What is VI (cycling) and why does it matter?

What is VI?  Variability Index is a key workout metric for those who ride with power.  A simple formula, VI is calculated by dividing your normalized power by average power.

Normalized Power vs. Average Power? Average power is a reflection of what you actually did during a ride, including coasting. Normalized Power approximates what you could have done with that same level of effort had you ridden at a perfectly steady pace, taking out the coasting.  Personally, I like NP to track performance across different disciplines and terrain.

You can see my VI from Saturday's ride.  1.10 is NOT steady riding.  It's surging, me hanging with a group that came by me about 10 miles in and holding on for dear life, burning matches.  A VI of 1.10 left me shattered!.  The intensity was only 75%, between Ironman and 70.3, but how I got, there is what did the damage.   Too many peaks vs a steady 75%.  Reviewing a power file you have to consider the VI or you are not looking at the entire story.   

From Training Peaks Blog 
How those watts are put out is also a key factor. An IRONMAN® is all about being steady and keeping the effort relatively moderate. Big spikes in power cause a much faster burn rate of glycogen, creating fatigue faster. It is better to keep your power as steady as possible. Using the Variability Index (VI), we can see how smooth or erratic the power output was. For every rider, pro or age grouper, a VI of 1.05 or lower is the goal. While it’s harder to do on a hilly course, it is still necessary to keep the effort steady. The bike course in Kona has around 3,000 ft. of elevation gain, so it’s not flat by any means. Still, every file from the pro athletes does have a VI of 1.05 or lower.   

Looking at my Kona 2022, I rode 1.05, IM StG 1.06 (much hillier), and Oceanside 1.03.  

The last 2 weekends, my VI was high, and neither Saturday did I have a quality run OTB. It would have been a struggle.   It's a good reminder and something to practice.  

This is 1.03 - steady pink lines

This is 1.10 looks more like a heart attack.  You can see the power spikes, and the high variability. 

Take a risk, pay the price!

This is the 6th time I have done the Palm Springs Brick Weekend! 

Tour de PS on Saturday 102 miles

Palm Desert 1/2 Marathon on Sunday   

I have done it in a lot of different ways. Total fun both days, no pressure, easy ride Sat and throw down the run Sunday, controlled ride Sat and see how the legs are Sunday, this weekend I had 0 plan; after a tough set of workouts Thursday, Coach said to have fun, no pressure,

Rolled out Saturday with 0 expectations, but the legs felt good; watts were coming easy, and it was teeing up to be a spectacular day. Rather controlled riding for 31 miles with some good climbing. I found a group, and it was too slow drafting. Hence, I went off the front and was able to get aero and have some fun, it was a solid 10 miles, and then I realized I had a large train behind me with no one willing to share the work; I decided to push it a bit and see who could stay on, the group broke up but so did I,  Blew up! By mile 60, I was in the hurt locker, legs fried with 40 miles to go. I found a new group and sat in for a long time, trying to recover downing calories and fluids.   I took a few turns, but the pace was getting too hard; I could barely hang on and would drift off and ride alone, suffering just as much but going much slower; by 75, I was having a pity party and watching my watts drop below my HR. I found more caffeine and a few people to limp along to the finish.  

If you look at the numbers, it shows 73% perfect, but check out the VI at 1.09, which shows the many, many matches I burned. Don't get me wrong, it was a ton of fun!   I have not buried myself like that in a while; at one point, I thought can I crack 5 hours? But that blew up when I died! It's good to be reminded how over-biking and power surges can royally fuck you. 

Hello Half Marathon, I had 0 expectations, and after about 2 miles, I decided to run by HR only. Keep my HR 150-155; the pace will be what it will be, which was about 20 sec/mile slower than I wanted. But I was only looking at HR, so I kept it in the right place. At mile 12, I could see Meg Ling, my athlete coming fast for me; I let her know she had 1 mile to pass me but then decided I would not make it easy. I threw down a decent mile, HR hit 173, and he beat me by 10 seconds! Happy to have an athlete outrun.  

Man on man, I am smoked! My head is all over the place. On the one hand, I am feeling good about bike fitness, and in the same thought, I am worried that Oceanside is in 6 weeks and my run fitness is far from where I want it. The usual up and down...but  I have Marilyn figure this out!

The weekend was so fun! House was full of athletes, John came along, and we had a great ti

me.   I love this about my job, this sport, and living a curated life!