Habitual physical activity in daily life correlates positively with markers for mitochondrial capacity

Departments of 1 Human Biology and 2 Movement Sciences, Maastricht University, Maastricht, The Netherlands Submitted 29 January 2008 ; accepted in final form 23 May 2008 Physical exercise training is a powerful tool to maintain or improve mitochondrial density and function (mitochondrial capacity). This study aims to determine whether mitochondrial capacity is also associated with habitual physical activity in daily life (PA DL ). The capacity of classic markers for mitochondrial density, i.e., the capacity of citrate synthase (CS) and succinate dehydrogenase (SDH), as well the capacity of cytochrome c oxidase (COX) and β-hydroxyacyl-CoA dehydrogenase (HAD), was determined in homogenized muscle biopsy samples obtained from the vastus lateralis muscle of nonexercising healthy young (age 20 ± 2 yr) subjects (31 women, 7 men). PA DL was measured during two periods of 14 days using a triaxial accelerometer for movement registration. CS, SDH, and COX were positively associated with PA DL [ P < 0.05, R = 0.36, 95% confidence interval (CI): 1.3·10 –4 to 2.2·10 –3 ; P < 0.05, R = 0.39, 95% CI: 1.1·10 –5 to 9.9·10 –5 ; and P < 0.05, R = 0.33, 95% CI: 7.5·10 –6 to 3.6·10 –4 , respectively], and HAD tended to correlate positively with PA DL ( P = 0.06, R = 0.31, 95% CI: –2.2·10 –5 to 1.1·10 –3 ). The population was subsequently stratified based on the intensity of the activities performed. CS was only associated with PA DL in subjects spending more time on high-intensity physical activity, whereas HAD was only associated with PA DL in subjects spending less time on low intensity physical activity. We are the first to report that even within the range of normal daily life activities, mitochondrial capacity is positively associated with the level of habitual physical activity in daily life. Thus an active lifestyle may help to maintain or improve mitochondrial capacity. accelerometer; intensity; citrate synthase; succinate dehydrogenase; cyctochrome c oxidase; β-hydroxyacyl-CoA dehydrogenase Address for reprint requests and other correspondence: M. den Hoed, P.O. Box 616, 6200 MD Maastricht, The Netherlands (e-mail: m.denhoed{at}hb.unimaas.nl )