If you learn to ride properly (helping the horse to carry you, not just sitting on it), then you get a great workout in thighs, calves and butt, especially. Lifting bales and sacks is great, too, again as long as you do it properly (use calves, knees and thighs, not your arms and back alone -- "bend zee knees!" was what I was always told... Trainer had a heavy accent, heh). Grooming well and mucking stalls is real good for upper arms, too. Yep, definitely good exercise if you do it right!