VO2 Max Intervals
In our last article we discussed performing threshold intervals. These are performed at the intensity you can sustain for 40-60 minutes. Typically these intervals are between 6-12 minutes in duration with a recovery that equals about 50% of the interval with a total of 40-60 minutes at threshold. These are our bread and butter sessions for courses with sustained climbing. For this week we tackle more intense, shorter interval sessions often to referred to as VO2max intervals, when to incorporate them, and how to properly execute a VO2max workout?
VO2max is defined as an individual’s highest rate of oxygen consumption (milliliters of oxygen per kilogram of body weight per minute). A common misconception is that interval training is strictly anaerobic. These types of intervals do have a big anaerobic component, but by definition have you operating near your peak oxygen consumption, which is the key. Most athletes can work at VO2max for only about 5 to 9 minutes, so intervals at VO2max need to be shorter than that. If the interval is too short, then the anaerobic contribution is big, but there is not enough time to actually get to VO2max. Personally I like 2-3 minutes ON with about equal recovery.
Pacing is critical. Suppose you are running those 800 meter bouts and you start out by sprinting the first 200 meters and then have a gradual slow-down for the next 600 meters. Your average pace might be on target, but you have failed to reach VO2max since you started with this huge anaerobic effort and then settled into a pace slower than your VO2max intensity.
There is something called a slow-component to VO2max. This means that for any pace above lactate threshold, you will eventually reach VO2max if the exercise is continued. So you do want to go fast, but to spend the most amount of time near VO2max, you want a pace you can sustain for 2-3 minutes. If performed correctly your oxygen consumption will approach VO2max about half-way through each hard effort. Remember, the magic happens during the second half of each bout. So if your workout is 6 x 2.5 minutes, you might in reality only spend a total of 7.5 minutes at 90-100% of VO2max, which is fine. If performed poorly you may only spend a few seconds of each interval at VO2max or none at all.
Poor pacing strategy with high power output at the start of each bout and power dropping on each bout. Also note the furthest distance achieved on the first effort based on the height of the elevation peak (grey).
Example: 7 x 3 minutes cycling at 110% FTP. Notice that power is maintained and heart rate ramps. Good pacing example with power output maintained.
Example: 10 x 2 minutes running uphill, with equal recovery (downhill jog). Make a line in the dirt and attempt to go slightly further for each effort. (elevation in white, heart rate in yellow)
An ideal range for work portion is about 1.5 to 4 minutes. We like the 2-3 minute range the best with a few exceptions. Work to rest ratios are usually around 1:1. The rest interval can be adjusted to increase or decrease the intensity of the workout. If you are having a hard time keeping pace, try adding 30 seconds rest. If you are completing the workout with energy to spare, try 30 seconds less rest the next time out.
Pace or power are your best guides for this type of training. Heart rate lags so far behind that it is not the best indicator and you don’t want to try to spike your heart rate to start each effort.
If you have power on the bike, I like to use 110% FTP for 3 minute bouts, and 115% FTP for 2 minute bouts. To find Functional Threshold power on the bike go here (Cycling Zone Calculator).
For running, a 5k race pace or slightly faster will get you there. A 15 minute 5k runner can just use their 5k pace, but a 25 minute 5k runner might need to increase the pace slightly. If you use our spreadsheet, then use your pace for the top of zone 4, beginning of zone 5. (Running Zone Calculator)
If you are performing intervals uphill and don’t have power or pace to guide you, try this approach. Warm up to the base of consistent climb. On your first bout, hold back a fraction and note your distance at 1 minute and 2 minutes. Make a mark in the dirt where you finish. Recover on the downhill and repeat the same section of the hill attempting to at least reach the same finishing mark or go slightly further.
A new training tool for runners is the Stryd power meter for running. This allows you to get real-time feedback so you can pace your efforts, especially uphill.
Example: Running 5 x 1000 meters with power and pace. The loop started downhill and finished uphill. Power for running follows your exertion better than heart rate or pace especially on variable terrain.
The Stryd power meter is a wearable 10g shoe pod that communicates with a Suunto watch.
I mentioned earlier that this is the most potent form of training. So your goal is to be able to maintain the quality for the entire workout. For most people this means 15-21 minutes of total hard work. So that is 8-10 bouts of 2 minutes, or 5-7 bouts of 3 minutes. Keep it simple. Shoot for a very similar intensity every time and if you start to slow down you have done too much.
A little bit can go a long way. I try to space out this type of training more than any other. For most people that means two quality sessions per week with one on the bike and one on the run. Training becomes more polarized during a VO2max cycle with recovery and endurance workouts separating VO2max bouts. Total training volume is reduced and avoid excessively long workouts during this time.
Soon Ripe, Soon Rotten
With this type of training, most people will plateau in about 6 weeks, so it is not the foundation of a training program. I like to sprinkle in this type of training as key races are approaching and save heavy blocks of VO2max interval training for the most important races of the season. Early season, this might just mean 2-3 key workouts heading into an event. For “A” races you can experiment with a longer block consisting of 3 weeks of VO2max workouts (two sessions per week).