The question is:
If slow twitch muscle fibers use triglycerides for fuel and fast twitch muscle fibers use glycogen for fuel, can triglyceride levels be affected by the intensity and duration of activity a person does?
The reason I ask this is that I was fitness tested at work today and I have a large proportion of fast twitch fibers relative to slow twitch fibers. That is, I suck at endurance but can do short bursts surprisingly well. This is particularly strange given that I don't do anything intensely but I do engage in endurance activities such as walking home from work (5 k) at least 3 times a week and going for a 45 minute walk on my break more often than not - I've been doing this for more than a year. My triglycerides are no problem and never have been. Logic says I should have more slow twitch fibers.
Do cardiovascular variables or the amount of weight I haul have anything to do with it?
How difficult is it to change fibre types by altering activity?
Any fitness/exercise experts out there?