Than what? Pulling badly on a rower and wrenching a spinal erector (hehe)? Pedalling at a gash angle on a bike and tweaking medial ligaments?
Physical activity is something most people aren't geared for any more due to sedentary lifestyles, so their chances of breaking themselves by jumping straight into [insert activity] is highly likely, anyway.
Yes but I'd say doing it at max effort is more likely to cause injury than doing it at a steady pace.