UPDATE: I'm bumping this post up as well, so all three "how to" are at the top of the stack.
The 6000m erg test has become a staple in the rowing world since the US National team instituted it nearly 10 years ago. Prior to the 6k, most long test pieces were twenty minutes in length, with the oarsman striving for the greatest distance rowed in that time frame. That test was a hold over from the gamut erg, which measured a number of revolutions produced by the rower over a set amount of time. I don't have any images of a gamut, but rest assured, gentle reader. The gamut was evil. They made the Concept II B look like a Cadillac.
The 6k is usually tested in the fall and winter, when crews are concentrating on endurance. Not only is endurance tested, but mental toughness. A coach's thinking assumes that anyone can "hold their breath" and "tough it through" a 2000m test. The 6k requires concentration and mental toughness over a long time that can't be faked.
The critical moment of a 6k happens in the middle of the piece. As I've said many times before, rowing races are usually won in the middle, when a crew's fitness and technique pay dividends over the explosiveness of the start or the burning agony of the sprint. A 6k emphasizes the middle of the piece, because the start and sprint are such smaller portions of the total work.
From 4000 meters to 2000 meters to go, the rower will struggle against increasing exhaustion. This is very different from the increasing lactic acid pain that builds during a 2k. Because of the emphasis on aerobic work, the exhaustion an oarsman battles during a 6k feels more like a power drain. The key to having a successful piece is consistency during this section. The oarsman should have found a sustainable rhythm fitting his goal during the first 2000m. Simply pulling the same average split through this section of the test will usually bring a positive result.
Sounds simple, right? Sure. I usually had the "I can't do this" moment during this stretch. Exhaustion sets in before the halfway point, and most people just want to back off just a little to conserve energy for the sprint. That's the problem and challenge of the 6k. If the rower backs off just one or two splits during the middle, those splits are usually gone forever. You can't just hop back "up" to that faster pace; that takes mental energy that should be reserved for the sprint. Now the rower is struggling just as hard to hold a slower pace. Think about it: the difference in real energy required to pull a 1:55 rather than a 1:57 is tiny, just a few percentage points. The mental energy required to get back to 1:55 after two minutes pulling 1:57 is massive.
Finally, why really "save" anything for the sprint at all? In order to make any significant of difference in the "average split" in the final 750m, the rower has to carve off 10 seconds per 500 and hold that through the final 750. If the rower has waited until the final 500, it is too late to "salvage" a good result. Once second "average split" is far too much to make up in the final 500m of a 6k.
I always started my sprint at 1500m to go, by pushing down whatever split I was pulling every stroke by one second. A longer "push" makes a bigger difference in the final time. There would always be energy for the final mad dash, which is really for the coach to watch his crew and measure how much pain tolerance everyone has.
What lesson to take from all this? Emphasize the middle of the piece. Every stroke is an opportunity to build your average towards what you want it to be. Push in the last 1500m and trust that your inner crazy will always be there for the final 500m. Just don't trust that final 500m to save you from a bad piece. As always, win your race in the middle.