Anaerobic Threshold

[axel_knutt]

Have a read of this conversation and see who you think has the best conception of what anaerobic threshold is:

M: If I exercise at x% MHR my speed is constant, if I then increase my HR to y% my speed increases, then after a few minutes goes down and down as lactate builds up. If I then return to x%, my speed drops further, but then after a few minutes it rises back to it's original level as the lactate clears. I assume that my anaerobic threshold is somewhere between x and y.

D: But doesn't your aerobic respiration take over at that point when you've exhausted your glycogen stores? Anaerobic respiration is the one that takes place initially with the burst of activity, and then the aerobic one replaces it.

M: Aerobic is what happens when your heart and lungs can provide enough oxygen to burn all the glycogen you're using.

D: My understanding is that it's like a sprint, when you run for a very brief period it's the anaerobic respiration when you use muscle glycogen but it's soon exhausted.

M: It's not about time duration it's about exercise level. If the exercise level is low enough for the heart and lungs to provide enough oxygen to metabolise all the glycogen aerobically you get no lactate build up so you can exercise indefinitely at that level. If you increase your exercise level you burn more glycogen, and the heart and lungs can't provide enough oxygen to metabolise all the glycogen aerobically, so some is metabolised anaerobically which produces lactic acid, which then builds up in muscles causing a reduction in output power.

D: Mmm, not sure you're right, my understanding is that glycogen metabolism is always anaerobic, it's a short term muscle store of energy so that's why you need to mobilise the aerobic system which as you say can go on indefinitely. That's why you hit the period of extreme cramp but if you carry on the aerobic system takes place using your glucose, glycogen is short term storage. That's why people train, so they can get into the aerobic respiration earlier and that's why you need good heart and lung function to run long distances. Someone was explaining about the Olympic 400m when they build up lactic acid by using up glycogen stores they have to have this switch, they have to suddenly go into aerobic respiration, they have to have this facility for moving between the two. All runners use up their glycogen quickly, but long distance runners do it aerobically.

M or D?

[Gearoidmuar]

M is closest.

Anaerobic threshold is defined by scientists as a particular level of lactate in the blood.

What runners call tempo runs are a little bit below it.

[axel_knutt]

That's gratifying, "M" is me, "D" is a doctor at my local hospital. It's also the answer I expected after rechecking my references, including Guyton&Hall recommended by the doc.
The argument started when I told him that I'd estimated my anaerobic threshold might be as low as 75%MHR, but it's the method suggested on Lance Armstrong's website.

[Gearoidmuar]

That's gratifying, "M" is me, "D" is a doctor at my local hospital. It's also the answer I expected after rechecking my references, including Guyton&Hall recommended by the doc.
The argument started when I told him that I'd estimated my anaerobic threshold might be as low as 75%MHR, but it's the method suggested on Lance Armstrong's website.

Well, I'm a doctor myself but know my sports stuff and can assure you that most Doctors know nothing at all about this area! They don't have to
.

[axel_knutt]

To be fair he was a neurologist.

I'd been showing him some measurements of my power output and how I'd estimated my AT to be possibly as low as 75%MHR, and he disputed that my measurements were valid, but I see that what I was doing is essentially they way Lance Armstrong describes on his website. (I assume it's also valid for non drug takers.... ) He recommended I read Guyton and Hall, but as far as I can see that's confirming what I said too. He was quite helpful though, I'd showed him some info about Overtraining Syndrome and he wrote to my GP asking her to review it and refer me to a sports doctor. It was the GP who refused point blank to discuss it.

I showed the cardiologist the graph of my power output a week or two ago as well, and she just couldn't grasp what I was getting at either. It's difficult to find much data for other people, but as far as I can tell I'm only producing about half the power that most others can manage.

I was talking about this again with the staff while I was having a perfusion scan yesterday morning, and the nurse just kept saying what do mean by "power". And that was while I was sat pedalling a dynamometer that was indicating my power output in watts. I kept pointing to the display and saying "look here" but she still didn't get it.

I seem to recall something on Radio 4 fairly recently bemoaning the fact that doctors are taught little or nothing about sports medicine at medical school.

[Gearoidmuar]

To be fair he was

I seem to recall something on Radio 4 fairly recently bemoaning the fact that doctors are taught little or nothing about sports medicine at medical school.

I didn't learn a single thing about it in university, but I graduated in 1974. For a few years I used to give a lecture on the cycling side of it to postgraduates doing a course on sports medicine. I used to deal with things like specific cycling injuries, bike position, overtraining syndromes, nutrition and all that. I had no training in it apart from widespread reading and personal experience.

Power output in the trained individual has a huge genetic component. My daughter is a terrific athlete, runner and triathlete and people in the running business always ask "where does she get it from?". Answer, her mother. My wife was a very good runner and her father was a schoolboy champion middle-distance runner. If you don't have the genes (I don't) you won't be a great athlete, but that will not stop you from enjoying it!

[axel_knutt]

Power output in the trained individual has a huge genetic component

Indeed. Did you see the Horizon episode a while back about Prof Jamie Timmons work? He has developed a DNA test which he claims has strong predictive ability re. trainability. He has found a genetic sub group who he calls non responders, and who make almost no improvement no matter how much they train. You can find out if you're one for a couple of hundred quid.

This is an interesting book too. Mannings argument is that the expression of the homeobox genes is epigenetically influenced by the mothers testosterone levels during gestation. This then affects a whole host of traits, from sexuality to susceptibility to autism/cancer/heart disease/infectious disease, but among the most prominent are athletic ability and finger length. He has found then that finger length is a proxy for foetal testosterone, and thus reliably predicts athletic ability.

My finger length would appear to indicate that I'm less athletic than an average female by about the same margin as a female is behind an average male........

[Trev The Rev]

There is some interesting stuff here from Dr Andrew Coggan PhD

http://home.trainingpeaks.com/articles/ ... oggan.aspx

If you want to train with a power meter and you are at home with numbers Dr Coggan is your man.

However it should be remembered that cyclists were able to train effectively before the advent of power meters.