About a decade ago, my wife developed a mysterious neuropathy, since diagnosed as resulting from celiac's disease and dealt with, so I was consigned to half-bike riding. I had gotten myself into what I considered to be very good shape, averaging about 20 mph over moderately hilly terrain on a 100-mile round-trip commute three days a week. Then one fine day I had a little accident while coaching my son's soccer team. While I recovered from surgery, I was off the bike for three months.
Getting back on was slightly unpleasant for me. The first few weeks I was so slow and weak I had trouble finding the joy. Thank goodness my wife kept my food intake low so I didn't balloon up in weight during my lay off. Eventually, I got my strength back and riding was fun again. Better still, we solved my wife's issues and we have been back on the tandems for a number of years.