Developing motor competency in youths: Perceptions and practices of strength and conditioning coaches.

Motor competency is integral to the long-term athletic development of youths. Strength and conditioning (S&C) coaches are recommended to deliver motor competency interventions, yet no studies have investigated their perceptions and practices for developing motor competency in youths. Sixty-seven male, and 4 female S&C coaches completed an initial and follow up questionnaire using a 5-point Likert scale, rating 1] the importance of developing competence, and 2] how frequently they developed competence across 90 motor competencies. Over 55% of S&C coaches reported a broad range of "important" (69/90) and "frequently developed" (48/90) motor competencies. The most important motor competency was "deceleration" (4.9 ± 0.3), whilst "hip hinge (bilateral)" was the most practised (4.4 ± 0.5). S&C coaches targeted upper body pushing and pulling competencies more than their perceived importance, whilst agility (e.g., turning) competencies were targeted less than their importance. Further analysis showed S&C coaches who delivered 3-4 sessions per week targeted 15-18% more competencies compared to ≤ 2 sessions per week. Overall, these findings have strong implications for youth motor competency development including the reflection of important vs. practised competencies, coach education programmes, and consideration for how S&C coaches should seek to optimise motor competency development within youths.

Exploring the relationship between adolescent biological maturation, physical activity, and sedentary behaviour: a systematic review and narrative synthesis.

CONTEXT: Across adolescence, there is a notable decline in physical activity in boys and girls. Maturational timing may be a risk factor for disengagement from physical activity and increased sedentary behaviours during adolescence. OBJECTIVE: This systematic review aimed to summarise literature that examined the relationship between maturational timing, physical activity and sedentary behaviour in adolescents. METHODS: Six electronic databases were searched for articles that assessed biological maturation and physical activity (including sports participation and active transportation) or sedentary behaviours in adolescents. Two reviewers conducted title, abstract, and full-text screening, reference and forward citation searches. Included articles were evaluated for quality using a standardised tool. A narrative synthesis was used to analyse the findings due to the heterogeneity of the studies. RESULTS: Searches yielded 78 articles (64 unique studies) that met the inclusion criteria, representing 242,316 participants (153,179 unique). Studies ranged from 30.0% (low) to 91.7% (high) in quality. An inverse relationship between maturational timing and physical activity (in 50 and 60% of studies in boys and girls, respectively) and a positive relationship between maturational timing and sedentary behaviour (in 100% and 53% of studies in boys and girls, respectively) was most commonly reported. Evidence supporting an association between maturational timing, sports participation, and active transportation was inconsistent. CONCLUSIONS: While this review demonstrates some evidence for early maturational timing as a risk factor for disengagement from physical activity and increase in sedentary behaviours, the reviewed literature also demonstrates that this relationship is complex. Future research that tracks maturity-related variations in physical activity and sedentary behaviours over adolescence is warranted.

Physical Activity, BMI, and Blood Pressure in US Youth: NHANES 2003-2006.

PURPOSE: The objective of this study was to examine the independent and combined association of physical activity and body mass index (BMI) with blood pressure in youth. METHODS: Youth aged 8-18 years from the 2003-2006 National Health and Nutrition Examination Survey (NHANES) with BMI, blood pressure, and physical activity (accelerometer) were included in the analyses. A total of 2585 subjects (1303 males; 47% of all 8- to 18-year-olds) met these criteria. RESULTS: Obese youth had a systolic blood pressure that was 8 mm Hg higher than normal weight youth. A significant interaction between BMI and physical activity on blood pressure was found (P < .001), and group differences among the BMI/activity groups showed that the 3 obese groups and the overweight/least active group had significantly higher systolic blood pressure than the normal weight/active group across all analyses. The overweight/least active and normal weight/least active groups had significantly higher diastolic blood pressure than the normal weight/active group as well. CONCLUSIONS: This study showed a significant independent and combined association of BMI and physical activity with blood pressure in youth. Interventions need to focus on the reduction of fatness/BMI as a way to reduce the cardiovascular risk in youth.

Premier League academy soccer players' experiences of competing in a tournament bio-banded for biological maturation.

Individual differences in the growth and maturation have been shown to impact player performance and development in youth soccer. This study investigated Premier League academy players' experiences of participating in a tournament bio-banded for biological maturation. Players (N = 66) from four professional soccer clubs aged 11 and 14 years and between 85-90% of adult stature participated in a tournament. Players competed in three 11 vs 11 games on a full size pitch with 25-min halves. Sixteen players participated in four 15-min focus groups and were asked to describe their experiences of participating in the bio-banded tournament in comparison to age group competition. All players described their experience as positive and recommended the Premier League integrate bio-banding into the existing games programme. In comparison to age-group competitions, early maturing players described the bio-banded games more physically challenging, and found that they had to adapt their style of play placing a greater emphasis on technique and tactics. Late maturing players considered the games to be less physically challenging, yet appreciated the having more opportunity to use, develop and demonstrate their technical, physical, and psychological competencies. Bio-banding strategies appear to contribute positively towards the holistic development of young soccer players.

Reference Curves for Field Tests of Musculoskeletal Fitness in U.S. Children and Adolescents: The 2012 NHANES National Youth Fitness Survey.

Laurson, KR, Saint-Maurice, PF, Welk, GJ, and Eisenmann, JC. Reference curves for field tests of musculoskeletal fitness in U.S. children and adolescents: The 2012 NHANES National Youth Fitness Survey. J Strength Cond Res 31(8): 2075-2082, 2017-The purpose of the study was to describe current levels of musculoskeletal fitness (MSF) in U.S. youth by creating nationally representative age-specific and sex-specific growth curves for handgrip strength (including relative and allometrically scaled handgrip), modified pull-ups, and the plank test. Participants in the National Youth Fitness Survey (n = 1,453) were tested on MSF, aerobic capacity (via submaximal treadmill test), and body composition (body mass index [BMI], waist circumference, and skinfolds). Using LMS regression, age-specific and sex-specific smoothed percentile curves of MSF were created and existing percentiles were used to assign age-specific and sex-specific z-scores for aerobic capacity and body composition. Correlation matrices were created to assess the relationships between z-scores on MSF, aerobic capacity, and body composition. At younger ages (3-10 years), boys scored higher than girls for handgrip strength and modified pull-ups, but not for the plank. By ages 13-15, differences between the boys and girls curves were more pronounced, with boys scoring higher on all tests. Correlations between tests of MSF and aerobic capacity were positive and low-to-moderate in strength. Correlations between tests of MSF and body composition were negative, excluding absolute handgrip strength, which was inversely related to other MSF tests and aerobic capacity but positively associated with body composition. The growth curves herein can be used as normative reference values or a starting point for creating health-related criterion reference standards for these tests. Comparisons with prior national surveys of physical fitness indicate that some components of MSF have likely decreased in the United States over time.

Project FIT: A School, Community and Social Marketing Intervention Improves Healthy Eating Among Low-Income Elementary School Children.

Project FIT was a two-year multi-component nutrition and physical activity intervention delivered in ethnically-diverse low-income elementary schools in Grand Rapids, MI. This paper reports effects on children's nutrition outcomes and process evaluation of the school component. A quasi-experimental design was utilized. 3rd, 4th and 5th-grade students (Yr 1 baseline: N = 410; Yr 2 baseline: N = 405; age range: 7.5-12.6 years) were measured in the fall and spring over the two-year intervention. Ordinal logistic, mixed effect models and generalized estimating equations were fitted, and the robust standard errors were utilized. Primary outcomes favoring the intervention students were found regarding consumption of fruits, vegetables and whole grain bread during year 2. Process evaluation revealed that implementation of most intervention components increased during year 2. Project FIT resulted in small but beneficial effects on consumption of fruits, vegetables, and whole grain bread in ethnically diverse low-income elementary school children.

Association of the Family Nutrition and Physical Activity Screening Tool with Weight Status, Percent Body Fat, and Acanthosis Nigricans in Children from a Low Socioeconomic, Urban Community.

OBJECTIVE: To examine the association of the Family Nutrition and Physical Activity (FNPA) screening tool with weight status, percent body fat, and acanthosis nigricans (AN) in 6- to 13-year-old children from a low socioeconomic, urban community. METHODS: Children (n=415) from four elementary schools located around Flint, Michigan were assessed for body mass index, percent body fat, and AN. The FNPA screening tool was completed by parents. Mann-Whitney U tests were used to assess differences in FNPA score by sex and presence of AN. Logistic regression was used to evaluate the association of the FNPA (tertiles) with weight status and AN. RESULTS: Children with AN (13.7%) had a significantly lower FNPA score (56.3 + 7.1) compared with children without AN (61.0 + 7.1; P<.05). Children with FNPA scores in the lowest tertile (high-risk) had odds ratios of 1.74 (95% CI =1.05 - 2.91) and 2.77 (95% CI =1.22 - 6.27) compared with children with FNPA scores in the highest tertile (low-risk) for being overfat and having AN, respectively. CONCLUSION: Although the FNPA screening tool did not predict risk for being overweight or obese, it was significantly associated with an increased odds of children at risk for being overfat or having AN.

Prevalence of elevated mean arterial pressure and how fitness moderates its association with BMI in youth.

OBJECTIVE: Cardiorespiratory fitness is known to be cardioprotective and its association with the components of the metabolic syndrome in children is becoming clearer. The aim of the present study was to examine the extent to which cardiorespiratory fitness may offset the weight-related association with mean arterial pressure (MAP) in schoolchildren. DESIGN: Cross-sectional study. SETTINGS: Schoolchildren from the East of England, U.K. SUBJECTS: A total of 5983 (48% females) schoolchildren, 10 to 16 years of age, had height, weight and blood pressure measured by standard procedures and cardiorespiratory fitness assessed by the 20 m shuttle-run test. Participants were classified as fit or unfit using internationally accepted fitness cut-off points; and as normal weight, overweight or obese based on BMI, again using international cut-off points. Age-adjusted ANCOVA was used to determine the main effects and interaction of fitness and BMI on MAP Z-score. Logistic regression models were used to estimate odds ratios of elevated MAP. RESULTS: Prevalence of elevated MAP in schoolchildren was 14.8% overall and 35.7% in those who were obese-unfit. Approximately 21% of participants were overweight and 5% obese, while 23% were classified as unfit. MAP generally increased across BMI categories and was higher in the aerobically unfit participants. Obese-fit males had lower MAP compared with obese-unfit males (P < 0.001); this trend was similar in females (P = 0.05). CONCLUSIONS: Increasing fitness level may have a positive impact on the weight-related elevations of MAP seen in obese and overweight schoolchildren.

Associations Between Motor Competence and Physical Activity, Physical Fitness and Psychosocial Characteristics in Adolescents: A Systematic Review and Meta-analysis.

BACKGROUND: Motor competence is an integral component of the health and performance of youth. Numerous studies support the hypothesis that motor competence interacts with perceived motor competence and physical fitness during childhood to induce positive (e.g. healthy weight status) or negative (e.g. reduced physical activity engagement) trajectories. Yet, while adolescence is a key period of rapid growth and maturation, no systematic reviews and meta-analyses have examined the association between motor competence and physical activity, physical fitness and psychosocial characteristics solely within adolescents. OBJECTIVES: This study aimed to (1) analyse the scientific literature evaluating associations between motor competence and physical activity, physical fitness and/or psychosocial characteristics amongst adolescents; (2) evaluate the associations between motor competence and physical activity, physical fitness characteristics and/or psychosocial characteristics amongst adolescents; and (3) investigate the impact of moderator variables (i.e., age, sex, type of motor competence assessment) on the associations. METHODS: A systematic search of electronic databases was conducted, followed by a qualitative synthesis of study methods. Random-effects meta-analyses were performed to establish the magnitude and orientation of pooled correlation coefficients between motor competence and physical activity, physical fitness and psychosocial characteristics of adolescents, whilst considering potential moderators (i.e., age, sex, type of motor competence assessment). RESULTS: Sixty-one studies were included, totalling 22,256 adolescents. Twenty-seven different assessments of motor competence were used, with 31 studies utilising product-orientated (i.e. outcome) motor competence assessments. Meta-analyses of 43 studies showed that motor competence was positively associated with physical activity (r = 0.20 to 0.26), some physical fitness characteristics (e.g. muscular strength, cardiovascular endurance; r = 0.03 to 0.60) and psychosocial characteristics (r = 0.07 to 0.34), and inversely associated with weight status (r = - 0.36 to - 0.10), speed (r = - 0.31) and agility (r = - 0.37 to 0.41). Associations with flexibility were unclear. CONCLUSIONS: The results of this systematic review and meta-analysis support the hypothesised interactions of motor competence with physical activity (positive), physical fitness (positive except for weight status, speed and agility) and psychosocial characteristics (positive) in adolescence. However, methodological approaches vary considerably (e.g. variety of motor competence assessments utilised), with limitations of the current literature including an inadequate assessment of motor competence, a lack of longitudinal observations and a failure to account for biological maturation. Future research assessing associations between motor competence and physical activity, physical fitness and psychosocial characteristics of adolescents should include longitudinal observations of a combined motor competence assessment (i.e. process and product) and account for biological maturation. Improved evaluation using these recommendations could provide more accurate data, leading to more targeted interventions to improve adolescents' physical and psychosocial outcomes. CLINICAL TRIAL REGISTRATION: CRD42021233441 (PROSPERO ID).

Descriptive Epidemiology of Game-Related Youth Flag Football Injuries.

CONTEXT: Flag football is promoted as a safer alternative to tackle football. This may be 1 reason why participation rates have risen by 39% over the past 3 years. Despite rising participation, epidemiologic research on sport-specific injuries and associated relative risk is lacking. OBJECTIVE: To prospectively document the epidemiology of injuries in youth flag football. DESIGN: Descriptive epidemiology study. SETTING: Regional and national youth flag football tournaments. PATIENTS OR OTHER PARTICIPANTS: Athletes (N = 1939; 1744 boys and 195 girls), ages 6 to 12 years. An athletic trainer prospectively monitored the athletes for sport-related injury and exposures. MAIN OUTCOME MEASURE(S): Athlete risks of injury and injury rates were calculated overall and by sex. Injury characteristics were reported for the total population and by sex. RESULTS: Forty-seven injuries to unique individuals were recorded in 1939 athletes with a total of 9228 athlete-exposures (AEs). The overall risk of injury was 2.4% (95% CI = 1.79%, 3.21%), with an overall injury rate of 5.1 per 1000 AEs (95% CI = 3.75, 6.77). Of the 47 injuries, 36 occurred in boys (8365 AEs), and 11 occurred in girls (863 AEs). A higher risk in girls was evidenced by both the injury risk ratio (2.73; 95% CI = 1.41, 5.30) and injury rate ratio of 2.96 (95% CI = 1.51, 5.82). The most common injury sites were the head/face/neck (n = 15, 31.9%), followed by the ankle/foot (n = 9, 19.1%). The most frequent types of injury were contusion (55.3%), sprain/subluxation (14.9%), and general trauma (10.6%); 74.5% of all injuries resulted from direct impact. CONCLUSIONS: Although the competition injury rate for youth flag football was lower than the values from studies reporting comparable tackle football data, the frequencies by body part, type, and mechanism were similar. Given that most injuries were related to some form of impact and predominantly contusions, adopting minimal protective equipment or padding may reduce the numbers of these injuries.

Sedentary behaviors and emerging cardiometabolic biomarkers in adolescents.

OBJECTIVE: To examine the associations of objectively measured sedentary time and television (TV) viewing time with emerging inflammatory and endothelial function markers in adolescents. STUDY DESIGN: This study comprised 183 adolescents (88 girls), aged 13 to 17 years. Sedentary time and moderate-to-vigorous physical activity was objectively measured with accelerometry, whereas TV viewing time was self-reported. White blood cell counts and levels of C-reactive protein, complement factors C3 and C4, interleukin-6, adiponectin, leptin, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, E-selectin, L-selectin, and plasminogen activator inhibitor-1 were measured in fasted blood samples. RESULTS: Sedentary time was not significantly associated with any of the examined cardiometabolic markers after controlling for potential confounders. However, TV viewing time was positively associated with soluble endothelial adhesion molecules intercellular adhesion molecule 1 (standardized ß = 0.19, P = .008), vascular cell adhesion molecule 1 (ß = 0.17, P = .020), L-selectin (ß = 0.18, P = .013), and E-selectin (ß = 0.16, P = .023) concentrations, after controlling for sex, age, pubertal status, moderate-to-vigorous physical activity, body mass index, and total sedentary time. CONCLUSIONS: High TV viewing time may play a key role in cardiovascular and metabolic diseases through the cell adhesion molecules in adolescence.

Aerobic exercise is promoted when individual performance affects the group: a test of the Kohler motivation gain effect.

BACKGROUND: A key barrier to achieving recommended intensity and duration of physical activity is motivation. PURPOSE: We investigated whether a virtually present partner would influence participants' motivation (duration) during aerobic exercise. METHOD: Fifty-eight females (M(age) = 20.54 ± 1.86) were randomly assigned to either a coactive condition (exercising alongside another person, independently), a conjunctive condition (performance determined by whichever partner stops exercising first) where they exercised with a superior partner, or to an individual condition. Participants exercised on a stationary bike at 65 % of heart rate reserve on six separate days. RESULTS: Across sessions, conjunctive condition participants exercised significantly longer (M = 21.89 min, SD = ±10.08 min) than those in coactive (M = 19.77 min, SD = ± 9.00 min) and individual (M = 10.6 min, SD = ±5.84 min) conditions (p < 0.05). CONCLUSION: Exercising with a virtually present partner can improve performance on an aerobic exercise task across multiple sessions.

The PWC170: comparison of different stage lengths in 11-16 year olds.

It is unknown how the estimation of aerobic fitness in children and adolescents compares among physical working capacity (PWC) protocols with different stage lengths. The purpose of this study was twofold: (1) compare PWC tests with 2-, 3-, and 6-min stage lengths in youth, and (2) examine the relationship between PWC at a heart rate (HR) of 170 beats min(-1) (PWC170) and peak oxygen consumption (VO(2)peak). Fifty youth (31 m, 19 f), aged 11-16 years participated. Each participant visited the laboratory twice and performed three PWC tests (2-, 3-, 6-min stages) on a cycle ergometer. Tests usually consisted of three stages of increasing loads with the goal of reaching HR ≥ 165 beats min(-1). Individual regression lines were created to predict workload at HR = 170 beats ∙ min(-1) for each test. Participants completed two VO(2peak) tests, both running and cycling. Repeated measures ANOVA was used to compare PWC170 values. Pearson correlation was used to assess the relationships between VO(2peak) and power output for different PWC170 stage lengths. The three PWC170 protocols differ significantly; therefore, it is not advisable to directly compare results from different protocols. Furthermore, PWC170 showed moderate associations with VO(2peak), with the 2-min protocol showing the best correlation.

Screen time is more strongly associated than physical activity with overweight and obesity in 9- to 16-year-old Australians.

BACKGROUND: Both reduced moderate-to-vigorous physical activity (MVPA) and increased screen time have been implicated in the aetiology of childhood overweight/obesity. This study aimed to determine which behaviour had the stronger association with overweight/obesity. METHOD: 2200 randomly selected 9- to 16-year-old Australians provided four 24-h use-of-time recalls. Participants were classified into weight status categories and as high or low physical active, and high or low screen time according to Australian guidelines (≥60 min MVPA; ≤120 min recreational screen time daily). Multivariate logistic regression was used to calculate the odds ratios (OR) for overweight/obesity for each screen time and MVPA category. RESULTS: Increased likelihood of overweight or obese was often associated with high screen time (ORs, 2.13-2.55 for boys and 1.47-1.72 for girls), but only sometimes and less strongly associated with low MVPA (ORs, 0.49-2.55 for boys and 1.06-1.47 for girls). Analyses conducted for combined screen time and MVPA categories showed screen time to be a stronger indicator of weight status than physical activity, especially in boys. CONCLUSION: Overweight and obesity were more strongly associated with screen time than physical activity. Screen time may be an important target for interventions aimed at reducing childhood overweight and obesity.

Inter-relationships among physical activity, body fat, and motor performance in 6- to 8-year-old Danish children.

This study examined the interrelationships among physical activity (PA), percent body fat (%BF), and motor performance (MP) in 498 6- to 8-year-old Danish children. PA was assessed by accelerometer, %BF was calculated from skinfolds, and the Koordinations Test für Kinder along with a throwing accuracy test was used to assess MP. PA was not correlated with %BF, but was significantly correlated with MP. The strongest correlations existed between %BF and MP. Low %BF/High PA had higher MP scores compared with High %BF/Low PA, and within the High %BF groups MP was higher in the High PA versus Low PA group. When comparing PA by %BF and MP groups, boys in the Low %BF/High MP had higher PA than both the Low %BF/Low MP and High %BF/Low MP groups. In girls, PA was highest in the High %BF/High MP group. This study highlights the complex interrelationships among PA, %BF, and MP in children and the need to develop fundamental motor skills during childhood.

Optimising long-term athletic development: An investigation of practitioners' knowledge, adherence, practices and challenges.

Long-term athletic development practices have been recommended for the past two decades. However, limited research exists exploring the knowledge and skills required by practitioners to optimise long-term athletic development. Therefore, this study aimed to evaluate the knowledge, adherence, practices, and challenges of practitioners responsible for delivering long-term athletic development. A mixed methods survey was completed by 236 practitioners (e.g., sport coaches, physical education teachers) consisting of four parts; 1) demographics, 2) knowledge, 3) adherence, and 4) practices and challenges. Quantitative and qualitative data were analysed by Friedman's analysis of variance and thematic analyses, respectively. Quantitative findings showed practitioners 1) recognised their responsibility for delivering long-term athletic development, 2) have a familiarity with existing developmental models, and 3) had high adherence, focused upon health and wellbeing, to delivering long-term athletic development. However, practices associated with growth and maturity, monitoring and assessment, and the systematic progression and individualisation of training had lower adherence. Qualitative analysis indicated that practitioner's perceived definitions of athleticism and long-term athletic development were inconsistent, especially according to the psychological components (i.e., confidence). Practitioners' descriptions of their long-term athletic development practices identified two higher order themes; 1) goals, in which long-term athletic development "is for life" and the importance of "an individual centered journey" highlighted as sub-themes; and 2) realities of delivering long-term athletic development, whereby variety in programme delivery, monitoring development and practical challenges were noted as key priorities. Eight practical challenges were identified including governance and priorities, resources, education, early specialization, high training volumes, staff communication, parents and youth motivation. This mixed method survey highlighted a multitude of knowledge, adherence, practices and challenges towards long-term athletic development. These novel findings can help inform policy to optimise long-term athletic development and to support the complex problem of developing a healthier, fitter and more physically active youth population.

Youth motor competence across stages of maturity: Perceptions of physical education teachers and strength and conditioning coaches.

Physical education (PE) teachers and strength and conditioning (S&C) coaches are well placed to develop motor competence within youth populations. However, both groups' perceptions of important motor competencies are relatively unknown, especially when considering stage of maturity. Therefore, this study aimed to 1) present PE teachers and S&C coaches' perceptions of motor competence importance according to stage of maturity; 2) compare perceptions of motor competence between stages of maturity, and between PE teachers and S&C coaches; and 3) explore factors that influence PE teachers and S&C coaches' perceptions of motor competence importance. Via a mixed-method questionnaire, 47 PE teachers (professional experience = 10.3±6.6 years) and 48 S&C coaches (professional experience = 8.6±4.8 years) rated the importance of developing 21 motor competencies across four stages of maturity (childhood, pre-peak height velocity [PHV], circa-PHV, and post-PHV) using a Likert-scale (1 = not important, 5 = very important). Participants also provided open-ended explanations for their perceptions. Frequency analysis indicated that participants rated a broad range of competencies important, with S&C coaches rating more competencies important than PE teachers across all stages of maturity. Mixed-model analysis highlighted several differences in motor competence importance when comparing perceptions between participant groups, and between stages of maturity for PE teachers and S&C coaches. For example, S&C coaches rated strength-based motor competencies less important during childhood (d = -1.83 to -0.43), while PE teachers rated them less important during childhood (d = -2.22 to -0.42) and pre-PHV (d = -1.70 to -0.51) compared to other stages of maturity. Codebook thematic analysis showed several factors that influenced participant's perceptions of motor competence importance (e.g., participants understanding of themselves). The findings suggest that multiple environments may be required to adequately facilitate motor competence development amongst youth. Coach education should target misunderstandings around the risks of strength-based activity during early stages of maturity and the benefits of developing strength-based motor competencies across youth populations.

The biological control of voluntary exercise, spontaneous physical activity and daily energy expenditure in relation to obesity: human and rodent perspectives.

Mammals expend energy in many ways, including basic cellular maintenance and repair, digestion, thermoregulation, locomotion, growth and reproduction. These processes can vary tremendously among species and individuals, potentially leading to large variation in daily energy expenditure (DEE). Locomotor energy costs can be substantial for large-bodied species and those with high-activity lifestyles. For humans in industrialized societies, locomotion necessary for daily activities is often relatively low, so it has been presumed that activity energy expenditure and DEE are lower than in our ancestors. Whether this is true and has contributed to a rise in obesity is controversial. In humans, much attention has centered on spontaneous physical activity (SPA) or non-exercise activity thermogenesis (NEAT), the latter sometimes defined so broadly as to include all energy expended due to activity, exclusive of volitional exercise. Given that most people in Western societies engage in little voluntary exercise, increasing NEAT may be an effective way to maintain DEE and combat overweight and obesity. One way to promote NEAT is to decrease the amount of time spent on sedentary behaviours (e.g. watching television). The effects of voluntary exercise on other components of physical activity are highly variable in humans, partly as a function of age, and have rarely been studied in rodents. However, most rodent studies indicate that food consumption increases in the presence of wheels; therefore, other aspects of physical activity are not reduced enough to compensate for the energetic cost of wheel running. Most rodent studies also show negative effects of wheel access on body fat, especially in males. Sedentary behaviours per se have not been studied in rodents in relation to obesity. Several lines of evidence demonstrate the important role of dopamine, in addition to other neural signaling networks (e.g. the endocannabinoid system), in the control of voluntary exercise. A largely separate literature points to a key role for orexins in SPA and NEAT. Brain reward centers are involved in both types of physical activities and eating behaviours, likely leading to complex interactions. Moreover, voluntary exercise and, possibly, eating can be addictive. A growing body of research considers the relationships between personality traits and physical activity, appetite, obesity and other aspects of physical and mental health. Future studies should explore the neurobiology, endocrinology and genetics of physical activity and sedentary behaviour by examining key brain areas, neurotransmitters and hormones involved in motivation, reward and/or the regulation of energy balance.

Project FIT: rationale, design and baseline characteristics of a school- and community-based intervention to address physical activity and healthy eating among low-income elementary school children.

BACKGROUND: This paper describes Project FIT, a collaboration between the public school system, local health systems, physicians, neighborhood associations, businesses, faith-based leaders, community agencies and university researchers to develop a multi-faceted approach to promote physical activity and healthy eating toward the general goal of preventing and reducing childhood obesity among children in Grand Rapids, MI, USA. METHODS/DESIGN: There are four overall components to Project FIT: school, community, social marketing, and school staff wellness - all that focus on: 1) increasing access to safe and affordable physical activity and nutrition education opportunities in the schools and surrounding neighborhoods; 2) improving the affordability and availability of nutritious food in the neighborhoods surrounding the schools; 3) improving the knowledge, self-efficacy, attitudes and behaviors regarding nutrition and physical activity among school staff, parents and students; 4) impacting the 'culture' of the schools and neighborhoods to incorporate healthful values; and 5) encouraging dialogue among all community partners to leverage existing programs and introduce new ones. DISCUSSION: At baseline, there was generally low physical activity (70% do not meet recommendation of 60 minutes per day), excessive screen time (75% do not meet recommendation of < 2 hours per day), and low intake of vegetables and whole grains and high intake of sugar-sweetened beverages, French fries and chips and desserts as well as a high prevalence of overweight and obesity (48.5% including 6% with severe obesity) among low income, primarily Hispanic and African American 3rd-5th grade children (n = 403). TRIAL REGISTRATION: ClinicalTrials.gov NCT01385046.