I agree, a trip to Mars must be short with the surface exploration longer than the trip there.

From the article;
"Second, we must develop centrifugal gravity. Decades of trials show clearly that zero-g is very bad for us. The Russians who set the endurance records in space have never fully recovered."

The effects of bone/muscle lost must still be addressed in 0 g for long distant space travel and for extended stays regarding science research in space labs though.
What's after Mars once we have mastered man visiting Mars? Will we have the rocket technology to send humans on a round trip to Titan in a short enough travel time to discard the effects of 0 g on humans by then? Or will we have found a way to trick the body into thinking it needs to produce muscle mass and bone growth?

Hopefully ISS will not be abandoned and much more will be learned while we develope new methods of space travel.
SteveS