F.U.E.L Testing and Metabolism Part 2

April 18th, 2012 10:55am - Posted By: Adam St.Pierre, MS

Being a physiologist and athlete, I know the value of regular laboratory testing to dial in training zones, pacing strategies, and fueling strategies. At BCSM we offer a test called the F.U.E.L. test. The F.U.E.L. stands for Fuel Use Evaluation with Lactate profile. In this test we are looking at your total caloric expenditure as well as the amount of fat and carbohydrate being utilized by the body in addition to looking at your lactate profile to determine your optimal training ranges and predict race paces. Knowing all this data, we can then assist you in planning how many calories you should consume during long training sessions and races. The F.U.E.L. test provides a ton of information that is invaluable to any athlete looking to improve performance in races lasting longer than 2-3 hours.

Above are the results of a 2008 F.U.E.L. test I performed. Note that at 8:06 min/mi pace I burn nearly 1000 calories per hour, 740 from carbohydrate, 216 from fat. Knowing that I can only consume about 2-300 calories per hour while running at this pace while racing, it was only a matter of time until I would no longer able to maintain that workload, i.e. slow down.

After 2.5 years of training, largely focused on aerobic base development, my F.U.E.L. results looked like the below graph.

Note that I started at a faster speed, and finished at a faster speed, apparently my base training succeeded in making me faster! Also note that I’m burning more fat than carbohydrate at 8:06 pace, with a slightly decreased caloric expenditure, likely due primarily to losing a few pounds. Unfortunately, to maintain this pace for very long, I’ll still need to take in 300+ calories per hour from carbohydrate, which is tough to digest. I needed to become an even better fat burner, but I can’t really train any more than I have in the past 2 years. Is there another way to increase my reliance on fats during exercise?

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