Do you NEED to exercise? No. But if you don't exercise you better have great nutrition and lifestyle.

Muscle mass is a strong indicator of health span into old age.

Exercise can offset a poor diet and lifestyle to an extent.

Sauna and heat exposure help retain muscles in people who temporarily can't exercise (i.e. casts)

If you eat clean whole foods, have no nutritional deficiencies, get plenty of sleep, sunlight, grounding time, and are stress free... And have a active no sedentary lifestyle!!! You probably can get away without any exercise