Wednesday, October 22, 2014

Lies, damned lies and statistics – Lactate Threshold and VO2Max

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Determined that on the back of a mixed experience in Auckland, I was going to put in a really solid few months of winter training, I decided about a month ago that I was going to have my lactate threshold (LT) tested for both the bike and run.  And since it was easy to do the VO2 Max testing at the same time, I might as well get that done too.

The idea was to find my ideal heart rate zones for winter training, so that I could build a stronger aerobic base ahead of ramping up training for my first ‘A’ race of 2013, the Mallorca 70.3 in May.  With lactate build up the enemy of the endurance athlete (at least, in most cases), it made sense to me to work on ways to delay the onset of fatigue due to lactate build up, thus running or cycling faster before running out of steam.

After doing some research, I decided to get the tests done at Bath University’s sprawling sports complex (as someone who didn’t touch the gym throughout my whole time at University, I was somewhat in awe of the facilities they have at their disposal in Bath!).  Because I wanted to do separate tests for the run and cycle, it was decided I would do the treadmill one day and then the cycle the next.

Jonathan Robinson at Bath was to be my tester and he explained the process.  For the run tests, I would first have a small blood sample taken ‘at rest’, the I would run on the treadmill for bouts of three minutes, then have my blood taken again before jumping on for another three minutes at 1km/h faster than before. All the time I would be wearing the ‘gas mask’ which would be monitoring the amount of air drawn in with each breath and how much was expelled.  The blood tests would reveal the lactate build up as the intensity of the exercise increased, while the oxygen consumption would be used to calculate my VO2 Max.

The test would be concluded when I physically could not continue – so it was down to me to ‘man up’ and get my game face on.

The Run

Starting at a sedate 8km/h, my heart rate was nice and low and the first few stages went by uneventfully.  As well as monitoring my ‘vital signs’, I was also asked to state my perceived exertion towards the end of each interval.

To cut a long story short, I eventually maxed out at 17km/h (we got about 30 seconds into the 18km/h run before I gave up, so the last recording at 17km/h was used), with a heart rate of 187. Later analysis showed that my lactate build up had been very slow up until about 15km/h, at which point the accumulation increased significantly.  My final value at 17km/h was 5.44.  For the record, my VO2 Max was calculated at 58.3 (3.953L/min).

More important than the absolute figures is the line that is made by plotting them on a graph.  From this, Jonathan and his team could tell me that my run lactate threshold (i.e. the heart rate at which my body starts to increase its production of lactate) was 150bpm.  The second value provided was my ‘Individual Anaerobic Threshold’(IAT) – this is the point at which the body starts to really struggle to process the lactate (i.e the point at which things start going to pot!).  My value for this was 175, which is actually relatively high compared to my overall max HR of 187 (the bad news, was that this occurred at a speed of just 14.5km/h!).

So this tells me two things (or at least, it does when translated by Jonathan!): My LT is actually reasonably low and so I need to do more low HR run work to improve my running economy and drive my LT upwards.  The second is that my body actually copes with higher training heart rates quite well and my endurance isn’t bad.  The sharpness of the increase in lactate after my IAT is so sharp however, that it’s a little like an on/off switch. I can run reasonably comfortably at 170bpm, but push me much beyond 175bpm and I’m living on borrowed time!  So as well as putting more hours in at low HRs to increase my LT, I also need to work in the upper ranges as well to improve my IAT – this is going to be essential for me to meet my target run times for 5k, 10k and half-marathons.

After the test, I was a bit peeved I hadn’t gone faster. I’m pretty sure I was shot at the point I gave up, but five minutes later I felt ready to go again. Typical!

The Bike

The next day I returned to the lab for the bike test, conducted on an ergo trainer fitted with SRM power cranks.  The routine this time would be to start pedaling at a constant (normal) cadence – around 90-92 for me at a low power setting to start with – then it would increase by 25 watts every four or five minutes (I forget which!).  Again, we took a blood sample ‘at rest’ and then in the last 30 seconds of each interval. Unlike the treadmill, there was no rest while the blood was taken – you just keep pedaling while holding your hand out!

Again, the early stages of the test were fine and my perceived effort was low. Once the power got to 250 watts (20-25 minutes in), it was getting tougher and my heart rate had risen to 157bpm and climbing.  I eventually maxed out at a disappointing 300 watts and a heart rate of 180.   It’s a horrible feeling when your cadence is on a downwards spiral and there’s nothing you can do about it!  I managed to finish the 300 watt interval but as the power went up to 325 my legs just slowly ground to a halt.

For what it’s worth, my VO2 Max for the bike was calculated at 55.2, just a few points lower than my run score. My power to weight ratio came out at 4.42w/kg. Hardly the scores of a pro cyclist…  Interestingly, I was able to produce more lactate on the bike than I had on the run.

Again, the interpretation of the results was that I need to work on raising my lactate threshold, which was calculated to be around 147bpm (200 watts) with some time also spent on the IAT.

Using the statistics

A few days after the tests and Jonathan sent me a comprehensive report explaining the test results, providing my new heart rate training ranges and providing some advice on where to focus my winter training (this last part was by no means exhaustive or prescriptive, I’ve still had to do a fair bit of work to apply the suggestions to my individual training program).

Let’s deal first with the VO2 Max figures.  For what little I can tell (feel free to enlighten me if you have a different opinion!), the VO2 Max information is near-useless to an amateur athlete like me – it’s simply a figure you can pull out of your pocket the next time you want to get into a pissing contest with your mates (or not, if like me, you’re actually a little embarrassed by your ‘poor’ results – compared with the ‘normal’ male of 36-45 years old, my scores are beyond ‘excellent’ but in athletic terms they are very modest).  In short, I wouldn’t have paid for this test – it was just an interesting add-on to the main show, the lactate threshold.

And on this front I do now at least have a set of heart rate training ranges that I understand – and by that I mean they’re no longer just numbers to me, but are targets/limits that make sense for what I’m trying to achieve.

So when I’m working on lactate threshold, I now know that running at 145-150bpm is the right thing to do, rather than focusing on bashing out 5-minute kilometers for example.  But I also know that for at least two runs a week I want to get my HR up into the mid-160s to help improve my IAT – so winter is definitely NOT just going to be long slow runs for me!

On the bike, I now know that an ‘easy’ long ride really must not see my HR go much above 147bpm, unless I’m focusing on some harder intervals, in which case I want to be in the 155-163bpm range.

I think what’s been as useful as the new zones described above is a better understanding of how I need to actually train in ALL the ranges, but at different times and for different reasons.

My plan is to apply these zones as best I can (without getting hung up on them - another thing I am learning is how to train by 'feel') over winter and then probably go back to Bath in March for re-testing. Hopefully both my LT and IAT will have improved – and who knows, maybe my VO2 Max too (although less likely) – and then I will have another new set of heart rate zones to work on in the buildup to race season.

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Matt Fisher runs TriathletesDiary.com - so it's all his fault! He pretends to be a triathlete, but really he is a husband, father and company VP. But he has raced for the GB Age Group squad a few times and is a 2014 qualifier for the IM70.3 world champs

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