by Tim Curry, MS ACSM-RCEP

Often, many individuals really enjoy putting in very hard to maximal intensity training efforts….at least after they’ve finished their workout. We enjoy the feeling of accomplishment and like we’re getting the most out of the time we spend training. It’s also commonly believed that a substantial amount of time completing hard workouts is required to really maximize your performance levels and reach peak fitness. But, is this really the case? What do these efforts actually do? When and why should we do them? Let’s explore Zone 4+ training!

What is Zone 4?

Like every other training zone, Zone 4 has many names including threshold and lactate threshold. Generally, this zone is built to have a range that sits on both sides of your lactate threshold, with the actual threshold point in the middle. There are many ways to set this zone, including using a functional threshold power test, a VO2max test, a heart-rate-based test, and of course, a lactate threshold test. Regardless, the lactate threshold point, and the resulting Zone 4, are generally viewed as highly important. This zone is appropriate in a normal road time trial (40-60 minutes), or during the climbs in a cross-country mountain bike race. It is a critical point, above which our exercise time is very limited due to local changes (i.e. at your working muscles). It also forms the general threshold, above which spending time starts to “burn matches”. There is a lot of importance tied to this zone! 

The Benefits

Zone 4 training is going to induce some very important changes in our physiology. One of the big ones is increasing the transportation of lactate from muscle cells that make it but cannot use all of it into those that can, specifically highly aerobic cells. The use or transportation of lactate (along with some other metabolic products) is critical to keeping your muscle cells functioning at this higher intensity. It is important to note here that these changes can be held up by not spending enough time to develop your mitochondrial density in your aerobic cells through Zone 2 training. There is a misconception that Zone 4 training is all that is needed to enhance everything needed to improve your lactate threshold and therefore performance, but that is not correct. 


For simplicity, we will call everything above Zone 4 'Zone 5'. This includes everything from minutes-long very hard-intensity efforts for improving maximal oxygen uptake and usage by cells to seconds-long, all-out efforts to improve neural recruitment of muscle fibers for sprinting. In Zone 5 we are working near or above our maximal aerobic capacity, meaning we’ve maxed out the ability to get oxygen to cells and use it. 

Zone 5 is incorporated in just about every training plan, but the specifics of the plan can vary dramatically. A track cyclist specializing in individual pursuit will have a different layout than a 24-hour mountain bike racer. This is where working with an experienced, knowledgeable coach can make a major difference. The ability to analyze the metabolic demands of your event/goal and then design the appropriate training program, including appropriate Zone 5 work, can help you maximize your performance potential. 

Thankfully, there are things you can do to get started! Recommendations appropriate for the majority of athletes include incorporating specific training time in Zone 5 for what is commonly called VO2max intervals. Here is a basic workout example:

  • 10-15 minutes warm up (Zone 1-2)

  • 3-6 x 1 min high cadence (>110 but keeping proper form) and 1 min easy recovery

  • 2-4 x 1 min Zone 5 (very hard to very, very hard & no speech possible) and 1 min recovery

    • As your fitness improves or if you find these too easy, start by adding on additional intervals before increasing your time. Usually, as your time increases, the number of intervals completed will drop. Keep the time in Zone 5 below 2-2.5 minutes in order to keep the intensity at the correct level. Finally, ensure the time spent in Zone 5 is equal to your recovery time (1:1 work to rest). 

  • 15-20 minutes cool down (Zone 1-2)

Putting It All Together

These higher-intensity zones can be incorporated into blocks focusing on either one zone, or (with more careful planning) multiple zones. If you are new to creating training plans or are creating a plan for a team, start with one zone for high-intensity days. If you are working with four-week training blocks, pick one higher-intensity zone to incorporate. This makes planning far simpler and will help alleviate some stress from your season. As you advance you can begin experimenting with ways to incorporate multiple zones into your higher-intensity training days to better suit your goals. 

To learn more about the concepts covered in this article while earning NICA CEUs, check out our recommended courses below!

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