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The Scientific World Journal
Volume 2013, Article ID 237260, 7 pages
http://dx.doi.org/10.1155/2013/237260
Research Article

Substrains of Inbred Mice Differ in Their Physical Activity as a Behavior

1UR4 Aging, Stress, Inflammation, University Pierre et Marie Curie Paris 6, 7 Quai Saint Bernard, 75005 Paris, France
2Department of Anatomical, Histological, Forensic & Orthopaedic Sciences, Section of Histology & Medical Embryology, Sapienza University of Rome, Via Scarpa 16, 00161 Rome, Italy
3Interuniversity Institute of Myology, 00161 Rome, Italy
4Laboratory of Translational Cardiomyology, Department of Development and Regeneration, Katholieke Universiteit Leuven, 3000 Leuven, Belgium

Received 30 December 2012; Accepted 4 February 2013

Academic Editors: L. Guimarães-Ferreira, H. Nicastro, J. Wilson, and N. E. Zanchi

Copyright © 2013 Dario Coletti et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Recent studies strengthen the belief that physical activity as a behavior has a genetic basis. Screening wheel-running behavior in inbred mouse strains highlighted differences among strains, showing that even very limited genetic differences deeply affect mouse behavior. We extended this observation to substrains of the same inbred mouse strain, that is, BALB/c mice. We found that only a minority of the population of one of these substrains, the BALB/c J, performs spontaneous physical activity. In addition, the runners of this substrain cover a significantly smaller distance than the average runners of two other substrains, namely, the BALB/c ByJ and the BALB/c AnNCrl. The latter shows a striking level of voluntary activity, with the average distance run/day reaching up to about 12 kilometers. These runners are not outstanders, but they represent the majority of the population, with important scientific and economic fallouts to be taken into account during experimental planning. Spontaneous activity persists in pathological conditions, such as cancer-associated cachexia. This important amount of physical activity results in a minor muscle adaptation to endurance exercise over a three-week period; indeed, only a nonsignificant increase in NADH transferase+ fibers occurs in this time frame.