Endurance performance doesn't depend only on how hard you train, but on which system is currently your biggest limiter. Three areas matter above all: your maximal oxygen uptake, your ability to hold a high power output for a long time, and your aerobic base.
Simplified, VO₂max describes the size of your engine. Critical Power shows how much power you can ride steadily over a longer period. FatMax, or the base zone, describes the range in which your body works especially efficiently and provides energy economically.
The most important point: don't just train everything at the same time, but set your focus where your weakest value lies.
Raise the ceiling — VO₂max
If your Fractional Utilization is already high, for example around 80–85 percent, you are already using your existing engine well. In that case the limit lies more in the size of the engine itself. The goal is to take up, transport and utilise more oxygen in the muscles.
This requires intense but carefully dosed sessions:
- 5 × 4 minutes at 110–115 percent CP, with 4 minutes of easy recovery. Once a week over about 6 weeks. A very good standard session for VO₂max training.
- Progression for advanced athletes: 4 × 8 minutes at 105–110 percent CP, with 4–5 minutes of recovery. This variant clearly extends the time near maximal oxygen uptake. It is more demanding and should only be used once the 5 × 4 minutes can be ridden steadily and cleanly.
- 30/30 intervals: 30 seconds at about 130 percent CP, then 30 seconds at about 50 percent CP. 12–15 repetitions, 2 sets in total. This way you accumulate a lot of time at high oxygen uptake without each individual effort being completely exhausting.
- Advanced variant: 30/15 intervals. 30 seconds at about 125–130 percent CP, then only 15 seconds very easy. Start with 2 × 10 repetitions and only increase to 2 × 12–15 repetitions later. Because of the short recovery, oxygen uptake stays very high — effective, but clearly more demanding.
In VO₂max training, quality counts more than volume. If you can no longer hit the target power cleanly, the stimulus is often not better, just more fatiguing.
Lift the threshold — Critical Power
If your VO₂max is good but your Fractional Utilization is rather low, for example below 75–78 percent, you have a strong engine but can't yet use it for long enough. In that case the focus should be on Critical Power.
The goal is to accumulate more time near threshold and to hold high power under control for longer. Sessions just below, at, or slightly above CP are especially suitable for this:
- Over-unders: for example 3 × 12 minutes, with 6 minutes of recovery. Within each block you alternate between just below and just above CP, e.g. 2 minutes at 95 percent CP and 1 minute at 105 percent CP. This trains the ability to tolerate spikes in load and then keep applying controlled pressure afterwards.
- 3 × 15 minutes at 88–92 percent CP, with 6 minutes of recovery. Classic sweet-spot training: intense enough for an effective stimulus, but controllable enough to accumulate a lot of time in the target range.
- Long Z3 session: 90–120 minutes at about 75–85 percent CP. Useful as part of a longer ride, when you can really hold the intensity steady.
Especially in threshold training, what's decisive isn't how hard it feels at most, but how much clean time you accumulate in the target range. Riding too hard often brings more fatigue than additional benefit.
Build the base — FatMax and quality base training
Whether your focus is currently VO₂max or Critical Power: you should always train regularly in the base zone. It is the foundation that allows intense sessions to be processed well in the first place.
FatMax often lies roughly in the range of Zone 2, that is, around 65–72 percent CP. In this range your body works economically, improves aerobic energy supply, and learns to use fat more efficiently as an energy source.
But what matters is this: a long ride is not automatically good base training. What's decisive is how much time you actually spend in the planned zone.
Being out for four hours achieves little if you constantly coast, attack, barely pedal downhill, or let the group pull you out of the zone. A focused after-work loop of 75–90 minutes can be more effective if you stay consistently in Zone 2.
In practice this means:
- Ride longer sections deliberately and in a controlled way in Zone 2.
- When needed, build in Zone 2 intervals, for example 3 × 20 minutes or 2 × 30 minutes.
- Make sure to accumulate as much real time in the target range as possible during the ride.
- Avoid the typical "dirty ride" pattern: in the end you've collected some time in every zone — just not enough in the zone you actually wanted to train.
Zone 2 often seems unspectacular, but it is one of the most important building blocks for long-term development. Precisely because it doesn't feel hard, it is frequently ridden too imprecisely. Anyone who works cleanly here builds a more stable foundation for all more intense forms of training.