Two years ago I packed out a good sized cow 1.5 miles down a steep hillside in three trips. I was 67. I was sore and gimped up for a week. This year (69) I killed another good sized cow approximately 50 yards from the last one. I made 5 trips and a different route. I was fine except my lower back was sore for a day from bending over breaking it down. I walk 3+ miles every day with my pack with weight to get in shape. Thank God for EXO Mountain Gear.
My advice, get in shape, get a "good" pack and make more trips if needed.
P.S. Trekking poles for pack out. A must have.