Speedwork on flats: How to alternatve between Z3 and Z4

  • Creator
  • #48061


    I did a weekly Z3 (2 x 15 minutes) session on a flat dirt road for some weeks now and feel that it really helped me with my speed on the trails at sub AeT efforts. So I want to keep this weekly flat session and add some Z4 (5 x 4 minutes) in there too. I would consider two ways of doing so:

    1. Doing Z3 in one week and Z4 the other week.
    2. Doing a block (maybe 8 weeks) of Z3, then a block of Z4.

    I kind of like version 1 more, but am worried that two weeks between the Z4 sessions is too much to really make improvements here. Are there any best practices about this?

    Thanks and best regards


Posted In: Mountain Running

  • Participant
    Dada on #48068

    Following 🙂

    Emil on #48075

    There is another option – doing first the Zone 4 block and then the Zone 3 one. Some top athletes do the most race specific intensity closest to the race.

    nullkru on #48105


    Anonymous on #48110

    Yes, all three could work.

    What are you training for, and how far away is the event?

    First thought: the benefit of Z3-5 training will eventually plateau, so it’s not something that you can constantly increase. So timing is important.

    Jan on #48124

    I don’t need that speed training for any specific event. I just feel like raw speed is a weakness in my running and want to keep a faster session once a week as long as I am making improvements there. And I asked myself if I can expect improvements in Z4/VO2max if I only hit it once every 14 days.

    Anonymous on #48151

    Probably. I’ve seen improvements before on a 14-day cycle.

    Jan on #48174

    Good to hear, so I will try it. Thanks a lot!

    cramblda on #55198

    I know this is an older thread, but I’m curious how this is going for those of you using the flat Z3/4 work over that past year(s)?

    I spent the last few years doing most of my running on rolling terrain or steep trails, including my Z3/4 work. I only do my 2x Week 3-5 mile recovery runs on flat terrain.

    In 2020 due to the pandemic, I started doing more running on flat asphalt near my house mid-week, with my longer runs still on the trails. I noticed I could run much faster at recovery HR/Z1 on flat asphalt then the previous years – which I was of course happy to see. However, I could not get to AeT on flats for sustained distances due to the lack of ME (I assume) for leg turnover. Four years ago when I started all this training, my Z1 mile pace was about 10:30, now it’s 8:10 if I go approx 10 miles. My legs are working really hard while my HR is very low. A few years ago I was able to do tempo runs up to an hour long in the middle of my Z3 on flat asphalt. That wouldn’t be possible now on flat terrain. I can do an hour at AnT on a steep hill easily.

    I’m thinking I need to do some more flat speed work if I want to improve my aerobic economy. I probably need to start small with very short Z2, and then Z3 workouts in the range of just a handful of minutes, and then work up from there.

    Any thoughts or tips would be appreciated.


    John H on #55208

    David, that’s an interesting issue that I haven’t personally experienced, but having done a lot of flat-ground running training in the past, I believe you’re correct that speed work to improve your economy could be helpful. On hills, your legs just don’t have to turn over as quickly – or stride as far, it seems – to get your heart rate up.

    My running training has revolved around Jack Daniels, who explored (and originally researched) a lot of the concepts contained in TFNA/TFUA, and Daniels’s plans always include several weeks of 200- to 400-meter repeats at about your 1-mile race pace with full recovery between reps. He refers to this pace as repeat or R pace.

    If you have run a road race recently, you can use that to calculate that pace. If not, you can do it by feel – it’s basically just glorified striders, going fast but relaxed. It doesn’t correspond with an HR zone, because you don’t hold the pace long enough to get your heart rate that high. The idea is to purely stress your legs mechanically and to improve your efficiency at speed, hence the full recovery between reps. In my experience, it always felt like a light workout, and yet I would be a bit sore the next day if I hadn’t been training seriously.

    Maybe give these a try once a week for four to six weeks. Start with 200m reps and bump them up to 400s after a couple weeks (or a mix of the two). Make sure your total distance spent at this pace isn’t more than 5% of your total weekly mileage: Even though these workouts may not feel that hard, they do introduce a new stressor to your training and will require some recovery. After a bout with these sessions thrown in, your legs should have an easier time with the turnover and power required to hit zone 3 on flat ground.

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