The most important aspect of conditioning and intervals is that they work very generally and doesn't necessarily improve your ability in the activity you are doing, but rather train the capacity of your heart. A good heart relaxes more in between heart beats and compresses more efficiently.
More efficient compressions are obviously an advantage, but having a more relaxed heart is also quite advantageous when training. A relaxed heart between heartbeats can fill up with more blood, which results in more blood being pumped every time and therefore more oxygen getting out to the different muscles.
Rowing is good as an interval activity because of the large muscle groups being used during the workout. The same goes for running, cycling and cross country skiing. Large muscle groups demand more oxygen which increases the heart rate.
So if you are struggling with injuries because of running then you should consider doing like me. I try to use alternative interval sessions as a means to run longer when I first run. Yesterday I was about to vomit from doing a 4x4 rowing activity and my thigh wasn't even close to hurting! I can't wait to run longer this weekend!
Source: "TRI - Den Ultimative Træningsbok" by Torbjørn Sindballe