Zone 4, 5, & 6 Intervals

In this training tip, I am going to describe the three best zone 4, 5, & 6 intervals you can add to your training to increase your power output. There are watts to be gained from interval training especially if you've developed a good aerobic base from sweet spot training. I say 'best' as in simple, easy to follow, execute and and most importantly, effective. The Three Best Zone 4, 5, & 6 Intervals are:
  • Zone 4: 3 x 8 minutes ON 4 minutes off.
  • Zone 5: 2 sets of 2 x 3 min On 3 min OFF
  • Zone 6: 2 sets of 3 x 1 min On 1 min Off

In a seven training zones model Zones 4, 5, & 6 are to be conducted at an intensity that is as hard as the athlete can 'go' or as we like to say, 'full gas'. These are the fancy intervals where the power analysis is fun and improvement may be seen from average power output higher than the prescribed zones.


Zone 4 Threshold:

Zone 4 intervals are useful for climbing, time trials, mountain biking, gravel and fondo disciplines. Even multisport. Any event where you are required to ride steady hard for greater than 6-7 minutes and less than 60 minutes demands threshold power output. With those varying lengths, threshold intervals may be of any duration between 8 and 60 minutes. Although one 60 minute threshold interval is extremely difficult and instead we'll prescribed threshold intervals 3 x 20 minutes, 4 x 15 minutes, 2 x 30 minutes and even 6 x 10 minutes. All of these variations add up to one hour of threshold training.

I like to start athletes off with 2 eight minute threshold intervals (2 x 8 minutes for 16 minutes total threshold work) and then progress them up to 3 x 8 minutes (24 minutes total). Then really teach & coach them from their power data and sensations to go as hard as they can, "supra" threshold 103 - 110% of their FTP. Being able to do 24 minutes of threshold wattages greater than your FTP is nice arrow in your quiver for Strava KOMs as well as race day. Here is an example 3 x 8 minute threshold interval with a 2:1 work to rest ratio:

If climbs are available to the athlete, I do recommend performing their threshold intervals uphill, especially if the athlete is training for an event with climbing. However, threshold intervals can be successfully executed just as well on flat terrain and on the trainer with virtually the same physiological adaptations as long as the athlete hits their wattage targets. You can read more about time trial and climbing threshold intervals here & here.

Zone 5 VO2 Max:

When I took organic chemistry in college, I'll never forget the professors saying, "organic chemistry is what separates the men from the boys". Same goes for VO2 Max Intervals : these are some of the most difficult intervals there are YET they yield the greatest increase in power output. I like to progress athletes thru what I call the "3 > 4 > 5 minute VO2 progression" but the best VO2 Max interval workout to start with is four 3 minute VO2 intervals broken up into 2 sets of 2 x 3 minutes on 3 minutes off with a 6 minute set break:

This is 12 total minutes of VO2 work at a max effort, full gas, as hard as you can go. Using your powermeter a max effort with an accurately set FTP zone 5 VO2's are between 106-120% of their FTP. The power data about illustrates and well paced 3 minute VO2 max workout where the athlete pushes hard and really digs deep to hang onto to the zone 5 wattage in the 2nd half of the fourth and final interval.

Zone 6 Anaerobic Capacity:

1 minuters as we like to call them. The term anaerobic capacity comes from the athlete's ability to do or handle 10-20 or even 30 minute worth of anaerobic wattages in disciplines like criterium or cyclocross races. This anaerobic workout has 6 minutes worth of anaerobic capacity Zone 6: 2 sets of 3 x 1 min On 1 min Off > 120% of FTP

I have athletes conduct their Zone 6 workouts as hard and as at much wattage as they can make. Often times that may be greater than 125-150% of the FTP. The fun part of the analysis is to add up the average power of each interval, divide by the number of intervals to arrive at an Av 1 minute interval power number. For the power data above, the athlete smashed each interval and averaged 430 watts across all six 1 minute intervals. Having 430 watts as a carrot and a number to beat for future 1 minute intervals workouts helps with motivation too.

Summary and more Reading:

We talk a lot about intervals because they are so beneficial; here are 4 of our best interval training tips:


The Right Way To Perform VO2 Max Intervals with Your PowerMeter

Tabata's (advanced)

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About Frank Overton

Frank founded FasCat Coaching in 2002 and has been a full time cycling coach since 2004. His educational background includes a Masters degree in Physiology from North Carolina State University, pre-med from Hampden-Sydney College. Frank raced at a professional level on the road and mountain bike and currently competes as a "masters" level gravel and cyclocrosser. Professionally Frank comes from medical school spinal cord research and molecular biotechnology. However, to this day it is a dream come true for Frank to be able to help cyclists as a coach.

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