To best strengthen the argument that running is better for a person's health, you could provide evidence that specifically highlights the health benefits associated with running compared to walking. For example:
"Research shows that running can significantly improve cardiovascular health, leading to lower risks of heart disease, high blood pressure, and other related conditions, as it increases heart rate and promotes better blood circulation more effectively than walking."
This statement focuses on the specific health benefits of running that have a strong impact on overall health and clearly differentiates those benefits from walking, thereby strengthening the argument.