By Chris Carmichael, Founder and Head Coach of CTS

There is an entire generation of cyclists that views VO2 max as a genetically pre-determined performance ceiling. A more modern and nuanced take shows it to be quite responsive to training. With different types of workouts we can increase VO2 max itself, as well as peak power, fractional utilization, and power duration at VO2 max. That’s a lot of terms to throw around, but we’ll explain them as we go, tell you why they matter for performance, and how to improve them and get faster on the bike.

What is VO2 max?

VO2 max is the maximum volume of oxygen your body can take in and utilize per minute, so it is considered your maximum aerobic capacity. We express it two ways: absolute or relative. Relative takes a person’s weight into account and is expressed as Liters/kilogram/minute. Absolute is just Liters/minute. Several factors determine an athlete’s VO2 max:

  • Vital Capacity: the maximum amount of air your lungs can move in a single breath. This is where the idea that large lung volume is advantageous for endurance athletes. It is, but the mechanics of breathing affect vital capacity, so it is a percentage of total lung volume.
  • Cardiac Output: the volume of blood your heart can move in a minute. It is the product of stroke volume (volume of blood expelled with each heartbeat) and heart rate. The more oxygenated blood your heart can circulate, the better.
  • Oxygen-Carrying Capacity: Oxygen binds to hemoglobin found in red blood cells. The more hemoglobin you have and the higher your red blood cell count, the higher your oxygen-carrying capacity.
  • Oxygen Uptake: VO2 max is not just how much oxygen you can get into the bloodstream. It’s affected by how much of that oxygen your muscles can uptake and use. This is affected by capillarization, mitochondrial density, and the composition of muscle fiber types.
  • Body Weight: Losing weight increases relative VO2 max but not absolute.


VO2 max is trainable because some of the factors above can be improved through exercise, some more than others. Endurance training improves muscle capillarization and mitochondrial density, and can shift the composition of muscle fiber type. Training and nutrition result in greater hemoglobin and red blood cell production. As the heart muscle adapts to training, stroke volume increases, which increases cardiac output.

When you add up these improvements (and others not mentioned), exercise training can increase VO2 max by around 20%. And because oxygen delivery to working muscles is the primary limiting factor for endurance performance, a higher VO2 max provides an athlete with a greater potential for success.

VO2 max and Human Performance

A high VO2 max is a prerequisite for being an elite-level endurance athlete, but not a guarantee of elite-level performance. The performance side is determined by how much of it you can use, and for how long. This is where some of that terminology from the opening paragraph comes into play:

  • Peak power at VO2 max: the highest power you can generate at your VO2 max . This will be affected by cardiorespiratory function, but also by muscular and neuromuscular adaptations.
  • Power duration at VO2 max: the amount of time you can sustain work at your VO2 max
  • Fractional utilization: the percentage of your VO2 max you can sustain for prolonged efforts, typically expressed as Lactate Threshold as a percentage of VO2 max (cardiovascular) or Functional Threshold Power (FTP) as a percentage of VO2 max power (performance).

It’s important to recognize you can improve these measures of performance with or without improvements to VO2 max itself! That makes a big difference for aging athletes because VO2 max gradually declines after about age 40. Most athletes in their 50s – 70s still have room to increase it because it wasn’t optimized to begin with. But even if your VO2 max is decreasing, these performance measures can still increase.

Intensity required to improve performance

Most athletes associate VO2 max training with extremely hard interval workouts. That’s part of it, but all aerobic training plays a role. Time training at an endurance pace (EnduranceMiles, Zone 2) improves aerobic endurance and increases mitochondrial density and capillarization. FTP training increases fractional utilization, power you produce before blood lactate levels rise, and how long you can sustain it.

The intervals that directly stimulate adaptations to VO2 max  are short, high intensity efforts. To be effective, these efforts need to elicit 90-95% of your VO2 max. Individual intervals should be 2-5 minutes in duration at 106% to 120% of your FTP (more on this below). This is because higher power outputs (140% of FTP) for shorter durations (30 seconds) call on your anaerobic capacity. Lower power outputs and longer durations are more lactate threshold efforts.

Intensive vs. Extensive Intervals

Remember that from a performance perspective, cyclists want to increase peak power and power duration at VO2 max. Athletes accomplish these goals with two different types of interval training: intensive and extensive.

Intensive interval training focuses on shorter durations and higher intensities to increase maximum output. In this case, 2-minute intervals at the upper end of the intensity range: 120% of FTP. The goal is to increase your peak power at VO2 max from, say, 300 watts to 320 watts.

Extensive interval training utilizes longer durations at lower intensities to increase maximum capacity. In this case, 5-minute intervals at the lower end of the intensity range: 106% of FTP. The goal is to increase the amount of time you can sustain an effort at VO2 max intensity.

With either type of interval strategy, cyclists should aim for a total time-in-zone of 15 to 20 minutes. As an example, in a single workout, 8 x 2-minutes at 120% of FTP equals 16 minutes time-in-zone. A main interval set of 5 x 4-minutes at 106% of FTP equals 20 minutes time-in-zone.

Recovery time between intervals – intensive or extensive – should be 1:1 with interval duration. So, two minutes of easy spinning recovery between two-minute intervals. Beginners may benefit from extending recovery times to prioritize high-power efforts, particularly with intensive workouts.

Structuring Training

The scheduling of intensive or extensive training depends on your current fitness and your training goals. Beginners or athletes with lower power at VO2 max (despite perhaps a high VO2 max), should start with intensive work. They have a lot of room for improvement in peak power before focusing on power duration.

More highly trained cyclists often have higher peak power at VO2 max because of the traditional training methods. They often benefit from a focus on extensive VO2 max intervals so they can handle longer high-intensity efforts.

If you’re not sure which applies to you, start with intensive intervals so you’re working to extend the duration of a higher power output when you get to extensive work.

Weekly training structure

Whether you’re using an intensive or extensive interval style, these are very hard workouts. Fortunately, it doesn’t take a lot of time at this intensity to stimulate positive adaptations. You can make measurable progress from a relatively small number of exercise bouts (4 – 6 sessions).

The high intensity necessitates 36-48 hours between individual workout sessions. A typical week of training during a two-week VO2 block might look like:

vo2 max

This structure would be essentially the same whether a cyclist trains 8 hours or 15 hours per week. Athletes with more hours available for training would spend most of their additional time at an EnduranceMiles (Zone 2) intensity.

Through simple math we can derive the length of training blocks. If it takes 4-6 bouts of exercise to achieve positive results and we schedule two interval workouts per week, the block lasts 2-3 weeks. More experienced athletes may benefit from higher workout frequency and/or longer blocks, but the structure above is a starting point.

When should you train VO2 max?

There are two schools of thought on this. The first is that you train the least event-specific aspect of performance furthest ahead of your event. For some events, particularly ultraendurance events, this would put VO2 max work first. The second starts with aerobic base training, builds through FTP work, and layers VO2 work on top of that. Both have merit, depending on your goals.

For road racing, criteriums, cross-country and short track mountain bike, and cyclocross the longer buildup may be preferable. High peak power and power endurance are priorities to meet the specific demands of those disciplines. So, you want a big aerobic base and high FTP to support workouts that drive up power at VO2 max. And you want to maximize those markers for event day.

Athletes who are training for ultraendurance races or multi-day cycling adventures may benefit from training VO2 max early. This includes 100- to 200-mile gravel races, 100-mile mountain bike events, and non-competitive multi-day tours. A high VO2 max is good, but aerobic endurance and higher fractional utilization are more event specific. Training VO2 max early provides the physiological tools to enhance aerobic endurance and FTP as the event approaches.

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