I think it’s increase in gene flow
Usually during exercise, unlike during rest times the muscle cells need to respire more. So they need more oxygen and glucose for energy and the carbon-dioxide produced as waste must be removed quickly. So when person gets tired or breathes heavily during intensive workouts means they are in need of more oxygen. So the cells starts performing anaerobic(lactic acid ) respiration even though it releases less energy.
Cells have unique characteristics wherein each develop a specific function determined by the activation of certain DNA sequences to generate this specific cell into its supposed design, this is why cell specialization exists.
Hence, these cells can be directly identified with their morphological structures and the DNA sequences they posses.
