title: Tracking of physical activity and fitness during the early years.
abstract: The early years are characterized by rapid physical growth and the development of behaviours such as physical activity. The objectives of this study were to assess the 12-month changes in and the tracking of physical activity and fitness in 400 preschoolers (201 boys, 4.5 ± 0.9 years of age). Physical activity data, expressed as minutes per day and as the percentage of time spent at various intensities while wearing an accelerometer, were collected in 3-s epochs for 7 days. Short-term muscle power, assessed with a 10-s modified Wingate Anaerobic Test, was expressed as absolute (W) and relative (W/kg) peak power (PP) and mean power (MP). Aerobic fitness, assessed with the Bruce Protocol progressive treadmill test, was expressed as maximal treadmill time and heart rate recovery (HRR). Light physical activity decreased by 3.2 min/day (p < 0.05), whereas vigorous physical activity increased by 3.7 min/day (p < 0.001), from year 1 to year 2. Physical activity exhibited moderate tracking on the basis of Spearman correlations (r = 0.45-0.59, p < 0.001) and fair tracking on the basis of κ statistics (κ = 0.26-0.38). PP and MP increased from year 1 (PP, 94.1 ± 37.3 W; MP, 84.1 ± 30.9 W) to year 2 (PP, 125.6 ± 36.2 W; MP, 112.3 ± 32.2 W) (p < 0.001) and tracked moderately to substantially (PP, r = 0.89, κ = 0.61; MP, r = 0.86, κ = 0.56). Time to exhaustion on the treadmill increased from 9.4 ± 2.3 min to 11.8 ± 2.3 min (p < 0.001) and tracked strongly (r = 0.82, κ = 0.56). HRR was unchanged at 65 ± 14 beats/min (p = 0.297) and tracked fairly (r = 0.52, κ = 0.23). The findings indicate that fitness tracks better than physical activity over a 12-month period during the early years.
authors.affiliation: a Child Health and Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON L8S 4K1, Canada.|b Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada.
authors.forename: Hilary A T
authors.initials: HA
authors.lastname: Caldwell
authors.affiliation: a Child Health and Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON L8S 4K1, Canada.|b Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada.
authors.forename: Nicole A
authors.initials: NA
authors.lastname: Proudfoot
authors.affiliation: a Child Health and Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON L8S 4K1, Canada.|b Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada.
authors.forename: Sara
authors.initials: S
authors.lastname: King-Dowling
authors.affiliation: a Child Health and Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON L8S 4K1, Canada.
authors.forename: Natascja A
authors.initials: NA
authors.lastname: Di Cristofaro
authors.affiliation: b Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada.|c Department of Family Medicine, McMaster University, Hamilton, ON L8S 4K1, Canada.
authors.forename: John
authors.initials: J
authors.lastname: Cairney
authors.affiliation: a Child Health and Exercise Medicine Program, Department of Pediatrics, McMaster University, Hamilton, ON L8S 4K1, Canada.|b Department of Kinesiology, McMaster University, Hamilton, ON L8S 4K1, Canada.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Timmons
mesh_terms: D015992:Body Mass Index; D001835:Body Weight; D002652:Child Behavior; D002675:Child, Preschool; D015444:Exercise; D005080:Exercise Test; D005260:Female; D015438:Health Behavior; D006339:Heart Rate; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D010809:Physical Fitness; D057185:Sedentary Behavior
keywords: accelerometry; accélérométrie; activité physique; condition physique; early years; exercice physique; exercise; fitness; fréquence cardiaque de récupération; health; heart rate recovery; physical activity; premières années; preschooler; préscolaire; santé; suivi; tracking