FTP tells you where you are. VO₂max and VLamax tell you why—and what to do about it.
For 20 years, FTP has been the number cyclists chase. And it matters—but FTP is a result, not a cause. It emerges from the interaction of two underlying systems: your VO₂max (aerobic capacity) and your VLamax (how fast you produce lactate).
This interaction explains something FTP alone can’t: why two riders with identical threshold power race so differently. One dominates punchy XC courses but blows up on long climbs. The other grinds out 100-mile gravel races but can’t respond to attacks. Same FTP—different engines.
Most mountain bikers have never measured VLamax, and few have had their VO₂max properly tested. We use INSCYD to measure both in a single protocol and show how they combine to shape your sustainable power, your punch, your carb burn rate, and your endurance.
Here’s what that looks like:
What the INSCYD Test Measures
Through a structured series of efforts on your own power-meter-equipped bike, the INSCYD test builds a complete metabolic profile:
- VO₂max — Your aerobic capacity; how big your engine is
- VLamax — Your glycolytic power (anaerobic punch); how fast you produce lactate and burn carbohydrates.
- MLSS / Threshold — Your highest sustainable steady-state power
- Fat and carbohydrate oxidation curves — How you burn fuel at every intensity
- FatMax — The power output where you burn the most fat per hour; your most efficient endurance pace and where you recover from hard efforts fastest
- CarbMax — The highest power you can sustain indefinitely when fueling at ~90g carbs/hour; above this, you’re depleting carbohydrates faster than you can replace them
- Lactate production and clearance — How fast you accumulate lactate on hard efforts and how efficiently you recover
- Glycogen capacity — How large your internal carbohydrate tank is for longer events
This goes well beyond a standard FTP test or the VO₂max estimate on your watch. It’s a complete picture of how your body produces power—and where the real opportunities for improvement are.
How VO₂max and VLamax Interact
In endurance sport, a bigger aerobic engine—higher VO₂max—is always beneficial. But two athletes with the same VO₂max can race very differently depending on their VLamax.
A high VLamax gives you explosive power for XC starts, short-track attacks, and steep punchy climbs. But it also means you burn carbohydrates quickly and produce lactate faster at submaximal efforts. For long gravel races, marathon MTB, or multi-day bikepacking, a high VLamax can work against you—shortening how long you can ride strongly before glycogen and fatigue become limiting.
Let’s look at the full picture:
Your sustainable power, your fuel efficiency, and your endurance all emerge from the balance between these two systems. The low-VLamax athlete doesn’t just have a higher threshold—they also have a higher FatMax and CarbMax, meaning they burn more fat and can sustain higher power when fueling optimally. These differences compound over hours of racing.
Why Interpretation Matters
VLamax is trainable—more so than VO₂max. But how to train it, and whether you should, depends on your aerobic capacity, your current VLamax level, and your event demands. Two athletes with similar numbers might need very different approaches—the test gives you the data; the post-test consult translates it into training priorities that actually fit your situation.
What This Means for Different Types of Riding
XC and Short-Track
Explosive starts, repeated surges, steep punches over 45-90 minutes. Your test reveals whether your VLamax delivers the punch you need—and whether building it further would help or hurt your sustainable power across the full race.
Marathon MTB and Endurance XC
For 3-6 hour races, success comes from threshold power, smart climbing pace, and careful carb management. Your profile shows whether your VLamax is too high—wasting carbs early—and what shifting it would do for your endurance and late-race power.
Gravel Racing
Long sub-threshold efforts with unpredictable surges on climbs, in crosswinds, or over rough terrain. Your metabolic profile shows where you can sit all day, how big the surges can be before you start digging into reserves, and what carb intake keeps you competitive to the finish.
Bikepacking and Ultra-Endurance
Multi-day efforts hinge on managing energy across days, not just within a single stage. Your test defines an all-day, repeatable power that keeps you in a fat-dominant zone while protecting glycogen for when you need it.
Time-Crunched Athletes
If you juggle work, family, and training, you can’t afford to waste hours on the wrong intensity. Your INSCYD profile reveals which sessions give you the best return for your goals—so every hour on the bike counts.
Custom Training Zones
Your INSCYD test includes fully customized training zones built from your unique metabolic data—not just percentages of threshold power.
Here’s why this matters: the intensity that effectively builds VO₂max depends on your VLamax. A younger athlete with high VLamax might target 125% of threshold power for VO₂max intervals. That same athlete 25 years later, with lower VLamax, would blow up at 125%—they need closer to 110%. Generic zone calculators miss this entirely.
Your zones are designed to:
- Improve VO₂max without accidentally pushing VLamax in the wrong direction for your events
- Nudge VLamax down and improve fat oxidation for long-duration racing
- Maintain or build VLamax when explosive punch is your priority
- Identify your FatMax zone where you oxidize the most fat and clear lactate most efficiently
Use these zones yourself, share them with your coach, or integrate them into your training platform. The data is yours.
From Test to Action: FuelSport
Testing alone isn’t enough—the value is in how you use it. Every LW Coaching INSCYD test includes access to FuelSport, a planning tool that turns your metabolic profile into practical pacing and fueling decisions.
Power Budget
FuelSport pulls in your INSCYD-derived fat and carbohydrate utilization curves, lactate behavior, and estimated glycogen capacity. It answers the question every athlete actually cares about: “How hard can I ride for a given duration with a realistic fueling plan?”
You set:
- Target ride or race duration
- How much carbohydrate deficit you’re willing to accept by the finish
FuelSport returns sustainable power targets for different carb intake rates—all based on your physiology. This helps you avoid both under-riding and catastrophic over-pacing on long climbs, gravel sectors, and multi-hour efforts.
Some practical questions it answers:
- What normalized power can I sustain for a 4-hour gravel race?
- How hard can I go on back-to-back days without depleting glycogen before the finish?
- What’s my power ceiling if I can only take in 60g carbs/hour vs. 90g?
Fueling Plans
Because FuelSport knows how your body burns fuel at different intensities, it helps you match on-bike nutrition to your actual metabolic demands. You can build race and training fueling plans that respect your tank size, your burn rate, and the realities of eating while riding on dirt.
Performance Projections
Your test also includes a “virtual” projection—what happens to your power budget if you raise VO₂max by 5%? Lower VLamax? Drop a couple of kilograms?
This projection loads into your FuelSport account so you can visualize what you’re training toward, not just where you are today. It’s a useful way to set realistic goals and see the potential payoff of different training focuses.
Coming Soon: Ride Analysis
We’re building a ride-analysis tool that applies your INSCYD model to real workout and race files. It tracks estimated carb and fat oxidation, lactate accumulation, and glycogen levels second-by-second throughout your ride.
Upload a race file and see where power spikes drove lactate and accelerated carb burn. Spot patterns like “overpaced the first climb” or “glycogen got critically low at hour 4.” Then use those insights to refine pacing and fueling for next time.
Test → Plan → Ride → Analyze → Improve.
This feedback loop is included with your INSCYD package—you’ll get access as soon as the tool launches.
What You Receive
Every LW Coaching INSCYD test is built around actionable outputs, not just lab numbers:
✓ Complete INSCYD metabolic report (VO₂max, VLamax, thresholds, FatMax, fuel curves, lactate dynamics, glycogen capacity)
✓ Custom training zones based on your metabolic fingerprint and event goals
✓ 1:1 video call to explain your results and discuss training implications
✓ FuelSport access for ongoing power budgeting and fueling planning
✓ Performance projection loaded into your account
✓ Ride analysis access when the tool launches
✓ Data you can use independently or share with your coach
Who This Is For
INSCYD testing is valuable if you:
- Race XC, marathon MTB, gravel, or ultra and want to understand what’s actually limiting your performance
- Struggle with late-race fades, inconsistent pacing, or bonking despite solid fitness
- Have been training for years and feel stuck on a plateau
- Coach yourself and want data-driven training priorities instead of guesswork
- Work with a coach and want to give them better data to work with
- Have limited training time and need to know which intensities matter most for your goals
Prerequisites: You need a power meter, some experience using it, and the ability to complete steady intense efforts up to about 7 minutes. If you’re newer to structured training, focus on building those fundamentals first—INSCYD testing is here when you’re ready for it.
Athletes Using INSCYD + FuelSport
LW Coaching athletes have used INSCYD testing and FuelSport planning to dial in training, pacing and fueling for some of the toughest events in off-road cycling:
- Dave Harris — 24 Hours in the Old Pueblo, Single Speed Solo winner (age 60)
- Taylor Lideen — 24 Hours in the Old Pueblo, Overall Duo winner & course record (with Lachlan Morton)
- Dave Giefer — 24 Hours in the Old Pueblo, Solo Men’s winner
- Julie Garcia — ITI 1000, overall winner (1,000-mile winter bikepacking race)
Each of these athletes used their INSCYD profile to understand their metabolic strengths, set realistic power targets, and build fueling plans that got them to the finish—and onto the podium. Full case studies coming soon.
Why LW Coaching
- 25 years coaching mountain bikers — We’ve worked with off-road athletes at every level, from first-time racers to national champions. That experience shapes how we interpret your data for the specific demands of dirt.
- We race too — National championship titles and decades of competitive experience mean we understand the demands from the saddle, not just the spreadsheet.
- INSCYD expertise — Certified through Sebastian Weber’s Coaching Camp, with two years of applying INSCYD testing specifically to off-road athletes.
- Tools that close the loop — Your INSCYD data feeds directly into FuelSport for power budgeting and fueling plans, with ride analysis coming soon. Data becomes action.
The INSCYD protocol is validated against laboratory testing and used by elite programs worldwide. Learn more about the methodology →
Ready to See What’s Under the Hood?
Whether you coach yourself, work with someone else, or just want to finally understand how your body produces power on the bike—INSCYD testing gives you the metabolic fingerprint, custom zones, and FuelSport tools to train and race with more clarity.