Training & Testing: Finding the Balance Between Data and Feel

In the world of endurance sports, there’s a saying: “A session not recorded is a session that didn’t happen.” But how much testing is too much, and can you train effectively without drowning in data?
Let’s break down key testing methods—what they measure, how they’re done, and how to use them wisely.

1. Heart Rate (HR) & VO₂max
What? Measures cardiovascular efficiency and aerobic capacity.
How? Watches estimate VO₂max using algorithms based on heart rate and movement patterns. The shuttle run beep test provides a field-based estimate, but the gold standard is a lab test using a mask on a treadmill or bike to measure oxygen uptake directly.
Use it wisely: HR is a valuable tool for steady-state pacing but responds slowly to intensity changes and is affected by stress, sleep, and hydration. VO₂max is useful for tracking long-term fitness trends but doesn’t directly dictate race performance.

2. Functional Threshold Power (FTP) – Cycling Power Output
What? The maximum power (watts) you can sustain for approximately an hour, used to define training zones.
How? Often measured with a 20-minute all-out effort on a smart trainer, with power adjusted to estimate your 60-minute threshold. Lab tests with lactate analysis provide a more precise determination of your anaerobic threshold.
Use it wisely: FTP is a strong predictor of endurance performance, but real-world conditions like fatigue, terrain, and fueling significantly impact power output. It’s best used to guide structured training, not as an absolute measure of capability.

3. Critical Swim Speed (CSS) – Swimming Pace Indicator
What? The pace you can sustain for 1500m without fading, often used to set training intensities.
How? Typically calculated from two all-out efforts (e.g., 400m & 200m) using a simple formula.
Use it wisely: CSS is an excellent marker for endurance-based swim training but doesn’t account for technique efficiency. Combine CSS-based sets with stroke drills to improve overall performance.

4. Lactate & Blood Testing – Lab Precision
What? Measures physiological thresholds via blood lactate, hemoglobin, or glucose levels.
How? Blood samples are taken at increasing intensities to pinpoint aerobic and anaerobic thresholds more accurately than HR or power alone.
Use it wisely: Highly effective for elite athletes or those fine-tuning race performance, but for most athletes, structured training with HR, power, and RPE can yield similar benefits.

Training with Data—Without Losing Feel
​The best training blends both numbers and intuition. Here’s how:

• Use RPE (Rate of Perceived Exertion) alongside data. If your watch says you're in Zone 2 but it feels like Zone 4, trust your body.
• Look for trends, not single-session numbers. HR, power, and pace fluctuate due to fatigue, illness, or conditions. Don’t let one bad session discourage you.
• Train by feel sometimes. Elite athletes often do unstructured sessions where they pace themselves purely by effort. Compare this to your data afterward to refine your internal pacing skills.
• Race with confidence. If you’ve practiced listening to your body in training, you won’t panic in a race when numbers don’t align with expectations. Focus on effort, execution, and adaptation.

Data should be a guide, not a dictator. The smartest athletes know when to trust the numbers—and when to trust themselves.