|"Last 10!" (Photo: B. Kitch)|
One of the reasons people fall into the training trap of 'junk mileage' is that they have to reduce the intensity in order to be able to handle the volume without breaking down physically and/or mentally. Instead of logging 20-30k in a single session each day, it can be better to split that volume into two sessions of 10k-15k each, with a period of rest in between (i.e. one session in the morning and one at night).
There are three reasons behind the double. First, it just gives you two separate times during the day when your heart rate is elevated and your body is working to try to adapt and become more efficient. The cumulative effect of two workouts in a 24 hour period is slightly greater than the effect of one long workout, because after each workout your body is in a state of recovery and is continuing to work. The second (and arguably more important) reason is that it may allow you to go slightly faster, and not have to dig as deep as you might have to in one, long session.
Remember, you are training to go fast for 2,000 meters. The longer you go in a workout, the more you create, work, and develop slow twitch muscle fibers and endurance capabilities. This is not necessarily a good thing, as you don't want it to take away from your power, which is generated by fast twitch muscle fiber. You want your 2,000-meter time to be your relative strength. If you trained for power and speed all the time, you might be really good for 100-500 meters, but you might lack the endurance to pull a good 6k-10k. Conversely, if you're doing 15 and 20ks all the time with no speed work, you might become really good at 6k, 10k 15k, but you might lack the speed to have a great 500-meter and a strong 2,000-meter piece. The point is that you want to develop your aerobic base without neglecting or softening your speed and raw power. The third and final reason behind the double-day is that shorter pieces are easier to recover from, as they will not take as much out of you. It is much harder to recover from a 20k than a 10k. Also, in a 20k, in addition to running the risk of overdeveloping slow twitch muscle fiber and endurance at the expense of power, you may start utilizing muscle for fuel toward the end of the session, once your glycogen stores are depleted (assuming you aren't stopping your row to consume carbohydrates to replenish the glycogen). Obviously, you want to utilize as much glycogen and fat for fuel as possible without having to get into using muscle tissue.
That being said, the long steady state is a very valuable tool, and I do not think it should be done away with altogether. However, it is important for athletes not to go overboard, and end up dulling the edge on their speed/power, especially when the body is already struggling to recover from a great deal of quality volume. To further illustrate my point, an elite 100 meter sprinter like Tyson Gay or Usain Bolt wouldn't want to do a 5-10 mile run everyday, as it would (gradually) start to convert some of his fast twitch muscle fiber into slow twitch. Obviously, this is an extreme example, because these are purely anaerobic athletes, whereas rowers require great endurance and aerobic capacity, but even in a 2,000 meter rowing race, the need for power and the anaerobic component is significant. If we look to the build and the ability of the best rowers in the world, it is equally important to have power and endurance in rowing. We know that rowers must have great endurance and be very fit to excel, but we also know that they must have raw power and speed. Too much of one might take away from the others and we want to make sure they aren't working against each other.
Ultimately, the best way to get faster is to have 2-3 really high quality, high intensity speed or lactate threshold sessions a week, with everything else being about managing your aerobic development while letting your body recover on the easy days. It is much better to really bring it for those 2-3 sessions a week in which the intensity is through the roof, and go slightly easier on the easy days to allow yourself to do that, than it is to have 'mediocre' intensity everyday. Long aerobic training sessions definitely have their place when there is not time to train twice a day or in certain times of the year in one's training cycle (the further from the peak one is the more the long sessions can have their place), but mileage should still be carefully controlled and technique always monitored.
-Justin and the RR Team