Heading to a lab to do a blood lactate test is unfeasible for 99.9% of athletes. Sure, going all-out, taking bloods and measuring oxygen uptake looks rad (and is what got me excited about exercise science in the first place), but it takes some careful consideration and years of training to draw out the important points in the results. These tests are hard, time-consuming and expensive; and at best, the results will only serve as a benchmark and guide for training, which then needs to be retested periodically.
Fortunately some smart people on Dr Andrew Coggan's team created Functional Threshold Power (FTP). They realized that pretty much nobody was going to get a lab LT test done, and so to make use of these fancy new training tools called power meters, they needed some way to make use of the numbers. To test FTP, you could head out and do a TT effort with your power meter, do some quick calcs, and estimate your lactate threshold. Now, for little cost and half the time, you could get similar results to in the lab - all on your own.
FTP is great. You can use it to track improvements in your estimated threshold, and even set training zones.
If you've ever done an FTP test, you'll know how it goes: you do a solid warmup, and then on the trainer or a steady climb, you go at a hard, even pace at a maximal effort for 8 or 20 minutes. Take your average power and multiply it by 0.9 or 0.95 and you have your FTP. This is now your benchmark fitness and can be used to set training zones. If you improve your FTP, you would expect your MTB performance to improve, right?
BUT FOT MTB? WTF?!
As a young scientist in 2012, FTP threw up some serious red flags for me as a mountain biker. I had been using my MTB power meter for a few years, and noticed how HARD MTB was, and how often we needed to go way above FTP in any kind of race. It just didn't make sense that FTP would be important for any of the riding I was doing.
Here is a screen clipping out of TrainingPeaks showing power from a MTB XC race. The line across the middle is FTP. You can see how many times this rider went ABOVE FTP during the race. It was NOT steady like the FTP test.
My exact thought was:
HOW CAN A STEADY TEST BE IMPOTANT FOR MTBers?!?!
Well, I wondered. Then wondered some more.
Then I decided to do something about it.
With the support of Saris Cycling and the PowerTap, I traveled around the mid-atlantic region in the USA testing just this idea for MTB. First, we created the IP test for MTB racers. This was your standard warmup for the FTP test, followed by 45s max and 15s recovery for 20 minutes. We took the average of just the work intervals, and worked out the rider's IP W/kg (watts per kilograms, to make it relative to body weight). We alternated this test with your standard FTP test (20 min mean maximal power * 95%) the next week so that each rider did each test once. A week later, we joined all the riders together to do an XC race.
For this study, we hypothesized that IP would be a better predictor of Race Time than FTP since, well, the IP test was much more like MTB than the steady FTP test.
We even made custom numbers for everyone!
In the end, we got this study published in the Journal of Science and Cycling. It was my first ever publication and I was so pumped! We also presented the findings at the ACSM Annual Meeting and the MARC ACSM.
You can read the full article for free here.
We ran some relatively simple statistics since all we really wanted to know was whether FTP was important for MTB.
It was no surprise than IP was higher than FTP, because we didn't include the rest periods.
We did a correlation (linear regression model) to see if IP or FTP were better for MTB. The stats say that IP had a better relationship with race time, and that we could predict race time with greater certainty when using IP
So there it is - IP is better! But does this mean that FTP is not good for MTB?
If you look deeper into the results, we see that IP is really only slightly better than FTP for predicting how fast you will go in XC. Yes, it is a bit better, but unfortunately for this study, that did not mean that IP was guaranteed to become the new FTP.
The first argument for FTP, is that it can double up as a great way to calculate your training zones. This has been done time and time again. Take set percentages of FTP, and you get various training zones to make sure you are training the right energy system.
You can simply enter your FTP in to your TrainingPeaks profile, and zones are automatically calculated. I usually use Coggan zones. So unfortunately with IP, there is no valid way to set training zones.
We use these energy system training zones in all our training plans, including this popular FREE MTB training plan
Check out our podcast: Performance Advantage Podcast 51 | Training Zones: Science Simplicity & Effectiveness
Overall though, the most important point to note is that FTP and IP are very strongly related to each other(r^2=0.929).
This means that riders who had a high IP also had a high FTP!
But how can this be?!
Be sure to check out our MTB Power Meter Masterclass to simplify using your power meter
Here's a podcast episode I did on FTP for MTB as well
THE SCIENCE OF GOING HARD [OVER AND OVER AGAIN]
The fact that riders with a high FTP could also go harder across many short efforts was an idea that really stumped me as a young scientist. So I dug deeper.
As we know, FTP represents the highest rate of aerobic metabolism. But for MTB? Well, beyond that, there is a mass of previous work showing that the ability to do intermittent work is highly reliant on aerobic ability. See below for a small snippet from the paper along with references:
For MTB, we need to be able to go pretty hard over and over and over. I say pretty hard, because actually the power output during any type of MTB is usually not really that high - definitely a lot higher than FTP, but only for short times and separated by long breaks. You might throw down huge watts on a descent in and enduro or DH race, but really the best riders aren't going all-out that many times when downhilling (it is a waste of energy - read more here). Sure, you'll pedal hard on climbs, but this gets down closer to FTP the longer it is, even when racing.
Here's that race snippet again:
Athletes like Usain Bolt have to sprint one time.
For those sprinters, it is all-out and all-or-nothing. But f