Final answer:
The Modified Bruce and the Naughton treadmill protocols are designed for people with limited exercise capacity, such as those with cardiac disease or physical limitations, to assess cardiovascular fitness.
Step-by-step explanation:
The Modified Bruce and the Naughton treadmill protocols have been developed to accommodate individuals who may not be able to perform the standard Bruce protocol, which is a commonly used stress test to evaluate cardiovascular fitness. These modified protocols are designed for people with limited exercise capacity due to conditions such as cardiac disease, chronic illness, or physical limitations. The Modified Bruce protocol starts at a lower intensity and progresses at a slower rate than the standard Bruce protocol, while the Naughton protocol further reduces the starting intensity and makes slower increments in speed and incline.