UNDERSTANDING VO2 MAX AND HOW TO INCREASE IT FOR CYCLISTS

By Chris Carmichael, Founder and Head Coach of CTS

There is an entire generation of cyclists that views VO_{2 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 VO_{2 max}itself, as well as peak power, fractional utilization, and power duration at VO_{2 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 VO_{2 max}?

VO2 maxis 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. Relativetakes a person’s weight into account and is expressed as Liters/kilogram/minute. Absoluteis just Liters/minute. Several factors determine an athlete’s VO_{2 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: VO_{2 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 VO_{2 max}but not absolute.

Trainability

VO_{2 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 VO_{2 max}by around 20%. And because oxygen delivery to working muscles is the primary limiting factor for endurance performance, a higher VO_{2 max}provides an athlete with a greater potential for success.

VO_{2 max}and Human Performance

A high VO_{2 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 VO_{2 max}: the highest power you can generate at your VO_{2 max}. This will be affected by cardiorespiratory function, but also by muscular and neuromuscular adaptations.
Power duration at VO_{2 max}: the amount of time you can sustain work at your VO_{2 max}
Fractional utilization: the percentage of your VO_{2 max}you can sustain for prolonged efforts, typically expressed as Lactate Threshold as a percentage of VO_{2 max}(cardiovascular) or Functional Threshold Power (FTP) as a percentage of VO_{2 max}power (performance).

It’s important to recognize you can improve these measures of performance with or without improvements to VO_{2 max}itself! That makes a big difference for aging athletes because VO_{2 max}gradually declines after about age 40. Most athletes in their 50s – 70s still have room to increase itbecause it wasn’t optimized to begin with. But even if your VO_{2 max}is decreasing, these performance measures can still increase.

Intensity required to improve performance

Most athletes associate VO_{2 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 VO_{2 max}are short, high intensity efforts. To be effective, these efforts need to elicit 90-95% of your VO_{2 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 VO_{2 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 VO_{2 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 VO_{2 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 extensivetraining depends on your current fitness and your training goals. Beginners or athletes with lower power at VO_{2 max}(despite perhaps a high VO_{2 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 VO_{2 max}because of the traditional training methods. They often benefit from a focus on extensive VO_{2 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 VO₂block might look like:

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 oftraining 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 VO_{2 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 VO_{2 max}work first. The second starts with aerobic base training, builds through FTP work, and layers VO₂work 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 enduranceare 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 VO_{2 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 VO_{2 max}is good, but aerobic endurance and higher fractional utilizationare more event specific. Training VO_{2 max}early provides the physiological tools to enhance aerobic endurance and FTP as the event approaches.