Most fitness enthusiasts that exercise in a gym or at home on a regular basis on multiple days per week will spend many years reaching their fitness goals through aerobic-efficiency training. Research with these well-trained non-athletes has found that they will spend as much as _____% of their total training time in zone 2.

Most fitness enthusiasts that exercise in a gym or at home on a regular basis on multiple days per week will spend many years reaching their fitness goals through aerobic-efficiency training. Research with these well-trained non-athletes has found that they will spend as much as _____% of their total training time in zone 2.

Most fitness enthusiasts that exercise in a gym or at home on a regular basis on multiple days per week will spend many years reaching their fitness goals through aerobic-efficiency training. Research with these well-trained non-athletes has found that they will spend as much as _____% of their total training time in zone 2. 



A. 10
B. 25
C. 35
D. 50


Answer: D