In a comparative study, Klein and colleagues (1994) studied the overall fat metabolism ratios for endurance-trained and untrained men during low-intensity exercise routines. They sample a total of 10 men, 5 who were endurance-trained athletes and 5 who were untrained. They started off by calculating and analyzing the overall lipid activities and muscle activities while all 10 subjects were resting before the exercise routines began. They also calculated the free fatty acid (FFA) and glycerol rate of appearance (Ra) ratios. The calculated the lipid activities using indirect calorimetry as a determinant and the FFA and glycerol levels through the combination of glycerol (2H5) and palpitate (1-13C) one after another (Klein et al., 1994).
The results showed that the lipolytic reaction after 4 hours of high-intensity training routines showed no significant variations in the overall FFA and glycerol levels between the endurance-trained subjects (increase in a minimum of 1.02/kg to 3.76/kg and increase in a maximum of 9.85/kg to 24.64/kg) and the untrained subjects (increase in a minimum of 0.99/kg to 0.39/kg and increase in a maximum of 11.29/kg to 24.13/kg). The variation between the trained and untrained subjects occurred in the average triglyceride oxidation levels during the high-intensity exercise sessions. The trained subjects showed a high maximum of 7.51/kg and the untrained subjects showed a lowered maximum of 5.67/kg. Furthermore, during the recovery session of the exercises, the untrained subjects experienced a slower speed of decreased FFA and glycerol Ra levels in comparison with the trained subjects even though the overall decrease in the ratio was more or less similar as has been numerically exhibited above (Klein et al., 1994).
Analyzing the results of the above study, it is east to assert that the in spite of having similar FFA, lipolysis and glycerol levels, the endurance-trained individuals and athletes experience higher levels of fat burning then the untrained athletes. This is because they burn more fat tissues in their endurance exercise routines. Further analysis help us assert that the lipid activities get back to the baseline at a much slower rate for the untrained subjects then the male subjects.
In a separate and dissimilar study, Starling and colleagues (1996) took a different approach to analyzing the impact of endurance exercise by analyzing the impact that the diet of an individual has on his overall muscle triglyceride and endurance performance ratios. They took a sample of seven endurance-trained athletes who had the average of completing 120 minute cycling exercise with a maximum intake of oxygen at nearly 65% ratios. The diet changes introduced in the subjects daily routine included an intake of either a high-fat (Hi-Fat; with 68% of energy) or an isocaloric high-carbohydrate (Hi-CHO; with 83% of energy) diet for a total of 12-hour period. At the end of the 12 hours and after an overnight fast, the subjects went through an exercise routine of 1,600-kJ self-run cycling. Even though the muscle triglyceride levels before and after the cycling exercises were not so different before the new diet incorporation; the levels significantly increased for the Hi-Fat diet after it was incorporated into the daily intake of the athletes. The levels showed an increase in the minimum levels from 2.4 to 7.1 minutes and an increase in the maximum levels from 44.7 to 117.1 minutes for the Hi-Fat diet plans (Starling et al., 1996; see also Hochli et al., 1995; Morgan, 1992; McArdle et al., 1996c).
After analyses of the data and results from the above study, we can conclude that the diet of an athlete has a significant role to play on the overall impact that the endurance training exercises can have on muscle fat metabolism and oxidation levels that an individual goes through. Hence, it is extremely important to have a balance of not only the exercises, in term of the high-intensity and low-intensity exercise combinations as well as their durations, but it is also very important to make sure that the diet one has compliments each and every aspect that is being aimed to improve through the use of the exercise routines.
In this paper, the effects of endurance training were discussed with special reference to their impact on the muscle fat metabolism while prolonged exercises. The paper talked about the inconclusive nature of prior studies and then analyzed the prior result already achieved to form lucid conclusions on eth topic. The paper gave particular attention to the importance of exercise for athletes and how the use of endurance exercise impacts their muscle and fat metabolism. In the paper the differences in the fat metabolism between men who are endurance trained and those who are not were also discussed along with the influence of endurance training on muscle kinetics during high-intensity exercise, influence of repeated sprint training on pulmonary O2 uptake and muscle deoxygenation kinetics in humans, the effects of diet on muscle triglyceride and endurance performance as well as the possible increased physical activity decreasing the hepatic free fatty acid uptake. For further suggestions, one aspect that hasn't been discussed in the paper is the importance of the membrane transporters within the realm of endurance exercise. Hence, researches must analyze the aspects of molecular biology of membrane transporters as well as clear identification of the roles of membrane transporters and molecules must be done to really understand the effect that they have on the on fat metabolism levels of an athlete or an individual who is endurance-trained or untrained.
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