For maintaining minimal heart health, your wife's numbers may be adequate to lift you up above "sedentary". But, cycling always demands ever more.... or at least our vanity does. Last month I hiked the Upper Yosemite Falls trail on a hot day. It can be a quad and cardiovascular butt kicker especially for us grayheads. I doubt your wife's numbers would have gotten me to the top. But, to stay out of the hospital cardio ward a 60x3, diet, and some luck should work. Trouble is, hanging with fit 50Plussers requires more.... and cycling is never about "minimums"-- it's about Maximums whether that's 8mph on a huge trike on much faster on a full race machine.