title: Cross-Sectional Associations of Objectively-Measured Physical Activity and Sedentary Time with Body Composition and Cardiorespiratory Fitness in Mid-Childhood: The PANIC Study.
abstract: The minimum intensity of physical activity (PA) that is associated with favourable body composition and cardiorespiratory fitness (CRF) remains unknown.
  
  
  
  To investigate cross-sectional associations of PA and sedentary time (ST) with body composition and CRF in mid-childhood.
  
  
  
  PA, ST, body composition and CRF were measured in a population-based sample of 410 children (aged 7.6 ± 0.4 years). Combined heart-rate and movement sensing provided estimates of PA energy expenditure (PAEE, kJ/kg/day) and time (min/day) at multiple fine-grained metabolic equivalent (MET) levels, which were also collapsed to ST and light PA (LPA), moderate PA (MPA) and vigorous PA (VPA). Fat mass index (FMI, kg/m2), trunk fat mass index (TFMI, kg/m2) and fat-free mass index (FFMI, kg/m2.5) were derived from dual-energy X-ray absorptiometry. Maximal workload from a cycle ergometer test provided a measure of CRF (W/kg FFM). Linear regression and isotemporal substitution models were used to investigate associations.
  
  
  
  The cumulative time above 2 METs (221 J/min/kg) was inversely associated with FMI and TFMI in both sexes (p < 0.001) whereas time spent above 3 METs was positively associated with CRF (p ≤ 0.002); CRF increased and adiposity decreased dose-dependently with increasing MET levels. ST was positively associated with FMI and TFMI (p < 0.001) but there were inverse associations between all PA categories (including LPA) and adiposity (p ≤ 0.002); the magnitude of these associations depended on the activity being displaced in isotemporal substitution models but were consistently stronger for VPA. PAEE, MPA and to a greater extent VPA, were all positively related to CRF (p ≤ 0.001).
  
  
  
  PA exceeding 2 METs is associated with lower adiposity in mid-childhood, whereas PA of 3 METs is required to benefit CRF. VPA was most beneficial for fitness and fatness, from a time-for-time perspective, but displacing any lower-for-higher intensity may be an important first-order public health strategy. Clinical trial registry number (website): NCT01803776 ( https://clinicaltrials.gov/ct2/show/NCT01803776 ).
authors: PA Programme, MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrookes Hospital, University of Cambridge, Box 285, Cambridge, CB2 0QQ, UK.|Bradford Institute for Health Research, Bradford NHS Foundation Trust, Bradford, UK.
authors: Paul J
authors: PJ
authors: Collings
authors: PA Programme, MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrookes Hospital, University of Cambridge, Box 285, Cambridge, CB2 0QQ, UK.
authors: Kate
authors: K
authors: Westgate
authors: Institute of Biomedicine, Physiology, University of Eastern Finland, Kuopio, Finland.|Institute of Dentistry, University of Eastern Finland, Kuopio, Finland.
authors: Juuso
authors: J
authors: Väistö
authors: PA Programme, MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrookes Hospital, University of Cambridge, Box 285, Cambridge, CB2 0QQ, UK.
authors: Katrien
authors: K
authors: Wijndaele
authors: PA Programme, MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrookes Hospital, University of Cambridge, Box 285, Cambridge, CB2 0QQ, UK.|UKCRC Centre for Diet and Activity Research (CEDAR), University of Cambridge School of Clinical Medicine, Cambridge, UK.
authors: Andrew J
authors: AJ
authors: Atkin
authors: Institute of Biomedicine, Physiology, University of Eastern Finland, Kuopio, Finland.|Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors: Eero A
authors: EA
authors: Haapala
authors: Institute of Biomedicine, Physiology, University of Eastern Finland, Kuopio, Finland.
authors: Niina
authors: N
authors: Lintu
authors: Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland.
authors: Tomi
authors: T
authors: Laitinen
authors: PA Programme, MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrookes Hospital, University of Cambridge, Box 285, Cambridge, CB2 0QQ, UK.|Department of Sport Medicine, Norwegian School of Sports Science, Oslo, Norway.
authors: Ulf
authors: U
authors: Ekelund
authors: PA Programme, MRC Epidemiology Unit, Institute of Metabolic Science, Addenbrookes Hospital, University of Cambridge, Box 285, Cambridge, CB2 0QQ, UK. soren.brage@mrc-epid.cam.ac.uk.
authors: Soren
authors: S
authors: Brage
authors: Institute of Biomedicine, Physiology, University of Eastern Finland, Kuopio, Finland.|Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital and University of Eastern Finland, Kuopio, Finland.|Kuopio Research Institute of Exercise Medicine, Kuopio, Finland.
authors: Timo A
authors: TA
authors: Lakka
mesh_terms: D001823:Body Composition; D015992:Body Mass Index; D000072599:Cardiorespiratory Fitness / Q000502:physiology*; D002648:Child; D003430:Cross-Sectional Studies; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D009043:Motor Activity; D010809:Physical Fitness; D057185:Sedentary Behavior