Training effects in mice after long-term voluntary exercise

Background: Mice are an important animal model in exercise studies on the immune system, cancer, and aging. There is limited research about the training effects of long-term voluntary exercise in this species. Purpose: To describe the training effects in mice given long-term aerobic voluntary exercise. Methods: Female C57BL/6 mice were randomly assigned to 1) individual cages with in-cage running wheels with 24-h access (WR; N = 31), or 2) individual cages without running wheels for 16 wk (NR; N = 20). Run-to-exhaustion (RTE) times, VO2peak, speed at VO2peak, and citrate synthase (CS), succinate dehydrogenase (SDH), and phosphofructokinase (PFK) activity in the soleus, plantaris, and red and white gastrocnemius were assessed. Results: Final body weight and speed at VO2peak did not differ by training condition. WR mice had significantly longer RTE times (P < 0.001) and higher VO2peak (P < 0.05) compared with NR mice. Higher CS and SDH activities were found in WR compared with NR mice for soleus (P < 0.01). red gastrocnemius (P < 0.01). and plantaris (P < 0.01) muscles. PFK activity was higher in WR mice in white gastrocnemius compared with NR mice (P < 0.01). Conclusions: Voluntary running wheel activity for 16 wk in female C57BL/6 mice resulted in longer run times to exhaustion. higher VO2peak, and higher SDH and CS activities in oxidative muscles. These findings suggest that wheel running in female C57BL/6 mice: 1) produces a measurable aerobic training effect and 2) is an effective exercise modality for long-term training studies.