Computrainer Lactate Test protocol + comment.

I tested one of my athletes today for lactate threshold wattage and HR on the bike. This is a simple outline to help people do their own test at home on themselves.
I have been tested myself about 10 times on the bike using blood analysis and doing this diagnostic protocol is superior.. and it's also expensive. I found that by learning the protocol, and even tweaking it a little bit, I could perform the same test by myself and get results that would be good enough to show if my LT was improving or not. Testing twice per year at a lab or finding someone with the fancy portable analyzer, like Chuck , to help find a true baseline is a good idea. In the winter time I would incorporate this test in to my long warm-ups for workouts. Here is the protocol that I have found to be the most effective for me, and it is a Conconi step test.
I would recommend not eating within two hours of doing this and it is imperative that you start this well hydrated! Dehydration will skew this test more than anything. The Computrainer should be in "stand alone mode" and in your BIG RING with ~15-16t in the back.. through out the test you should try to hold a normal race cadence.
Warm-up well. Today- Mike warmed up for 25:00 with several "intervals" in the last 5:00 to elevate HR. If you need more time then take it.
You should start the test at a wattage that puts your HR in the low Zone 2 range. This is where experience and past data will allow this test to be more effective. The more you do it the better you will get at it. For Mike we start at ~150 watts and his HR will be ~130. The goal is to be able to plot ~10-15 data points in the graph that you will use to find your LT (see pic below)..
Then: You need to increase wattage at set intervals until you are unable to pedal at your normal cadence (and I have actually found that once you get experienced at this and can actually feel your lactate threshold.. you can stop far sooner once you start to see HR deflection). I have also found that using only an increase in 5 watts every 1 minute works better for graphing. In a lab they will often use an interval of 4:00 which I have always found to be too broad of a time frame for HR reaction. A lot can happen in just 4:00 yet the graph won't show it..
Through out this test you need to glance at a Borg Scale of Perceived Exertion:
* 7 Very, very light
* 8
* 9 Very light
* 10
* 11 Fairly light
* 12
* 13 Somewhat hard
* 14
* 15 Hard
* 16
* 17 Very hard
* 18
* 19 Very, very hard
* 20

and note the wattage at which you reach a PE 17-18.. or about the same exertion as a one hour time trial in a race (Olympic distance for elites or a Sprint distance for many).
There is one more data point that you need to watch for in this test and it's called the ventilatory threshold or VT. This will be a shift in your breathing from deep and relaxed to labored, or the point at which you will have a difficult time forming a sentence. Note the wattage at this moment (and it really will come on suddenly- over the course of a minute your breathing will shift drastically).
The test can be terminated within 15 watts of reaching VT or once you start to lose pedal efficiency.. There is no need to go to failure or to even go that anaerobic. Remember- this is a BASIC and repeatable test that will not pin point your LT but will allow you to closely predict it.
Cool-down or begin your workout.
Now- after you have finished.. you should be able to plot a graph using your wattage on the x axis and the HR in the Y axis.. below is a picture of one of Mike's tests from December (starting his base training) of 2006. As you can see in the graph the point at which he hits VT is at a HR 155. He went to near failure at the very end of the page at 230 watts. Mike had also indicated a PE of 17 at the 205 watt mark. Looking at the graph you will also see the point at which his HR "deflects" or stops rising significantly. All of these points add up to an estimation of an LT HR at ~156 and a wattage of ~205.

We later confirmed these results with lab tests that verified that we were close enough to train at HR zones specific to Mike's fitness.
There you have it. I just typed this all off the top of head and I am sure I left something out.

Comment: Ironboom asks: Thanks for the write up. That is great and very timely for my own training. Once you have determined your HR and watts at LT, how do you figure out your training zones based on HR and zones based on watts? And finally, if you don't mind answering, which zone do you recommend or did you race in for Ironman?

Ironboom- Once you have established threshold watts you can use this chart expressed in percentage of threshold power:
Zone 1 <55%>
Zone 3 76-90% At the low end: Ironman race effort for some. 1/2 Ironman race effort.
Zone 4 91-105% Lactate threshold or Tempo.
Zone 5 106-120% of FTP (VO2max)

For HR Zones I would recommend using Friel's

One thing you may find happening is that your power zones do not line up with your HR zones. Ie: your Zone 2 wattage is putting you in to Zone 3 HR. This is to be expected because the two values are measuring different aspects of intensity. I recommend using one to determine effort- then watch the other and see where it tends to sit. If you only have a Computrainer- then I would recommend that during all of your workouts you pay close attention to your HR at various wattages and your PE. That way when you go outside with a power meter you will have a better understanding of the intensity you are riding at.
For my own values: Twice I rode 4:50 at Ironman Hawaii. Each time I averaged HR 161 and 158 and both times I ran 2:56 and 2:58. My LT HR both times was in the 173-176 range.. so this placed me firmly in Zone 3.
I placed 16th and 13th respectively (which has nothing to do with HR, just my ego ;)). No power data.