Your "perceived exertion" (how much of an effort you're putting in) is measured on the Borg scale, which allows you to give yourself a score .
Physical activity seen as "no exertion" (like resting flat on the floor) would get a rating of six, while "maximum effort".
The sweet spot for a brisk stroll is a perceived effort rate of 12 to 14, which suggests a moderate degree of exercise.
"You're breathing heavily, [but] you can hold brief conversations; it's still somewhat comfortable, but it's becoming more challenging."
The Borg scale is useful since it is based on how you feel rather than a preset formula that may not apply to your fitness level.
Age-related declines in muscle mass and aerobic capacity contribute to a slower typical walking pace.
The slowdown in our average walking pace gets more evident as we enter our 60s, from a decline of 1%-2% per decade before age 62 to a decline of 16% per decade after age 62.
According to studies, the typical person's walking pace declines by 0.00037 meters per second per year, making it take roughly 1.2 minutes longer for a 60-year-old.