Moderate-vigorous physical activity is the most efficient at improving fitness

In the largest study performed to date to understand the relationship between habitual physical activity and physical fitness, researchers have found that higher amount of time spent performing exercise (moderate-vigorous physical activity) and low-moderate level activity (steps) and less time spent sedentary, translated to greater physical fitness.

source https://www.sciencedaily.com/releases/2021/08/210827133756.htm