Breaking the Wall

Hey Sasha,

What does it mean to "go anaerobic"? I have heard multiple people say this on the blog, and I don't quite know what it means. Is it the point at which you feel that you will have to slow down later if you push hard now, or is it any pace that is harder than threshold?

It is both. You can hold your threshold for as long as 1 hour. If you go faster than threshold, every second per mile costs you in the exponentially quicker arrival of fatigue.

When you run, you derive energy from two sources - aerobic (using oxygen) and anaerobic (not using it). The ultimate anaerobic run is 800 meters. The marathon is mostly aerobic, I believe 98%. 10 K is about 92% aerobic if I remember right.

Sasha: Nice workout. Did you get the infamous "track hack" from running hard indoors? That's always the worst part of indoor track.

To throw in my two cents on the anaerobic question, from an exercise physiology standpoint, anaerobic refers to any energy system working in the body that doesn't require oxygen. These would be creatine phosphate stores (which you can go on for about 8 seconds) and glycogen used in glycolysis (about 1:30 if you're well-trained or a natural mid-d guy). Everything else involves burning O2 and the production of lactate--which contrary to popular belief is a useful fuel before it accumulates to the point where it can't be cleared fast enough (acidosis or, more simply, tying up).

The cool thing biologically is that you're usually using multiple systems in a race. For the real long stuff (e.g. marathon), you want to keep it almost all aerobic because you've got a virtually unlimited supply of fat to burn given its fantastic energy/mass ratio and only a finite amount of CP and glycogen.

You can assess the point where you're exceeding aerobic capacity by taking blood lactate measurements and looking for the point where you pass about 4 mmol lactate/L blood (this value is different for everyone and realistically you'd only do in a lab) or simply do it by heart rate.

Here's the useful part of my blathering: The heart rate point where you start going anaerobic is referred to in the literature as V4 after the 4 mmol of lactate; although we know by now that this is a misnomer since it's different for everyone. Anyway, in general as your exertion level increases, so does HR. This is because you're running almost all aerobic at those easier levels. More importantly for this discussion, this relationship is linear. If exertion is on the y-axis and HR is on the X, when you start seeing a less steep slope in your line (a break point), this is V4. It means that the heart can only output so much blood (take in O2 and clear CO2) and other (anaerobic) systems have started to compensate. You can find your own V4 with a good heart rate monitor and a little bit of desire to hurt.

To clarify Sasha's point, the 100 meter dash is actually the ultimate aerobic event. I'm guessing he said the 800 since what you're essentially being asked to do is stretch that 1:30 minutes of available energy into some time human beings can actually run. I'd say the 800 meters is the ultimate pain event!

Sam - thanks for the explanations and clarifications. Yes, I did get a bit of a "track hack", but it was not bad.

The linear break method to detect my anaerobic threshold is a bit of a challenge, as I do not have a lot of room for maneuver once I cross it. Below is my regular HR data - varies plus or minus a couple of beats either way depending on the day, but fairly consistent, speed/HRM:

7.5 mph - 120

8.0 mph - 125

8.5 mph - 129

9.0 mph - 133

9.5 mph - 139

10.0 mph - 145

10.5 mph - 153

11 mph - 161

11.5 mph - 167

12 mph - 171

171 is as high as it will go without a hill. With a hill I can hit 175 for a very brief moment, but cannot sustain it. So at jogging speeds my dHR/dV is around 9 bpm/mph. When I approach my marathon race pace it is the highest - 16 bpm/mph. When I start approaching my 5 K race pace it drops to 8 bpm/mph.

I race a marathon at the HR of 157 when in good shape, around 90% of my max. I've also had a VO2 Max test done, which recorded 75.9 with RER hitting 1.00 at VO2 of around 68.