“Getfit” isn’t a command, but rather a friendly challenge from MIT Health (formerly MIT Medical) to spend the cold months exercising with a group of people you choose in any way you choose. This year, the popular winter fitness program is celebrating its 20th year. What began as a goal-oriented exercise incentive for MIT Health staff in its pilot year, and expanded in 2005 to the entire MIT community, has now become a cherished tradition for many. Tom Goodwin, a staff member in MIT Health who has participated every year,…