Three Measures of Endurance Performance

Over the past couple of decades coaching endurance athletes, I’ve noticed a consistent relationship between three key performance metrics. Whether this relationship is push-pull or more synergistic is still up for debate—but one thing is clear: when these three improve, so does overall performance.

These metrics are:

• Power or velocity at aerobic threshold (AT)
• Average power during a 6-minute max effort
• Peak power during a 10-second sprint

When we pair this external data with internal load measures—heart rate, EPOC, TRIMP, and RMSSD from Firstbeat—we get a more complete picture. We’re not just looking at output anymore; we’re looking at what it costs the athlete metabolically to produce that work. That combination gives us valuable insight into economy and efficiency.

Consistent Patterns in Progress

Over the course of a training year, I’ve repeatedly seen athletes improve their power or velocity within a range of 15–30% across these three areas. Here’s a snapshot from one 18-year-old cross-country skier I coached over a six month training period:

Measured Change	Percent Improvement
Peak Power/Velocity	30%
Power/Velocity at 6 min	30%
Power/Velocity at AT	23%

That aerobic threshold number is usually the lowest. My take? It just takes longer to develop. I’ve seen the same uneven improvement curve in runners and mountain bikers. It doesn’t seem to matter which sport—this relationship holds up.

Why These Metrics Matter

From years of experience, I believe these three parameters form the foundation of endurance performance measures and they can be done as simple field test. They help you assess progress, pinpoint what’s working, and identify what needs adjustment.

They also align with the three core physiological elements of endurance training:

1. Neuromuscular performance (strength and peak power)
2. Sustainable power at VO₂max intensity
3. Power or velocity at aerobic threshold

A particularly important connection is between peak velocity and 6-minute velocity—this defines your speed reserve. It is the muscles that create the metabolic demand to improve the aerobic capacity and the speed, so we have to be able to move faster to improve our capacities. A larger speed reserve gives you more room to build aerobic capacity and race-specific fitness. Without it, your ceiling for improvement is limited. While heart rate is a great measure to control intensity, heart rate does not tell us if we are increasing capacity.

How to Train These Capacities

The path to better performance is straightforward. Focus on these three areas, keep it consistent, and you’ll see steady development.

1. Aerobic Threshold: Build the Base

Guideline: Keep most distance training at 60–70% of max heart rate, and no more than 75%.

Yes, it may feel painfully slow at first—but that’s the point. This is where aerobic adaptations happen, and trying to rush it by training harder just delays the process. As your aerobic system and peak power improve, you’ll start producing more velocity and power at this effort level.

I’ve found the sweet spot for session duration is 90 minutes to 2 hours. Build that up before increasing frequency.

2. Peak Power: Don’t Let Speed Fade

Speed is one of the first things to go if you don’t train it. That’s why I include short sprint sessions focused on maximum recruitment of motor units and fast-twitch muscle fibers. It’s not just about sprinting—these sessions also help improve aerobic efficiency and VO₂max velocity.

Sample Workout:

• One set of 5–6 reps
• Accelerate to max or near max velocity for 5–10 seconds, then hold max speed for 10 seconds
• Rest 3–4 minutes between reps for quality
• Over time, build to two sets with more 6-8 reps
  Note: An effective strength program is essential to support speed gains.

3. VO₂max: Max Sustainable Effort

VO₂max training should focus on increasing the speed or power you can sustain near your VO₂max—not just boosting the number itself. These efforts are typically around six minutes in length and should be a year-round staple.

Key Details

• Intervals in the 3–8 minute range
• Intensity at 88–92% of max heart rate
• Include some shorter intervals (30–90 seconds) to build speed and tolerance
• Use equal or slightly shorter recovery between reps

Keep It Simple—Stay Focused

For most athletes who aren’t already at an elite level, I’ve found that keeping training simple and focused on these three pillars is the most effective way to improve. There are other pieces, of course—technique, fueling, recovery—but these three metrics consistently point the way forward.

When they’re all improving together, performance follows.