Carbohydrate intake during exercise
Last reviewed: 23.04.2024
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Carbohydrate nutrition during a 1-hour load provides athletes with longer loading times and / or more powerful jerks at the end of the load. Coyle et al. Proved that consumption of carbohydrates during cycling at 70% V02max leads to fatigue for 30-60 minutes later.
Coyle et al. Compared the effect of carbohydrate nutrition on the onset of fatigue and reduced efficiency of cyclists. Carbohydrates allowed athletes to extend the load time by an average of 33 min (152 min compared to 126 min) until fatigue was achieved. This diet maintained high blood glucose levels.
Coyle et al. Measured also the indices of this long, intense bicycle race on the background of carbohydrate nutrition and without it. On time without carbohydrate intake fatigue occurred 3 hours later and was preceded by a decrease in blood glucose levels. When cyclists were given carbohydrates at the time of food intake, the blood glucose level was stable, and the athletes could lengthen the ride time by an additional 1 hour, before the fatigue. Both groups used muscle glycogen at the same rate, and endurance was increased by maintaining blood glucose levels, rather than preserving glycogen.
Carbohydrate nutrition maintains the level of glucose in the blood at a time when glycogen stores in the muscles are decreasing.
The characteristics of running with carbohydrate nutrition and without it were also evaluated. During the 40 km race in the heat of Millarg-Stafford et al. Determined that carbohydrate nutrition (55 g-h) increased the blood glucose level and allowed runners the last 5 km to run significantly faster than the race without taking carbohydrates. In running on a treadmill at 80% V02max, Wilbert and Moffatt found that running time when consuming carbohydrates (35 g-h) was 23 min longer (115 min) than without carbohydrates (92 min).
Carbohydrate nutrition can also improve performance in sports that require stops and traffic (football, basketball), where intensive and short-term efforts are needed. Davis et al. [26] evaluated the effect of carbohydrate nutrition on the indices during an intense bicycle race with interruptions. Athletes performed repeated one-minute jerks at 120-130% V02max, separated by 3 minutes rest, before the appearance of fatigue. Before the start of the race and every 20 minutes during it, athletes took a portion of a sedative drink or a 6% carbohydrate-electrolyte drink, which gave 47 grams of carbohydrates per hour. The average time to fatigue in the case of taking carbohydrates was 89 minutes (21 spurt) compared to 58 minutes (14 jerks) in the case of placebo. The results of this study show that the benefits of carbohydrate nutrition are not limited to increasing the duration of intense exercise.
The improvement in carbohydrate nutrition before loading was in addition to the indices obtained with the carbohydrate feed during the load. Wright et al. [27] showed that bicyclists who received carbohydrates 3 hours prior to and during the time of exercise could carry the load for a longer time (289 min), unlike those who received carbohydrates either before the load (236 min) or the time of it (266 min).
Combined nutrition gives higher indices than only carbohydrate. However, the growth in pre-carbohydrate nutrition was lower than when small amounts of carbohydrates were consumed during exercise.
The main role of carbohydrates in beverages replacing water is to maintain the concentration of glucose in the blood and increase the oxidation of carbohydrates. Carbohydrate nutrition improves performance during a load of 1 hour or more, especially when muscle glycogen stores are negligible.
In fact, the consumption of carbohydrates and the replacement of water with beverages improve sports performance.
Belois and Coyle evaluated the effects of liquids and carbohydrates individually and in combination during a 1-hour intensive bicycle race. In four tests, athletes received: 1330 ml of water, which replenished 79% of perspiration; 1330 ml of liquid with 79 g of carbohydrates; 200 ml of water, which replenished 13% of perspiration; 200 ml of liquid with 79 g of carbohydrates. When a large volume of liquid or 79 grams of carbohydrate was given separately, each athlete improved by 6% compared to the placebo test. When a large volume of liquid and carbohydrates were used in combination, the indices improved by 12%.
Coyle and Montain offer athletes to improve performance take 30-60 grams (120-240 kcal) of carbohydrates every hour. This amount can be obtained either from products or from a liquid rich in carbohydrates.
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