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Long Intervals 4×4 min vs 4×8 min vs 4×16 min


What long intervals are the best to improve your Threshold Power and VO2 Max?

Today I want to research what intervals are the best for you.

What is your guess?

  • 4×4 min
  • 4×8 min
  • 4×16 min

Testing Group and Training Protocol


35 cyclists (29 male and 6 female) with VO2 Max 52 ± 6 mL kg/min were separated into 4 groups. Training protocol was applied for 7 weeks. Intervals were prescribed at the maximal tolerate intensity.

The first group was doing only low-intensity training (8 cyclists), 4-6 sessions at low-intensity/week.

The second group (9 cyclists) was doing 2 sessions/week with 4×4 min intervals at intensity 94 ± 2 HR peak (2 min recovery between intervals) plus 2-3 low-intensity sessions/week.

The third group (9 cyclists) was doing 2 sessions/week with 4×8 min intervals at intensity 90 ± 2 HR peak (2 min recovery between intervals) plus 2-3 low-intensity sessions/week.

The fourth group (9 cyclists) was doing 2 sessions/week with 4×16 min intervals at intensity 88 ± 2 HR peak (3 min recovery between intervals) plus 2-3 low-intensity sessions/week.



Threshold improvement was highest after 4×8 min intervals, 16.2%! 9.2% after 4×16 min intervals, 8.2% after 4×4 intervals, and even 7.7% after low-intensity training.

VO2 Max Power increased by 8.5% after 4×8 min intervals, 5.2% after 4×4 min intervals, 3.0% and 2.6% after 4×16 min intervals and low-intensity training



The goal was to compare the physiological impact of intervals at the threshold and VO2 Max intensity on recreationally trained cyclists. We could see the best results for 4×8 min intervals in increasing threshold power as well as VO2 Max power. We need to take into consideration that a test group of cyclists was recreational level. That’s why we can see faster improvement in threshold and VO2 Max values.

Remember to always adjust your training plan to your needs, but it is definitely worth it, to try Polarized Training. Let me know if you need the help of a coach.

Coach Damian

Damian is a head coach and founder of Cyklopedia, which was created with one goal to help everyone be faster cyclists by structured training plans, healthy recipes, and nutrition plans. Damian is racing and coaching for over 10 years, working with athletes all around the world.


  • Avatar Noah Claes says:

    how much recovery between sets?

  • Avatar MarvL says:

    The test is skewed/ misleading in my opinion. The groups did not accumulate the same amount of time at V02. If they would have the current literature shows almost identical adaptations. In addition no where does it show how effective they were at execution of those intervals. If you can hold the power for 16 min……’s NOT your V02 max power period. That is closer to 5-6 min max. Sieler has many studies with various endurance sports that show it’s time at intensity that creates adaptations. Some people may not have/want to invest the additional time at those intensities and the related percentages will help them understand what they are missing.


    • Avatar MarvL says:

      One last note. The 4×4 shows the greatest percentage gain of V02 per minute of work. Likely due to the ability of test subjects to actually hit and hold the intensity targets.

      • Coach Damian Coach Damian says:

        We always need to have in mind that this is one research, and other research on bigger groups could show little different results. Training is a very individual thing.

    • Coach Damian Coach Damian says:

      it is true, and testing on such a small group can be sometimes misleading, in Cyklopedia we always stress how important it is to have an optimized training plan for every individual.

  • Avatar Zakk says:

    What do you recommend for beginners?
    4X8 90%MHR?
    I did it yesterday again but i feel the 4 series is not enough.
    If 4×8 good what about 6-8×8?

    • Coach Damian Coach Damian says:

      Hello, it depends on your actual fitness and your goals, if that feels too easy for you, you can always increase the intensity to 100%, 105%, and 110% of FTP.

  • Avatar Isaac says:

    HI, I did 4x8x2s yesterday as a part of a ride. Am I able to ride at a normal pace for the rest of that ride or should i just take it easy?

  • Avatar Isaac says:

    Okay, Great! thanks for the help

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