Very interesting article in the latest edition of Health Psychology.

Health Psychology, Vol 30(1), Jan 2011, 67-74. doi: 10.1037/a0021859

People, including myself, often underestimate how much they will enjoy exercise, what's interesting is the finding that the underestimate seems to occur across all types of exercise.

The key to get people to exercise is to increase their expected enjoyment in the exercise, particularly if you can make the beginning part of engaging in exercise seem more enjoyable.