Hot Air …

Over the last few days I’ve estimated my VO2max by some of the many methods available to those unfortunate enough to lack a gas analyzer and cycle ergometer.

The first couple of methods don’t involve getting up out of your chair, the second is the simplest – the inputs are just your resting pulse and your age. The next two involve exercise. The inputs are your weight and active pulse or measured power.

The Rockport test doesn’t involve exercising at maximum capacity, at least not unless you are totally out of shape, therefore it is suitable for elderly gentlemen. The six minute power is meant to be a maximal effort.

It is interesting how close the results cluster together. Whether that is anywhere near a lab measured VO2max is an unknown.





World Fitness


World Fitness


Resting Pulse

Take pulse

MDApp method 1



Walk 1 mile fast

MDApp method 2


6 minute power


Michael Konczer


VO2max peaks in young adults and then declines at about 1% a year. Young and middle aged men can halve the rate of decline by regular vigorous exercise but the rest of us are stuck with it. It is largely the consequence of a declining maximum heart rate. The second most important culprit is increasing body fat.

After 70 it’s supposed that VO2max drops off a cliff but the evidence is getting pretty thin at that stage. Clearly nobody told Giuseppe Marinoni who set the Hour Record in the men’s 80 to 84 category last year by cycling 39.004 km.

Great things are still possible.

Running on Fat …

Back in my marathon days (30+ years ago) I remember reading a prediction that it wouldn’t be long before women were beating the men over the magic distance of 26.2 miles. The logic was very simple, fat is an excellent fuel, fit women athletes carry more fat than fit men athletes therefore women would be better over long distances than men once they matched the men in training.

So far it hasn’t happened, fastest man – Eliud Kipchoge of Kenya 2:01:39 fastest woman Brigid Kosgei also from Kenya 2:14:04. Getting on for 10% slower.

At about 9 calories per gram fat is an excellent fuel trouble is for endurance sports the body is very happy burning glucose and glycogen even though they pack only 4 calories per gram. Stores of glycogen exist in muscle and in the liver amounting to about 600 grams. In ball park figures that’s about 2400 calories for a marathon requiring about 2600. A runner can expect to absorb 50 to 60 grams of glucose from the gut per hour which easily makes up the shortfall.

So fat burning doesn’t really get into the equation during an elite marathon. If it did even the thinnest male athlete has enough fat to go the distance.

Glycogen is king. Glycogen replenishment happens faster after a carbohydrate rich meal. What are the implications for the athlete following a keto diet? Depends who you ask. According to Harvey, Holcomb & Kolwicz the keto athlete is operating at a distinct disadvantage although it is an excellent diet for weight loss.

Dr Caryn Zinn on the other hand is more optimistic …

while Professor Asker Jeukendrup sums up what is known but leaves the question open. That article is well worth reading.

Fat oxidation rates are on average 0.5 grams per min at the optimal exercise intensity. So in order to oxidise 1kg of fat mass, more than 33 hours of exercise is required! Walking or running exercise around 50-65% of VO2max seems to be an optimal intensity to oxidise fat. The duration of exercise, however, plays a crucial role, with an increasing importance of fat oxidation with longer exercise.

There is no doubt that the reforming couch potato can successfully lose weight and burn fat at moderate rates of exercise on a keto diet. Fat around the middle is as much a handicap as lead in the saddle bags. VO2max is the upper limit of your ability to burn fuel a good measure of your fitness. More precisely it’s milliliters of oxygen consumed in one minute, per kilogram of body weight (mL/kg/min) at sustained maximum effort. In other words get the kilograms down and the VO2max goes up without any extra training.