Precise calorie measurement

The most precise way to measure how many calories we burn is to measure the oxygen we consume and the carbon dioxide we breathe out. As we know the chemical reactions for fat and carbohydrate metabolism, in both cases we can work out the ratio of oxygen going in to carbon dioxide going out. From this, we can calculate how much of our energy is being derived from fat and how much from carbohydrates and, finally, knowing the total volume of oxygen consumed, we can then accurately determine how many calories we are burning at a given heart rate. The only real approximation here is to ignore the very small amount of energy we derive from protein (and alcohol!) metabolism. This test is usually performed with a respirometer as part of a VO2max test, whose principal aim is to determine your maximum oxygen uptake. The test can also be used to measure your anaerobic threshold, beyond which you are no longer to metabolize fats as the reactions are too slow for the rate of energy required, as well as your aerobic threshold, below which the calories you burn are mostly from fat.

The latest Garmin Forerunner models (305, 405, 405CX, 410, 310XT and 610) are able to upload a special file created by doing a New Leaf fitness test which is then used to calculate accurate calorie burns in function of heart rate. DC Rainmaker, in his excellent blog that I read every day, has not only just done one of these tests but he has explained in a post how one can "hack" an XML file in such a way that you can upload the results from any VO2 max test. This is good news for me because there is no New Leaf center where I live so I will definitely try this out next time I do one. I'm interested to know whether it is possible to upload a different profile for running and for cycling as the fat / carbohydrate ratio for a given heart rate will be different in each case. This is because you use a different muscle mass in each sport and there will be a different mix of type I (oxidative) and type II (fast twitch) muscle fibers and a correspondingly different VO2max.

Another thing altogether is being able to precisely measure how many calories we take on, short of burning an identical plate of food to the one we are about to eat. Knowing only one side of the calorie balance equation with precision is of limited use... But it can be a good way to equate the training load of running at low intensity with cycling at high intensity, for example (the idea behind TRIMPS or TRaining IMPusles).

Racing weight

I thought I'd see how my efforts to get down to racing weight for the Marathon at the end of November were going. When I say "racing weight", the truth of the matter is that I don't have enough experience to say what my true, optimal racing weight should be; I have several references, like what I used to weigh when I was competing in rowing in my teens and early twenties (gulp) and - more realistically - what I weighed when I did my (even if I say so myself) spectacular time in the Half Marathon back at the end of January. I am convinced that the two principal predictors of my running race performance are (1) heat and (2) weight (and in that order).

The start of the graph marks when I first started taking seriously this business of counting calories. Then, as you can see, I focused on training for my Ironman which had a by product of making me heavier, especially in the upper body, but also in the legs. So I got back down to it again at the end of July starting from the impressive heights of over 90 kilos and have more or less steadily been whittling away the weight at the same rate as before. Except, that is, for that anomaly, which corresponds to the two weeks holiday in the US. To be fair, that was probably due to water retention, bloating and god-knows-what from the long journey and let lag and so on, as it came back down to where it should have been pretty quickly.

The red dot is where I am aiming to get to - 82 kilos (which will be the lightest I have been in well over ten years) by the end of November. I think it is feasible while at the same time getting in enough energy to fuel my training safely.

My latest obession: What goes out, must come in

I realized recently that it didn't make much sense to think only about output, that's to say, exercise, without controlling the input - calories. I previously thought that you could think of your stomach as a kind of bank account where you would make deposits and withdrawals and, as long as you didn't get overdrawn or deposit too much (haha), it would all work out in the long run. Apparently, it doesn't work like that. The human body responds to the stimuli we give it and I was giving mine mixed messages. If you burn more calories in a given day then you should eat more that same day. In fact, trying to always eat less is counterproductive because your appetite forces you to compensate eventually - either that, or you start to lose muscle mass which isn't good if you are planning to run a Marathon. Much better to work in harmony with your body rather than against it and try to match your calorie intake with your consumption. What you should be doing, according to the latest research, is eating smaller meals more regularly and taking advantage of the "window" of about 30 minutes after exercising, when your body is particularly predisposed to absorbing nutrients. In practice, this means counting calories which is, as the Spanish would say, un coñazo.

I found a pretty cool ipod app which makes it a bit easier to keep track and, the surprising thing is, in spite of the huge error margin (I mean, does a croissant have 150 or 450 calories??) it more or less seems to balance up at the end of the day and - get this - it is working! I've been running for 3 years now and I wouldn't say that I am overweight, but I could be a bit leaner  if only for the reason that, if someone asked me to carry a plastic bag with a couple of kilos of fat around the Marathon, I would gracefully refuse. Also, if you look at how much money people spend on shaving a few grams off their bikes, I can safely say that I am saving myself an absolute fortune (which I can then spend on other triathlon related goodies, of course).

I now find my days off training quite annoying (I used to look forward to them) because I have to be careful what I eat (around 2,000 kcals a day); on a good day I may have to pack in 4,000 kcals, which is quite a feat. I've managed to shave off 3 kilos so far and, according to my bathroom scales (which I'm sure have an incentive to flatter me), my percentage of body fat is down to an unbelievable (for me) 8%. Its definitely true that the belly is shrinking away, but I fear that those abdominal muscles that I last saw 22 years ago will never see the light of day again. But that is not the aim! At least, that is what I keep telling myself...