Herbert wants to purchase a piece of fitness equipment to focus on his cardio endurance. What is the LEAST helpful purchase for him to make in an effort to reach his cardio endurance goal?

a treadmill
a bike
a nautilus machine
an elliptical machine​

A nautilus machine would be the least helpful purchase for Herbert to make in order to reach his cardio endurance goal. Nautilus machines primarily focus on strength training and muscle building, rather than cardiovascular exercise. Therefore, it would not be the most effective choice for improving cardio endurance.