7k in 30 minutes - interval suggestions

[H2O]

My personal opinion: VO2 max intervals are the most productive.

The easiest is to do a single 2K very nearly flat out (just maybe without sprint at the end). Keep as even a pace as possible, you should be worried already 400m in, definitely suffering at 1K. It takes a while to get the pace right.
It needs to be hard enough for you to be in doubt pretty quickly whether you will get to the end of this or not.

The more highly trained you, the fewer you can do per week. In the beginning you can do 2 per week, since you are not yet able to really get near to your limits (it only feels that way) and still have to find your pace. Later you do only one per week. Doing a single 2K means that you do not have to worry about rest intervals, which simplifies everything.

Equivalent intervals: 2 x 1500m, 4 x 1000m, rest = work (or a tiny bit more).

I have gotten good results in the past doing this plus one 20 minute max effort per week and lots of much easier rowing.

[iain]

My personal opinion: VO2 max intervals are the most productive...

I have gotten good results in the past doing this plus one 20 minute max effort per week and lots of much easier rowing.

IIRC the best correlation for these types of duration TTs is with "power produced at threshold". This has 2 components that can be considered separately
: VO2 max and the proportion of VO2 max that you can sustain. The sessions quoted are believed to have a good benefit for the former, but you need to low longer (>5min / interval at or above current 30' pace) to improve the latter. That said, I don't know any specific research to demonstrate this.