BackgroundGiven the rapid development during the early years (0-4 years), an understanding of the health implications of physical activity is needed. The purpose of this systematic review was to examine the relationships between objectively and subjectively measured physical activity and health indicators in the early years.MethodsElectronic databases were originally searched in April, 2016. Included studies needed to be peer-reviewed, written in English or French, and meet a priori study criteria. The population was apparently healthy children aged 1 month to 59.99 months/4.99 years. The intervention/exposure was objectively and subjectively measured physical activity. The comparator was various volumes, durations, frequencies, patterns, types, and intensities of physical activity. The outcomes were health indicators ranked as critical (adiposity, motor development, psychosocial health, cognitive development, fitness) and important (bone and skeletal health, cardiometabolic health, and risks/harm). The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework was used to assess the quality of evidence for each health indicator by each study design.ResultsNinety-six studies representing 71,291 unique participants from 36 countries were included. Physical activity interventions were consistently (>60% of studies) associated with improved motor and cognitive development, and psychosocial and cardiometabolic health. Across observational studies, physical activity was consistently associated with favourable motor development, fitness, and bone and skeletal health. For intensity, light- and moderate-intensity physical activity were not consistently associated with any health indicators, whereas moderate- to vigorous-intensity, vigorous-intensity, and total physical activity were consistently favourably associated with multiple health indicators. Across study designs, consistent favourable associations with health indicators were observed for a variety of types of physical activity, including active play, aerobic, dance, prone position (infants; ≤1 year), and structured/organized. Apart from ≥30 min/day of the prone position for infants, the most favourable frequency and duration of physical activity was unclear. However, more physical activity appeared better for health. Evidence ranged from “very low” to “high” quality.ConclusionsSpecific types of physical activity, total physical activity, and physical activity of at least moderate- to vigorous-intensity were consistently favourably associated with multiple health indicators. The majority of evidence was in preschool-aged children (3-4 years). Findings will inform evidence-based guidelines.Electronic supplementary materialThe online version of this article (10.1186/s12889-017-4860-0) contains supplementary material, which is available to authorized users.

The early years represent a critical period for promoting physical activity. However, the amount of physical activity needed for healthy growth and development is not clear. Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework, we aimed to present the best available evidence to determine the relationship between physical activity and measures of adiposity, bone and skeletal health, motor skill development, psychosocial health, cognitive development, and cardiometabolic health indicators in infants (1 month - 1 year), toddlers (1.1-3.0 years), and preschoolers (3.1-4.9 years). Online databases, personal libraries, and government documents were searched for relevant studies. Twenty-two articles, representing 18 unique studies and 12 742 enrolled participants, met inclusion criteria. The health indicators of interest were adiposity (n = 11), bone and skeletal health (n = 2), motor development (n = 4), psychosocial health (n = 3), cognitive development (n = 1), and cardiometabolic health indicators (n = 3); these indicators were pre-specified by an expert panel. Five unique studies involved infants, 2 involved toddlers, and 11 involved preschoolers. In infants, there was low- to moderate-quality evidence to suggest that increased or higher physical activity was positively associated with improved measures of adiposity, motor skill development, and cognitive development. In toddlers, there was moderate-quality evidence to suggest that increased or higher physical activity was positively associated with bone and skeletal health. In preschoolers, there was low- to high-quality evidence on the relationship between increased or higher physical activity and improved measures of adiposity, motor skill development, psychosocial health, and cardiometabolic health indicators. There was no serious inconsistency in any of the studies reviewed. This evidence can help to inform public health guidelines. (PROSPERO registration: CRD42011001243).

Accumulating evidence suggests that young children spend excessive time being sedentary. The purpose of this systematic review was to determine the relationship between sedentary behaviours and health indicators during the early years (ages 0-4 years). Using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) framework, this review aimed to present the best available evidence on the threshold of sedentary behaviour associated with healthy measures of adiposity, bone health, motor skill development, psychosocial health, cognitive development, and cardiometabolic health indicators in infants, toddlers, and preschoolers. Online databases, personal libraries, and government documents were searched for relevant studies. Studies that included an intervention (or experimental) group or prospective analysis were included. Twenty-one unique studies, representing 23 papers and 22 417 participants, met inclusion criteria; 7 studies included information on infants, 13 on toddlers, and 10 on preschoolers. Of these, 11, 6, and 8 studies reported data on adiposity, psychosocial health, and cognitive development, respectively. No included study reported on motor skill development, bone, or cardiometabolic health indicators. In conclusion, this review found low- to moderate-quality evidence to suggest that increased television viewing is associated with unfavourable measures of adiposity and decreased scores on measures of psychosocial health and cognitive development. No evidence existed to indicate that television viewing is beneficial for improving psychosocial health or cognitive development. In several instances a dose-response relationship was evident between increased time spent watching television and decreased psychosocial health or cognitive development. This work may be used as evidence to inform public health guidelines. (PROSPERO registration: CRD4011001280.).

The Canadian Society for Exercise Physiology (CSEP), with assistance from multiple partners, stakeholders, and researchers, developed the first Canadian Physical Activity Guidelines for the Early Years (aged 0-4 years). These national guidelines were created in response to an urgent call from public health, health care, child care, and fitness practitioners for healthy active living guidance for the early years. The guideline development process was informed by the Appraisal of Guidelines for Research Evaluation (AGREE) II instrument and the evidence assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system. The recommendations are informed by evidence from a systematic review that examined the relationships between physical activity and health indicators (healthy body weight, bone and skeletal health, motor skill development, psychosocial health, cognitive development, and cardio-metabolic disease risk factors) for three age groups (infants aged <1 year; toddlers aged 1-2 years; preschoolers aged 3-4 years). The new guidelines include a preamble to provide context, followed by the specific recommendations. The final guidelines benefitted from an extensive on-line consultation process with input from over 900 domestic and international stakeholders, end-users, and key informants. The final guideline recommendations state that for healthy growth and development, infants (aged <1 year) should be physically active several times daily - particularly through interactive floor-based play. Toddlers (aged 1-2 years) and preschoolers (aged 3-4 years) should accumulate at least 180 min of physical activity at any intensity spread throughout the day, including a variety of activities in different environments, activities that develop movement skills, and progression toward at least 60 min of energetic play by 5 years of age. More daily physical activity provides greater benefits.

The Canadian Society for Exercise Physiology (CSEP), with assistance from multiple partners, stakeholders, and researchers, developed the first Canadian Sedentary Behaviour Guidelines for the Early Years (aged 0-4 years). These national guidelines are in response to a call from health and health care professionals, child care providers, and fitness practitioners for guidance on sedentary behaviour in the early years. The guideline development process followed the Appraisal of Guidelines for Research Evaluation (AGREE) II framework. The recommendations are informed by evidence from a systematic review that examined the relationships between sedentary behaviour (predominantly screen time) and health indicators (healthy body weight, bone and skeletal health, motor skill development, psychosocial health, cognitive development, and cardio-metabolic disease risk factors) for three age groups (infants aged <1 year; toddlers aged 1-2 years; preschoolers aged 3-4 years). Evidence from the review was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. The new guidelines include a preamble to provide context, followed by the specific recommendations. The final guidelines benefitted from extensive on-line consultations with input from >900 domestic and international stakeholders, end-users, and key informants. The final guidelines state: for healthy growth and development, caregivers should minimize the time infants (aged <1 year), toddlers (aged 1-2 years), and preschoolers (aged 3-4 years) spend being sedentary during waking hours. This includes prolonged sitting or being restrained (e.g., stroller, high chair) for more than 1 h at a time. For those under 2 years, screen time (e.g., TV, computer, electronic games) is not recommended. For children 2-4 years, screen time should be limited to under 1 h per day; less is better.