If you cut the trip time down far enough, the need for artificial gravity is greatly diminished. Taking Musk's ITS/MCT plan as an example, the trip will take on

If you cut the trip time down far enough, the need for artificial gravity is greatly diminished. Taking Musk's ITS/MCT plan as an example, the trip will take only 2-3 months and the destination (Mars) has 0.38 Earth gravity. In that situation, there should be little to no physiological issues and the astronauts should be more than strong enough to deal with Martian gravity levels upon arrival, especially if they exercise on the way over. Mission plans that call for much slower travel (6+ months) are much more likely to cause trouble for the travelers, which in why in my opinion any plans that are seriously considered should minimize travel time as much as practically possible. The logistics in getting a craft into space, getting it spinning appropriately to produce artificial gravity, and hurling it towards Mars are significantly more complicated than, say, refueling in orbit to allow for reduced travel time.