Sex differences in voluntary running behavior between C57BL/6 and BALB/cJ mouse strains do not correspond to changes...

Area of Science:

• Exercise physiology
• Metabolic adaptations
• Animal models

Background:

• Exercise adaptations exhibit significant variability influenced by sex and genetic background.
• Understanding these differences is crucial for interpreting metabolic and physiological responses to physical activity.

Purpose of the Study:

• To investigate sex- and strain-specific differences in physiological adaptations following voluntary wheel running exercise.
• To examine submaximal and maximal oxygen consumption (VO2), respiratory exchange ratio (RER), and body composition in C57BL/6 and BALB/cJ mice.

Main Methods:

• Four weeks of voluntary wheel running in male and female C57BL/6 and BALB/cJ mice.
• Sub-maximal and maximal treadmill tests conducted in a metabolic chamber.
• Analysis of running volume, VO2, RER, body composition, and blood lactate levels.

Main Results:

• Running volume varied significantly across sexes and strains, not consistently predicting physiological changes.
• Female C57BL/6 mice showed higher submaximal VO2 compared to males and female BALB/cJ mice.
• Male BALB/cJ mice exhibited enhanced endurance capacity and a decrease in RER during maximal testing; female C57BL/6 mice improved body composition.

Conclusions:

• Sex and strain are critical factors influencing exercise adaptations in mice.
• Standard VO2 testing may not fully capture adaptive responses to voluntary wheel running.
• Future research should account for sex- and strain-specific variations in exercise studies.