Training: Training Adaptations Affect Fuel Use
Quality training provides stimuli that lead to adaptions and improvement in exercise and sport performance. Link to Exercise Physiology: Training for more information regarding training. For power athletes like ice hockey players, recovery during rest periods between short bouts of high intensity training allows creatine phosphate stores to be replenished. For endurance athletes like cross country skiers, metabolic adaptations to endurance training greatly enhance aerobic metabolism. Thus, working muscles of endurance trained athletes are able to more efficiently use oxygen to metabolize carbohydrates and fats.
Training Graphic Here
This graph is presented as an example of how endurance training affects fuel use during exercise, The graph (Martin, 1993) displays endurance training effects on substrate use during exercise at a given absolute intensity (64% of pre-training VO2max). Subjects were tested prior to training and then again after 12 weeks of strenuous endurance training (running and cycling). Endurance training resulted in the following statistically significant changes in substrate use during exercise:
- Reduced carbohydrate oxidation
- Reduced plasma fatty acid oxidation
- Increased intramuscular fat oxidation
What training adaptations produced these effects? Remember that mitochondria are the sites of aerobic metabolism. In response to endurance training, mitochondria within trained muscles increase both in size and in number. Thus, one functional adaptation to endurance training is an increased capacity for aerobic metabolism. In this study, while total fat oxidation was significantly increased after training, these results suggest that intramuscular triglyceride, in particular, is the specific type of fat oxidized at a faster rate as an adaptation to endurance training. In addition, increased intramuscular fat oxidation was associated with reduced utilization of muscle glycogen.
