Harvieu25

when you are making the transition from aerobic to anaerobic?

GravelMN

The lactate threshold (the point where your body begins producing lactate at a faster rate than it can clear) is extremely hard to pinpoint without lab tests.

There is always some aerobic and anaerobic metabolism going on with any exercise. At low intensity your aerobic energy production greatly outweighs the anaerobic, but as intensity increases the balance shifts toward anaerobic. Your body can compensate (buffer) this up to a point but as intensity increases you will eventually cross the threshold. It isn't like you throw a switch and go from one form of metabolism to the other, you just pass the point where anaerobic activity exceeds your ability to compensate for its byproducts.

So I guess my answer is that you won't know the exact point, but you can estimate it by when your legs begin to burn rather than just get tired or sore and you start sucking wind. There are some DIY drills you can do to get a decent estimate but if you want real accuracy, you are looking at a sports medicine clinic and blood tests.

chaadster

I can't tell out on the road, but when working out on the stationary, I feel like my breathing smooths out and gets deeper, like deep lung. It feels like a "second wind" to me.

Harvieu25

Can you tell by when the legs start to flood with the burn?

I warm up for ten minutes before starting to increase the effort and when I am on an endurance ride I try to keep below the point of the legs burning, but on steep climbs (>7%) I don't have the fitness or gearing to deal with keeping heart rate down and keeping the fire out of the legs. I can slow my cadence to 70 but below that I am defenseless. I can only tolerate this so many times on a 50+ mile ride before the fatigue sets in the legs and I am done.

I have been working on hill repeats/intervals and my ability to clear the lactate is getting better.

I guess what I was really wondering is, if at the point you feel the flood entering the legs, is that the biggest indicator of going anaerobic?

Thanks.

chaadster

No.

wolfchild

Transition form aerobic into anaerobic all depends on your fitness level and conditioning...An unfit person can reach their lactate threshold at 55%VO Max... a well trained and well conditioned athlete will reach their lactate threshold at 70%-80% VO Max...An unfit out of shape person will reach an anaerobic zone from walking up 1 flight of stairs.... a highly fit individual can run up 10 flights of stairs while wearing a 50 pound weight vest before reaching an anaerobic zone.

Heathpack 

Yes.

OP, the burn is from hydrogen ion (ie acid) accumulation in your legs. This is a by-product of energy metabolism that takes place outside the mitochondria- ie anaerobic metabolism. Lactate is used to buffer out these hydrogen ions and therefore the increase in lactate in your body is a marker of anaerobic metabolism.

What I personally experience when I'm over (lactate) threshold (ie into anaerobic metabolism) for a significant period of time is first the burn in legs and about 15 seconds later an increase in resp rate. I'm pretty sure the increased resp rate is primarily an attempt at a respiratory compensation for a metabolic acidosis- meaning when the pH of your blood becomes too low (ie too acidic), you can increase your rate of breathing to eliminate more carbon dioxide, which functions in the body as an acid. If you decrease your effort, the increased resp rate also helps bring oxygen into the system, which is necessary to bring your energy production back into the mitochondria (ie switch you back into aerobic metabolism).

OP is describing exactly what happens when someone rides a bike and becomes fatigued. For the most part, fatigue occurs because of repeated muscle exposure to hydrogen ions. Hydrogen ions accumulate because you have repeated moments of anaerobic metabolism. You can either accumulate these moments slowly or do a big effort and cook yourself pretty quickly. For example, I can do 120% over my threshold power for almost exactly 10 minutes. At 10 min 15 seconds, my legs (which have already been burning) will be unable to sustain the effort any longer. About 15 seconds after that, my resp rate will spike. Or I can ride a pace which averages say 65% threshold power for 10 hours before I experience the same fatigue.

OP, as you get fitter, your VO2max improves, this is your maximal rate of oxygen utilization. When your VO2max improves, you spend more time in aerobic metabolism and fatigue is delayed. Once you improve your VO2max, then with increased fitness, you start increasing the power at which you switch to anaerobic metabolism- ie you raise your threshold and also increase the amount of time you can work at this level. So that delays onset of fatigue as well.

So keep working at it. Repeatedly going briefly over threshold is one of the best things you can do from a training perspective- that's what interval workouts consist of.

Harvieu25

Thanks!

I've been doing intervals, i.e.- hill repeats on a hill which is 6% and .625 mile long and takes 3 minutes + at 10 mph to get up. I have been doing this every Sunday and it seems to be helping greatly with overall power, endurance and speed.

valygrl

Interesting to note how different people are. I have never sustained 120% of threshold for 10 minutes. my 5-minute max is more like 120%

Carbonfiberboy 

Heathpack has talent. Plus she trains that talent like a maniac. I'm known as The Demented. Heathpack is Double Demented.

For me, I know when I've gone anaerobic because I can no longer sustain fast, deep breathing. I start to pant uncontrollably. Heathpack is correct. It's not oxygen debt, you're trying to get rid of CO2. I can hold it for 8' intervals. Don't know power. I shoot for 3-4 beats over lactate threshold heart rate for intervals. Before the panting starts, I can tell just by pedal pressure. It'll take a couple minutes of this for my heart rate to go past LTHR.

Anaerobic intervals are the best thing, sure 'nuf. You know you've been for a hard ride when your lungs hurt.

caloso

I'm really impressed. My 10min best is 112%.

Seattle Forrest

Yeah, there's a used/worn/kind of hurt feeling in your lungs afterwards. Serious anaerobic work releases lots of endorphins too, I get home and feel relaxed. Sometimes I'll do hill repeats after a bad day.

Heathpack 

Sorry, I just looked up the workout in question.

It was 3 x 10min at 113%, not 120%. Its confusing because we actually don't express the power targets in that manner, as a percentage of FTP, we use targets that have a shorthand code. I had it in my head that the target in question was a 120% target. But its not. Just 113%. And I could not make the power target on the 2nd and 3rd intervals.

Mere mortal here. Carry on.