The reconstitution of the stock of glycogen by the intake of food after exertion is an extremely important point to be taken into consideration. As was perfectly demonstrated by Costill (cf. “A Scientific Approach to Distance Running”), normal foods (with 50-55 % of glucids or carbohydrates) cannot reestablish this stock rapidly, when it has been gradually exhausted by, for example, intensive daily training. It could take several days and is therefore a factor to be taken into consideration when preparing for a competition. Particularly close attention should therefore be paid to the intensity of training in the last two weeks, and the diet should be arranged accordingly. On this point we should also note that well-controlled training encourages the use of fats during a marathon and thus permits an economy of “highoctane fuel”, i.e. glycogen.
Diet and Performance
It is thanks to our diet that we are able to reconstitute the reserves of energy which we need in our normal lives or that we have just used up in the course of a physical exertion. Normal diet is intended to meet the requirements of normal life and does not correspond either in quantity or quality to the exceptional requirements of intense, prolonged exertion, whether it be training or competition. The experiments to which we have referred had as their aim research into the extent to which it is possible to increase the capacity of our tanks for high-octane fuel and thereby
improve the performance or duration of exertion.
The first scientific work (1939) highlighted both the role of glycogen and that of a highcarbohydrate diet. However, it was in 1967 in particular that the Bergstrom Team succeeded, after a series of studies, in perfecting a method combining diet and intense training which resulted in a massive increase in the stocks of glycogen. They demonstrated that if the muscles which were to be used during a long period of exertion were first exhausted, it was possible to increase our stocks of glycogen and thereby continue a high-speed exertion for longer (which is what happened for Ron Hill, for example). This “overcompensation”, as the Americans called it, was achieved by highcarbohydrate foods in the days before a competition, after having exhausted as much as possible the reserves of glycogen by intense exertion. It is this combination of diet and training which allows the massive increase in the stocks of glycogen, that is the high-octane fuel of our bodies.
The results achieved in the laboratory on human subjects give results in figures which speak for themselves. Expressed in minutes, they show the length of time during which the subjects were able to exert themselves to complete exhaustion at 70 % of their maximum capacity. Different types of diet were tested during the days preceding the experiment, and the following table shows the results of this.
- Proteins + fats : 60 minutes.
- Normal balanced diet : 115 minutes.
- High-carbohydrate diet : 170 minutes.
- Scandinavian dissociated diet: 240 mi-
A very large number of international specialists use, with variations, the formulae we have described and this is no doubt the reason for both the improvements in times which have been achieved by men and women and the fresh state in which runners arrive nowadays. Finally, we will make a remark which will situate the problem well by recalling that at the last New York marathon the Norwegian Grete Waitz achieved almost the same time in the second half of the marathon as in the first. We think that no comment is needed. One element which seems to us to be essential in order to understand part of the mechanism properly is the following : The consumption of glycogen by our bodies is practically constant while we have available even small reserves. The role of the manipulation of our diet to increase our reserves will therefore come into play during the last part of a marathon, particularly after the 30/35th kilometre and of course at the end of the race. The time lapse required for reconstituting or increasing one’s stocks of glycogen, i.e. at least three days of a highcarbohydrate diet, should be borne in mind at all times.