Improving VO2 Max: Protocols for the HYROX Athlete.

The most effective way to improve VO2 max is to do intervals of 3-5 minutes each, approaching about 90% of max heart rate, once or twice a week, supported by a broad low-intensity aerobic base. For the HYROX athlete, these intervals can be done not only running but also on ergometers like the rower and SkiErg, raising the aerobic ceiling without increasing running load. In this article we explain what VO2 max is, its role in HYROX and four core protocols you can apply in practice.

What is VO2 max?

VO2 max is the maximum amount of oxygen the body can use per unit of time during exercise. It's usually expressed in milliliters per kilogram of body weight per minute (ml/kg/min). This value depends on the amount of blood the heart pumps per beat, the blood's oxygen-carrying capacity and the muscles' ability to use that oxygen. In short, VO2 max is the engine displacement of your aerobic motor.

Genetics significantly affects your starting VO2 max and how high it can rise. Still, meaningful gains with regular endurance training are common in untrained or lightly trained people. In athletes with a long training history, gains come more slowly, and most of the performance improvement comes from other components such as threshold, economy and durability.

The role of VO2 max in HYROX

HYROX is a predominantly aerobic race: most of the energy in an effort lasting 60-120 minutes is produced through oxygen-dependent pathways. VO2 max sets the ceiling of this system. The higher the ceiling, the lower your race pace sits relative to it. For example, of two athletes running the same pace, the one with the higher VO2 max works at a smaller percentage of their capacity and tires less.

But VO2 max alone doesn't win the race. Performance is the combination of three components:

1. VO2 max: The ceiling of aerobic capacity.
2. Threshold: How much of that ceiling you can use for a long time. For details, see the lactate threshold article for more.
3. Economy: How little oxygen you need to sustain a given pace. Its running equivalent is covered in in the running economy article in more detail.

A fourth HYROX-specific component is station strength: an athlete who isn't strong on the Sled Push will lose time at that station no matter how high their VO2 max is. That's why VO2 max work should be part of a balanced program, not the whole program.

How do you measure or estimate VO2 max?

The most accurate measurement is a graded test on a treadmill or bike in a lab, with breath gas analysis. Sports medicine centers and performance labs offer this test. In the field, there are a few practical options:

• Smartwatch estimate: Calculated from heart rate and pace data. The absolute value can be off, but it's useful for tracking the trend.
• Time trial tests: Tests like a 5-kilometer or 12-minute maximal run are performance indicators strongly related to VO2 max. They're ideal for tracking your own progress rather than an absolute value.
• Ergometer test: Your 2000-meter row or 1000-meter SkiErg time gives an idea of aerobic capacity with the upper body involved too.

Whichever method you choose, it's important to repeat it under the same conditions: same course, similar weather, similar freshness. Your results without recording them in your training log recording them makes progress visible.

Four core VO2 max protocols

The goal of VO2 max training is to accumulate time with the heart and muscles working close to maximal capacity. That's why rep durations are usually between 2 and 5 minutes; shorter reps are used with short rest.

4 × 4 minutes

This is a long-established, simple protocol. The first minute of each rep is the period when heart rate rises; the really valuable part is the last 2-3 minutes, when heart rate approaches its peak. Pace should stay constant from the first rep to the last. If your fourth rep is noticeably slower than your first, your starting pace is too fast.

30/30 intervals

Thanks to the short fast segments, they feel easier mentally and let you reach high speed without technique breaking down. Because of the short rests, heart rate doesn't fully drop between reps and builds up to a level close to VO2 max as the block progresses. This is the safest entry protocol for beginners. Start with two blocks × 8 reps in your first session; within a few weeks, move up to three blocks × 10 reps.

5 × 3 minutes

A good middle ground for athletes with a running background. Because the reps are a bit shorter than in the 4-minute protocol, the pace can be kept higher; this adds a further contribution to running economy and speed reserve. A track or flat course is ideal for this session. 3-minute reps on a hill reduce impact load while also working hip and calf strength; this variation is covered in in the hill running article in more detail.

Ergometer options

The rower, SkiErg and air bike let you reach a high heart rate without the impact load of running. For the HYROX athlete they have another advantage: direct technical carryover to the race's two ergometer stations. Doing one weekly VO2 max session running and the other on an ergometer is a smart balance for load management. The contribution of these tools to running is covered in rowing and SkiErg alternatives we covered in the article.

Weekly dose and place in the program

VO2 max sessions are among the most demanding sessions in the program. One session a week is enough for most athletes; a second session can be added only in certain blocks of preparation and during periods when you're recovering well. What surrounds these sessions matters too:

• The day before a VO2 max session should be easy; it shouldn't come back-to-back with a heavy leg strength day.
• If there's also a threshold session in the same week, there should be at least one easy day between them.
• Most of your weekly endurance volume should still stay at low intensity (zone 2). The reasons are explained in the zone 2 training article in more detail.

The emphasis also changes with the preparation phase. Far from the race, VO2 max work can be more dominant to raise your overall aerobic ceiling. With 6-8 weeks to go, race-specific hybrid sessions and threshold work take center stage; VO2 max sessions are maintained at reduced frequency. This phased structure is covered in the periodization guide in more detail.

A HYROX-specific VO2 max session

In addition to classic intervals, a session using the HYROX format both pushes your aerobic ceiling and builds race-specific adaptation. Example:

1. 15-minute warm-up: easy jog, dynamic movements, 3 short accelerations.
2. 5 rounds: 3 minutes of hard running (RPE 8-9) + immediately followed by 250 m on the SkiErg or rower at a hard pace.
3. 3 minutes of walking or very easy jogging between rounds.
4. 10-minute cool-down.

In this session, the transition between running and the ergometer should be fast, but station technique shouldn't break down. If technique is breaking down, shorten the ergometer distance. You can find similar interval templates in the interval training templates article. At Hybrid, sessions like these are at the heart of the Hybrid Conditioning classes .

Common mistakes

• Turning every session into a VO2 max session: Constant high intensity gives a sense of progress in the short term, but within a few weeks fatigue builds up and progress stalls.
• Starting the first rep too fast: It reduces total quality time. The goal is a steady, repeatable effort.
• Skipping the warm-up: Going into high intensity cold both reduces performance and increases injury risk. Warm up for at least 12-15 minutes.
• Neglecting recovery: Without sleep, nutrition and easy days, the adaptations you expect from intervals won't come.

Tracking progress and safety

To see VO2 max progress, repeat the same test every 6-8 weeks: a 5 km time trial, a 2000 m row or your watch's estimate. Alongside this, track the change in pace and heart rate in the same interval session: if you can do the same 4-minute rep faster at a similar heart rate, you're on the right track. Knowing that progress is usually fast in the first months and slower afterward helps you set the right expectations.

High-intensity intervals place a serious load on the cardiovascular system. If you have a history of heart disease or high blood pressure, or a family history of early heart problems, talk to your doctor before starting this kind of training. If you experience chest pain, palpitations, dizziness or unusual shortness of breath during training, stop the session immediately and see a health professional. If you want to build your program with a coach, you can message us.