People that are starting out then yes there is a higher risk of getting injured,
when im in full swing training (not now that it holidays) Every, and i mean every run session is as hard as i can go based on the distance i have to run. If i get close to the goal and im not buggered, i go harder.
Now this isnt a daily occurance, i may do this 2-3 times a week in accordance with the rest of my training program as its essentially strength based.
Basically all i need to is run 2.4km to pass my fitness tests for my job, that doesnt mean i just do 2.4km runs.
For instance we might do a 5km run, or 3x 2.4km or not long ago we did a 6km 7kg weighted run. These are all very intense workouts unless your a dedicated runner. These sessions arent just run by any tom dick or dumb prick, they are run by well trained PTs, (and they arent like 95% of the morons you find at your local gym)
Based on this training i have conditioned myself to run 5km in under 20min and a 2.4km run in under 8min 50 @ 87kg, thats more then 2 min under the required time i need to run for my age.
train hard fight easy