determine if Time 1 measures predicted physical activity at 12-month follow-up after adjusting for baseline activity.

Results

The model explained 28% and 34% of the variance in physical activity and intention, respectively. Model fit indexes indicated the data were a good fit to the model; however, only self-efficacy was associated with physical activity at 12 months. There was no support for intention or outcome expectations as proximal determinants of behavior. Self-efficacy was associated with outcome expectations and parental support; however, only outcome expectations predicted intention.

Conclusions

Current findings indicate a large proportion of the variance for physical activity and intention remains unexplained and that the proposed pathways in the SCT model were not fully supported. Future model testing may need to consider augmentation or integration of theoretical models, which may include ecological components if we are to advance our understanding of physical activity behavior in this subgroup of the adolescent population.     

Induction and Efficacy: A Case Study of New Zealand Newly Qualified Secondary Science Teachers

This paper reports on 20 newly qualified secondary science teachers (NQSSTs) participating in a New Zealand study on teachers?? early professional learning. The focus of our study is how these new teachers were nurtured to become competent science teachers, confident of their ability to positively influence student learning. Based on responses to a graduating questionnaire and three interviews across their first 18?months of teaching, we look at the effect of induction and contextual factors on the teachers?? efficacy. While the NQSSTs overall reported relatively constant ratings of self-efficacy, they demonstrated different patterns of declared efficacy across this 18-month period. Findings regarding the influence of induction practices and contextual factors on the efficacy of these teachers are mixed.     

The use and usefulness of a parent questionnaire to help schools identify disability

The Equality Act 2010 will be implemented in full in 2011, and schools in the UK will have to provide special aids or services for children with disabilities where this provision is considered reasonable. This paper reports on staff perspectives on the use and usefulness of a parental questionnaire on disability from a sample of 49 schools (mainstream and special) located in 12 local authorities. Most schools found the process of administering the parent questionnaire undemanding; just under half of the sample indicated that they would take some action as a result of the data collected from the parental questionnaire (e.g., to inform plans for targeting or monitoring support for children, and to contact parents and follow‐up issues they had mentioned); and about one‐third of schools recorded unanticipated findings from the parental questionnaire, that is, the identification of children whose disabilities were not previously known to the school. Implications for schools are discussed.