During the long runs in Kenya (and in Ethiopia, too) normally the athletes drink only water. Sometime we meet runners going without any assistant (no car following them) in courses of 45 km, of course without any possibility to drink. Not only, but one of the most difficult problems to solve for training kenyan marathon runners is to teach them to drink. Many of them think that not drinking can strengthen their endurance in very bad conditions of weather. And, also when they drink, a lot of time they only put little water in their mouth, and after they spit out without swallowing.
Different is the situation during the race. Many athletes (not all, but many) use maltodestrines,if they have european or american coaches, knowing the system.
For example, in preparation of WCh of Osaka 2007, that we knew were very hot and humid, I went with Shami for any specific workout at lower altitude (Keiyo Valley), at 11:00 o'clock in the morning, in order to have full adaptation to the conditions of the race. Several times Luke Kibet came with our group. During that period, I always used Maltodestrines (in powder), melted in water, trying to create the best concentration for each athlete. In fact, the reaction in the stomach is individual, changing from every athlete. Somebody cannot use, because feels acidity after drinking, for some other everything is ok. In the case of Shami, we found a good solution using 2 normal spoons of powder in 250 ml of water. The same we use in Osaka, where he was able to win silver, in spite to have a sciatic problem that didn't allow him to run faster than 3:10 per km.
But also in the Italian Methodology of 20 years ago (producing Bordin, Pizzolato, Poli, Bettiol and many ladies), we used sometimes to go for long run WITHOUT using any refueling, in order to oblige the body in seeking the residual energy in some store, that normally is closed.
Similar situation we use when we go for SPECIAL BLOCKS of VOLUME (for example, in the morning 10 km in 33' + 15 km at MP (3'04" is 46'), the same in the afternoon). This means 20 km at 90% of MP + 30 km at MP in the day. In order to stimulate the body in using ALL the risources for lasting at MP, between the first and second session the athlete easts only vegetables and drinks water, without filling his tank again with carbohydrates. The final goal is to teach to the runner to use ALL the resources that he has.
That's the reason because a lot of km at low intensity, for an athlete already mature, cannot produce any effect.
What we need, is not a global very high volume,but the ability in growing, year after year, IN THE LENGTH OF THE SINGLE RUN AT HIGH INTENSITY. To increase the SPECIFIC MARATHON ENDURANCE is a physiological problem, as the athlete must change his ability in building the right fuel, using LESS percentage of glycogen and MORE percentage of fat for the same speed. We can reach this effect only using SPECIFIC SPEED for long time,not a lot of volume not stimulating the body in "scratching the bottom of the barrel".