Abstract
A unique polygenic model of rat physical activity has been recently developed where rats were selected for the trait of low voluntary wheel running. We utilized this model to identify differences in soleus and plantaris muscles of sedentary low voluntary wheel running rats and physically active low voluntary wheel running rats exposed to moderate amounts of treadmill training. Three groups of 28-day-old male Wistar rats were used: (1) rats without a running wheel (SEDENTARY, n = 7), (2) rats housed with a running wheel (WHEEL, n = 7), and (3) rats housed with a running wheel and exercised on the treadmill (5 days/week for 20 min/day at 15.0 m/min) (WHEEL + TREADMILL, n = 7). Animals were euthanized 5 weeks after the start of the experiment and the soleus and plantaris muscles were excised and used for analyses. Increases in skeletal muscle gene expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha and fibronectin type III domain-containing protein 5 in WHEEL + TREADMILL group were observed. Also, WHEEL + TREADMILL had higher protein levels of superoxide dismutase 2 and decreased levels of oxidative damage. Our data demonstrate that the addition of treadmill training induces beneficial muscular adaptations compared to animals with wheel access alone. Furthermore, our data expand our understanding of differential muscular adaptations in response to exercise in mitochondrial, antioxidant, and metabolic markers.
Highlights
Low daily physical activity is associated with obesity and numerous metabolic maladies
The 5-week duration of this study extends on current knowledge of low voluntary wheel running rodents after 6 days of wheel running (Roberts et al 2013) and is the first study to demonstrate adaptive responses to extended duration exercise participation in this important animal model
The creation of the low voluntary wheel running model is an important facet of understanding the ongoing trend and resulting consequences of sedentary lifestyles occurring throughout the U.S Our data demonstrate that even moderate levels of physical activity are sufficient to decrease body mass compared to sedentary behavior
Summary
Low daily physical activity is associated with obesity and numerous metabolic maladies. Physically inactive people are at increased risk for more than 35 clinically relevant poor health conditions and premature death (Bauman et al 2012). 58% of children (6–11 years of age) and about 92% of adolescents (12–19 years) do not meet recommended doses of daily physical activity (Troiano et al 2008). It is important to note that low daily physical activity levels are associated with a more glycolytic skeletal muscle phenotype (Short et al 2005) and high levels of daily physical activity promote a more oxidative skeletal muscle fiber type (Holloszy and Booth 1976) as well as an increase in intramuscular mitochondrial content (Holloszy 1975) and antioxidants (Powers et al 1999). Physical activity increases the intramuscular expression of putative myokines
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