INSCYD Metabolic Testing
Understanding what limits your performance
FTP, heart rate and standard training zones only tell part of the story.
You may be training consistently and still plateauing. You may climb well but struggle to repeat hard efforts. You may feel strong in training but not convert that into better race or event performance.
INSCYD metabolic testing helps explain why.
It provides a detailed physiological profile of how you produce energy across intensities – including aerobic capacity, glycolytic contribution, threshold characteristics, lactate dynamics, and fuel use. Instead of relying on broad estimates or generic zones, training can be guided by your physiology.
When training time is limited, the right focus matters more than simply doing more.
Included in the Executive Performance Programme and as a standalone service
HOW IT WORKS
The test can be completed remotely, either outside or indoors, using your power meter, and consists of 4 intervals (that can be done on 2-3 separate days for max freshness):
- 20 second SEATED sprint
- 3 minute maximal effort
- 6 minute maximal effort
- 12 minute maximal effort
TEST METRICS & INSIGHTS
VO₂max
Maximum aerobic capacity
VO₂max estimates the upper limit of aerobic energy production. In performance terms, it defines the ceiling of your aerobic system and strongly influences your ability to sustain high power outputs.
Why it matters:
A higher VO₂max increases the size of the aerobic engine available for climbing, sustained race efforts, and long-term performance development. It also gives context to how much room there may be to improve threshold and high-end aerobic power.
VLamax
Maximum glycolytic rate
VLamax estimates the rate at which energy can be produced through anaerobic glycolysis. This is one of the most useful metrics for understanding rider phenotype and how power is being generated.
Why it matters:
VLamax helps explain whether you are more glycolytic or more aerobically efficient, which affects sprint capacity, punch, repeatability, threshold characteristics, and substrate demand. It is also highly relevant when deciding whether training should target greater aerobic development, reduced glycolytic contribution, or a different balance between the two.
Threshold
Maximal sustainable power
Threshold reflects the highest intensity that can be sustained with relative metabolic stability. It remains one of the most important performance markers in cycling, but on its own it does not explain why it sits where it does.
Why it matters:
INSCYD places threshold in context by relating it to VO₂max, VLamax and lactate dynamics. That makes it more useful for training design, because it helps show whether threshold is being limited by aerobic ceiling, glycolytic profile, durability, or metabolic efficiency.
LT1
First lactate turn point / aerobic threshold
LT1 estimates the upper boundary of predominantly aerobic work, where lactate remains close to baseline and metabolic strain is still relatively low.
Why it matters:
This is highly relevant for setting endurance intensity accurately. For riders with limited time, it improves the quality of lower-intensity training by making sure endurance sessions are controlled enough to build aerobic capacity and durability without creating unnecessary fatigue.
Fat oxidation
Aerobic fuel utilisation
Fat oxidation estimates how effectively you can generate energy from fat at different intensities. It is a useful marker of metabolic efficiency and aerobic robustness.
Why it matters:
Higher fat oxidation generally supports better durability in longer rides and reduces the relative carbohydrate cost of sub-threshold work. For endurance-focused cyclists, this has clear implications for pacing, fueling, and the ability to maintain performance over time.
Carbohydrate combustion
Carbohydrate demand across intensities
This estimates how much carbohydrate is required to support work at different power outputs. It gives a more practical view of the metabolic cost of training and racing intensities.
Why it matters:
This is especially useful for fueling strategy. It helps quantify how expensive tempo, threshold, and higher-intensity work are metabolically, which improves planning for hard sessions, long climbs, races, and endurance events.
Lactate dynamics
Production, accumulation and clearance under load
INSCYD models how lactate behaves as intensity increases, including how quickly metabolic stress rises and how efficiently your physiology can remain stable near key thresholds.
Why it matters:
This helps explain why some riders can repeat hard efforts, recover between surges, or sustain high power late into an event, while others accumulate fatigue earlier. It is particularly useful for understanding race demands, interval response, and event specificity.