This Pretty Much Sums up Rowing:

From a 1996 New Yorker article:

The paradox of rowing is that this most physically demanding of sports is about eighty per cent mental, and the higher you rise in the sport the more important mental toughness becomes. Rowers have to face the grim consequences of starting a two-thousand-metre race with a sprint--a strategy no runner, swimmer, cyclist, or cross-country skier would consider using in a middle-distance event. Since rowers race with their backs to the finish line, the psychological advantage of being ahead in the race--where you can see your opponents but they can't see you--is greater than the physiological disadvantage of stressing the body severely so early in the race. If you get behind, something like "unswing" can happen: the cumulative effect of the group's discouragement can make the individuals less inspired. Therefore, virtually every crew rows the first twenty or thirty strokes at around forty-four strokes a minute (which is pretty much flat out) before settling down to around thirty-seven for the body of the race.

As a result of this shock to the system, the rower's metabolism begins to function anaerobically within the first few seconds of the race. This means that the mitochondria in the muscle cells do not have enough oxygen to produce ATP, which is the source of energy, and start to use glycogen and other compounds stored in the muscle cells instead: they begin, as it were, to feed on themselves. These compounds produce lactic acid, which is a major source of pain. In this toxic environment, capillaries in the hardest-working muscles begin to dilate, while muscles that aren't working as hard go into a state of ischemia--the blood flow to them partially shuts down. Meanwhile, the level of acid in the blood continues to rise. Mike Shannon, a sports physiologist who works at the new Olympic training center, outside San Diego, told me that the highest levels of lactic acid ever found in athletes--as measured in parts per million in the bloodstream--were found in the blood of oarsmen, about thirty parts per million. "That's a tremendous amount of pain," he said.

Marathon runners talk about hitting "the wall" at the twenty-third mile of the race. What rowers confront isn't a wall; it's a hole--an abyss of pain, which opens up in the second minute of the race. Large needles are being driven into your thigh muscles, while your forearms seem to be splitting. Then the pain becomes confused and disorganized, not like the windedness of the runner or the leg burn of the biker but an all-over, savage unpleasantness. As you pass the five-hundred-metre mark, with three-quarters of the race still to row, you realize with dread that you are not going to make it to the finish, but at the same time the idea of letting your teammates down by not rowing your hardest is unthinkable. Therefore, you are going to die.