1. ¹Institute of Sport Science and Clinical Biomechanics, University of Southern Denmark, Main Campus, Odense University, Odense, Denmark
2. ²MRC Epidemiology Unit/University of Cambridge, Cambridge, UK
3. ³Department of Physical Education and Health, Örebro University, Örebro, Sweden
4. ⁴Institute of Sport Science, University of Copenhagen, Denmark
5. ⁵Norwegian University of Sport and Physical Education, Oslo, Norway

Correspondence: Dr S Brage, MRC Epidemiology Unit/University of Cambridge, Strangeways Research Laboratories, Wort's Causeway, Cambridge CB1 8RN, UK. E-mail: sb400@medschl.cam.ac.uk

Received 22 November 2003; Revised 23 February 2004; Accepted 16 March 2004; Published online 24 August 2004.

Abstract

OBJECTIVE: To explore the association between measures of insulin resistance with objectively assessed physical activity.

DESIGN: School-based, cross-sectional study.

SUBJECTS: A randomly selected sample of 589 children (310 girls, 279 boys, mean (standard deviations, s.d.) age=9.7 (0.44) y, weight=33.6 (6.4) kg, height=1.39 (0.06) m) from Denmark.

METHODS: Fasting blood samples were analysed for serum insulin and glucose. Physical activity was measured with the uniaxial Computer Science and Applications (CSA) model 7164 accelerometer, worn for at least 3 days (10 h day^-1). Adiposity was assessed by the sum of four skinfolds. Multiple linear regression were performed to model insulin and glucose from average CSA output, adjusted for age, gender, puberty, ethnicity, birth weight, parental smoking, socioeconomic group, and CSA unit. In addition, we adjusted for skinfold thickness.

RESULTS: Mean fasting serum glucose ranged from 4.1 to 6.5 mmol l^-1 with a mean (s.d.) of 5.1 (0.37) mmol l^-1. Fasting insulin was negatively correlated with CSA output on levels of adjustment. Fasting glucose was not significantly associated with physical activity. However, in girls both indices of insulin resistance were significantly related to activity, whereas in boys none of the associations were significant.

CONCLUSION: Physical activity is inversely associated with fasting insulin in the nondiabetic range of fasting glucose. The relationship was stronger for insulin than for glucose, indicating compensatory action by the cells. Our data emphasise the importance of physical activity in children for the maintenance of metabolic control.