For what it's worth:
There was a recent thread on fueling in the Boulder Tri Club group and I am posting a quote from Neal Henderson of the Boulder Center for Sports Medicine here:
"Fortunately, for those of you still reading there is a way that you can actually establish your actual energy expenditure rate while riding and running is through testing in a physiology lab. The specific procedure is called indirect calorimetry where we measure the amount and percentages of oxygen and carbon dioxide in your breath while progressively working hard. At BCSM, we call this a FUEL test- Fuel Use Evaluation with Lactates. Basically you do a lactate profile test (for more info watch the following video from Active Cities USA), and we also measure your oxygen consumption (and carbon dioxide production). In doing this test, you receive training zones based on your lactate threshold and also recommendations on pacing for Ironman, 1/2 and Olympic distance races based on power, RPE, and heart rate. And of course, you'll also receive your energy expenditure values in terms of kcal of carbohydrate and fat at the range of intensities. Attached is an example of my data from a FUEL test (as well as VO2 max). I used this information in training for riding the 24 Hours of Moab (solo). Based on this information, I intended to average an intensity of about 175 watts (or HR of 120 - which I averaged 122 beats/min for 25 hours and 9 minutes in the race) and to intake 450-500 kcal of carbohdrate per hour (which I did). Now, there are old exercise physiology texts that say the most carbohydrate that can be taken up in 80 grams per hour (or 320 kcal), but unfortunately it's old information. New research (and about 20+ years of experience in ultra-distance physiology assessments performed in conjunction with races and training) show that athletes taking in between 450 and 550 kcal of CHO end up being able to use about 420 kcal per hour. In doing this, a blend of carbohydrate sources is ideal. Bob Seebohar has a nice article on this topic on page 15 of the Inside Triathlon June 2007 issue (yes, the sex issue with at least one BTC member profiled ; ) Another article that I've co-authored for First Endurance summarizes some of this information. This is the link for that article:
http://www.firstendurance.com/newsletter_carbs.htm... So, hopefully this helps! It is important to train with exactly what you plan on using on race day to ensure that all of the kinks get worked out. Something that goes down fine in training might not work for you at race effort, or after swimming, etc. Remember, all BTC members receive discounts on physiology tests at BCSM. You can contact Avery Marzulla, Cc'd above, or give her a ring at (303) 441-2285 if you have any questions about the tests. Also, Karrie Bach is our dietitian who can also help you with fueling needs - she goes over the energy expenditure part of the FUEL tests while I explaing the lactate profile (and VO2 max portion if done) results. Happy training & racing, Neal
Neal Henderson, MS CSCS
Sport Science Manager, Boulder Center for Sports Medicine
www.bch.org/ sportsmedicine"