Cardiac drift

I got the following from XFR Bear:

I was intrigued by your training. At first sight I just thought you were doing standard base training. I tried this but it drove me nuts - all that running slowly. I sort of follow the theory but it does my head in doing it, so I was hoping to combine it with some harder sessions, which seems to be what you're doing? How have you found it?

And also - I have a big problem with cardiac drift - how did you tackle this?

This question gets to the core of base training - It's not all slow running! The 2 parts of the question are also actually the same question, if you are following the methods laid out in the Hadd article, which most of us Base Trainers are doing.

Let's first look at the subject of cardiac drift. What is it? To answer that indirectly, it's the reason I got into base training in the first place. To answer it directly, have a look at the following heart rate plot of me at the 2003 Worthing 20. I ran the race at a steady 10:00mins/mile using my Timex Speed/Distance monitor. I tried to run as steadily as I could, to see the effects of cardiac drift over the course of 20 miles. Here's the result:


The steady increase in heart rate is clear to see, but is even more graphically (?) illustrated by looking at the average heart rate for each 2 mile section:
131, 135, 135, 138, 140, 141, 141, 142, 144, 146


I remember seeing in a book called "Training, Lactate, Pulse Rate" plots of heart rates of athletes and cyclists. They were all beautifully level. No sign of the increasing HRs I was getting. There was also advice that a particular race should be run at, e.g., 85% of Working Heart Rate. What did this mean? Should I start out at this rate? Should I try to arrange my pace so that I finished at this rate? Or should I try to average out at that rate? In some early races I tried to go off at the specified HR with disastrous results - total burn out - I slowed dramatically after only 2 miles. Even going off at a more conservative pace and trying to hold my target HR once I'd settled, resulted in a gradual slowing down during the race. What was happening? Heart rate monitors are rubbish!

I assumed that there was just something different about how my body worked. I kind of got used to the fact that I'd have quite a rise in HR and planned for it, so I could just about pace a race on HR, but it wasn't ideal. Some years later I found a reference to Cardiac Drift on the internet. It was only a definition, describing increasing lactate levels, but it seemed to imply that it was perfectly normal (I suppose it is!) and was simply how the body worked. I accepted that there was nothing wrong with me and kept training as normal - my club diet of fast anaerobic intervals and a couple of longer steady pace runs in the week.

Then, in a discussion thread on the Runner's World website, I commented that someone was getting cardiac drift, and it appeared to be perfectly normal, when up popped a super-hero kinda guy called Pantman, to correct me. Pantman seemed to be saying that you could train away cardiac drift. It was simply a symptom of poor aerobic conditioning. He pointed me at the Base Training thread, and my training style was changed forever.


So why do we get this steady increase in heart rate or cardiac drift?

Put simply, it's a steady build up of lactate in the muscles. Muscles don't like the acidic environment that lactate (or lactic acid) creates and so the efficiency drops and more blood needs to be pumped to keep the work rate up. Eventually the muscles get poisoned and stop working when overloaded by lactate - feeling the burn.

I used my words carefully there, because some people seem to regard lactate/lactic acid as a poison - a toxin that stays around in the muscles and causes you to ache the following day. This is simply untrue. In fact the muscles can actually use lactate as an energy source. This is the fourth energy system which I hinted at in my Base Training summary posting The Lactic Enemy.

Your aerobic energy system can use the lactate produced by your anaerobic system as an energy source. At slow speeds/HRs this works quite well. In fact, when you start to run slowly your lactate levels can initially drop to a level lower than the natural lactate level when resting. Your aerobic system is saying "Give me what you've got" and mopping up any lactate it can find.

As speed increases, your anaerobic system starts to produce more lactate, which your aerobic system happily burns, but lactate levels start to rise slightly as the balance starts to shift a little. Up to the point where your system can mop up the lactate completely, there is no increase in the level of lactate, and you can maintain the same pace and HR for quite some time.

Eventually though, a pace is reached where any faster and lactate levels and HR start to rise steadily - cardiac drift. This point is known as the Maximum Steady State or MSS. (I believe this is also known as the aerobic threshold, but will need to check this.)

If you are seeing symptoms of cardiac drift, then you are running at a pace above your MSS. How long you can keep this up depends on the level of drift. Clearly though, if you intend to run a marathon, you need to minimise cardiac drift. Your MSS is effectively your marathon pace. For those who aren't going to do a marathon though, stick around. You still need to minimise cardiac drift if you are to get the best performance. The lower the drift, the higher a pace you can sustain for a period of time, be it short distances or long.

I should mention there is also something known as Maximum Lactate Steady State, MLSS, but this involves a laboratory protocol checking lactate levels, and because it involves 20minute treadmill sessions, and a rest, apparently comes out with a speed 3% higher than marathon speed. Unless any of you have a laboratory handy, I suggest we ignore that one!

What we all need then, marathoners or not, is good aerobic conditioning. By developing our aerobic systems to the max, we can mop up all that lactate causing the drift, and sustain a good speed right to the line.

So how do we get good aerobic conditioning? Base training of course! Lots and lots of aerobic running!


So that's just endless days of slow boring running then? No! Definitely not!

There is no doubt that lots of slow running will have an effect on your aerobic conditioning. You will get faster as your running efficiency improves. Some people on our BT thread have shown remarkable improvements with very little quicker running. However, if you re-read the Hadd article, you will notice that there is an amount of faster, but still aerobic, running mixed in. Why?

Suppose your MSS, or marathon pace, is currently 140bpm (mine is at least this, as I'll discuss shortly). One way to improve your marathon time is to simply get faster at 140bpm. BT will probably do this with lots of slow running. I say probably - we are all different and some may not progress as quickly as others in the absence of faster running.

Another way of getting a faster marathon time though is to try to raise your MSS up a few beats. At 145bpm you will naturally be running faster. Provided you can do this without accumulating lactate, then this is a good route to a faster marathon time. Hadd reckons that you can get your MSS up to 20bpm below max, which for me is 154bpm - lots of scope for improvement!

This, then, is where work sessions come in. I've not seen any evidence to suggest that slow running won't raise your MSS, however, the overwhelming amount of literature suggests that to be truly effective you have to be running at, or above, your MSS. It seems sensible to me, that if you want to train your body to efficiently control lactate levels, then stimulating it with an amount of lactate would be a good course of action.

We are still talking aerobic running though! We are not talking about speedwork here! Remember that running anaerobically is to the detriment of your aerobic system (see my posting The Lactic Enemy).

There is some difference in opinion as to the best approach here. Arthur Lydiard in 'Running with Lydiard' appears to have lots of daily running at around MSS pace in the conditioning phase. Remember though that he is talking about advanced runners who are doing 2 sessions a day. The other session would be easy jogging. For most mortals, daily MSS runs would be too much I think.

Pete Pfitzinger/Scott Douglas' approach along with most of the others I've read calls for tempo runs: medium distance runs containing middle sections of 3 or 4 miles of faster running, at paces nearer half marathon to 10k speed. This though is training of the Lactate Threshold, another laboratory determined and rather arbitrary level, which is difficult for us ordinary folk to monitor. It is the pace you can sustain for an hour, or more precisely the point at which blood lactate levels reach a specific level (4mmol/litre). It is desirable to have this threshold as high as possible, but it is very difficult to monitor progress. Tempo runs at the paces described may be effective sessions, but I find them too much in the context of daily running.

Hadd's approach for me seems more intuitive, in that he is targeting the MSS, which is far easier to monitor. He has 2 work sessions per week apart from the long run, one at around MSS, and the other a little higher. I do the first session as a steady run at a pace and HR I can sustain for the duration (MSS). The second session I do as either long intervals - repetitions of 1 to 2.5 miles with 2 or 3 minutes recovery at HRs a few BPM higher than MSS - or I do a tempo run of 3 or 4 miles at a pace above MSS, but lower than that recommended by Pfitzinger. Currently my steady run is at 80% maxHR (139bpm for me) and the tempo/intervals at 83% maxHR (144bpm for me).

The key to Hadd's method is the softly softly approach. Keep plugging away and be patient. Once you are able to run for 10 miles at a constant pace (I think for us slower types it could be less than 10 miles - let's say 1 hour at least), then, and only then, consider moving up in heart rate.

So this is how I am interpreting Hadd's approach: I am starting to do regular 'drift tests'. For this I get up to the speed/HR I am doing my steady runs at, and then run laps of my 'hood recording the time and average HR for each lap. I like to run at a constant pace using my Garmin Forerunner, rather than constant HR, as I find it easier. You can try running at constant HR if you prefer. I record my time for each lap, and so I know my times are accurate and not subject to the vagaries of GPS reception.

For the last test I did, the intention was to run at 80%maxHR 139bpm. Unfortunately it was too soon after my chest infection, so my pace was way down on what it would normally be. I was running at 9:00/mile rather than the 8:30 I should have been capable of. For this reason I will have to redo it to make sure I still have no drift at the higher pace. However, the results serve to illustrate how the test works:

Drift test: Table of paces and HRs for each 1.5 mile lap

Lap	Mins/mile	bpm
1	9:05	131
2	9:03	138
3	8:57	141
4	9:02	139

I had already run a mile warmup, but even so it still took the first lap for my heart rate to stabilise. From the results I think you can see that I have no drift! The higher figure of 141bpm could even simply be the slightly faster pace of that lap. Of course this test was only 6 miles of effort. My next one will be 5 laps of 1.5 miles. Provided I can run that at my fully fit 8:30/mile and 139bpm, then I will be ready to move my training paces and HRs up slightly. I'll try just a few % initially and see how it goes.

Remember: "Protect what you've got before reaching out for more" as they seem to say a lot round here!

Finally, the usual caveats apply: I think I have all the facts right, but if I've got anything wrong, please tell me!

Happy base training!