Mountain Bike Specific Training: Part 1 – Chronic Intensity Load

I’ve been using this off season to think about training smarter. With my coach Dave Schell, I’ve been working on optimising the tools we’re using to measure my training. Most of the online tools we’re currently using have been developed with road cyclists and triathletes in mind. The problem is this: the tools are skewed by using aerobic and continuous exercises as their datasets. Mountain Biking is a discontinuous mix of anaerobic effort and recovery. The models have been developed around making training optimal for events like a 40 km time trial on the road. This doesn’t work for mountain biking.

Mountain Biking (and cyclocross, and crit racing for that matter…) is different. Duration is not the key to success. The appropriate volume of the correct intensity is the key to success.
But TrainingPeaks (and by proxy most coaches) use a metric called the Chronic Training Load to measure how much training an athlete has done, and how fit they have become as a result. Chronic Training Load is basically a weighted 42 day average of your training. It’s problem is that it weights the duration of exercise very heavily when figuring out how hard a ride is. That’s not appropriate for Mountain Bikers. Instead of using the Training Stress Score to build a model of Chronic Load, we are using the Intensity Factor that is built into TrainingPeaks.

Standard Chronic Training Load:

CTL= [Todays TSS * (1-e^(-1/42)] + [Yesterdays CTL * (e^(-1/42)]

We replaced the TSS score (the main weight of duration) with Intensity Factor:

Chronic Intensity Factor: 
CIL = [(100 * Todays IF) * (1-e^(-1/42)] + [Yesterdays CIL * (e^(-1/42)]


TSS = [(s x NP x IF) / (FTP x 3,600)] x 100

s = Time in seconds

NP = Normalized Power

FTP = Functional Threshold Power



This is a quick screen capture from the performance management chart in WKO4. The traditional CTL measure is displayed with light blue bars. As is normal, CTL builds from the beginning of the year as your accumulated training load builds through the base miles.
CIL is described by the dark blue line. It also builds through the early season as intense training accumulates.
What is really noticeable is when CTL and CIL deviate. Starting in late May (my peak race season), CTL suggests that my training load is decreasing as my duration decreases in response to more racing. CIL continues to increase and remains high through July, which more accurately reflects the intensity of the training and racing.
For the MTB racer and potentially crit rider, using CIL in conjunction with CTL would be very valuable. In the early season, it is very useful to ensure that the base miles a rider is completing contains enough quality – if CTL increases much faster than CIL that might be a problem. During race season, the steady decline of CTL can be a worry for coach and athlete – is fitness really decreasing? Using CIL here would show that the quality is either remaining or increasing even as CTL decreases.