Imagine you're setting off on a round-the-world trip in your car. You wouldn't just fill up the tank and go, would you? Surely you'd take the car to a garage first: check the engine, change the oil, make sure the brakes are fine. So why is it that, when preparing for the main race of the season, so many of us treat our own body with less care?

Starting ultramarathon preparation without a preliminary “vehicle inspection” is like building a house without a foundation. You can buy the most expensive “building materials” (shoes, watches, gels) and hire the best “foreman” (a coach), but if there are cracks in the base, the whole structure will collapse sooner or later.

3.1. The Principle of “Fix First, Build Later”

Testing at the start of preparation is not a whim and not a waste of money. It's the smartest step you can take. Its purpose is not just to learn your “record” numbers, but to identify weak spots and imbalances.

Maybe you have a wonderful “engine” (a high VO2max) but also a huge “hole in the gas tank” (a high VLamax), and you burn carbohydrates like a steam locomotive. Or, on the contrary, you are very economical, but your “fat engine” (FatMax) only kicks in at a turtle's pace.

Testing gives you a map. It shows where you are now and helps you plot the shortest and safest route to your goal. Without it, you'll be wandering in the dark, risking getting “lost” in overtraining or injuries.

3.2. The “Gold Standard”: Gas Exchange Analysis

The most accurate and complete “inspection” available today is a laboratory test with a metabolic analyzer. Yes, this is the procedure where they put a fighter-pilot mask on you and make you run on a treadmill to complete exhaustion. It looks intimidating, but it's worth it.

What this test gives you:

An exact VO2max. You'll learn the real “size of your engine.”
Your FatMax. The most valuable data point for an ultramarathoner! The analyzer will show exactly at which heart rate you burn the most fat. That will be your “cruising speed” for long training sessions.
Energy sources. By analyzing the composition of your exhaled air, the analyzer plots an RER (respiratory exchange ratio) curve. It shows clearly at what intensity you're running on fat and when you switch over to carbohydrates. It's like peering into your own “engine bay” in real time.

Such tests are available at specialized sports-physiology laboratories in most large cities. Several testing protocols are usually offered — from basic ones to extended packages with a full metabolic profile and body composition analysis (see the list of laboratories in the “Useful Resources” section on the contents page).

📖 Case study: Alexey, 38, marathoner

Alexey had run 5 marathons in 3:45–4:00. He decided to try his first 70 km ultra. He prepared as if for a marathon: lots of tempo work, intervals, a weekly volume of 60–70 km. At kilometer 40 of the ultra he “blew up”: out of energy, cramps, nausea. He dropped out of the race.

After the failure he came in for a metabolic test. The results were a surprise:

VO2max: 52 ml/kg/min (a good result for an amateur)
FatMax: only 55% of maximum heart rate (very low!)
The RER showed that even during easy running he was burning carbohydrates — fat was barely being used at all

The problem: Alexey had been training too fast. His “easy runs” were in Zone 2–3 (75–80% of max heart rate), where the body relies on carbohydrates. The fat engine was never being developed.

The solution. His training was completely rebuilt:

80% of the volume in Zone 0–1 (heart rate 120–135 instead of the usual 145–160)
Long runs strictly at the FatMax heart rate
His pace dropped from 5:30/km to 6:30–7:00/km, but that was exactly the stimulus he needed

The result after 4 months:

Repeat testing showed his FatMax had shifted to 65% of max heart rate
At the FatMax heart rate he now ran 40 sec/km faster
His next 70 km ultra — a 9:15 finish without a single crisis

The lesson: more is not always better. Faster is not always better. Testing revealed that Alexey had been training inefficiently for years. One test saved him years of wandering in the dark.

3.3. Lactate: A Spy in Your Blood

Another powerful diagnostic tool is a graded test with lactate measurement. A tiny drop of blood is taken from your finger after each running segment at increasing speed. It sounds a bit harsh, but in practice it's almost painless.

What that drop of blood can tell you:

Your thresholds (LT1 and LT2). The curve will show clearly where your aerobic and anaerobic thresholds lie. You'll know your heart rate zones exactly, instead of guessing with averaged formulas like “220 minus age.”
Your VLamax. From the steepness of the lactate curve, an experienced specialist can estimate your VLamax — that very “hole in the gas tank.”

3.4. Careful With Lactate!

Lactate measurement is a powerful tool, but it demands care. It's like an expensive Swiss chronometer: handle it carelessly and it will lie to you. Dehydration, a poor finger prick, sweat getting onto the finger — any of these can distort the result. So trust your testing only to experienced specialists and laboratories.

3.5. “Folk” Methods: Heart Rate and How You Feel

“That's all wonderful,” you may say, “but there are no such laboratories in my city, and it probably costs an arm and a leg anyway.”

Don't despair! Even without access to the “gold standard,” you don't have to train blind. You always have two reasonably reliable tools:

A heart rate monitor. Your watch is not just a fashionable gadget. It's your onboard computer. Yes, heart rate is affected by a thousand factors: heat, stress, that cup of coffee, lack of sleep. But if you keep a training diary and analyze the data, over time you'll learn to understand the “language” of your heart.
RPE (Rate of Perceived Exertion) — the scale of subjective effort. Put simply — how you feel. The ability to “listen” to your body is a skill that can be trained just like a muscle. Learn to tell pleasant fatigue from exhaustion, and “working” breathlessness from the alarming kind.

The ideal option is to combine all the methods. Laboratory data gives you an accurate “map,” while heart rate and perceived effort help you navigate that map on your daily “expeditions.”

Helpful tip: for calculating your training zones yourself, predicting your finishing time and estimating your key markers (VO2max, lactate thresholds), there are specialized online calculators — for example, VO₂max calculation by nine methods and LT1/LT2 threshold detection. They will help you plan your preparation even if you have no access to laboratory testing.

In the next chapter we'll finally move from theory to practice: we'll figure out which “buttons” to press (which zones to train in) to improve all the markers we've just learned about.