I have heard several Pros on TR specifically Amber and Alex refer to KJs when describing the effort of work during a training ride or race.
My question is: Should I track my KJs on my head unit display? If yes, what does this info tell me and what should I do with it during the ride?
I am adjusting my data screens as to what info I want to see and I have always ignored KJs. I´am just trying to narrow down what I need during a ride or race. Garmin Strava and TR all provide total KJs in their post workout analysis.
I normally use Garmins Auto drink and eat to remind me to fuel during outdoor workouts and races.
On my 530 I have kJ on a summary stats page. Mostly for quick reference if I miss the eating reminder.
The eating reminders show half the kJ worked, so if the reminder says 400 calories, I can scroll to my stats page and see 800kJ. The reminder isn’t always exactly at twice, so maybe it shows 812kJ.
Here is an example from early in an easy endurance workout:
Personally I don’t find it worthwhile to look at very often, so it is on my summary page along with power metrics (avg, NP, TSS and IF).
If you start looking at completed workouts you’ll see a pattern. For example
an hour of .65 IF endurance is about 630 kJ, or in terms of on bike calories I’m going to consume 300 calories (my target is to eat 40-60% of calories burned).
So for a 2 hour .65 IF endurance ride, it will burn about 1260kJ which means packing 600 calories. And here is an endurance ride the following week:
showing that for around .65 IF (its a little higher) and ~260W ftp, the calorie burn is about twice the similar 1 hour endurance ride from the week before.
Somewhat related, Alan Couzens recently posted a thread on Work Capacity and Work Rate focusing around the use of the KJ metric and what you should be using it for - he does raise some good points I think:
Whether you should be looking at it on a ride is a different question but one reason you might have it available to review during a ride could be for allow you to see when you have burned a certain number of KJs before starting some specific intervals or work. Snippers from this article came to mind!
The ability to be dynamic under fatigue was also important. I didn’t do a good job of quantifying this one, but one sentiment was clear – many of our athletes had the peak power values to be competitive in the top 10, but they lacked the fatigue resistance to access power over threshold past 2500 kJ. This was a key area to work, top-end power, but after 2500 kJ of work.
along the lines of those articles you provided, there are some good charts in WKO that show changes in power curve after 500kJ / 1000kJ / 1500kJ / etc.
But sometimes I have less structured rides, and then I’ll pay more attention to kJ and TSS to decide which route (and intensity) to take back home.
I actually track kJ on my primary screen because its a trigger for me to consume more calories. I do pretty well with fueling in most situations, but in races its easy to fall behind, particularly during the hectic moments. Looking down and seeing I’m 1,500kJ into the day is a really good reminder for me to grab something when I have the mental and physical bandwidth to handle it
Like others, I just have KJ’s on a second summary screen that has other things like TSS, time of day, temp, NP, etc. and I mainly just have it to look at on long rides so I can say “oh wow I burned a lot of calories!” But it doesn’t change anything about my ride in the moment.
