Usaj, A., Lojen, S., Kandare, F., & von Duvillard, S. P. (2009). The influence of two types of endurance training on carbohydrate and fat oxidation rates. ACSM 56th Annual Meeting, Seattle, Washington. Presentation number 981.

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"It is generally accepted that endurance training decreases carbohydrate oxidation rate and enhances fat oxidation rate at the same absolute exercise intensity. However, the characteristics of endurance training may differ greatly according to the intensity and duration of individual session, frequency, and length of training."

This study ascertained whether different training effects regarding carbohydrate oxidation rate, fat oxidation rate, and the rate of exogenous carbohydrate oxidation occur with different characteristics of cycling endurance training. Ss were randomly divided into two groups. The lactate threshold group (N = 4) exercised for two hours at lactate threshold intensity three times per week. The onset of blood lactate accumulation group (N = 3) trained for one hour at onset of blood lactate accumulation intensity six times per week. Both groups trained for one month. Both groups were tested at a similar absolute intensity corresponding to pre-training lactate threshold and for two hours. Tests were performed with a carbohydrate solution (15% sugarcane solution, naturally labeled by 13C). Values obtained during a 100-120 minute interval were compared to before and after training in each group.

None of the three oxidation rates showed a significant training effect in the lactate threshold training group. However, in the onset of blood lactate accumulation group, the carbohydrate oxidation rate and the fat oxidation rate were significantly changed. Pre- and post-training exogenous carbohydrate oxidation rates were not different between training groups. Adaptations in the exogenous carbohydrate oxidation group were more homogenous than those in the lactate threshold group.

Implication. The more intense onset of blood lactate accumulation training utilizes carbohydrate more rapidly and increases fat oxidation rates more than less intense lactate training. Both training forms demonstrate a clear tendency to reduce the rate of exogenous carbohydrate oxidation.

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