VO2Max Intervals on the Bike

I've had a power meter on my bike for nearly 2 years now and I absolutely love it. It has made a huge difference to pacing, both in training and racing. When training sessions refer to Sprint, Olympic, 70.3 or Ironman efforts, I know exactly the wattage I need to maintain. With fresh legs it is very easy to go out too hard and blow up, but now I know the wattage I can hold in different situations (ie. hill climb or time trial). I often still try and push beyond my limits, but only by a sensible margin so the blow ups are usually only small.

However up til now I've ignored the more scientific training sessions achievable with a power meter. That situation changed today with my VO2Max intervals up a nearby hill on Two Bays Rd in Mt Eliza. In simplistic terms, VO2Max is a measure of how much oxygen your body can process - V = volume, 02 = oxygen, Max = maximum. The ability to process oxygen is probably the most important factor in becoming a good endurance athlete.

Although I refer to it as scientific, this session was actually quite simple. First you need to know your Functional Threshold Power, usually referred to as your FTP - which represents the highest power wattage you can hold for 1 hour (I'll let you use Google to learn more). From your FTP you can calculate your VO2Max training range which is 106-120% of your FTP. I estimate my FTP to be 300 watts, so my VO2Max range is between 318 and 360 watts. The length of each interval needs to be between 5 and 8 minutes. Less than 5 minutes is not long enough to receive the benefit and most people will not be able to hold VO2Max wattage for over 8 minutes.

Now the session itself. You need to find a hill climb that will take somewhere between 5 and 8 minutes and ride up this hill (multiple times) keeping your wattage in the VO2Max range. You will be relatively fresh for the first 2 attempts, so you need to take note of the average wattage for the 3rd attempt. Subtract 5% from this wattage number and that is the power you need to average above for every subsequent interval. As soon as you fail to average this power for a climb hill - your session is over.

The Two Bays Rd climb in Mt Eliza seemed like a good hill for this session. It is about 2km long with an average gradient of 4.7%, but the middle 1km is probably around 6%. I decided to start the first interval from the second speed hump as this is where the gradient starts to pick up. Unfortunately even though I pushed through to the round-a-bout, the lap ended up only being 4m37s long. I started the subsequent laps earlier and my second climb took exactly 5 minutes - perfect.

My first 3 intervals had average power of 348, 348 & 333 watts. So 5% deducted from 333 leaves 316 which is the wattage I needed to keep above for all subsequent climbs. The fourth lap was 332 watts, but on my fifth climb I really struggled and could only maintain 313 watts, so no more climbs. I was exhausted and glad that the ride home was not very long and mostly downhill.