Thursday, March 7, 2013

Hill climb repeats

Such a cold day yesterday here in GA. Very windy, grey and cold air made it a perfect day to hide between Kennesaw Mountain trees and go for some hill repeats. That climb is awesome. The gradient is steady which makes it perfect for steady uphill intervals. It is 2,3km long, 165m total elevation and takes anywhere between 7min to 8min30sec depending on your intensity and if you're going for the odd strava KOM.

I headed there doing a nice little 35min warm up including a low/moderate intensity climb, went back to the base of the climb and started my planned workout. On schedule was 5 x 8min at 105% of FTP with rest time being the time it took to descend the mountain, which is about 3min30sec. Very nice and challenging workout. Managed all intervals almost at 110% of FTP which is pretty good and tells me im in pretty good shape at the moment, unless all the food and booze made me pack an extra 5kg since we arrived here. Hills repeat is pretty MTB specific on a muscle contraction and recruitment perspective. It generally makes you work in quadrant II and forces you to maintain good steady power. The descend was so cold I couldnt ride much longer and had to head back home after my repeats. My time up the climb was about 7min35sec which is decent since I was on a MTB with tires at 25psi. The strava KOM is set at 6min35sec if I recall correctly, which would make it do-able on a road bike at full gas effort taking the right lines up the climb. But im not too much into strava.

This workout is the perfect counter exemple of my last post on The Benefits Of Long Rides. It lacked a bit of intensity to be called a proper high intensity workout but lets consider it that way for the sake of the post. Remember the long rides physiological effect on mitochondria density and size? It was produced via complexe molecular reactions that could be summurized that way: 

Repeated low energy muscle contractions > Icreased intramuscular calcium concentrations > activation of CaMK > activation of the Master-Switch > mitochondria biogenesis = mitochondria adaptations.

Now high intensity workouts also have an important impact on mitochondria adaptations. Though they are stimulated by a different mecanism in the body that involves different molecular components compared with the ''long ride'' chain reaction, they result in the same Master-Switch stimulation.

High intensity training, what, or where is it?

Typically high intensity training is define as being above the second ventilatory threshold, usually above 4mmol blood lactate concentration or when the body can't manage the lactate accumulation. For FTP users out there, I would say from 110% above is a safe bet. Training at high intensities is generally done using work and rest intervals of different durations in order to accumulate a total amount of training stress at a target intensity. There are plenty of possible combinations ranging from micro-intervals to longer work intervals alternated with equivalent or shorter rest intervals. Generally, work and rest intervals durations will be dependent on the quality you want to train. That could actually make the subject of an entire post and even a phd thesis...

How it happens?

As opposed to long distance riding, high intensity efforts involve high energy muscle contractions. These contractions require a lot of adenosine tri-phosphate (ATP) which is simply the high energy molecule derived from nutrients. ATP is the body's energy for all physiological process and high energy muscle contractions require a lot of ATP. This requirement partialy depletes ATP stores which leads to an increase in the concentration of adenosine mono-phosphate (ATP with 2 phosphates removed). Increased AMP activates an enzyme called activated protein kinase (AMPK). AMPK is the signalor for the Master-Switch PGC-1alpha that eventually stimulates mitochondria biogenesis.

So what now?

High intensity training has its place in a training program. Obviously such a type of training has to be monitored carefully with appropriate volume and recovery. It also has a lot of other benefits and one I would like to discuss in a furter blog post is the muscle fibers recruitment and its impact on subsequent adaptations when using such a high intensity training approach.


  1. Hi Vincent,

    Very interesting blog, and comments on training particularly those about using shorter, more intense intervals for "winter training". Will be reading to see how it works out over the winter months, and coming into spring :-)


  2. Hi Aaron

    thanks for you comment.

    I have some experience with high intensity winter training, as it is what I have done last year. I am heading into my winter training soon and will update my blog to let my readers know how it goes. Feel free to contact me or comment anytime you need.